Relationships between personality traits and the physiological stress response in a wild mammal

Glucocorticoids(GCs)are involved in the regulation of an animal's energetic state.Under stressful situations,they are part of the neuroendocrine response to cope with environmental challenges.Animals react to aversive stimuli also through behavioral responses,defined as coping styles.Both in captive and wild populations,individuals differ in their behavior along a proactive-reactive continuum.Proactive animals exhibit a bold,active explorative and social personality,whereas reactive ones areshy,less active-explorative and less social.Here,we test the hypothesis that personality traits and physiological responses to stressors covary,with more proactive individuals having a less pronounced GC stress response.In wild populations of invasive gray squirrels Sciurus carolinensis,we measuredfecal glucocorticoid metabolites(FGMs),an integrated measure of circulating GCs,and 3 personality traits(activity,sociability,and exploration)derived from open field test(OFT)and mirror image stimulation(MIS)test.Gray squirrels had higher FGMs in Autumn than in Winter and males with scrotal testes had higher FGMs than nonbreeding males.Personality varied with body mass and population density.Squirrels expressed more activity exploration at higher than at lower density and heavier squirrels had higher scores for activity exploration than animals that weighed less.Variation in FGM concentrations was not correlated with the expression of the 3 personality traits.Hence,our results do not support a strong association between the behavioral and physiological stress responses but show that in wild populations,where animals experience varying environmental conditions,the GC endocrine response and the expression of personality are uncorrelated traits among individuals.

Preventing species invasion:A role for integrative taxonomy?

Integrative taxonomy,a multi-disciplinary approach adding modern techniques to traditional morphology-based methods(e.g.molecular and morphological criteria),can play an important role in bioinvasion research to identify introduced taxa,discover pathways of introduction and inform authorities to control and prevent fu­ture introductions.The present study is the first on introduced populations of Callosciurus,Asiatic tree squir­rels,known as potentially invasive species in Europe(Italy,Belgium and France).We combined molecular(mi­tochondrial DNA markers:CoxI,D-loop)and morphometric analysis on skulls,comparing them to the widest morphological and molecular datasets ever assembled for Callosciurus.Squirrels collected in Italy and Belgium share the same haplotypes and skull characteristics,but are conspicuously different from the French population in Antibes.Genetic data revealed close similarity between French squirrels and Pallas’s squirrels,Callosciurus erythraeus,from Taiwan,China.Italian and Belgian squirrels formed an independent taxonomic lineage in ge­netic analyses,whose taxonomic rank needs further investigation.The morphological and morphometric charac­teristics of these 2 populations are,however,similar to known specimens assigned to Callosciurus erythraeus.These results may indicate a common origin for the populations found in Belgium and Italy.In contrast,French specimens suggest an independent introduction event of squirrels originating from Asia.