DEPARTMENT OF FISH AND GAME JUNEAU, ALASKA. STATE OF ALASKA Bill Sheffield, Governor

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1 ~LASKA DEPARTMENT OF FSH AND GAME JUNEAU, ALASKA STATE OF ALASKA Bill Sheffield, Governor j DEPA!<.THENT OF FSH AND GAME Don v1. Collinsworth, Commi s sioner library DVSON OF GAME US. f-"i-;1, 8, Wildlife Service W. Lewis Pamplin, Jr., Director,c,l t:. 1v JJ r-ocd Steven R. Peterson, Research Chie ~~gt_j~, Alaska DEMOGRAPHY OF THE DELTA CARBOU HERD UNDER VARYNG RATES OF NATURAL MORTALTY AND HARVEST BY HUMANS By James L. Davis and Patrick Valkenburg Progress Report Federal Aid in Wildlife Restoration Proj e ct W-22-2, Job 3.27R QL uss D Persons intending to cite this material should obtain prior permi ssion from the author ( s) and/ or the Alaska Department of Fish and Game. Because most reports deal with preliminary results of continuing studies, conclusions are tentative and shou+d be identified as such. Due credit would be appreciated. (Printed May 1984)

2 PROGRESS REPORT (RESEARCH) State: Alaska Cooperator: Larry B. Jennings Project No.: W-22-2 Project Title: Big Game nvestigations Job No. : R Job Title: Demography of the Delta Caribou Herd Under Varying Rates of Natural Mortality and Harvest by Humans Period Covered: 1 July 1982 through 3 June 1983 (including data through November 1983) SUMMARY During this reporting period, we radio-collared and obtained morphometric and physiological data from 13 Delta Herd caribou (Rangifer tarandus granti). Twelve of the caribou captured were 1-month-old females, which makes a total of 37 known-aged females radio-collared in the Delta Herd. The immobilizing dose of 5 mg acepromazine plus 4.5 mg etorphine was an improvement over past doses of 5 mg etorphine or 4. 8 mg etorphine plus 2-3 mg Rompun. The mean live weight of the 12, 1-month-old female caribou captured in 1983 was not significantly different (Student's t, P >.1 for each year) than the mean weight of caribou frorilthe 3 previous cohorts at comparable age. The peak of calving was about 21 May in Calf production remained high with 8n calves:loo caribou older than calves noted on the core calving areas. By 15 June 1983, a ratio of 51 calves:loo females older than calves was observed. Movements and distribution of radio-collared Delta Herd caribou were similar to past years, and data from 1979 through the present were summarized and appear in Appendix A. The role of disturbance on the Delta Caribou Herd was reviewed. Two papers about disturbance (Disturbance and the Delta Caribou Herd; The Reaction of Caribou to Aircraft: A comparison of 2 herds) were presented at the 1st North American Caribou Workshop in Whitehorse, Yukon (28-29 Sep 1983) and appear as Appendices C and D. Censuses of the Delta and Yanert Caribou Herds were conducted on June The Delta Herd was estimated to number 5,425, and the Yanert Herd numbered 929. Projections from 1982 for the Delta Herd suggested that the Delta Herd should have numbered over 7, in The lower estimate from the census cannot be i

3 adequately explained, but it appears that a portion of the herd was not located during the June 1983 census. After an estimated harvest of over 1, Delta caribou in fall 1983, a 1-day census of caribou associated with radio-collared Delta caribou produced an estimate of 5,3 on 4 October There is limited evidence that herd recruitment in was lower than the preceding 5-year mean. Natural mortality rates appeared higher in Key words: caribou, censusing, Delta Herd, demography, population dynamics, Rangifer, Yanert Herd. ii

4 CONTENTS Summary i Background Objective Procedures Study Area Radio-collaring/Morphometry/Physiology Relocating Radio-collared Caribou Calving/Productivity/Recruitment Herd dentifies ~ Delta and Yanert Censuses Harvest Natural Mortality and Population Dynamics Results Radio-collaring... 6 mmobilizing Caribou Morphometry/Physiology Relocating Radio-collared Caribou... 7 Calving Chronology and Distribution.. 8 Productivity/Natality Recruitment Herd dentities Delta and Yanert Censuses..11 Harvest Natural Mortality and Population Dynamics Analysis of Past Data Acknowledgments Literature Cited Figu,res Tables Appendix A. Locations of Radio-collared Delta Herd Caribou, (ordered by accession number) Appendix B. Census of the Delta and Yanert Caribou Herds, June Appendix C. Disturbance and the Delta Caribou Herd Appendix D. The Reaction of Caribou to Aircraft: A comparison of 2 herds BACKGROUND Davis and Neiland (1975) reviewed and compiled all available data for the Delta Caribou (Rangifer tarandus granti) Herd (DCH) in Additional background information was presented by Davis and Preston (198), Davis and Valkenburg (1981, 1983), anrl Davis et al. (1982, 1983). <' Proximity of the DCH to Fairbanks, considerable background information on the herd, and options to intensively manage (i.e., manipulate) the herd make it ideal for long-term demographic study. During the past 13 years, the DCH declined dramatically (from 5, in 1969 to 2,5 in 1975) and increased even more dramatically (from 2,5 in 1975 to 7,+ in 1982). During this 1

5 time, extremely high and low levels of both natural mortality and harvest occurred, and much was learned about caribou population dynamics. More importantly, much was learned about the largemammal-and-man-predator-prey-system in Game Management Unit 2A (Gasaway et al By continuing to study the DCH' s demography and simultaneously increasing study of the herd's behavior, nutrition, energetics, and interaction with the biotic and abiotic environment, we should ultimately understand caribou ecology to the degree presently demanded by 'the. growing pressures on caribou and their habitat.. Since study of the DCH was intensified in 1979, considerable data on herd movements and distribution have been collected incidentally to fulfilling major objectives. Skoog (1968:22, 655) and Bergerud ( 1974) have discussed mechanisms of how movements and distribution of caribou affect herd demography. As caribou population density increases in a given herd, caribou travel more widely and may begin using more marginal ranges. Use of marginal ranges could result in higher mortality and possibly lowered natality or increased morbidity due to greater energy expenditures, poorer quality forage, and greater vulnerability to predation. mplications of movements and distribution of caribou herds to population demography are sufficient to warrant collation and analysis of existing movement and distribution data for this progress report. f the DCH continues to increase, any change in movements and distribution will be better interpreted if earlier patterns are well documented. The present management goal for the DCH is to maintain a precalving herd of 5,-6,. However, reevaluation is continuing and other goals may become more appropriate. OBJECTVE To determine the demography of the DCH natural mortality and harvest by humans. under varying rates of PROCEDURES Study Area The study area (Fig. 1) included the range of the DCH and the Yanert Caribou Herd (Davis and Valkenburg 1983). n this report, all reference to the DCH prior to 198 includes the Delta and Yanert Herds. 2

6 Radio-collaring/Morphometry/Physiology From 1 July 1982 through 3 June 1983, we captured, radio-collared, and obtained morphometric and physiological data from 13 caribou. All except 1 were 1-month-old females, and all were captured on 1 April There are now 37 known-aged females, from 4 separate cohorts, radio-collared within the range of the DCH. n addition, there are 3 female and 1 male Delta caribou with active radio collars, but whose age is known only by estimate from cementum annuli of an incisiform canine tooth (Hiller 1974). The caribou captured in 1983 were all captured by chemical immobilization following the procedures described by Valkenburg et al. (1983) and Davis and Valkenburg (1983). The only change was in the immobilizing drug: each caribou was darted with a 5 ml dart containing ~.5 ml (1 mg/ml) acepromazine (Ayerst Laboratories nc., New York, N.Y.) and 4.5 ml (1 mg/ml) of etorphine (M99, D-M Pharmaceuticals, nc., Rockville, Md.). Radio collars were constructed of triple-layered, rubberized machine belting to which a hermetically sealed metal box containing the transmitter and batteries was attached. A highly visible, vinyl-covered canvas collar (15.2 em wide and 71 or 86 em long with 1 em high numerals of a contrasting color) was pop-riveted to each radio collar. The entire unit weighed less than 85 g. All radios contained movement-sensitive mortality switches (Telonics nc., Mesa, Ariz.) Normal pulse frequency was approximately 6 beats/min. When movement ceased for approximately 4 hours, the pulse doubled or tripled. Relocating Radio-collared Caribou Radio-collared caribou were relocated from fixed-wing aircraft (Bellanca Scout and Piper Super Cub) equipped with 2 "H" antennas (Telonics nc., Mesa, Ariz.). We used a Telonics nc. radio receiver/scanner and monitored some or all of the radio-collared caribou during 18 flights (Table 1). We also received some reports from the public on the locations of collared caribou, and 1 hunter returned the collar of a caribou he shot. We tried to observe the radio-collared caribou during each relocation. During each sighting, we recorded group size, location, presence ~ or absence of a calf, group composition, habitat, reaction to the aircraft, presence of other radio collars in the same group, snow condition, and other appropriate information. During the calving period, we recorded antler development, whether or not the females had distended udders, and the presence or absence of a newborn calf. All radio collars were equipped with movement sensitive mortality switches that enabled us to audibly determine if a radio-collared caribou had died. We investigated the cause of death of all dead caribou found, including those without radio collars. 3

