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Matthew_Moore_TWS_2008

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Refinement of a Camera Census Technique at Three White-tailed Deer DensitiesMATTHEW T. MOORE, Caesar Kleberg Wildlife Research Institute Texas A&M University-Kingsville, TX 78363Introduction• White-tailed Deer Managers– Habitat management– Population management• Population Management– Need for estimates of population sizeIntroduction• Commonly used census methods for white-tailed deer– Spotlight counts– Aerial counts– Mark-recapture– Harvest surveysIntroduction• Limitations of these techniques– Dependent upon habitat conditions– Complicated methods – Expensive• Need for a easy to use, cost effective, yet versatile white-tailed deer census techniqueIntroduction• The use of camera censuses has recently gained popularity among white-tailed managers• Previous research on camera censuses– Mississippi (Jacobson et al.1997)– Texas (Koerth et al. 1997)• Questions remain concerning the accuracy of these techniquesObjectives• Test the accuracy of the technique described by Jacobson et. al. in The Wildlife Society Bulletin (1997, 25(2):547-556), on three different densities of white-tailed deer• Try to determine if there are biases associated with sex, density, or timing of census• If there are biases, try to determine their sourceStudy Areas• 2 Ranches in the South Texas Brush Country– Comanche Ranch– Faith RanchStudy AreasStudy Areas• 3 200-ac high fenced enclosures• Target Densities– Low = 10 deer (1 deer / 20-ac)– Medium = 25 deer (1 deer / 8-ac) – High = 40 deer (1 deer / 5-ac)• Each Enclosure Contains a Closed Population of White-tailed Deer with a Known Number of Marked IndividualsMethods• 4 Camera Stations Per Enclosure• Coverage area of 1 camera per 50 acres – Three Metal T-post• Two to support the camera• One was painted and placed ten meters in front of the camera and used as a reference point– Cuddeback Digital Game Camera• Pictures were stored on San Disk Compact Flash Cards• Time delays were set for four minutesMethods• Baited with 5 lbs. shelled corn on the first day of the sampling period– Replenished as necessary – No pre-baiting was conducted• Checked daily for 14 consecutive days• Photos were downloaded and reviewed – Deer were tallied into categories– The camera estimate described by Jacobson was applied to estimate the population sizeData Collection• First 14 day census was conducted February 3rd – 17th, 2007 • Second 14 day census was conducted September 29th – October 13th, 2007Jacobson Camera Estimate• Original study was conducted in Mississippi– Open population– Accounted for spikes with a ratio• Spike: Branched Antlered Buck– Accounted for fawns•Fawn: DoeJacobson Camera Estimate• B = Number of identified uniquely antlered bucks •Nb=Total occurrences of antlered adult deer•Nd= Total occurrences of non-antlered adult deer•Pd= Ratio of does: bucks•Pd= Nd/ Nb•Ed= Estimated doe population•Ed = B x Pd • Population size= B + EdJacobson Camera EstimateComanche Low Density Oct. 2007• B = 3 uniquely antlered tagged bucksJacobson Camera EstimateComanche Low Density Oct. 2007•B= 3 tagged bucks•Nb= 350 occurrences of tagged bucks •Nd= 200 occurrences of tagged does•Pd= Ratio of tagged does: tagged bucks• Pd= 200 / 350 = 0.571Jacobson Camera EstimateComanche Low Density Oct. 2007•B= 3 tagged bucks•Nb= 350 occurrences of tagged bucks• Nd= 200 occurrences of tagged does•Pd= Ratio of tagged does: tagged bucks•Pd= 200 / 350 = 0.571•Ed= Estimated doe population• Ed = 3 x 0.571 = 1.7 estimated tagged doesJacobson Camera EstimateComanche Low Density Oct. 2007•B= 3 tagged bucks•Nb= 350 occurrences of tagged bucks•Nd= 200 occurrences of tagged does•Pd= Ratio of tagged does: tagged bucks•Pd= 200 / 350 = 0.571 •Ed= Estimated doe population•Ed = 3 x 0.571 = 1.7 estimated tagged does• Population size= 3 + 1.7 = 4.7 deerTagged Deer Estimates From October 2007 Baited SurveyUnderestimate of the Tagged PopulationEstimated Total of Tagged Deer Using Jacobson’s Camera EstimateTotal Number of Tagged DeerNumber of Tagged DoesNumber of Tagged BucksLowDensityComancheRanchTagged Deer Estimates From October 2007 Baited SurveyUnderestimate of the Tagged PopulationEstimated Total of Tagged Deer Using Jacobson’s Camera EstimateTotal Number of Tagged DeerNumber of Tagged Does3Number of Tagged BucksLowDensityComancheRanchTagged Deer Estimates From October 2007 Baited SurveyUnderestimate of the Tagged PopulationEstimated Total of Tagged Deer Using Jacobson’s Camera EstimateTotal Number of Tagged Deer4Number of Tagged Does3Number of Tagged BucksLowDensityComancheRanchTagged Deer Estimates From October 2007 Baited SurveyUnderestimate of the Tagged PopulationEstimated Total of Tagged Deer Using Jacobson’s Camera Estimate7Total Number of Tagged Deer4Number of Tagged Does3Number of Tagged BucksLowDensityComancheRanchTagged Deer Estimates From October 2007 Baited SurveyUnderestimate of the Tagged Population4.7Estimated Total of Tagged Deer Using Jacobson’s Camera Estimate7Total Number of Tagged Deer4Number of Tagged Does3Number of Tagged BucksLowDensityComancheRanchTagged Deer Estimates From October 2007 Baited Survey- 33%Underestimate of the Tagged Population4.7Estimated Total of Tagged Deer Using Jacobson’s Camera Estimate7Total Number of Tagged Deer4Number of Tagged Does3Number of Tagged BucksLowDensityComancheRanchTagged Deer Estimates From October 2007 Baited Survey- 44%-4%- 30%- 16%- 42%- 33%Underestimate of the Tagged Population15.719.216.78.44.14.7Estimated Total of Tagged Deer Using Jacobson’s Camera Estimate2820241077Total Number of Tagged DeerHighHighMediumMediumLowLowDensityFCFCFCRanchTagged Deer Estimates From February 2007 Baited Survey- 36%- 15%- 28%- 30%- 23%Underestimate of the Tagged Population9.09.415.04.94.6Estimated Total of Tagged Deer Using Jacobson’s Camera Estimate14112176Total # of Tagged DeerHighHighMediumMediumLowLowDensityFCFCFCRanchStatistical Analysis• Percent difference between estimated and known population–ANOVA MODELS (alpha=0.05)–Males and Females–No significance • Density• Date• Density*dateTagged Deer Estimates From 2007 Baited Surveys- 25%-26%- 33%Underestimates Averaged Across Dates and RanchesHighMediumLowDensityStatistical Analysis• Number of photos per tagged deer–Separate analyses by


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