Can low-precision population and survival estimates of deer be accurate?

Publication Date


Journal or Book Title



To obtain baseline density data for population modeling and zone-specific management of deer (Odocoileus spp.), we monitored 34 radiocollared white-tailed deer (O. virginianus) in and around Myles Standish State Forest, southeastern Massachusetts, during winters 1997-2000. Our objectives were to 1) identify factors influencing the precision of aerial population estimates; 2) estimate cause-specific mortality rates of adults; 3) use population estimates, mortality rates, and other reasonable assumptions to calculate an average harvest; and 4) compare this estimate with state-reported harvest to assess the accuracy of our density and survival data. Two to 5 mark-resight helicopter surveys completed in each of 3 successive winters resulted in density estimates ranging from 4.7-6.5 deer/km2 (x̄=5.7 deer/km2). The low proportion of marked individuals in our survey areas (annual x̄=8-10%) was due to poor capture success, while low observability (annual x̄=7-15%) was due to lack of snow cover and the preponderance of pine (Pinus spp.) cover. These conditions resulted in low-precision estimates (x̄ 90% Cl=59-222% of point estimate). Annual survival of 22 adult female deer (>1.0 yr old) was 0.87 (95% Cl = 0.79-0.96) versus 0.81 (95% Cl=0.68-0.96) for 12 adult males. Sources of female mortality included hunting (annual rate=0.05), poaching (0.03), and unknown causes (0.06); males were hunted (0.16) and died from unknown causes (0.03). Adult deer density and cause-specific mortality data, combined with assumed estimates of age ratios (30% fawns) and adult sex ratios (60% F) in winter, predicted annual legal harvest of 0.14 adult females and 0.30 adult males/km2, which approximated the recorded harvest for the surrounding management area (0.17 and 0.30, respectively). Despite low precision, mean point estimates of deer density and survival could be accurate.







This document is currently not available here.