7 Calving/Productivity/Recruitment Calving distribution, success, and chronology of the Delta and Yanert Herds were monitored by fixed-wing surveys of radio-collared and associated caribou on 6 days in late May (Table 1). No surveys were conducted from the ground. Herd productivity and recruitment were investigated by measuring natality, estimating mortality rates by monitoring radio-collared caribou, and by modeling of the Delta Herd's population dynamics. Sex and age composition surveys of the herd were conducted in May and October. L. Jennings and P. Karczmarczyk conducted a standard fall composition survey on 4 October 1983 (Table 2) using a helicopter to classify caribou from the air, supplemented by classification from the ground using a 2X-6X spotting scope. Herd dentities Movements of the Delta and Yanert Herds were monitored to determine if any interactions or interchange occurred between the neighboring Macomb, Denali, and Nelchina Herds. This effort was complemented by continuing studies of the other herds, particularly the Nelchina caribou (Pitcher 1983) and Macomb Herd (D. Johnson, Alaska Dep. Fish and Game files). Delta and Yanert Censuses The modified aerial photo-direct count-extrapolation (APDCE) census procedure (Davis et al. 1979) was used during the 1983 Delta Herd and Yanert Herd censuses. The principal modification of the APDCE technique developed by Hemming and Glenn (1968) involved adjustments that preclude relying on summer and fall herd composition data to extrapolate the population estimate. A more recent modification is the use of radio-collared caribou to locate aggregations to be photographed or visually counted in APDCE or modified APDCE censuses. The Delta and Yanert Herds were censused concurrently on 14 and 15 June. Three spotter-planes (2 Super Cubs and a Bellanca Scout) were used, 2 of which were equipped with radio-tracking gear. Most aggregations were photographed by a DeHavilland Beaver with a belly-mounted 9 x 9 inch Fairchild T-11 aerial camera using black and white Kodak XX Aerographic film (ASA 125). Some of the smaller aggregations were photographed with 35mm Ektachrome 2 positive film and hand-held auto-wind cameras. The June 1983 DCH census produced a smaller estimate of herd size than expected based on projections of recruitment and mortality since the June 1982 census. Uncertainty caused by the lower population estimate and concern generated by an estimated harvest of 1,-1,5 caribou from the DCH during the hunting season in August and September 1983 were the impetus to conduct another 4

8 census of the DCH on 4 October The census was designed to produce the highest known minimum population estimate with the least amount of cost while simultaneously locating the herd for sampling of herd sex and age composition. P. Valkenburg and R. Boertje audibly located 38 of 41 radio-collared Delta caribou (including 1 Yanert Herd caribou that moved to the Delta Herd in 1982) using a Bellanca Scout for the reconnaissance, and they visually counted and/or photographed (with 35mm SLR cameras) all caribou associated with the radio-collared caribou. We subsequently learned that 2 of the unlocated radio-collared caribou were dead prior to 4 October They directed L. Jennings and P. Karczmarczyk, in a helicopter, to the aggregations and the helicopter crew obtained sex and age composition data. Harvest Harvest figures for 1983 were not available by the end of the reporting period. Harvest was subjectively estimated by L. Jennings based on contacts with local air taxi pilots, hunters, and observations of Fish and Wildlife Protection Officers and Department biologists. Natura~ Mortality and Population Dynamics The natural mortality rate of caribou older than calves was estimated by determining the natural mortality rate of female radio-collared caribou (Davis and Valkenburg 1981, Davis et al. 1982). Natural mortality of calves was estimated through serial herd composition surveys and modeling. The mortality rate of radio-collared caribou was calculated from a procedure empirically derived by W. Gasaway (Gasaway et al. 1983) as follows: percent dying annually = ~ where a = number of mortalities tallied among radio-collared animals b = estimated number of collared animal-years (if the time interval differs from 12 months, units will not be in years). A collared animal-year is equivalent to 12 collared animal-months; a collared animal-month is equivalent to 1 radio collar functioning on 1 animal for 1 month. b is estima_ted as follows: where b = c d e c = mean number of months that collars transmitting, excluding animals that died were 5

9 d = total number of radio-collared animals, including animals that died e = time interval--12 months for annual mortality (the number of months differs from 12 when calculating seasonal rates of mortality). This formula underestimates mortality rates when there are both a seasonal peak in mortality and radio transmitter failure during the observation period. However, we know of no better estimator of mortality rates. Radio-collaring RESULTS Twelve caribou were radio-collared during this reporting period, and 1 additional caribou was captured but not radio-collared (Table 3). At the end of this reporting period, we had 7 Yanert caribou (all adult females) and 38 Delta caribou (1 adult male, 26 adult females, and 11 yearling females) with functioning radio collars. mmobilizing Caribou Davis and Valkenburg (1983) concluded that a larger dose of M99 than they had been using, or a better immobilizing drug than M99 or M99 plus Rompun, was needed for immobilizing Alaskan caribou- primarily because of unsatisfactorily long drug induction time or incomplete immobilization. The combination of acepromazine and M99 used in 1983 seemed to be a vast improvement. Drug induction times were recorded for 11 of the 12, 1-month-old caribou imrnobi1ized in nduction time ranged from 3 to 18 min (x = 7.2 ± 4.8), and all caribou were satisfactorily immobilized (Table 4). n contrast, in , 11-month-old caribou were immobilized using 4.8 mg of M99 plus 2 mg Rompun, immobilization time ranged from 11 to 4 min (x = 21. ± 11.7), and only 4 caribou were satisfactorily immobilized. The others were caught and physically restrained. There was no significant difference in body weights between the groups handled in 1982 and n 1983, a 22-month-old female was darted inadvertently and released after being ear-tagged. Morphometry/Physiology The mean live weight of the 12, 1-month-old female caribou captured in 1983 was not significantly different (Student's t, P >.1 for each year) than the mean weight of caribou from the 3 previous cohorts at comparable age (Table 5). 6

10 Sera and whole blood samples were collected from all caribou captured in Data from analysis of the blood will appear in the final report. Eruption patterns of incisiform teeth were recorded for all the 1-month-old caribou (Table 6), and there was a direct correlation between body weight and advanced eruption of permanent teeth. Relocating Radio-collared Caribou Relocations of all caribou collared since 1979 were plotted on maps (Appendix A), and generalized movement patterns noted. More thorough analysis and discussion of movements and distribution will appear in the final report. During winter , most of the DCH occupied the area west of Wood River, and only a few had moved east of the Wood River by the end of March when the hunting season closed. This trend of increased wintering in the extreme western portion of the herd's range has been consistent since the herd began increasing in the mid-197's. Prior to the DCH's decline in the early 197's, caribou annually wintered in the Nenana River valley, but it was never documented if these wintering caribou were Delta or McKinley (Denali) caribou or both. A 2nd trend in movements seems apparent since the herd began increasing after n the early 197's, most postcalving aggregations remained in the traditional calving area east of the East Fork of Little Delta River until after mid-june. Since 1977, these postcalving aggregations have been distributed farther to the west (in the vicinity of the West Fork of Little Delta River) by mid-june. During much of the fall hunting season in 1983, distribution and movements of the DCH made it possible for hunters to see hundreds of caribou within a few days and to be selective. n mid-august, the herd was widely distributed, but many caribou were available to hunters along the Liberty Bell Mine Trail near Ferry. n late August, caribou moved east along the foothills as far as owa Ridge, then turned west again in early September. Many caribou reached the Totatlanika River by 9 September before abruptly turning east again on the loth. They apparently traveled east to the Little Delta River in September, then turned west again about the 2th. Rutting occurred largely west of the Totatlanika River, and when the caribou were censused on 4 October, most were approaching the Nenana River and still apparently moving west. During late October, we received reports of caribou in the Healy area and of some caribou crossing the Parks Highway. However, when we next located the collared caribou on 9 November, most had moved to the vicinity of owa Ridge, where all but 2 of the radio-collared caribou were found. 7

11 Calving Chronology and Distribution t appears that the calf:cow ratio peaked on 21 May 1983 (Fig. 2) or shortly thereafter in the DCH. On 21 May, 24% of 543 adult caribou observed on the calving grounds were antlerless and 8 calves:1 caribou older than calves were observed on the core calving areas. Almost all of the caribou older than calves were adult females, but a few were undoubtedly yearlings. Monitoring radio-collared cows suggested a similar or slightly earlier calving peak. We began monitoring radio-collared caribou on 18 May and continued checking females that had not yet been seen with a calf every other day until 31 May. On 19 May, 9 of 12 pregnant (determined by distended udders) radio-collared Delta caribou were accompanied with newborn calves, and 1 of these still retained hard antlers. Of 13 pregnant radio-collared Delta caribou observed on 21 May, 9 were accompanied with newborn calves. n 1983, calving in the DCH occurred primarily in the same areas as in past years (excepting 1982). By far, most calving females were observed in the traditional core calving areas (Fig. 3) east of the East Fork of Little Delta River. West of there, more nonpregnant females, yearlings, and males were present. Only 2 DCH males had active radio collars during calving time in One was on the upper Tatlanika River on 18 May; the other was near Dry Creek. No composition surveys were conducted in the Yanert Herd's range during the calving period in However, we did monitor radio-collared Yanert caribou from 19 May to 29 May. Of the 8 females collared in 1981, 1 was never relocated, and 1 (BKY 34) has been associated with the Delta Herd since fall Four of the other 6 were relocated on 19 May 1983, and 2 were not pregnant. One of the pregnant females was accompanied by a calf on 19 May, but the other was not. The other 2 radio-collared Yanert caribou were relocated on 27 and 29 May, and both were accompanied by calves and retained their hard antlers. Calving in the Yanert Herd in 1983 was similar to that recorded in the past 2 years. Calving caribou were widely scattered in the high mountains (1, 5-2,2 m) between the upper Wood and Yanert Fork Rivers. All radio-collared cows calved at the heads of Dick, Edgar, Big Grizzly, and Little Grizzly Creeks. Productivity/Natality n 1983, only 1 of 9 radio-collared 2-year-olds produced a calf (Table 7) on its 2nd birthday. This was similar to 1982 when none of the 7 radio-collared 2-year-olds reproduced. n contrast, a majority of the females born in 1978 produced calves in 198 (Tables 7, 8). Possible reasons for this variation in productivity in 2-year-olds were discussed previously (Davis and Valkenburg 1983). 8

