White-tailed deer, coyotes, and the ecology of fear in a longleaf pine savanna
Cherry, Michael John
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Predators can exert powerful influence on their prey, independent of direct killing, by inducing antipredator responses. Coyotes (Canis latrans) have recently achieved abundances capable of influencing white-tailed deer (Odocoileus virginianus) population demography in the southeastern USA, but the effects of antipredator responses have not been reported. I conducted a multifaceted investigation of coyote and white-tailed deer interactions, using population monitoring data, harvest data, and results from controlled experimentation with predator exclosures. This work provided evidence that coyotes can influence white-tailed deer space use and vigilance while foraging, and documented a negative relationship between coyote abundance and body mass of adult female deer during an 11-year period. I compared multiple measures of reproductive success during a 7-year period that encompassed high and low coyote-deer ratios to elucidate the relative contributions of direct predation and predation risk effects to an observed increase on recruitment as measured by fawn-adult female ratios. Fawn survival rates were similar between periods, but the proportion of females with evidence of ovulation increased during the period of low coyote-deer ratios. Increases in ovulation were similar to increases in the proportion of females with evidence of lactation and fawn-adult female ratios. While direct killing by predators greatly influenced survival of fawns during both periods, changes in recruitment resulted from variations in fecundity. I tested hypotheses predicting the consequences of 10 years of predator exclusion on oak (Quercus sp.) recruitment and the density of selected deer forage species. Oaks are an important component of the longleaf pine savannas, and factors influencing their recruitment are of significant importance to the restoration and management of the longleaf pine (Pinus palustrus) ecosystem. Predator exclusion increased oak recruitment and decreased the density of selected deer forage species in a frequently burned longleaf pine savanna. Thus, coyote predation risk can influence white-tailed deer herbivory and thereby potentially affect composition of groundcover and hardwood understory in longleaf pine ecosystems. This study demonstrates that coyotes can have strong predation risk effects on white-tailed deer populations, and ignoring these effects may result in dramatic underestimation of impacts of expanding coyote populations on ecosystems.