Surgical Sterilization to Control an Urban Population of White-Tailed Deer: Preliminary Results
Overabundance of white-tailed deer (Odocoileus virginianus) in urban and suburban landscapes poses a challenge to wildlife managers and local municipalities.2 Culling via lethal means can provide effective population control, but is not an option in many urban settings due to logistic and sociopolitical considerations.
A 4-yr project was developed to determine if surgical sterilization of females could regulate a population of white-tailed deer in Highland Park, Illinois, an urban environment. We used density-dependent population models to calculate that we would need to sterilize 80% of the females in the population to achieve population leveling, and then reduction over the next 4–6 yr. Helicopter surveys from 1994–2001 provided a mean uncorrected count of five deer/square mile; with an approximation of 50% detection rate, the estimated population was 10 deer/square mile. Between January 2002 and April 2004, we captured 181 individual deer at least once using baited clover traps or darting deer over a bait pile. Sixty-six deer were anesthetized, surgically sterilized by tubal ligation, sampled, marked and collared; 35 female deer received the same handling but were not surgically sterilized, and 79 males were anesthetized, sampled and marked. All captured females received a telemetry collar and were monitored throughout the study period.
Our current population model focuses on density-dependent sterilization to maintain deer at a fixed population level, in the absence of natural density dependence. Mortality and dispersal rates were determined from our empirical data, while recruitment was estimated from previous studies in similar urban settings in the Midwest. At levels of variance used in the literature,1 our model predicts that density-dependent sterilization can maintain populations near goal levels with minimal risk of local extinction. Model predictions are tested using empirical data collected during the study.
This work is supported by a grant from the City of Highland Park (Illinois) and assistance provided by the Highland Park Police Department.
1. Hobbs, N.T., D.C. Bowden, D.L. Baker. 2000. Effects of fertility control on populations of ungulates: general, stage-structured models. J. Wildl. Manage. 64:473–491.
2. Warren, R. J. 1997. The challenge of deer overabundance in the 21st century. Wildl. Soc. Bull. 25:213–214.