12 Natality among female radio-collared Delta caribou 36 months old and older has averaged 81% (weighted annual mean) (34/42 females) from 1979 through n 1982, the natality rate of radio-collared female Delta caribou older than 2 years was 7% (7/1), and in 1983 the rate was 87% (13/15). This difference is not statistically significant (chi-square = 1. 4, 1 df,. 4 > p >. 3). Even though reproduction by 2-year-old cows seems to have essentially ceased since 198, overall herd productivity has remained at a high level. As noted above, calf production on the core calving areas was 8 calves:loo caribou older than calves in 1983 and for all calving caribou (Fig. 3) a ratio of 75 calves: 1 adults not including obvious bulls and yearlings was observed. By 15 June, a ratio of 51 calves:loo females older than calves was observed. From these above ratios, it is clear that herd productivity is high and early postnatal mortality of calves is relatively low. Recruitment Recruitment continues to be an important parameter that is particularly difficult to accurately measure. We normally consider recruitment to be the rate of breeding stock replacement. Because the only way to accurately measure recruitment entails measuring changes in absolute numbers of various cohorts over time, we normally resort to estimating recruitment from 1 or more indices. Most frequently, the percentage of calves in a population becomes the index for estimating recruitment. Several major assumptions are inherent in estimating recruitment from the proportion of calves in the herd. Because barren-ground caribou are socially segregated based on sex and age most of the year, it is generally assumed that the rut is the only time the herd is homogenously mixed, and that a representative sample of true herd sex and age structure can be obtained then. Davis et al. (1979) have demonstrated that this assumption may often be invalid, but a more reliable method of consistently and efficient1y determining true herd composition has not been discovered. To estimate survival of the calf cohort from rut (when the assumed valid calf percent of herd figure is obtained) to when the cohort becomes 1 year old (i.e., overwinter survival), a comparison of calf: cow ratios between rut and spring is made. Assumptions implicit in this step are that both sets of ratios are representative of the population and that cow mortality is not occurring between rut and late winter or some estimate of the rate of cow mortality must be incorporated into calculations. f yearlings are not considered as breeding stock or if mortality from 12 months to 24 months is different than post-24 months, then these considerations also must be incorporated into calculations. 9

13 Davis and Valkenburg (1983) discussed recruitment in the DCH from 1979 through 1982 as follows: "Mean calf percentage of the herd in fall is our best available index to recruitment and was x = 21.9 ± 5.34 for 1976 through To calculate the percent increase (from the preceding year) that 21.9% calves in fall represents, a ratio conversion can be used as follows: 21.9 (1-21.9) _ x, therefore, x = 28 (%). - 1 Thus, a mean of 21.9% calves present in fall represents a mean calf increment from the preceding year of 28%. Davis and Preston (198) estimated calf survival from October 1978 to May 1979 to be 8-92% (based on radio-collared caribou), and there is no indication it has changed (Davis and Valkenburg 1981a, Davis et al. 1982). The potential 28% increase from calves present in fall can be adjusted to % to allow for mortality to yearling age. This then suggests that mortality of caribou yearlings and older should have ranged from a low of to 2.8% up to 4.4 to 7.8% from 1976 through These results are consistent with the results discussed in the Natural Mortality and Harvest sections of this report." Composition of the Delta Herd was estimated twice in fall On 8 October 1982, a sample contained 29 calves:1 females older than calves and a comparable sample on 26 November 1982 was 38:1. Sampling in April 1983 produced a ratio of 29:1. From these ratios, worst and best case scenarios produce overwinter calf survival estimates of 76-1% without correcting for adult mortality. Estimates of female adult natural mortality in the DCH, based on monitoring radio-collared individuals between 1979 and 1983, have ranged from %/year. (These estimates are probably conservative because the radio-collared adults are all less than 6 years old.) Factoring in the worst case adult female mortality of 6%, estimated calf survival for would have been 7-94%. Using the ratio conversion used in 1982 (Davis and Valkenburg 1983) to calculate the percent increase from the preceding year that a given percent of calves in fall represents for the recruitment year would be as follows: 16 to 19 1b-16 t:o-19 = 1 ~, x = 19 to 23.5% less overwinter mortality. Applying the 7-94% survival calculated above, we get estimated yearling age recruitment of 13.3 to 22.1% for the spring 1983 population. These values can be compared to the mean of %. Herd dentities To be discussed in final report. 1

14 Delta and Yanert Censuses A total of 6,354 caribou were counted in the range of the Delta and Yanert Herds on 15 and 14 June Of the total, 5,425 were judged to be Delta Herd caribou, and 929 were judged to be Yanert Herd caribou (Appendix B). Attempting to independently census the 2 herds was greatly confounded because practically the entire Delta Herd was distributed in the upper Wood River drainage in an area that is frequently occupied by Yanert caribou. Rapid and continuous movement of aggregations between the Yanert and Wood Rivers further confounded the censuses. There is considerable circumstantial evidence that we may have missed a portion of 1 or both herds during the census because of rapid movements from or between areas assigned to different crews. The caribou were located in extremely mountainous terrain that precluded continuous communication between all survey aircraft and hence some question remains about census coordination. Because of uncertainties stemming from the June 1983 census, a cursory census was conducted on 4 October During the 4 October 1983 census, 5,51 caribou were counted. This was thought to be a conservative count, because only radio-collared individuals, associated caribou, and those found incidentally to radio-tracking were counted. n addition, the helicopter used to conduct composition counts on 4 October located about 1 additional caribou in transit to the aggregations associated with the radio-collared caribou. For these reasons, it seems probable that 5,3 would be a conservative estimate for the Delta Herd in October All radio-collared Yanert caribou were in the Yanert drainage so it was assumed that the Yanert Herd was not mixed with the Delta Herd during the October census. Although the 1983 harvest report card data are not yet available, the Department's subjective estimate of harvest is that at least 1, caribou were killed between 1 August and 4 October f the 1, harvest is added to the 4 October count of 5,3, then there should have been at least 6,3 Delta caribou in June 1983 when only 5,425 were counted. Harvest The hunting season for the Delta and Yanert Caribou Herds was scheduled to run from 1 August 1983 through 31 March 1984, with a bag limit of 1 caribou (Table 9). Because of movements and distribution of the Delta Herd in fall 1983, hunter success was apparently very high and, although harvest report data are not yet available, it appears that over 1, caribou were harvested by mid-october ~

15 Based on the apparently large harvest through October, the outlook that the herd would remain relatively available to hunters, and the 1983 censuses producing lower population estimates than projected from 1982, the hunting season for the DCH was closed by emergency order on 28 October 1983 (Table 1). The Yanert Fork drainage remained open. Natural Mortality and Population Dynamics Davis and Valkenburg (1983) summarized the population dynamics of the DCH through June 1982, including a discussion of natural mortality rates. Because of the questionable results of the 1983 population censuses, it seems that there is little to gain in discussing recent population dynamics prior to conducting a 1984 census. A couple of considerations do warrant mention, however. Yearling recruitment in may well have been below the preceding 5-year mean: 13-22% in versus 22-26% for 1976 to n addition, there is limited evidence of increased natural mortality in adult females in The mean annual natural mortality rate of all female Delta caribou radio-collared since the inception of this project in 1979 (January 1979 through October 1983) was 3% per "collared-animal year." From 1979 through October 1982, natural mortality of adult females averaged 1. 6% compared to 5. 8% from October 1982 through October Our calculated mortality rates are undoubtedly lower than experienced by the population. Mean age and maximum age of the radio-collared females are undoubtedly much younger than the population as a whole because radio-collared females are all from 1978 or more recent cohorts. n addition, Davis and Valkenburg (1981) presented evidence that natural mortality of males is normally substantially greater than in females. Two unexpected observations regarding population dynamics were noted in The projected herd size for 1983 was not substantiated by censusing in Secondly, the apparently large harvest in 1983 of over 1, caribou, which we suspected might include 75% or more males, did not appreciably lower the October 1983 bull:cow ratio (Table 2) as we suspected it should. These observations will be elaborated on as additional data are obtained. Analysis of Past Data The role of disturbance on the DCH was reviewed. Two papers about disturbance (Disturbance and the Delta Caribou Herd; The Reaction of Caribou to Aircraft: A comparison of two herds) were presented at the 1st North American Caribou Workshop in Whitehorse, Yukon (28-29 Sep 1983) and appear as Appendices C and D. 12

16 ACKNOWLEDGMENTS We thank L. Jennings for major involvement in censusing and obtaining composition data and for always willingly discussing the biology of the herd; E. Crain, R. Boertje, P. Karczmarczyk, S. DuBois, and T. McCall helped in 1 or more aspects of field work and data analysis. W. Regelin assisted in radio-collaring caribou and critiqued this manuscript. J. Barnett and s. Peterson provided final editing. LTERATURE CTED Bergerud, A. T The decline of caribou in North America following settlement. J. Wildl. Manage. 38(4) : Davis, J. L., and K. A. Neiland A study proposal: evaluation of condition of animals in the Delta herd and its bearing upon reproduction. Alaska Dep. Fish and Game, Fairbanks. 4pp. (Unpubl. rep.)., and D. Preston Calf mortality in the Delta -----=--~ Caribou Herd. Alaska Dep. Fish and Game. Fed. Aid in Wildl. Rest. Prog. Rep. Proj. W Juneau. 29pp., and P. Valkenburg Yearling mortality in the -----=~~ Delta Caribou Herd. Alaska Dep. Fish and Game. Fed. Aid in Wildl. Rest. Final Rep. Proj. W and w-21-1, Job 3.26R. Juneau. 18pp., and ,c=-a-r---.-i~bou Herd under harvest by humans. Wildl. Rest. Prog. 5pp Demography of the Delta varying rates. of natural mortality and Alaska Dep. Fish and Game. Fed. Aid in Rep. Proj. W-22-1, Job 3.27R. Juneau.,, and S. Harbo Refinement of the aerial photo-direct count-extrapolation caribou census technique. Alaska Dep. Fish and Game. Fed. Aid in Wildl. Rest. Prog. Rep. Proj. W Juneau. 23pp ~~~-', and R. Boertje Demography of the Delta Caribou Herd. Alaska Dep. Fish and Game. Fed. Aid in Wildl. Rest. Prog. Rep. Proj. W Juneau. 24pp.,, and Demography and ----,l~i~m-l~.t~ing factors of Alaska's Delta Caribou Herd, Acta Zool. Fennica 175: Gasaway, w., R. Stephenson, J. Davis, P. Shepherd, and. Burris nterrelationships of prey, man, and wolves in interior Alaska. Wildl. Monogr. No pp. 13

