Use of infrared thermography to detect reactions to stressful events:does animal personality matter?

The study of the relationship between animal stress and personality for free-ranging animals is limited and provides contrasting results.The perception of stressors by an individual may vary due to its personality,and certain personality traits may help individuals to better cope with them.Using non-invasive infrared thermography(IRT),we investigated the link between physiological and behavioral components expressed during an acute stress event by free-ranging Fremont’s squirrels(Tamiasciurus fremonti).We expected that,during the acute stress event of being approached by the researcher,individuals that showed a fast pace-of-life syndrome(bolder,more active,and less social/more aggressive)based on an arena test would exhibit stronger sympathetic-adrenal-medullary system reactivity showing a more intense stress-induced hyperthermia(high core body temperature and low peripheral temperature)than individuals with a slow pace of life(shy,less active,and more social).We successfully employed IRT technology to images of Fremont’s squirrels with identification of the individuals’body parts(eye,nose,ear,hind foot).However,we found no support for our hypothesis.Squirrels’body surface temperatures told us more about a squirrel’s external environment and less about the thermal state of the body in that environment following a stressful event.Further studies need to assess how to make IRT effective and efficient in the field and improve its performance in studying the relationships between physiology and personality in wildlife.

Living on the edge: morphological and behavioral adaptations to a marginal high-elevation habitat in an arboreal mammal

Habitats are characterized by different local environmental conditions that influence both behavior and morphology of species,which can result in habitat-dependent phenotypic differences among animals living in heterogeneous environments.We studied 3 alpine populations of Eurasian red squirrels(Sciurus vulgaris),1 living in a marginal high-elevation habitat at the edge of the species’altitudinal distribution,and 2 occurring in higher-quality habitats.Here,we investigated whether squirrels living in the marginal area differed in 2 morphological parameters(body size and body mass)and/or in the expression of 4 personality traits estimated with an openfield test and a mirror image stimulation test(activity,exploration,activity-exploration,and social tendency).Furthermore,we tested whether within-individual variance of the traits(behavioral plasticity)was higher in the edge habitat.Male squirrels in the edge habitat were smaller and weighed less than in the other study areas,while among females,size–habitat relationships were less marked.These sex-specific patterns were explained by a strong association between body mass and reproductive success in female squirrels.Squirrels in the marginal habitat were more active,explorative,and had a more social personality than in the other habitats.However,in contrast to our predictions,behavioral plasticity was smaller in the marginal habitat,but only for the trait exploration.Our results suggest that animals choose the habitat that bestfits their personality,and that habitat-related differences in selective pressures may shape animals’morphology.