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Little brown bats (Myotis lucifugus) are a widely distributed species in North America that have been decimated by the fungal disease white-nose syndrome. As such, little brown bats are the focus of monitoring and research initiatives that often include capturing and handling free-ranging individuals. We examined the stress response of 198 adult female little brown bats after being captured from three bat houses, during the summer. Our objective was to inform best practices to researchers capturing and handling bats in the wild. We compared the stress response among bats held for <3 min (baseline), 15–30 min, or >30 min, and then among bats held alone or in a group with conspecifics. We measured the levels of plasma total and free cortisol, maximum corticosteroid binding capacity (MCBC), and blood glucose. Relative to baseline, total and free cortisol levels were significantly higher in bats held for 15–30 min and higher still in those held for > 30 min. Blood glucose levels were elevated after >30 min of holding. MCBC levels showed no differences among holding times. We detected a weak effect of social holding condition, with solitary-held bats having lower total cortisol levels than group-held bats, but MCBC, free cortisol, and blood glucose levels showed no effect of social holding condition. Our findings demonstrate that capture time should be minimized and suggest that little brown bats should be handled and released within 30 min of capture as means of reducing stress. Further, solitary holding did not appear to increase stress measures, which supports holding bats individually after capture, instead of in groups, to reduce risk of pathogen and parasite transmission. [ABSTRACT FROM AUTHOR]

Pregnancy and lactation are key times in the life of female mammals when energetic resources must be brought to bear to produce and nurture offspring. Changes in glucocorticoid (GC) levels are central to this objective, due to their roles in modulating development and physiology and in mediating energetic tradeoffs. We examined GC changes over reproduction in a species living in a harsh seasonal environment: the arctic ground squirrel (Urocitellus parryii). Females become pregnant immediately after emerging from a ∼9month hibernation, and then must begin this pregnancy during an additional month of freezing temperatures and limited food availability. We measured plasma levels of total cortisol, corticosteroid-binding globulin (CBG), and free cortisol in unstressed females at three stages: not-visibly pregnant, visibly pregnant, and lactating. Total cortisol levels were similar in all stages, but CBG levels increased 4-fold from the not-visibly pregnant stage to visibly pregnant and lactating stage. As a result, the free cortisol fraction declined from 51% of total cortisol when females were not-visibly pregnant to only 5% when they were visibly pregnant (remaining low and stable throughout pregnancy) and 10% when they were lactating. This pattern is markedly different from that seen in other mammals, where 10% or less of GCs are free and these tend to increase during gestation. We postulate that the high free cortisol just prior to visible pregnancy is a seasonal adaptation relating either to the pronounced physiological changes the female must undergo after emerging from hibernation and immediately getting pregnant, or to the mobilization of body reserves for energy to permit pregnancy, or both. Thereafter, high CBG levels may shield the developing offspring from the negative effects of cortisol overexposure., (Copyright © 2015 Elsevier Inc. All rights reserved.)