17 Hemming, J. E., and L. P. Glenn Caribou report. Alaska Dep. Fish and Game. Fed. Aid in Wildl. Rest. Prog. Rep. Proj. W-15-R-3. Juneau. 41pp. Miller, F. L Biology of the Kaminuriak population of barren-ground caribou. Part 2: Dentition as an indicator of age and sex; composition and socialization of the population. Can. Wildl. Serv. Rep. Ser. No pp. Pitcher, K. W Big game studies. Vol. V. Phase Prog. Rep. Susitna Hydroelectric Proj. Fish and Game. Juneau. 11pp. Skoog, R. o. granti) 699pp. Caribou. Alaska Dep Ecology of the caribou (Rangifer tarandus in Alaska. Ph.D. Thesis. Univ. Calif., Berkeley. Valkenburg, P., R. D. Boertje, and J. L. Davis Effects of darting and netting on caribou in Alaska. J. Wildl. Manage. 47(4) : PREPARED BY: APPROVED BY: James L. Davis Game Biolog1st Patrick Valkenburg Game Biologist 4{..r'tu':l' (}.4 tr.,..f, )eq=r QB.J.. u1rector, Divi's.i:on of Game.4:..tfr+ fa (J?eUn.v.ey j~ Research Chief;vu1v1s1on or Game SUBMTTED BY: Wayne L. Regelin Regional Research Coordinator 14

18 l'%j 1-' \.Q. ' ' ' ' ' ' ' ' ' ' ' ' a..-~'---- S1 ~~--... ~..... /.... ~~"',,, c c

19 eo 7 6 til! B so ~ ~ ~ 1-' '1 H ~ ~ ~ r til ~ Based on a sample of 7. radio-collared adult cows Calves/1 older than calves, 198 '~.rl... ""... /..~ 1 ~ ~~~ p A ! ~ Calves/1 older than calves, ~' ~... / \ //' A / / Calves/1 cows, 19A2 / / '..., Calves/1 older than calves, HJ\Y Fig. 2. Calving chronology in the Delta Caril:ou Herd, 1979, 198, 1982, and JUNE 23

20 KEY: Area A= B = c = D = E = Calves/1 caribou older than calves Sample Size. /.}) 'J! \' "~6f.",', '".., r '). r~ 83 1,442 / \.. ~ ;...,. :..,- '' ~ 1 '. l... 'f /. ' -',J,..' "'. / \ \ \ i :' ;. 'h. 1,. 1 ;./.L. l '....' J \ \ j fom 1 t. OH.r..r. y.. ::..., ( }. ) ) _) \( l, ~~~ /'.! '7' r) f:-~~ ~ 1-\~- \. lb~-;?v;c;rt ~J~~/ ~;;- ;~-t~ ~~>,.. -~~,..., 'l ~'} : t ~~ :~: -~ ;.... '...-/._f.,. -..:.,._v.'v... -;,."'.. :""J _V,~...,.,,"'t.{:( '''<.,.... :-. i :._\.-. '\ l~-.-:.~ _-_... '" _..,t/j ' "', J a 'D L J"' Fig. 3. Calving distribution and calf production by area in the Delta Caribou Herd, 21 May 1983.

21 Table 1. Dates of flights from which radio-collared Delta Herd caribou were relocated, 19 November October Date Aircraft Remarks 19 Nov Jan Feb Mar Apr Apr Apr May May May May May May Jun Jun Jun Aug Oct 1983 Scout Scout Super Cub Scout Bell 26B helicopter Super Cub Bell 26B helicopter Super Cub Super Cub 2 Super Cubs Super Cub Super Cub Super Cub Scout Beaver, Scout, 2 Super Cubs Scout, 2 Super Cubs, Bell 26B helicopter Scout Scout, Bell 26B helicopter Tagging Spring composition survey 18

22 Table 2. Sex and age composition of Alaska's Delta Caribou Herd, Yr1g Calf Cow Bull Bulls/ Yrlg/ Calves/ % in No. % in No. % in No. % in No. Sample Date 1 cows 1 cows 1 COWS herd yrlg herd calves herd cows herd bulls size 1/13-15/ /21-23/ /29-11/1/ ,139 1/27-31/ ,185 1/23-24/ ,5 1/23-25/ ,141 6/11-12/75 3 < Fall 1975 No counts conducted 6/3/ ,365 6/6-22/ ,99 1/29-11/1/ , /16-19/ ,224 \, 1/26-11/2/ ,365 6/13-14/ /26/ /23/ /7/ /14/ ,29 1/15-11/3/ ,369 6/17/ /2/ ,553 5/23/ /8/ ,349 11/26/ ll/26/82a /2/ ,79 6/15/ , ,587 1/4/ ,333 a Yanert Herd.

23 Table 3. Permanent accession numbers and other pertinent information for radio-collared Delta and Yanert Herd caribou, Year Date Accession Col~ar of collared No. a No. birth Sex (recollared) Herd Comments 11,972 YR F l/4/79 Delta BKY-36 (2/ll/82) 11,973 YR F l/4/79 Delta BKY-28 (2/ll/82) 11,974 '(R F l/8/79 Delta BKY-37 (2/ll/82) 11,975 YB M 1/9/79 Delta Killed by wolves 2/79 11,976 YR M 1/9/79 Delta Missing 4/79 11,977 YR F 1/9/79 Delta BKY-49 (2/26/82) 11,978 BKY M 1/9/79 Delta Died of unknown causes 3/79 11,979 YR M 1/4/79 Delta Shot 11/8 11,98 BKY M 1/1/79 Delta Missing 2/79 11,981 YR F 1/1/79 Delta BKY-2 (5/3/81) Died from recapture 11,982 YR F 1/1/79 Delta BKY-78 (2/ll/82) 11,983 BKY M 1/1/79 Delta Killed by grizzly 8/8 11,984 YR F 1/11/79 Delta BKY-47 (2/26/82) 11,985 YR M 3/3/79 Delta BKY-79 (2/ll/82) 11,986 BKY M 1/ll/79 Delta Missing 2/79 11,987 YR M 1/8/79 Delta Shed collar 5/79 11,988 YR F 1/4/79 Delta BKY-25 (2/26/82) 11,989 BKY M 1/11/79 Delta Shed collar 6/79 11,99 BKY F 1/8/79 Delta Died during collaring 11,991 BKY M 1/1/79 Delta Radio failed 9/8 11,992 BY M 1/11/79 Delta Radio failed 11,993 YR F 3/3/79 Delta BKY-26 (2/26/82) 11,994 YR F 3/3/79 Delta Radio failed 11,995 BKY M 3/3/79 Delta Missing 7/17/79 11,996 YB M 3/3/79 Delta Never heard 2

24 Table 3. Continued. Year Date Accession Col~ar of collared a No No. birth Sex (recollared) Herd Comltlents ~ 11,997 YR F 3/3/79 Delta Alive, but BKY-2 (2/26/82) collar on mortality pulse 12,341 BKY F 2/8/81 Delta 12,342 BKY (?) M 2/8/81 Delta Killed 2/81 (wolves?) 12,343 BKY F 2/8/81 Delta 12,348 BKY F 2/27/81 Delta 12,349 BKY (?) F 2/27/81 Delta 12,35 BKY (?) F 2/27/81 Delta 12,36 BKY F 3/22/81 Delta 12,361 BKY M 3/22/81 Delta 12,362 BKY-18 pre-1978 F 3/22/81 Delta 12,363 BKY-29 pre-1979 F 4/18/81 Yanert 12,364 BKY-3 pre-198 F 4/18/81 Yanert 12,365 BKY-31 pre-1979 F 4/18/81 Yanert 12,366 BKY-32 pre-1979 F 4/18/81 Yanert Missing since 4/18/81 12,367 BKY-33 pre-198 F 4/18/81 Yanert 12,368 BKY-34 pre-1979 F 4/18/81 Yanert 12,369 BKY-35 pre-1979 F 4/18/81 Yanert 12,37 BKY-7 pre-1979 F 4/18/81 Yanert 12,43 BKY F 5/3/81 Delta 12,431 BKY F 5/3/81 Delta 12,432 BKY F 5/3/81 Delta 12,546 BKY F 5/3/82 Delta 12,547 BKY F 5/3/82 Delta Eaten by grizzly 12,548 BKY F 5/3/82 Delta 12,549 BKY F 5/3/82 Delta 12,56 BKY F 5/3/82 Delta 12,561 BKY F 5/3/82 Delta 12,562 BKY F 5/3/82 Delta 12,563 BKY F 5/3/82 Delta 12,564 BKY F 5/3/82 Delta 12,565 BKY F 5/3/82 Delta 12,566 BKY F 5/3/82 Delta 12,83 BKY F 4/1/83 Delta 12,84 BKY F 4/1/83 Delta 12,85 BKY F 4/1/83 Delta 12,86 BKY F 4/1/83 Delta 12,87 BKY F 4/1/83 Delta 12,88 BKY F 4/1/83 Delta 12,89 BKY F 4/1/83 Delta 21

25 Table 3. Continued. Accession No. a Co lear No. Year of birth Sex Date collared ( recollared) Herd Comments 12,81 12,811 12,812 :1..2, ,814 12,815 BKY-45 BKY-44 BKY-17 None BKY-46 BKY F F F F F F 4/1/83 4/1/83 4/1/83 4/1/83 4/1/83 4/1/83 Delta Delta Delta Delta Delta Delta Note: Underlined collar numbers are those that were functioning during the period covered by this report. a Each caribou was assigned an accession number that remained unchanged even when recollared. b YR BY yellow numbers on red collar; BKY = black numbers on yellow collar; blue numbers on yellow collar... 22

26 Table 4. nduction time for 1-month-old female caribou from the Delta Herd immobilized with 4.5 mg etorphine hydrochloride combined with 5. mg acepromazine maleate, 1 April Accession No. Collar No. a nduction time (min) Recovery time afteb 1 mg diprenorphine hydrochloride Weight kg lb Comments 12,83 BKY Quivering contractions 12,84 BKY ,85 BKY-41 6 (?)? Heavily sedated 12,86 BKY ,87 BKY N w 12,88 12,89 BKY-48 BKY ,81 BKY ,811 BKY st dart bounced out, down 3 min after 2nd dart 12,812 BKY ,813. None Greatly increased induction 12,814 BKY-46 > times possibly related to 12,815 BKY reduced ambient temperature ~ All collars are yellow with black numbers. All caribou given diprenorphine hydrochloride intramuscularly except BKY-44 given intravenously.

