Surgical Sterilization as a Management Technique in Suburban Deer Populations

Abstract

Overabundant suburban deer (Odocoileus spp.) are a source of human-wildlife conflict in many communities throughout the United States. Deer-vehicle collisions, tick-borne pathogens, impacts on local vegetation, and other negative interactions are the typical reasons cited for initiating a deer management program. Social attitudes, legal constraints, and perceived safety concerns lead many communities to examine nonlethal management options. Surgical sterilization is currently the only nonlethal method available to permanently sterilize females with a single treatment. There are limited data demonstrating methods and outcomes in management programs that sterilize a high percentage (>90%) of the local population, particularly regarding the impact of immigration on non-isolated populations. We present data from 6 surgical sterilization sites with geographically open populations in California, Maryland, Michigan, New York, Ohio, and Virginia, USA. From 2012-2020, we sterilized 493 deer primarily via ovariectomy. We conducted annual or periodic population estimates using camera surveys, road-based distance sampling, and intensive field observations to assess population trends. Initial densities ranged from about 6-63 deer/km2. Study sites ranged from 1.2 km2 to 16.5 km2, and initial populations ranged from ~47 to 169 individuals. For our 6 study sites, we noted an average reduction in deer abundance of approximately 25% (range: 16.2%-36.2%) from Year 1 to Year 2. Four years after the first treatment, at monitored sites (n = 4) using this management method, we noted an average total population reduction of about 45% (range: 28%-56%). During the first year, the average cost per deer handled was $1,221 (range: $864-$1,998). These projects demonstrate that significant reductions in local deer densities using high percentage surgical sterilization programs can be achieved in non-insular locations. Sustained sterilization efforts are necessary, as is the case with all deer management programs in open landscapes.