Social, state-dependent and environmental modulation of faecal corticosteroid levels in free-ranging female spotted hyenas

Abstract

Little is known about to what extent the sensitivity of the hypothalamic^pituitary^adrenal (HPA) axis may be state dependent and vary in the same species between environments. Here we tested whether the faecal corticosteroid concentrations of matrilineal adult female spotted hyenas are in£uenced by social and reproductive status in adjacent ecosystems and whether they vary between periods with and without social stress. Females in the Serengeti National Park frequently become socially subordinate intruders in other hyena territories by undertaking long-distance foraging trips to migratory herds, whereas in the Ngorongoro Crater they usually forage inside their own small territories on resident prey. The faecal corticosteroid concentrations in Serengeti females were signi¢cantly higher than in Ngorongoro females. Energy expenditure by lactation is exceptionally high in spotted hyenas and this may be re£ected in their corticosteroid levels. The faecal corticosteroid levels in both populations were higher in lactating than in non-lactating females. During periods of social stability, faecal corticosteroid concentrations increased in non-lactating females but not in lactating females as social status declined. Lactating Serengeti females had signi¢cantly higher faecal corticosteroid concentrations during periods with acute severe social stress than during periods without, indicating that the HPA axis is sensitive to social stimuli even in lactating females. So far few studies have used non-invasive monitoring methods for assessing social stress in freeranging animals. This study demonstrates for the ¢rst time, to the authors' knowledge, that corticosteroid concentrations may di¡er between periods with and without social stress for a free-ranging female mammal and that the modulating e¡ect of social status may depend on reproductive status.

Cortisol mediates cleaner wrasse switch from cooperation to cheating and tactical deception

“…For instance, in many cooperative breeder species, dominant animals experience elevated GCs, which have associated costs, but this is usually accompanied by higher access to mates or resources (Creel, 2001). Moreover, the rise in metabolic demands (and as a consequence, increased GC concentration) is associated with several other social conditions such as parenting and lactation, or partnership instability (Goymann et al, 2001). Our findings suggest that higher levels of circulating cortisol are associated with an alternative behavioural strategy ("biting" cleaners, Bshary, 2002a), which should occur in response to an increase in energetic requirements.…”

Socioecological variables predict telomere length in wild spotted hyenas

“…Metabolic stress may cause high concentrations of reactive oxidative species and stress hormones, which are known correlates of telomere shortening [17]. In spotted hyenas in Tanzania, dominance rank predicted circulating glucocorticoid concentrations among non-lactating females, with lower concentrations found in high-than low-ranking females [18]. Our finding that highranking hyenas display longer telomeres than low-ranking hyenas is consistent with earlier work, and further suggests that social subordination has important consequences at the cellular level.…”

Developmental and geographic variation in stress hormones in wild Belding's ground squirrels (Spermophilus beldingi)

“…Acute stress responses are triggered by unpredictable events such as predator attacks, sudden severe weather or agonistic social interactions, whereas chronic stress stems from long-term adverse environmental conditions, such as unpredictable decreased food supply or either low or high social status (e.g. Morton and Sherman, 1978;Kotrschal et al, 1998;Lima, 1998;Cavigelli, 1999;Hubbs et al, 2000;Creel, 2001;Goymann et al, 2001;Abbott et al, 2003;Sands and Creel, 2004). Both types of stress can directly influence survival and reproduction (reviewed in Buchanan, 2000;Wingfield, 2004; see also Jennings et al, 2004;Boonstra, 2005;Spencer et al, 2005), yet surprisingly very little is known about the activity of glucocorticoids and the HPA axis in early development.…”