27 Table 5. Means and standard deviations of body measurements (em) and weights of radio-collared 1- to 11-month-old female caribou, Delta Herd, 1979, 1981, 1982, and Year Shoulder height Total length Chest girth Metatarsal length Hind foot length Face length Neck circumference kg Body weight lb ±5.3 1i = ±6.5 N = ±4.3!:! = ±1.3!:! = ±2.3 li = ±2.3 li = ±2. li = ±3. 7 N. = ±8.1 N..= ±3.9 N. = ±6.6.N. = 6 15.±7.1 li = ±1. li = ±3.3 N = ±1.5 l'::l = ±2.4.N. = ±7.5.N. = ±16.5.N. = ±7. N = ±4.4 N = ±1.1.N. = ±1.9 N.. = ±2.5 N.. = ±2.6 ti = ±5.6 N.=ll 137.8±12.5.N.=ll ±6.8 B = ±5..N.=11 38.±1.3!:! = ±1. 9 li = ±4.1 N = ±1.5 N = 9 64.±5.4..N. = ±12. li. = 12 1\.),f::.

28 Table 6. Stages of eruption of incisiform teeth of 1-month-old female Delta caribou, Accession i1 i2 i3 c1 Weight No. R L R L R L R L kg lb 12,83 D D D D D D D D , ,85 D D D D D D D D ,86 p p D A D D D D ,87 D D D D D D D D ,88 A A D D D D D D ,89 D D D D D D D D ,81 E A D D D D D D ,811 E E D D D D D D ,812 D D D D D D D D ,814 D E D D D D D D ,815 p p E E D D D E D = Milk tooth. E = Erupting tooth. An erupting tooth has a stained portion but has not migrated to its position of permanent orientation. A = Absent tooth (permanent tooth not yet erupted) P = Permanent tooth. 25

29 Table 7. Reproductive history of radio-collared female caribou from the Delta and Yanert Herds, Accession Collar Year Year of Produced a calf No. No. a collared birth Comments 11,972 BKY No Yes Yes Yes Yes 11,973 BKY No No Yes No Yes 11,974 BKY No Yes Yes Yes Yes 11,977 BKY No No Yes Died 11,981 BKY No Yes No Died 11,982 BKY No Unk No No No 11,984 BKY No Yes Yes No Yes 11,988 BKY No No No Yes Yes 11,993 BKY No Unk Yes Yes Yes 11,994 YR No Yes Yes Radio failed 11,997 BKY No Yes Yes Yes No 12,341 BKY No No Yes 12,343 BKY Unk No Yes 12,348 BKY No No Yes 12,349 BKY ? Yes Unk Yes 12,35 BKY ? Yes Yes Yes 12,36 BKY No No Yes 12,362 BKY pre Yes Yes Yes 12,363 BKY pre Yes No No Yanert Herd 12,364 BKY pre No Yes Yes Yanert Herd 12,365 BKY pre Yes Yes Yes Yanert Herd 12,366 BKY pre Not seen since collaring 12,367 BKY pre Yes Yes Yes Yanert Herd 12,368 BKY pre Yes Yes Yes Yanert Herd 12,369 BKY pre Yes Yes Yes Yanert Herd 12,37 BKY pre Yes Yes No Yanert Herd 12,43 BKY No No Yes 12,431 BKY No No Yes 12,432 BKY No No Yes 12,546 BKY No No 12,547 BKY Died 12,548 BKY No No 12,549 BKY No No 12,56 BKY No No 12,561 BKY No No 12,562 BKY No Yes 12,563 BKY No No 12,564 BKY No -- Died 12,561 BKY No No 12,562 BKY No Yes 12,563 BKY No No 12,564 BKY No -- Died 12,565 BKY No No 12,566 BKY No No -- a BKY = black numbers on yellow collar; YR = yellow numbers on red collar. 26

30 Table 8. Age-related natality rate of radio-collared female caribou from the Delta and Yanert Herds, Natality of females by age 48 months 24 months 36 months and older All females Year (%) ( %) ( %) (%) 198 6/9 (67) /9 (67) /1 (1) 9/12 (75) 1/1 (1) 17/21 (81) 1982 /7 () -- 7/1 (7) 13/25 (52) /9 (11) 7/7 (1) 1/15 (66) 16/34 (47) Means 8/26 (31) 16/21 (76) 18/26 (69) 52/89 (58) 27

31 Table 9. Harvest of Delta caribou, a Males Year N (%) Females N (%) Sex unk N (%) Total Extrapolated total (81) 25 (17) 3 ( 2) 147b c NA (75) 54 ( 24) 2(1) (72) 68 ( 25) 9 (3) (62) 226 (36) 12(2) (72) 132(25) 13 (3) 517 NA (7) 6 7 ( 3) through , No open season (1) (fall) (winter) ll (total) (fall) (winter) (total) a Harvest from Subunit 2A and part of 2C. b From 1969 Alaska Department of Fish and Game survey and inventory progress report. c From J. Sexton memo 12/3/7. 28

32 Table 1. Hunting seasons and bag limits for Delta caribou, a Year Season Bag limit Aug-31 Mar 3 caribou Aug-31 Mar 3 caribou Aug-31 Mar 3 caribou Aug-31 Mar 3 caribou Aug-31 Mar 3 caribou b 1 Aug-31 Dec 1 caribou c 1 Aug-2 Sep 1 caribou through No open season d 1 Sep-3 Sep 1 Aug-3 Sep 15 Nov-31 Dec 1 Aug-3 Sep 1 Dec-31 Mar 1 Aug-31 Mar 1 male by drawing permit~ 2 permits issued. 1 caribou by drawing permit from 1 Aug-3 Sep~ 15 permits issued, up to 25 will be issued to nonresidents. Antlered caribou may be taken from 15 Nov-Dec 31 by registration permit. A total of 4 caribou may be taken. 1 caribou by drawing permit from 1 Aug-3 Sep~ 175 permits issued, up to 3 will be issued to nonresidents. Antlered caribou may be taken from 1 Dec-31 Mar by registration permit. A total of 5 caribou may be taken. One caribou b a Su b um.t. Amended c d Amended. Amended 2A and part of 2C. by emergency announcement to close 2 Sep. by emergency announcement to No Open Season by emergency announcement to close 28 Oct. 29

33 Appendix A. Locations of Radio-collared Delta Herd Caribou, January 1979-November 1983 (ordered by accession number). NOTE: For economy in printing, only a few representative figs. (Fig. A-1, A-8, and A-63) appear in Appendix A of this report. For those interested, Figs. A-1 through A-66 are on fiie with the authors and will be forwarded on request. Write: Alaska Department of Fish and Game, Game Division, 13 College Road, Fairbanks, Alaska

34 t'%j....q ):1 1-' t'%j () ~ 1-' () n llj 1"1... " c 1 llj n () Ul Ul... ::J == 1-' 1-' \. -...] 1\.)... ><: ~ lj1 -...] ttl :;.: ><: w '1..,.. --., r~. ''... -j

35 !!::' (X) llj () () (1) {) {)... :::s == 1-' 1-' \D -...] \D

36 ll... Jl \ - : ' K '.. '. '. ~...,... '.' ~ ~~ '. i ' '.~. '''. ~..,T.. -1-,:t.J.!: [,,,.. ~ ;.;:. { h :\ i \- ~,,;~.1 ~r ~: : ~:.;~l~-~ :.:.,...,, l :.-.. ' : l t 1', '"! ;.\~ '. \. \ t, 1 ' \ 1 "'11 fl l-..,.., 1'., ' \ " :- :' : '..' ' -,.. 1 ''! ' :. f,<\ ~-.., -. 1, 1 ' 1 j "' \,, r : -,. -...'. ~, r.. :' 11 J'. -..;. ' ': ~ -.:-, ~ ',... '; l :'. :.: r.....,... ~. \ ( ' ' ' l \.... ',, l "' '\ ' ',, ' '1..'. ~ '.. '!11'1:.. ( 'f, \. \ ; n k f ;' \., ':'_, --r\... ' l:l,, ( fj' ')\< v)lj ' ' - ' lj.,' '. J J ':, ' ' \., 'i \ < l., ',\ \ :f.. \.,:;;:--~ f;~ ~;~.A' ~,.-, r.<- :.r- -' ---=.,;. ;:';~.-./ \..... \.' 1.,.;- ~ l ' ',..., l ' ~ ',,...._ i F,.,~,..', ' t.,.,.,.. ( #J ".. ~,.t3'..-. -~. ( :, o o L f..,,.. ~.. ' \...,!J.. ). r.:.. "'. \,,:, Fig. A-63. Female caribou, accession #12367 (BKY-33)

