Effects of SpayVac?????? on urban white-tailed deer at Johnson Space Center



Journal Title

Journal ISSN

Volume Title


Texas A&M University


White-tailed deer (Odocoileus virginianus) populations in the United States have increased in recent years, particularly in urban and suburban landscapes where traditional measures of population control are difficult to implement. As a result of rapid urban development in the last several years, the Lyndon B. Johnson Space Center (JSC) located southeast of the Houston, Texas metroplex has become a refuge for an increasing, isolated urban white-tailed deer population. The use of the immunocontraceptive SpayVac?????? has been proposed as a feasible measure in controlling the JSC deer population; however, the potential effects of the vaccine on deer movements are unknown. Furthermore, there is a need to estimate deer densities when using intensive management practices (e.g., contraceptive program) which requires an assessment of methods to estimate urban deer densities. The objectives of my study were to (1) compare female movements and ranges between deer treated with SpayVac?????? versus non-treated (control) deer, (2) determine if the timing of SpayVac?????? treatment affected efficacy, and (3) compare mark-resight and distance sampling methodologies in estimating urban deer densities. I captured and radio-marked 59 adult female deer at JSC. I found annual ranges between treated (mean 95% kernel = 82 ha, mean 50% kernel = 11 ha) and control (mean 95% kernel = 77 ha, mean 50% kernel = 11 ha) deer were similar (P > 0.05). Furthermore, I found daily movements between treated (mean = 430 m) and control (mean = 403 m) deer also were similar (P > 0.05). The use of SpayVac?????? did not alter movements and ranges of treated deer, and is unlikely to increase deer-vehicle collisions due to increased movements. I found the timing efficacy (i.e., time needed for vaccine to prevent pregnancy) of SpayVac?????? was 0% for does treated closer to the breeding season than previously believed. For JSC, this expands the application time for SpayVac?????? treatment to a 5-6 month window rather than the 2-3 month window as previously recommended. I found mark-resight estimates (160-174 deer) were congruent with minimum known alive estimates at JSC (158), whereas distance sampling estimates (83-114) were biased low. The use of non-random road counts likely resulted in the low estimates using distance sampling. I recommend that future efforts to monitor population densities at JSC use mark-resight estimates along with the on-going contraceptive program.