Responses Of Foraging Behavior In Reed Voles (Microtus Fortis) To Heterogeneity Habitat

The foraging behavior of small mammalian herbivores is the outcome of adaption to specific habitats,which including foraging actions such as searching,handling(cropping and chewing)prey,and vigilance actions such as scanning,listening,sniffing and so on.It is still unknown whether these complex and varying foraging environment have effects on vigilance action,resulting in variation in their foraging behavior and energy intake rate? To evaluate the effects of the height of surrounding obstruction on foraging behavior and energy intake rate of voles(Microtus forties),we devised concentrated homogeneity food patches of fresh of leaves of clover(Trifolium hybridum L)that were obstructed by three height of brown paper to imitate the vegetation obstruction to vole's vision around food patches;To evaluate the effects of food heterogeneity on foraging behavior and energy intake rate of voles,we devised concentrated heterogeneity food patches of fresh of leaves from five vegetation;To evaluate the effects of predator and food heterogeneity on foraging behavior and energy intake rate of voles,we used cat(Felis catus)as predator placed on one side of the behavioral observing equipment with concentrated heterogeneity food peaches.The sequence and parameters of foraging behavior in reed voles were measured to examine the effects of these factors on their energy intake rate.Our results showed that,(1)no significant difference was detected in the foraging subject with different heights of obstruction in foraging behavior.The dynamic analysis of variation in foraging behavior parameters showed that in each biting bout,individuals maintained the total foraging interruption time by modulating the frequency and duration of vigilance behavior in each foraging bout,thus maintaining a steady ingestion time.The results also indicated that the voles maintained their intake rates at different levels of vision obstruction via altering and optimizing their behavior.These results verified the instantaneously dynamic change of energy gain by measuring the actual foraging interruption time caused by vigilant behavior.The variation in vigilance intensity,i.e.,vigilance frequency,in voles did not reflect the cost of decreasing food intake caused by foraging interruption,rather the duration of vigilance action in foraging processes was a reliable indicator of dynamic change in intake rates.(2)Voles foraging in heterogeneity food patches displayed strong selection to food vegetation,result in their energy intake rate,bite rate and bite size significantly decreased compared to individuals foraging in food homogeneity patches.Bite size of male voles was significantly large than female,which result in energy intake rate of male voles was high than female.These results suggested that behavior action of searching,identifying,and selection to vegetation in reed voles can significant reduce voles' energy intake rate;Response of foraging behavior in male and female to food heterogeneity patches is differently.(3)Predator risk can reduce the selection index of reed voles to food vegetation,resulted in ingesting more species of vegetation and took larger bite size.Compared to foraging in the patches without predator risk,voles foraging under predator risk condition,took less time to scan surrounding and more time to stare at predator.Voles can maintain their interruption time steady,then keep their foraging time steady via staring at cat while they are chewing plants.Male voles also took large bites size and high energy intake rate than female.This is no significant different between male and female among others parameters.Our results suggested that although foraging under predator risk condition,voles also are able to maintain their interruption time steady and energy intake rate as possible via altering and optimal their vigilance behavior.These researches verified our hypothesis that(1)reed voles can maintain their intake rates in different levels of vision obstruction via altering and optimizing their behavior;(2)Voles foraging in food heterogeneity patches display behavior action,such as searching,identify and selection food resource,which prolonged individuals' interruption time,result in individuals' energy intake rate significant declining;(3)Reed voles can maintain their interruption time,resulted in maintaining energy intake rate steady as possible via reducing the time of scanning surrounding and increasing the time of staring at predator.Consequently,investigating the effects of vigilance behavior on intake rates by measuring the foraging cost caused by the foraging interruption time as an indicator could be an effective way to evaluate adaptive foraging strategies in different situations in small mammalian herbivores.