37 Appendix B. Location, size, and composition of postcalving aggregations during the censuses of the Delta and Yanert Caribou Herds, 14 and 15 July 1983 (see Fig. B-1). Group no. Count method Number of caribou and composition 1 and 2 (same as 16) 3a 3b 4 5' a 27a 28 29a 3a 31a 32a 33a 34a 35a 36a 37 9x9 aerial photo 9x9 aerial photo visually estimated 9x9 aerial photo visually estimated 9x9 aerial photo visually counted visually counted 9x9 aerial photo 9x9 aerial photo 9x9 aerial photo 9x9 aerial photo 9x9 aerial photo visually counted 9x9 aerial photo visually estimated 9x9 aerial photo 9x9 aerial photo 9x9 aerial photo visually counted visually counted visually counted visually counted visually counted visually counted visually counted visually counted 35mrn photos 35mrn photos visually counted visually counted visually counted visually counted visually counted visually counted visually counted Total caribou counted 592 (mixed) 59 (mixed) 3 (mixed) 25 (mixed) 1 (mixed) 1, 7 34 (mixed) 34 (mixed) 5 (mixed) 8 (mixed) 218 (mixed) 261 (mixed) 122 (mixed) 2 (mixed) 35 (mixed) 157 (mixed) 35 (mixed) 89 (mixed) 246 (mixed) 38 (mixed) 479 (mostly males) 144 (mostly males) 83 (mostly males) 328 (mixed) 9 (1 calf) 213 (mixed) 35 (mixed) 11 (6 females, 5 calves) 417 (mixed) 56 (mostly males) 77 (mostly males) 4 (mostly males) 34 (mostly males) 3 (females and calves) 9 (mostly males) 18 (mostly males) 221 (7 calves) 6,354 a These groups, totaling 929 caribou, were probably Yanert Herd caribou. 34

38 ... U1 ~ ~ CD co w

39 Appendix C. Disturbance and the Delta Caribou Herd James L. Davis, Patrick Valkenbur~, and Rodney D. Boertje Alaska Department of Fish and Game 13 College Road Fairbanks, Alaska 9971 Abstract: The Delta Caribou Herd has been exposed to more disturbance than any other Alaskan Caribou Herd. Frequent bombing, strafing, artillery firing, and low-level overflights by military and civil aircraft have occurred on traditional calving areas and adjacent ranges. Exposure to dense wildfire smoke during calving in 1979 and 1983, and selection of a 3-year-old burn for calving in 1982 apparently did not adversely affect calving success. Despite these disturbances and others, the herd has increased at an annual rate of 19-22% since 1976, and is now larger than ever recorded. We infer from these and other observations that the Delta Caribou Herd is reasonably plastic in adapting to a wide range of "significant disturbances." NTRODUCTON Since 195 the Delta Caribou (Rangifer tarandus granti) Herd (DCH) has been exposed to more man-made auditory and visual disturbance than any other Alaskan caribou herd. Continuing concern about the possible detrimental effects of disturbance on caribou (see Plenary Session n Luick et al. 1975) warrants an analysis of DCH population dynamics and behavior in relation to disturbance. Like several other Alaskan caribou herds, the DCH' s size has varied considerably since 195, including a sharp decline in the early 197's. Speculation about factors contributing to this decline included possible disturbance from military and civilian activities in the area (Alaska Department of Fish and Game (ADF&G, 1976). Consequently, when we began investigating factors limiting the DCH in the mid-197's, we considered the possible role of man-made disturbance. We considered man-made disturbance in 3 broad categories: 1) sensory stimuli, 2) physical alteration of habitat, and 3) the presence of physical structures. Sensory stimuli include artillery, wildfire, aircraft, all-terrain vehicles, and mining and hunting activities. Alterations of habitat include the effects of burning~ mining~ and littering with military debris such as targets, shell cases, missiles, and parachutes. Physical structures include developments such as roads, pipelines, mines, airfields, railroads, communities, and industrial complexes. 36

40 n evaluating the effects of disturbance on the DCH, we discuss correlations between herd productivity and population trend in relation to disturbance, and consider herd behavior in relation to disturbance, with particular emphasis on the calving period. Though caribou workers hold diverse views about caribou behavior and the effects of disturbance, most concur that caribou are most sensitive during calving (Bergerud 1978, Klein 198, Cameron 1983). STUDY AREA Skoog (1968) originally described the range of the DCH. Based on subsequent study, Hemming (1971) modified Skoog's description and described the physical environment. Little change has been warranted since Hemming's revision. 2 The DCH currently ranges over about 9,6 krn on the north slopes of the Alaska Mountain Range between the Nenana River on the west and the Delta River on the east (Fig. 1). The area lies approximately 11 krn south of Fairbanks. The Alaska Range rises abruptly from its foothills and consists of rugged, glaciated ridges 1,83-2,74 rn in elevation interspersed with glacier-capped mountains exceeding 3,66 rn. The northern foothills of the Alaska Range are flat-topped ridges, 61-1,37 rn in elevation separated by rolling tussock tundra, muskegs, and spruce-covered lowlands. North of the foothills lies the predominantly spruce-covered Tanana Flats. The entire area is drained by the Tanana River. The study area is largely snow free from May until October. Annual temperature range is approximately 29 C to -51 C. Annual precipitation averages about 3 em; snow accumulation averages to 5 ern and rarely exceeds 8 ern. Ground vegetation in the foothills and mountains is frequently exposed during the winter because of strong winds. Although the herd is widely distributed from the mountains to the flats during winter, foothills appear most used. As calving time approaches, cows and many short yearlings move into the upper portion of the Little Delta River and Delta Creek to the traditional core calving areas (Fig. 1), which have been used since at least the 195's. Most calves are born on tussock tundra, but many others are born in the low shrub and sparse spruce-dominated areas. Most bulls and some short yearlings remain widely scattered throughout the herd's entire range during calving. METHODS Pre-1974 caribou data were obtained from files and unpublished reports of the Alaska Department of Fish and Game (ADF&G) and from personal communication with ADF&G biologists M. Buchholtz and L. Jennings. 37

41 Most post-1974 caribou data were obtained from our field observations. Since 1972, estimates of herd size were obtained from aerial photo-direct count-extrapolation (APDCE) censuses (Gasaway et al. 1983). Methods for estimating caribou natality, productivity, recruitment, harvest, survival, and sex/age composition were previously described or referenced (Davis et al. 198, Davis et al. 1983, Gasaway et al. 1983, and Valkenburg et al. 1983). Estimates of amounts and chronology of artillery firing, aircraft flights, bombing, and gunnery are based on records provided by the U.S. Army and the Federal Aviation Administration. Fire data are from the authors' observations and from U.S. Bureau of Land Management and U.S. Army records. Population Size RESULTS Davis et al. (1983) summarized the DCH' s demography from 195 through Between the mid-193's and 1954, the DCH apparently numbered less than 1,. There were an estimated 1,5 caribou by 1957 and 5, by 1963 (excluding calves). Estimates from 1963 through 197 were consistently about 5,. Estimates prior to 1972 included about 1, caribou in the present range of the Macomb Caribou Herd (Davis 198). n 1973, the 1st aerial photo-direct count-extrapolation (APDCE) census of the DCH estimated 2,198-2,49 caribou. Subsequent APDCE census estimates were 3,7-3,961 in 1979; 4,194-4,448 in 198; 4,18-5,32 in 1981; and 6,5-7,5 in (Ranges are not confidence intervals, but are separate extrapolations by 2 methods.) Davis and Preston (198) speculated that the population declined between 1973 and 1975, but began increasing in 1976, based on composition and productivity data. Natality/Survival Prior to 1969 no production/survival data were collected. Estimates of natality and survival of calves exist for most years since 1969 (Table 1) and natural mortality rates of cohorts older than calves have been determined since 198. From monitoring radio-collared caribou and population modeling, Davis and Valkenburg (1983) concluded that natural mortality in the DCH was quite low between 1976 and 1982, and that natural mortality of males was considerably greater than that of females. n addition, they concluded that between 1976 and 1982 the annual natural mortality of caribou older than calves ranged from a low of 3% to a high of 4-8%. 38

42 Sensory Disturbance Figure 1 depicts several areas where sensory disturbances occur with the greatest intensity and frequency. Military restricted areas R-222 and R-2211 are sites of regular bombing, strafing, and artillery firing. Low-flying military aircraft are present on nearly a daily basis and ground maneuvers intermittently occur. Actual quantification of use of these areas since 195 is beyond the scope of this discussion. However, available information supports our contention that these areas have been sources of substantial sensory disturbance to the DCH for several decades, particularly during calving. According to Federal Aviation Administration staff and military range control personnel, R-2211 averaged about 32 operations (i.e., 32 aircraft days) per week during That means an average of more than 6 aircraft used the area every day of the year, excluding weekends. Many of these operations included use of the associated low level jet airways (Fig. 1). Aircraft using the restricted areas include A-lOs, Cessna 2s, large and small helicopters, and several types of fighter/bomber jets. The range control officer for R-222 commented that almost every day, excluding weekends, aircraft fired 2 mm cannons and/or dropped bombs in R-222. He also commented that the area had been in continuous use since about 195. On about 2 May 1982, however, when we discovered the unusually close proximity of calving caribou to the impact area and notified the military, they suspended activities until after calving. Similarly, in 1983, the army resource specialist responsible for the area requested and received a suspension of activities during May. The target area in R-222 is located near the center of the restricted area along Delta Creek (Fig. 1); therefore, the primary disturbance is auditory in most years. Prior to 1976, the 2 long-axis boundaries of R-2211 extended to R-222. Military aircraft frequently fly in this area and other portions of the DCH' s range using civil visual flight rules (VFR). n addition, designated low level airways (Fig. 1) are frequently used by many civil aircraft. Most of these flights are several hundred meters or more above ground level. Several hundred civil aircraft frequent the herd's range each year. Over 7 light single engine aircraft are located in the greater Fairbanks area alone. Many of these aircraft are "STOL" aircraft capable of operating in much of the herd's range. Clearly, the DCH's range is frequented by large numbers of military and civil aircraft. Because of recent concern over the possible effects on caribou of aircraft disturbance (Klein 1973, Calef et al. 1976, Miller and Gunn 1979), we measured the response of the DCH to overflights 39

