Abstract
Vigilance behavior may directly affect fitness of prey animals, and understanding factors influencing vigilance may provide important insight into predator-prey interactions. We used 40,540 pictures taken withcamera traps in August 2011 and 2012to evaluate factors influencing individual vigilance behavior of white-tailed deer (Odocoileus virginianus) while foraging at baited sites. We used binary logistic regression to determine if individual vigilance was affected by age, sex, and group size. Additionally, we evaluated whether the time of the day,moon phase,and presence of other non-predatorwildlife species impacted individual vigilance. Juveniles were 11% less vigilant at baited sites than adults. Females were 46% more vigilant when fawns were present. Males and females spent more time feeding as group size increased, but with each addition of 1 individual to a group, males increased feeding time by nearly double that of females. Individual vigilance fluctuated with time of day andwith moon phase but generally was least during diurnal and moonlit nocturnal hours, indicating deer have the ability to adjust vigilance behavior to changing predation risk associated with varyinglight intensity.White-tailed deer increased individual vigilance when other non-predator wildlife were present. Our data indicate that differential effects of environmental and social constraints on vigilance behavior between sexes may encourage sexual segregation in white-tailed deer.
Highlights
Non-consumptivepredation effects can impact interactions of prey specieswith their environment and may negatively affect fitness [1].High predation risk may reduce fitnessby simplifying an animal’s decision making rules,which potentially hinders optimal use of resources, when foraging areas are separated from escape cover [2]
We investigated potential factors that influence individual vigilance of foraging white-tailed deer anddetermined if sex, age class, andgroup size influenced vigilance behavior.We expanded on Lark and Slade [23] by using camera traps, which allow the evaluation of vigilance relative to time of day,moon phase, and the presence of other non-predator wildlife species and provide the opportunity to collect large volumes of data while minimizing the potential bias of human presence
After the 14 days of camera trapping, we collected all pictures and tallied the number,sex, and age of deer, their vigilance level, the time and date of the picture, presence of other wildlife species, and the moon phase (New, First quarter, Full, Third quarter, as described in Rockhill et al [33]).We considered a deer to be in a feeding posture if its head was below its stomach lineand classified it as non-feeding posture when its head was above the stomach line
Summary
Non-consumptivepredation effects can impact interactions of prey specieswith their environment and may negatively affect fitness [1].High predation risk may reduce fitnessby simplifying an animal’s decision making rules,which potentially hinders optimal use of resources, when foraging areas are separated from escape cover [2]. Behaviors that potentially reduce fitness may include reduced feeding durations [4,5], decreases in dielactivity [6], changes in group size [7,8], changes in habitat use [9,10,11,12], and increases in vigilance while foraging [13]. Ungulates generally accept the cost of vigilance during foraging because the cost of decreasing intake is a lower proximal threat to the individualfitness than increased predation risk [7]. Individuals may increasegroup sizes to decrease individual vigilance during foraging without increasing predation risk [8]
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