Reproduction elevates the corticosterone stress response in common fruit bats

Abstract

Changes in reproductive state or the environment may affect the sensitivity of the hypothalamicpituitary-andrenal (HPA) axis. However, little is known about the dynamics of the resulting corticosteroid stress response, in particular in tropical mammals. In this study, we address the modulation of corticosterone release in response to different reproductive conditions and seasonality in 326 free-living common fruit-eating bats (Artibeus jamaicensis) on Barro Colorado Island in Panama during dry and wet seasons. We present strong evidence that stress sensitivity is primarily modulated by reproductive condition. In reproductively active females, corticosterone increases were more rapid and reached higher levels, but also decreased significantly faster than in inactive females. The corticosterone response was weaker in reproducing males than in females and delayed compared to non-reproductive males. Testes volume in reproductively active males was negatively correlated with corticosterone concentrations. Our findings suggest differentiated dynamics in the corticosterone stress response between sexes, potentially reflecting conflicting ecological demands. In females, a strong acute corticosterone response may represent high stress-and risk-sensitivity that facilitates escape and thus helps to protect reproduction. In males, suppression during reproductive activity could reflect lowered stress sensitivity to avoid chronically elevated corticosterone levels in times of frequent aggressive and therefore costly inter-male encounters.

Testosterone is associated with harem maintenance ability in free-ranging grey-headed flying-foxes, Pteropus poliocephalus

“…A wing vein blood sample (200 ml) was obtained using an insulin syringe within 180 s of capture. Plasma was separated and stored as described previously (Klose et al 2006). Males were marked with colour steel bands and individually housed nearby for 72 h, with ad libitum access to a standardized fruit diet and water.…”

Ambient temperature is more important than food availability in explaining reproductive timing of the bat Sturnira lilium (Mammalia: Chiroptera) in a montane Atlantic Forest

“…They are also slow-breeding, mostly with one or two offspring a year, which makes every reproductive season very important (Barclay and Harder 2003). A variety of factors are regarded as determinants of reproductive timing, including endogenous causes, especially the hormonal cycle (Klose et al 2006), and exogenous causes, represented mainly by diet, food availability, day length, rainfall, and temperature (Kunz 1982;Handley et al 1991;Kalko 1998;Arlettaz et al 2001;Barclay et al 2004).…”

“…This permits linkage of seasonal variation in food over time with reproductive seasonality, thus allowing accurate assessment of the relative strength of this and other exogenous factors such as ambient temperature. Thus far, our knowledge on the reproductive ecology of frugivorous leaf-nosed bats is still limited, encompassing only a few species, which is remarkable little given the high diversity and ecological importance of this group (Zortéa 2003;Mello et al 2004;Klose et al 2006).…”

Does adrenal responsiveness vary with sex and reproductive status in Egernia whitii, a viviparous skink?

“…Such responses may, however, include 5 suppression of reproductive activity via inhibition of the hypothalamo -pituitary-6 gonadal (HPG) axis: current survival is then traded off aga inst future reproductive 7 success (Klose et al, 2006;Wingfield, 2003). Modulation of adrenocortical activity 8 during particular stages of life history may therefore be an important factor in 9…”