43 during 1979 through 1983 (Valkenburg and Davis, this workshop). Either Delta caribou have become habituated to aircraft disturbance or they never learned to fear aircraft to the degree of some other caribou herds. Snow machines and all-terrain vehicles have varied in abundance in the DCH' s range (see Valkenburg and Davis, this workshop). Hunters annually have spent thousands of man-days hunting caribou from the late 196's through 1973 and from 198 to the present. Even during when caribou hunting was not permitted, many hundreds of people hunted moose, sheep, and bears in the DCH's range. The DCH's past exposure to loud noises from thunderstorms may be a factor in their present apparent habituation to sensory disturbances. Thunderstorm activity is relatively high in the Alaska Range in the summertime, as evidenced by the electrocution of 53 caribou in the DCH in June 1972 (Shaw and Neiland 1973). Some mining has occurred in the area annually since 195, and a few people have resided in the DCH's range since the 195's. n aggregate, we believe that the DCH has been exposed to more sensory disturbance, on a mean annual basis, than any other Alaskan caribou herd. Habitat Alteration Although fire records are incomplete, it appears that few fires larger than 4 ha have occurred in the DCH's range in the past 3 ye!ars. Three major fires are delineated in Fig. 2. n June 1971, a lightning strike resulted in a 7,82 ha burn about 1-2 km northwest of the traditional core calving areas. n 1979 a fire was burning prior to the onset of calving and smoke was prevalent on the traditional core calving area throughout the calving and postcalving period. The exact cause of this 46,54 ha fire is unknown but it started in an artillery/bombing impact area (we suspect that military exercises started the fire). This 46,54 ha fire burned to the northern boundary of the traditional core calving areas (few unburned inclusions occurred). A 2,235 ha fire started on 9 May 1983 from artillery and burned until August, and this fire burned a major portion of the traditional core calving area (leaving many small unburned inclusions). Smoke was prevalent throughout the calving and postcalving periods. Physical Structures Few significant physical structures exist in the DCH' s range. Perhaps 2-3 small airstrips and approximately 3 dwellings are present. A few roads extend from the Nenana River on the west to the Totatlanika River, but vehicular traffic is limited. nterestingly, a major highway and railroad as well as a river 4

44 valley exist near the DCH's range border to the west, and a major highway and river valley mark the existing eastern boundary. Although major crossings have occurred, it is unclear if these physical structures contribute to boundary demarcation. No physical structures coincide with northern and southern boundaries. DSCUSSON Aggregate sensory disturbance within the range of the DCH has apparently been continuously increasing for decades. This applies both to the entire range and to the traditional calving area. n spite of this, the DCH has continued use of its traditional calving area, and since 1976 has been one of the fastest growing herds in Alaska. Mean annual growth has been 19-22% (Davis and Valkenburg 1983), and the present size of the herd is the largest in written history. n view of the concern that has been given to wildfires and the welfare of caribou (Klein 198), we believe several observations of the DCH are important. Although most concern regarding wildfires on caribou range centers on winter range rather than calving areas, it is unclear if this emphasis has been based on recognition of differing seasonal needs of caribou or resulted from a de facto omission because most caribou calve on alpine or arctic i:undra where wildfires are rare. Regardless, caribou calving areas are frequently considered "critical habitat" and the previous near universal concern about detrimental impacts of wildfire has influenced some management decisions regarding calving habitat. For example, draft management plans for the DCH (ADF&G,1976) emphasize protection of calving grounds from fire. Also many northern Natives have stated to the authors that caribou will avoid areas where smoke is present. Our observations of the DCH are inconsistent with the above concern about fires on or near calving areas. n 1982, the DCH was apparently precluded from calving in its traditional core areas because of persistent snow cover and instead used an alternate calving area roughly within the area burned in 1979 (Fig. 2) even though snow conditions were as favorable in unburned areas northeast, northwest, and west (of the 1979 burn} where some calving occurs in most years. Calving in 1982 was quite successful, which suggests that caribou may have considerable plasticity in their habitat requirements (Table 1). Calving caribou were exposed to heavy wildfire smoke throughout calving in 1979 and 1983 with no apparent adverse effects. Considering productivity (Table 1) and population growth of the DCH in recent years, it is evident that existing physical structures are not limiting factors. Nor have we been able to correlate trends in herd growth and/or productivity with levels of disturbance. Davis et al. (1983) demonstrated an inverse relationship between herd performance (i.e., size and recruitment) and predation. 41

45 SUMMARY AND CONCLUSONS n spite of the DCH' s exposure to the highest levels of mean annual disturbance of any Alaskan caribou herd, the DCH has grown at an annual rate of 19-22% annually since 1976 and is one of the fastest growing herds in Alaska. Sensory disturbances have included almost daily bombing, strafing, artillery firing, and high levels of low-flying military and civil aircraft year round on traditional core calving areas and adjacent areas. Military aircraft and several hundred civil aircraft frequent the herd's entire range. Delta caribou were heavily exposed to wildfire smoke throughout calving in 1979 and 1983 with no apparent adverse effects. Habitat disturbance included burning of an area adjacent to the core calving area in n 1982 this burned area was selected for calving presumably due to heavy snow accumulation on the traditional core calving area. Again, we observed no adverse effects on productivity indicating that caribou are more plastic in their selection of calving habitat than previously recognized. Major highways and railroads on or near the herd's boundaries also apparently are not important limiting factors. n conclusion, high levels of sensory and habitat disturbance have been of minor importance as limiting factors. n contrast, Davis et al. (1983) showed that harvest and predation by wolves were major limiting factors prior to ACKNOWLEDGMENTS This work was funded by Federal Aid to Wildlife Restoration Project W Many Alaska Department of Fish and Game personnel were helpful including M. Buchholtz, L. Jennings, and D. Simpson. We thank the U.S. Army, particularly J. Kerns and K. Spiers, and the Federal Administration Agency for making their records available. We particularly thank our clerical staff for their special considerations caused by our hurried schedules. Special thanks to go to C. Nuckols and L. McManus. R. D. Cameron and W. Regelin critiqued the manuscript. LTERATURE CTED Alaska Department of Fish and Game Delta caribou management plan. Pages in Alaska Wildlife Management Plans nterior Alaska-Draft Proposal. Juneau. 2pp. Bergerud, A. T Caribou. Pages in J. L. Schmidt and D. L. Gilbert, eds. Big Game of North-xffierica (Ecology and Management), Stackpole Books, Harrisburg, Pa. Calef, G. W., E. A. DeBock, and G. M. reaction of barren-ground caribou 29 (4) : Lortie to aircraft. The Arctic 42

46 Cameron, R. D in Arctic Alaska. ssue: Caribou and petroleum development Arctic. n press. Davis, J. L Status of Rangifer in the USA. Pages in E. Reimers, E. Gaare, and S. Skjenneberg, eds. Proc. 2na-nt. Reindeer/Caribou Symp., R ros, Norway, Direktoratet for vilt og ferskvannsfisk, Trondheim., and D. Preston Calf mortality in the Delta Caribou Herd. Alaska Dep. Fish and Game. Fed. Aid in Wildl. Rest. Prog. Rep. Proj. W~l7-11. Juneau. 29pp. ----~~~~ ----~~~~' and P. Valkenburg Demography of the Delta Caribou Herd under varying rates of natural mortality and harvest by humans. Alaska Dep. Fish and Game. Fed. Aid in Wildl. Rest. Prog. Rep. Proj. W Juneau. 5pp.,, and R. D. Boertje Demography of ----~t'h-e~d=elta Caribou Herd, Acta Zoologica Fennica 175: ~---', and H. V. Reynolds Population dynamics of Alaska's Western Arctic caribou herd. Pages in E. Reimers, E. Gaare, and S. Skjenneberg, eds. Proc. 2n~nt. Reindeer/Caribou Symp., R ros, Norway, Direktoratet for vilt og ferskvannsfisk, Trondheim. Gasaway, W. C., R. o. Stephenson, J. L. Davis, P. E. K. Shepherd, and. E. Burris nterrelationships of wolves, prey, and man in nterior Alaska. Wildl. Monogr pp. Hemming, J. E The distribution and movement patterns of caribou in Alaska. Alaska Dep. Fish and Game. Wildl. Tech. Bull. No. 1. Juneau. 6pp. Klein, D. R The reaction of some northern mammals to aircraft disturbance. Pages in X nt. Cong. Game Biol. Stockholm, Sweden Reaction of caribou and reindeer to obstructions--a reassessment. Pages in E. Reimers, E. Gaare, and S. Skjenneberg, eds. Proc. 2nd:fnt. Reindeer/ Caribou Symp., R ros, Norway, Direktoratet for vilt og ferskvannsfisk, Trondheim Fire, lichens, and caribou. J. Range Manage. 35 (3) : Luick, J. R., P. C. Lent, D. R. Klein, and R. G. White (Eds.) Proc. 1st nt. Reindeer/Caribou Symposium. Biol. Pap. Univ. of Alaska. Spec. Rep lpp. 43

47 Miller, F. L., and A. Gunn. Responses of Peary caribou and muskoxen to turbo-helicopter harassment, Prince of Wales sland, Northwest Territories, Occas. Pap. No. 4. Can. Wildl. Serv., Edmonton. 9pp. Shaw, G. E., and K. A. Neiland Electrocution of a caribou herd caused by lightning in central Alaska. J. Wildl. Dis. 9: Skoog, R. o Ecology of the caribou (Rangifer tarandus granti) in Alaska. Unpubl. Ph.D. Thesis, Uni v. Calif. Berkeley. 699pp. Valkenburg, P., and J. L. Davis. This workshop. A comparison of the reaction to aircraft of caribou from two herds in Alaska., R. D. Boertje, and J. L. Davis. darting and netting on caribou in Alaska. n press. ---.,..---~ Effects of J. Wildl. Manage. 44

