Survey Techniques For White-tailed Deer. Mickey Hellickson, PhD Orion Wildlife Management

Transcription

1 Survey Techniques For White-tailed Deer Mickey Hellickson, PhD Orion Wildlife Management

2 SURVEYS two basic types: (1) Total Counts best but rarely feasible. may be possible on small, high-fenced areas. (2) Strip Counts most common method where biologists don t attempt to count every deer, but instead count only a strip of the entire area. Almost always underestimates the actual population size, but provides a good index and trend data for comparison from year to year.

3 Types of Survey Methods Track counts Windshield counts Pellet group counts Aerial surveys Observation data Spotlight counts Trail camera census

4 Track Counts Commonly used in 1940 s & 50 s in the SE, but now only used in conjunction with scientific studies to measure movement into & out of study areas.

5 Windshield Counts A good method on refuges or lightly hunted areas where deer are highly visible. Provides accurate age & sex ratio information under these circumstances.

6 Hunter Observation Data Hunters record deer sightings throughout the hunting season

7 Specific Information Collected Hunters Record: Area/stand Date/time Number, sex, and age of deer observed Buck quality

8 Spotlight Counts Formal method of spotlighting deer to estimate population characteristics Developed in Texas during the 1970s

9 EVALUATION OF SPOTLIGHT-DEER COUNTS Conducted 184 counts over a 10-mi route on Welder Wildlife Refuge during Aug-Oct of 1976 (n = 84) & 1977 (n = 100). Nocturnal time period affected density estimates (with counts lowest during 1 st time frame after sunset & highest during 2 nd time frame), but month of count did not affect density. Count variability averaged 26-27%. Fawn:doe ratios increased from Aug-Oct. Temp & RH correlated with number of deer sighted. Spotlight counts less biased estimates of deer density than helicopter counts, but precision of ratio estimates (does/ buck & fawns/doe) was lower. Spotlight counts biased toward does. K. R. Fafarman & C. A. DeYoung Wildlife Society Bulletin 14:

10 How to Conduct Spotlight Counts Establish a nonoverlapping route of at least 10 miles Route should traverse all habitat types Minimum of 2 counts needed more recommended

11 Visibility Index (Determining Area Sampled) Area Sampled (Visible Acres) = Total Yards of Visibility / (# of 1/10 mile stops + 1) x (# of miles x 1,760/ 4,840)

12 Camera Survey Most accurate method available to estimate whitetailed deer density

13 Steps in a Camera Survey 1. Identify sites 2. Pre-bait sites 3. Set up cameras 4. Maintain sites 5. Analyze photos & data

14 1. Identify Sites 1 per 100 acres Select high deer use areas Closed canopy Low understory

15 2. Pre-bait Sites Pre-baiting is VITAL to success! 2 weeks prior to census Whole corn is best Shut down feeders

16 5. Data Analysis Count bucks, does, and fawns Age bucks Unique bucks

17 5. Data Analysis For this example, we ll say we took the following pictures during our survey: Buck photographs = 105 Doe photographs = 110 Fawn photographs = 50 No. of unique bucks = 10

18 Identifying Unique Bucks (number of individual bucks) Age bucks first Separate individuals by unique body & antler characteristics Common biological tags include scars, notched ears, distinct color patterns, and unique antler characteristics Be cautious of Day vs. Night Separate the bucks and TRIPLE check your work

19 Buck Identification Tips Most Common Mistakes/ Problems: Identifying too many individuals (e.g., same buck counted as 2 different bucks) Counting as a unique buck with only 1 or 2 pictures

20 5. Data Analysis Population Estimate No. of bucks = 10 No. of does = (110 doe photos/105 buck photos) * 10 unique bucks = 11 does No. of fawns = (50 fawn photos/105 buck photos) * 10 unique bucks = 5 fawns Photographed Population = 10 bucks +11 does +5 fawns = 26 deer

21 Additional Information Gained from Trail Camera Surveys Ratio of buck photos taken during daylight No. individual bucks per camera site No. mature bucks per camera site Habitat features important to mature bucks Important to conduct annual TC survey during the same time frame each year while also using the same CS so that data are comparable across years.

22 Buck no. 7 Angle - B Age 5 ½ Est. gross B&C Points - 14 Camera site Lodge pines Comments Great buck - shooter

23 Survey Methods: -On average, these surveys are 36% accurate (only count 1/3 of the deer flown over on the transect line). FALL (PRE SEASON) HELICOPTER CENSUS -Helicopter surveys are the most accurate method for determining sex & age ratios because deer are encountered at random (less bias). -Provides accurate data on buck:doe ratios, fawn:doe ratios, & buck age structure, & important trend data on deer density.

24 WINTER (POST SEASON) HELICOPTER CENSUS Post-season surveys are more accurate than pre-season surveys because of increased visibility a higher percentage of the deer you fly over are spotted by the observers. On average, these surveys are 65% accurate.

25 Helicopter Surveys Well researched by CKWRI DeYoung 1985 Beasom et al Leon et al DeYoung et al. 1989a DeYoung et al. 1989b Sullivan et al. 1990

26 Helicopter Transects (count in fixed strip or )

27 Helicopter Transects (count in fixed strip or line transect)

28 HELICOPTER SURVEY ACCURACY Determined accuracy of pre- (Chaparral WMA; n = 8) & postseason (Rancho Blanco; n = 6) 100%-coverage surveys by comparing to mark-recapture estimates. Found pre-season surveys averaged 36% of the markrecapture estimate, while post-season surveys averaged 65% of the estimate. C. A. DeYoung Wildlife Society Bulletin 13:

29 BIAS IN SEX AND AGE COMPOSITION OF DEER OBSERVED FROM HELICOPTERS Evaluated resightings of marked deer during replicated (n = 6-8) pre-season surveys on 4 ranches. No bias found in sex or age composition. Concluded the sight & sound of a helicopter approaching at low altitude frightened all deer equally, but too few fawns in sample. Found no decline in number of deer counted during repeated flights (i.e., deer did not become less frightened of the helicopter). F. G. Leon III, et al Wildlife Society Bulletin 15:

30 CLASSIFYING BUCKS FROM A HELICOPTER Classified bucks previously captured, marked, & aged into 2 categories (<3.5 & >4.5) when re-sighted during 28 preseason surveys on 2 ranches. Used antler mass & spread, tine length, musculature, & chunky appearance as characteristics for classifying. Successfully classified 329 of 369 bucks (89%) into the 2 categories (range = %). C. A. DeYoung, et al Proc. Annu. Conf. SE Assoc. Fish & Wildl. Agencies 43:

31 EFFECTS OF INCREASING CANOPY COVER ON HELICOPTER SURVEYS Concluded that a gradual increase in mesquite canopy cover during , caused a gradual decrease in deer observability during pre-season surveys, resulting in an erroneous downward trend in deer abundance. A post-season survey during January 1986 resulted in a count 2.5 times higher than the pre-season survey during fall T. R. Simpson and S. E. Bentsen th Annual Meeting of the Texas Chapter of The Wildlife Society, Corpus Christi, TX.

32 Helicopter Survey Summary Overall: Accuracy about 35% and variable Count-to-count variability high, use for trend Sex ratio unbiased but variable count-to-count Undercount of fawns compared to adults; variable Buck classification to young and mature good Obtain counts on other species such as quail Good, quick feel of deer population Scouting

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