Detection and avoidance of predators in white-tailed deer (Odocoileus virginianus) and mule deer (O-hemionus)

In this paper, we investigate the relationship between early detection of p redators and predator avoidance in white-tailed deer (Odocoileus virginianu s) and mule deer (O. hemionus), two closely related species that differ in their habitat preferences and in their anti-predator behavior. We used obse rvations of coyotes (Canis latrans) hunting deer to test whether the distan ce at which white-tails and mule deer alerted to coyotes was related to the ir vulnerability to predation. Coyote encounters with both species were mor e likely to escalate when deer alerted at shorter distances. However, coyot e encounters with mule deer progressed further than encounters with white-t ails that alerted at the same distance, and this was nor due to species dif ferences in group size or habitat. We then conducted an experiment in which a person approached groups of deer to compare the detection abilities and the form of alert response for white-tails and mule deer, and for age group s within each species. Mule deer alerted to the approacher at longer distan ces than white-tails, even after controlling for variables that were potent ially confounding. Adult females of both species alerted sooner than conspe cific juveniles. Mule deer almost always looked directly at the approacher as their initial response, whereas white-tails were more likely to flee or to look in another direction with no indication that they pinpointed the ap proacher during the trial. Mule deer may have evolved the ability to detect predators earlier than white-tails as an adaptation to their more open hab itats, or because they need more time to coordinate subsequent anti-predato r defenses. Corresponding author: Susan Lingle, Department of Psychology and Neuroscien ce, University of Lethbridge, Lethbridge, AB T1K 3M4, Canada. E-mail: susan .lingle@uleth.ca.