15 THE KIDNEY FAT INDEX AS AN INDICATOR OF CONDITION IN VARIOUS AGE AND SEX CLASSES OF MOOSE J. R. McGillis Canadian Wildlife Service Abstract: Kidney fat indices were obtained from 623 moose (A1ces a1ces andersoni) killed in ungulate reduction programs at Elk Island National Park, Alberta. Kidney fat indices of pregnant females were greater than those of non-pregnant females in the same age classes, and were greater than males of any age class. Rump fat measurements were correlated with kidney fat indices for one group of 244 moose studied. Available information on winter mortality within the park suggests that the sex and age classes of moose having the lowest kidney fat indices have the greatest rates of mortality. Riney (1955) discussed the suitability of the use of various indices of annual condition in the study and management of red deer (Cervus e1aphus) in New Zealand. He concluded that the kidney fat index (K.F.I.) offered the most suitable means of assessing the physical condition at various seasons of the year. Flook (197) investigated the kidney fat index of wapiti (Cervus canadensis). He found that males older than calves, having entered the winter with lower fat reserves than females, tended to
W6 reach potentially critical levels before females. They are thus more vulnerable to winter mortality caused by an inadequacy of energy. A minor die off of wapiti in Elk Island National Park in late March of 1971 was limited almost entirely to large, well antlered males. The present study of kidney fat and associated condition factors was conducted on the moose (Alces alces andersoni) of Elk Island Park, Alberta over a period of four winters, 1968 to 1972. During this time the moose population density varied from 7 to 14 per square mile. During this same period the park supported 4 to 7 wapiti, 3 to 6 white-tailed deer (Odocoileus virginianus), and as many as 16 bison (Bison bison)per square mile. The author wishes to acknowledge the assistance of D. R. Flook, J. P. Kelsall, E. S. Telfer and H. Armbruster, all of the Canadian wildlife Service, Edmonton, Alberta. Thanks are extended also to the warden staff at Elk Island National Park whose help in the field, often under the most extreme conditions of cold, was deeply appreciated. METHODS The site of the study, Elk Island National Park, is approximately 3 miles east of Edmonton in east-central Alberta. The Park is at the north end of the Beaver Hills on the cooking Lake moraine at an elevation of 24 ft. The vegetation is primarily
W7 aspen parkland with an intrusion of boreal elements. Previous to 194 fires altered the original climax white spruce (Picea glauca) cover to a seral stage dominated by aspen (Populus tremuloides) and balsam poplar (Populus balsamifera). The park consists of adjacent 5 and 25 sq. mile areas, each fenced around the perimeter. Between 1968 and 1972 approximately 824 moose were among the ungulates shot during population control programs at Elk Island. The data presented here were collected during the programs of January 1968, January-February 1969 and December-January of 1971-72. Park wardens shot moose in the field. The animals were bled and blood samples were taken to be tested for brucellosis. The animals were then taken by truck to the park abattoir. Before entering the abattoir I measured and weighed them. A truck with a power winch and gin pole, and a chatillon 1 ton capacity scale, were used to weigh each animal. In the abattoir the kidneys and surrounding fat were collected, as well as the dentary bones, and pregnacy data. Back fat measurements were taken in the 1968 slaughter. We followed Riney's (1955) procedure of arriving at the kidney fat index except that we included the capsule of connective tissue (Tunica fibrosa) with the weight of the perinephric fat. This elevated the kidney fat index value so that any values below 5 per cent indicated a complete lack of kidney fat. To measure the depth of subcutaneous
18 rump fat a cut 15 cm. long was made at right angles to a point on the backbone 25 cm. anterior to the base of the tail. The greatest depth of fat along this cut was measured to the nearest millimeter. Measurements less than 1 mm. in depth were recorded as one mm. We collected dentary bones from all animals except calves and yearlings, which we aged by tooth eruption and replacement patterns. Older moose were assigned to age groups by the number of annuli in the dental cement (Sergeant and Pimlott, 1959). A first incisor was removed, ground between two 6-inch emery wheels and the annuli counted using reflected light. RESULTS AND DISCUSSION In each of the three years, calves had the the lowest K.F.I. with little difference between the index of males and females. There was however, a marked difference when comparisons were made between the indices of the calves in separate years. In 1968 the index for both sexes was 13, in 1969,.. 7, and in 1971-72 it was 22 for the female calves and 24 for the males. During the 1968 slaughter 12 calves, because of their emaciated condition, were condemned as unfit for human consumption by a Department of Agriculture veterinarian. These 12 animals had a mean K.F.I. of 8 compared to 13 for the age class as a whole. The low indices in 1968 and in 1969 (Figs. 1 and 2) were perhaps a reflection of very high moose densities in the park which, in 1968, reached at least 14 per square mile. At this population
