Heads up! Variation in the vigilance of foraging chipmunks in response to experimental manipulation of perceived risk

Abstract

Vigilance is a behavior in which an organism is gaining information about its environment, often used for predator detection. Vigilance is influenced by the risk that an organism perceives. Animals may vary their use of vigilance behaviors by modifying not only the percent time they dedicate to vigilance, but also the duration of vigilance bouts, rate of vigilance bouts, and type of vigilance posture. Assuming these different vigilance tactics come at different costs to the individual, different sources of perceived risk should elicit specific vigilance strategies. Here, we experimentally altered the sight lines of foraging Eastern chipmunks (Tamias striatus). We carried out our field work in three locations in Michigan that vary from low (an island site) to high predator pressure. Our results show that chipmunks respond to changes in their immediate microhabitat by altering the rate of vigilance, regardless of predator density. On the other hand, chipmunks at sites with lower predator densities spend less time vigilant when compared to sites with higher predator densities and they utilize vigilance postures that decrease vigilance but do not completely halt feeding. Further research should aim to quantify costs and benefits of vigilance postures and strategies to further our understanding of how individuals balance the trade‐off between mortality and energy gain.

Gazing Strategies among Sentinels of a Cooperative Breeder Are Repeatable but Unrelated to Survival

“…The individual consistency in the head-turning frequency in breeders supports findings from other studies showing that measurements of vigilance can vary systematically among individuals through time [26,29,34,35,39,40]. Our results indicate that individual consistency can be found not only in the overall allocation of time to vigilance but also in the way vigilance is achieved from one moment to another.…”

“…The empirical evidence thus far supports the existence of consistent differences in vigilance. Individual differences have been documented in mammals [ 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ] and in birds [ 26 , 38 , 39 , 40 ]. In addition, individuals can also vary consistently in the way vigilance is adjusted to gradients in predation risk [ 26 , 29 , 41 ] although there are exceptions [ 31 , 34 , 40 ].…”

How to behave when marooned: the behavioural component of the island syndrome remains underexplored

“…island, insular*, archipel*). We also carefully checked the reference lists of all papers for additional sources.study speciestraitislandmainlanddrivermechanismtype of analysisreferencepersonality eastern chipmunk ( Tamias striatus )island chipmunks are less vigilant, but both island and mainland specimens adjust vigilance to microhabitat structureBeaver Island, Michigan, USAtwo sites on mainland Michigan, USAlower predation pressure on island (checked with camera traps)unknownfield experiments; personality variation measured[45] 14 species of macropodid marsupialsanimals on islands are less wary and allocate more time to foragingsatellite islands of AustraliaAustraliapredation pressureacknowledges possibilities of plasticity and selectionfield observations; comparative analysis[46] reindeer ( Rangifer tarandus )island reindeer are more vigilant on the island, but response distances are the sameEdgeøya, Norwayfour sites on Spitsbergen, Norwaypossibly higher predation (by polar bears) on islandresponse distance believed to be ‘hard-wired'field observations[47] bull-headed shrike ( Lanius bucephalus )longer FID in island shrikesKikaijima, Minami-daitojima and Nakanoshima Islands, Japanthree sites on main Japanse Islandsrisk of predation (by rats) higher on islandsgenetic change, plasticity and dispersal-related selection are consideredfield observations[48] 11 species of Falkland Island birdsFID is lower on island than on mainlandFalkland Islandsmainland Argentinaabsence of terrestrial predatorsprobably innate, evolutionarily acquired, but habituation also deemed possiblefield observations; comparative analysis[…”