Abstract: Prey species show specific adaptations that allow recognition, avoidance and defense against predators. For many mammalian species this includes sensitivity towards predator-derived odors. The typical sources of such odors include predator skin and fur, urine, feces and anal gland secretions. Avoidance of predator odors has been observed in many mammalian prey species including rats, mice, voles, deer, rabbits, gophers, hedgehogs, possums and sheep. Field and laboratory studies show that predator odors have distinctive behavioral effects which include (1) inhibition of activity, (2) suppression of non-defensive behaviors such as foraging, feeding and grooming, and (3) shifts to habitats or secure locations where such odors are not present. The repellent effect of predator odors in the field may sometimes be of practical use in the protection of crops and natural resources, although not all attempts at this have been successful. The failure of some studies to obtain repellent effects with predator odors may relate to (1) mismatches between the predator odors and prey species employed, (2) strain and individual differences in sensitivity to predator odors, and (3) the use of predator odors that have low efficacy. In this regard, a small number of recent studies have suggested that skin and fur-derived predator odors may have a more profound lasting effect on prey species than those derived from urine or feces. Predator odors can have powerful effects on the endocrine system including a suppression of testosterone and increased levels of stress hormones such as corticosterone and ACTH. Inhibitory effects of predator odors on reproductive behavior have been demonstrated, and these are particularly prevalent in female rodent species. Pregnant female rodents exposed to predator odors may give birth to smaller litters while exposure to predator odors during early life can hinder normal development. Recent research is starting to uncover the neural circuitry activated by predator odors, leading to hypotheses about how such activation leads to observable effects on reproduction, foraging and feeding. © 2005 Elsevier Ltd. All rights reserved.

Abstract: Vervet monkeys give different alarm calls to different predators. Recordings of the alarms played back when predators were absent caused the monkeys to run into trees for leopard alarms, look up for eagle alarms, and look down for snake alarms. Adults call primarily to leopards, martial eagles, and pythons, but infants give leopard alarms to various mammals, eagle alarms to many birds, and snake alarms to various snakelike objects. Predator classification improves with age and experience.

Abstract: We examined how social context and experience affected development of antipredator behaviour and subsequent postrelease survival in the black-tailed prairie dog. Captive-reared juveniles were initially exposed to four stimulus animals: a ferret, a rattlesnake, a hawk and a cottontail control (pretraining tests). Subjects were then trained with or without an adult female demonstrator. Training involved exposure to each stimulus animal two to three times over 5 weeks. After training, each juvenile was retested with each stimulus animal (post-training tests). During pretraining tests, juveniles responded differentially to the stimulus animals. They were least active with the snake, fled the most in tests with the hawk, and were less vigilant with the ferret than with the snake. Following training, juveniles trained with experienced adults were more wary with all three predators than juveniles trained without an experienced adult present. We then compared the antipredator behaviour of captive-reared juveniles trained with experienced adult females with that of wild-reared juveniles of the same age. For all behavioural measures except shelter use, wild-experienced animals differentiated more strongly among predator types than did captive-trained juveniles. One year after reintroduction, survivorship of juveniles trained with experienced adults was higher than that of juveniles trained without experienced adults, but did not differ from that of wild-reared juveniles. These findings provide the first evidence that social transmission of antipredator behaviour during training can enhance long-term survival following release and that as long as a social training regime is used, predator avoidance training can emulate experience acquired in the wild.

Abstract: According to the selfish herd hypothesis, animals can decrease predation risk by moving toward one another if the predator can appear anywhere and will attack the nearest target. Previous studies have shown that aggregations can form using simple movement rules designed to decrease each animal's Domain of Danger. However, if the predator attacks from outside the group's perimeter, these simple movement rules might not lead to aggregation. To test whether simple selfish movement rules would decrease predation risk for those situations when the predator attacks from outside the flock perimeter, we constructed a computer model that allowed flocks of 75 simulated fiddler crabs to react to one another, and to a predator attacking from 7 m away. We attacked simulated crab flocks with predators of different sizes and attack speeds, and computed relative predation risk after 120 time steps. Final trajectories showed flight toward the center of the flock, but curving away from the predator. Path curvature depended on the predator's size and approach speed. The average crab experienced a greater decrease in predation risk when the predator was small or slow moving. Regardless of the predator's size and speed, however, predation risk always decreased as long as crabs took their flock-mates into account. We conclude that, even when flight away from an external predator occurs, the selfish avoidance of danger can lead to aggregation.