19 level the range began to deteriorate seriously. In 1969 with the population levels still high and range in poor condition, the Edmonton area recorded the fourth coldest winter since 1881. By 1971-72 ungulate control programs had reduced the moose population to seven per square mile, the browse had begun to improve and the fall and winter, up to the time of the slaughter, had been mild with very little snow. These factors were likely the reason for the high K.F.I. of the calf class at this time (Fig. 3). 16 14 12 1 X 8 W Z 6 I- Li: 4 >- W Z 2 16 6 5 7 15 19 5... 31 " " " " '......., Bulls -- -.. --- Cows, non pregnant.. "Cows, pregnant 15c===:J Number and range of samples f 2... i/'.5 1.5 2.5 3.5 4.5 5.5 6.5-7.5 AGE IN YEARS 8.5+ Fig. I Kidney fat index of moose collected January 1968
11 12 1 23 14 21 12 14 4 _Bulls --... --Cows, non pregnont 8... +... Cows, pregnant X W 4 Cl... 12c::==:J Number and range Z '. 6 of samples I 5 r- 23 I... I,...... 4 I... I 5 7, I '. >- W Z 2 2 Cl.5 1.5 2.5 3.5 4.5 5.5 6.5-7.5 6.5+ AGE IN YEARS Fig. 2 Kidney fat index of moose Collected January and February 1969 Animals l years of age or older exhibited a marked difference between the K.F.I. of male and female animals. The females had a higher index than did the males. The pregnant animals in this age class had a higher index than those not pregnant. This phenomenon has been noted in domestic cattle. Morrison (195B) states that pregnancy tends to make animals gain in weight and fatten more rapidly. Riney makes no reference to any difference in the index of pregnant and non-pregnant female red deer. A small sample of moose is to be collected at monthly intervals at Elk Island this winter. It should be possible to determine if, during the latter stages of pregnancy, the K.F.I. of pregnant
111 16 X W Z t;,{ LL.: >- w z 14 12 7 1.' BO 8, """, 6 4 2 13 I, :' / I I I 14,,,, 2 5.' '".. '.. ' 12......... 1 " " 8 '. '. '.. 2 1 "'" Bulls - -... - - Cows, non pregnant... Cows, pregnant 1 c::==::j Number and range of samples.....5 1.5 2,5 3,5 4.5 5.5 6.5-7.5 B.5+ AGE IN YEARS 5 Fig. 3 Kidney fat index of moose Collected December and January 1971-1972 animals declines to a value lower than that of non-pregnant animals of the same age class. Riney (1955) stated that in New Zealand mature red deer stags in early fall had the highest K.F.I. he recorded. A small series of eight adult moose was collected from Elk Island Park by the author, between mid-august and mid-november in 1968. Unfortunately the quantitative data are not available at this time but as I recall the index of the first animals collected
112 ranged from 1 to 2 per cent and then declined to a minimum level by mid-november. This pattern was comparable to that for a series of adult male wapiti collected in Banff'National Park in 1965, of which the K.F.I. ranged from 1 in mid-august to 7 in mid-october. The index then rose in November before another decline as winter advanced (Flook 197). At the latitudes of Banff and Elk Island the rutting season of wapiti precedes that of moose by approximately a month which explains why the K.F.I. of wapiti reached its low point a month before that of the moose. Unlike the wapiti, the male moose do not appear to recover any of the fat lost during the rut, before the onset of winter (Fig. 3). Comparisons of the K.F.I. for January 1968, January-February 1969 and December 1971-January 1972 are given in Figures 1, 2 and 3 respectively. Of the 47 calves, (31, 16 dd) collected in the 1968 slaughter, only one male had a measurable amount of rump fat and it was only 1 mm. thick. This animal had a K.F.I. of 52, the highest of any calf taken in the 1968-72 period. The whole weight was 45 lbs. and the dressed weight was 53.3 per cent of the whole compared to 47.5 per cent for the others in its age and sex class. A comparison of the rump fat with the K.F.I. of animals collected in January 1968 is given in Table 1.
KIDNEY FAT INDEX: LESS THAN 5% KIDNEY FAT INDEX: LESS THAN 5% Age No. DeEth of RumE Fat in mm. Age NO. DeEth of RumE Fat in mm. Mean Range Mean Range MALE MALE 15 1 1 1 1 15.8-2 1 2 12 1.2-4 2 3 1 1.1-2 3 4 11 1.8 1-3 4,...,... w 5 12 2.3 1-1 5 FEMALE FEMALE 31 1 11 3.4 1-8 1 13 9 1-25 2 3 5.3 1-1 2 9 15.6 5-3 3 3 5.3 1-1 3 13 13.3 1-28 4 2 3 2-4 4 5 11. 6 8-2 5 + 4 9 2-22 5 7 13.4 1-2
114 SUMMARY Kidney fat indices are given for 623 moose killed at Elk Island National Park between 1968 and 1972. Pregnant animals in the 2-5 year age class had the highest kidney fat index, followed in descending order by nonpregnant cows, adult bulls and finally, calves. There was no significant difference in the index of male and female calves. discussed. The relationship of rump fat and the kidney fat index is LITERATURE CITED Blood, D. A., J. R. McGillis and A. I. Lovass. 1967. Weights and measurements of moose in Elk Island National park, Alberta. canadian Field-Naturalist 81(4): 263-269. Flook, D. R. 197. of wapiti. Number 11. A study of sex differential in the survival Canadian Wildlife Service report series - 71 pp. Flook, D. R., and J. R. McGillis. 1968. Aerial count of moose, elk and deer. Elk Island National Park, December 11 to 13, 1968. Typescript report in files of canadian wildlife Service, Edmonton. 8 pp. Morrison, F. B. 1958. Feeds and feeding, abridged. Ninth edition The Morrison Publishing company, Ithaca, NeW. York. 695 pp. Riney, T. 1955. Evaluating condition of free-ranging red deer (Cervus elaphus), with special reference to New Zealand. New Zeal. J. Sci. Technol. 36: 429-463. Sergeant, D. E., and D. H. Pimlott. 1959. moose from sectioned incisor teeth. 23(3): 315-321. Age determination in J. Wildl. Mgmt.,