Foraging, feeding, and physiological stress responses of wild wood mice to increased illumination and common genet cues

In nature, animals are exposed to a broad range of threats imposed by predators, which may strongly influence the ecology of prey species directly or indirectly by affecting their behavior via fear of predation. Here, we studied wood mice Apodemus sylvaticus behavioral and physiological responses to simulated predation risk. Risk avoidance was analyzed by live trapping with control traps and traps treated with feces of common genet Genetta genetta （direct cue of risk） under new moon nights and following by simulated full moon conditions （indirect cue）. The time devoted to foraging behavior and capture time were analyzed by video recording mice activity around traps. Food intake was calculated based on the amount of bait remaining in each trap. Fecal cortico- sterone metabolites （FCMs） were measured by enzyme-immunoassay as indicators of physio- logical stress responses. Fewer wood mice were captured during full moon, yet only non-breeding adult males clearly avoided common genet odor. Mice were captured sooner at night during the simulated full moon conditions and later in predator-treated traps. Foraging activity was lower when individuals faced predator＇s feces, but neither food intake nor FCM levels were affected by predation risk cues. Direct and indirect cues of predation risk selectively affected wood mice behavior, although behavioral responses seem to be modulated by different costs-benefit balances related to the individual＇s perception of risk. The lack of physiological responses to predation risk cues suggests that wood mice did not perceive them as reliable stressors or the response was too small or transient to be measured by FCM.

Turning in mid-air allows aphids that flee the plant to avoid reaching the risky ground

When forced to drop from the plant,flightless arboreal insects can avoid reaching the risky ground by maneuvering their body through the air.When wingless pea aphids(Acyrthosiphon pisum)are threatened by natural enemies,they often drop off their host plant while assuming a stereotypic posture that rotates them in mid-air,aligning them with their feet pointing downwards.This position may increase their chances of re-clinging onto lower plant parts and avoid facing the dangers on the ground,although its effectiveness in realistic field conditions has not been tested.We performed both laboratory and outdoor experiments,in which we dropped aphids upon host plants to quantify clinging success in plants with different characteristics such as height and leaf size.Live aphids had twofold higher clinging rates than dead ones,indicating that clinging success is indeed affected by the active aerial-righting of dropping aphids.The ability to cling was positively dependent on the plants’foliage cover as viewed in vertical direction from above.Therefore,we released aphids in commercial alfalfa(Medicago sativa)fields with varying plant heights and foliage cover and induced them to drop.Most(up to 75%)of the aphids avoided reaching the ground in taller plants(65 cm),and 17%in shorter plants(21 cm),demonstrating the efficiency of the aphids’response in averting risks:both those of an approaching enemy on the plant and the plethora of new risks on the ground.Evidently,even in complex field environment,the aerial-righting mechanism can substantially reduce the possible risks following escape from a predator.