Alarm walking in Columbian black-tailed deer: Its characterization and possible antipredatory signaling functions

Many antipredator behaviors advertise honestly an individual's health and awareness of predators, reducing the probability of further attack. We presented full-sized models of felid predators to Columbian black-tailed deer (Odocoileus hemionus columbianus) and observed a unique conspicuous gait pattern, the alarm walk, which has not been described in the literature. We conducted frame-by-frame analyses of gait timing and leg movement from video recordings of alarm walking and normal walking. Compared with normal walking, contact durations of all legs during alarm walking were greater and deer lifted their foreleg carpal joint higher off the ground, suggesting that alarm walking requires a level of control and flexibility in leg movement not possible in arthritic or lame individuals. Although phases of limb movement (i.e., midtime lag between fore and hind legs) were reliably different, there was no difference in the angle of foreleg lifting between the 2 walking styles. Performance of alarm walking was correlated with foot stamping, and was observed more often when the predator model was out of view. Although there was no direct evidence supporting any 1 function of alarm walking, available evidence suggests that alarm walking might have the dual function of signaling to a stealthy predator that it has been detected and that the displaying deer is healthy and capable of escaping, both of which should deter further pursuit.