48 NATONAL PARK MLES 1 2 ~ K L.OMETERS.,flo [ s '' 4 ~ Glo~i r BltJCk ~ Delta Herd's range Designated low level airways Designated low level jet airways Traditional calving areas Military restricted areas (jets, artillery, bombing) Fig. 1. Range of the Delta Caribou Herd and location of major sources of potential disturbances. 45

49 ALASKA \ ~ MySfiC -P_ «'_, Mounta1n - -s>,.., 5..._,_... <"' : K A :.:...,_._.,-.. Yan n Gtactlf MLES io <LOMETERS 2 A f?~?.~o ;'' SiCC~r G>.,~\ ~ ~ atoc 11 ~.-?co,d.r GOCitlf' raditional core calving area core calving Fire 1971 ( (7,82 ha) Fire 1979 (46,54 ha) Fire 1983 (2,235 ha) Fig. 2. Major wildfires adjacent to the Delta Caribou Herd's traditional core calving areas and 1982 core calving area. 46

50 Table 1. Spring and fall calf:cow ratios in the Delta Caribou Herd, i Calves:1 cows Sample Calves:1og cows Year spring a size. fall Sample size , , ,139 1,184 1,5 1, , , (7l)c 951(586)c , (72) c --(259) c 34 1,55.1, ,369 1,553 1, (8)c 1,587(3,982)c a b c Spring indicates s~mp1ing calving. in mid-june almost 4 weeks after the peak of Fall indicates sampling from October to early December. Values in parentheses were obtained between 2 and 3 May near the peak of calving. 47

51 Appendix D. The Reaction of Caribou to Aircraft: A comparison of two herds Patrick Valkenburg and James L. Davis Alaska Department of Fish and Game 13 College Road Fairbanks, Alaska 9971 Abstract: Aircraft overflights cause Western Arctic Herd caribou (Rangifer tarandus granti) to flee more often and to continue running more than Delta Herd caribou. Delta caribou have apparently become habituated to aircraft or never learned to fear them, whereas Western Arctic caribou have either had insufficient exposure to aircraft or, more likely, perceive them as a threat. Delta Herd caribou have been exposed to high levels of human activity including aircraft overflights, but they are not hunted directly from motor vehicles to any degree. Western Arctic caribou, on the other hand, are probably less subjected to human activity, but they are regularly pursued from snowmobiles and, to some extent, aircraft. The emphasis in disturbance studies should be changed from simply documenting overt reactions to determining predictable aspects of inherent and learned behavior, and ultimately finding ways to promote habituation. NTRODUCTON With the 197s came an unprecedented amount of development in the Arctic. Understandably, those responsible for or interested in the management of northern wildlife species viewed this with alarm. Of particular concern was the reaction of caribou to disturbance, particularly by aircraft, and numerous studies resulted (Klein 1973, McCourt et al. 1974, Calef et al. 1976, Miller and Gunn 1978, Davis and Valkenburg 1979). A recurring concern was that various dire consequences, such as abortion, increased incidence of disease, and decreased productivity could result from disturbances including aircraft overflights (Geist 1971). That animals often become habituated to aircraft was generally downplayed. n retrospect, many earlier concerns about aircraft harassment were unjustified, but at least if we have overreacted it was on the side of caution. Examples of the habituation of mammals to man 1 s activity are common in more populated regions but are relatively rare in the Arctic (Fletcher and Busnell 1978). Modern man 1 s disturbances 48

52 are a relatively new phenomenon in the North and arctic mammals appear to fall into 3 categories with regard to their reaction to man's activity. First, there are those that have little or no previous experience and usually act frightened but sometimes act curious (i.e., Peary caribou (Rangifer tarandus Pearyi) and musk-oxen (Ovibos moschatus)), and wolves (Canis lupus) on the arctic islands (Miller and Gunn 1978, Grace 1976). Second are those that have become habituated and either react very little or are even attracted (i.e., caribou being attracted to logging noises on the Gaspe Peninsula (Geist 1971) or bull caribou paying little attention to truck tr~ffic on the North Slope Haul Road in Alaska). Finally, there are animals that have come to associate man's activity and noises with danger (i.e., wolves in areas where they are hunted from the air) During our studies of caribou in northwest Alaska and the central Alaska Range, we noticed that Western Arctic Herd caribou reacted more to aircraft than Delta Herd caribou, and we began collecting data to quantify this. The purpose of this paper is to report the habituation of the Delta caribou to aircraft and discuss the apparent lack of habituation in Western Arctic caribou. METHODS Using standard collaring techniques (Valkenburg et al. 1983), we instrumented 99 caribou in northwest Alaska and 65 in the central Alaska Range between 1979 and These caribou were then monitored about 6 times per year with light, fixed-wing aircraft in northwest Alaska and slightly more often in the Alaska Range. The radio collars transmitted on individual frequencies and had numbered "visual" collars attached. During most relocations, we flew low enough to read the "visual" collar to avoid making mistakes in identification. Aircraft used and relocation techniques were similar in both areas, and in most cases multiple "passes" were made to collect pertinent data about the individual and its associated group of caribou. n some cases, each "pass" was considered to be a separate observation of a group even though the same caribou were being observed. This approach was used because there was little difference in reaction between initial and subsequent passes. We recorded the vertical and horizontal distance from the aircraft to the caribou group, group size, and the overt reaction of the caribou to the aircraft on a scale of 1 to 5 (Klein 1973, Calef et al. 1976). The 5 response classes were: 1. Panic response. Animals were out of control; they stumbled, collided with one another, and ran into obstacles such as willow patches or trees. 2. Strong escape response. Animals trotted or ran and continued running after the aircraft had passed. There was some subjectivity in distinguishing this response class from class 1. 49

53 3. Mild escape response. Animals moved away from the aircraft or from the original direction of movement in the case of traveling animals. This class included only animals which walked or trotted a short distance. 4. Stationary response. Animals stopped feeding, rose from resting position, or assumed alarm posture (Pruitt 196). 5. No visible response. Animals continued feeding or resting or, if moving, continued at the same pace in the same direction. We also gathered and analyzed data on history of harvest levels, hunting patterns, and levels of aircraft use in both the Delta and Western Arctic Herd ranges since 197. For the Western Arctic Herd, information on previous disturbance and hunting patterns is largely descriptive, but relatively accurate records of harvest level, hunting methods, and access were available from harvest report cards used by most hunters in the Delta Herd 1 s range. RESULTS Comparison of the Reaction to Aircraft Between Herds Western Arctic Herd caribou tried to escape by running (response classes 1, 2, and 3) from the overflying aircraft during 8% of the passes, whereas Delta Herd caribou tried to escape during only 25% of the passes (Fig. 1). Furthermore, escaping Western Arctic Herd caribou were more likely to continue running after the aircraft had passed (response categories 1 and 2) than Delta caribou (Fig. 1). This difference in reaction was further illustrated by the reaction of cow/calf pairs during overflights. n order to determine whether or not a radio-collared female had a calf with her in late summer, we often relied on a calf 1 s tendency to run to its mother when disturbed by the tracking aircraft. This method worked well with Western Arctic caribou, but was unreliable in the Delta Herd because caribou often did not respond to the plane. We did not find any relationship between the type of reaction and the proximity of the aircraft. A subtle relationship may exist between proximity to the aircraft and reaction class but sample size was insufficient to clarify it. Group size did not appear to influence the type of reaction. Because our radio-tracking methods were similar and standardized between herds, we did not try to investigate relationships between degree of reaction and group activity, composition, or other variables. History of Hunting Patterns and Disturbance in the Western Arctic Herd Harvest of Western Arctic Herd caribou probably averaged 2,-25, caribou out of a total of 1,-3, caribou from before 196 through Between 1976 and 1983, the 5

54 harvest has probably averaged 3,-6, out of a total of about 75, in 1977 up to 171, in At least 95% of the harvest was by local subsistence hunters, and since about 197 the majority of the harvest has been with aid of snowmobiles. A commonly used hunting practice has been to pursue caribou from snowmobiles and then shoot at the running animals either from the snowmobile or from the ground after stopping the machine. Until spring 1977, caribou could be shot during the same day in which a hunter was airborne, and a small number of Western Arctic caribou were taken in this way. Between 1977 and 1982 this practice was illegal. Regulations in 1983 permit hunting of caribou the same day as airborne in the area occupied by the Western Arctic Herd. Aircraft overflights are a regular but relatively infrequent event in the lives of most Western Arctic caribou, although the frequency of such overflights has undoubtedly increased since the early 197s. Groups of caribou wintering around villages are likely subjected to more overflights than caribou in more remote areas but it is unlikely that the groups near villages are comprised of the same individuals from year to year {Valkenburg et al. 1983). History of Hunting Patterns and Aircraft Use in the Delta Herd Unlike northwestern Alaska, the central Alaska Range occupied by the Delta Herd has had a long history of intensive aircraft use. Fairbanks {population about 6, in 198) is 6 miles (96 km) to the north, and there are many private planes based there. The central Alaska Range has been a popular hunting area since the 195s, and parts of the area are also used as practice areas by the military {Davis and Valkenburg, this workshop). Delta Herd caribou were heavily harvested during fall and winter between 197 and The season was closed from 1974 until 198 (Table 1). Herd size declined from about 3, to 1,5 between 197 and A limited fall permit hunt for bulls only was reopened in 198 when the population was estimated to be about 4,5. n , the winter season was reopened. Herd size by 1982 had increased to 6,5-7,5 caribou... From 1971 through 1973, 5% of all successful caribou hunters used aircraft for transport, and 36% used other motorized ground vehicles including snowmobiles. Despite the use of ground vehicles, Delta Herd caribou are probably rarely chased during hunting because the terrain is broken and not conducive to high speed travel. After the hunting season was reopened in 198, there were 2 major changes in the hunting regulations. Hunters could no longer fly and shoot caribou during the same day, and some of the Delta Herd's range was closed to the use of motorized ground vehicles. However, these changes did not appreciably alter the average proportion of caribou taken by aircraft users {55%) and users of other motorized ground vehicles {33%). Apparently, there were many caribou available in the portion of the range open to motorized vehicles. 51