Max Planck Institute for Ornithology

Hormone physiology and life history of spotted hyaenas

The main focus of the spotted hyaena hormone project was two-fold.
First, we studied the role of androgens in female dominance of this species. Our results provided little support for a theory of selection for female dominance and hyper-aggressiveness through enhanced secretion of androgens. Rather, our data were consistent with the alternative view that female virilization (masculinization) is a byproduct of selection for precocial aggressive cubs of both sexes. According to this view, high investment in lactation favored selection for accelerated fetal development, high neonatal aggression, and facultative siblicide.

Second, we were interested in the relationship between environmental and social factors and fecal corticosteroid metabolites ("stress-hormones") in this highly social species. We showed - for the first time in a free-living female mammal - that corticosteroid metabolite concentrations differed between periods with and without social stress and that the modulating effect of social status on corticosteroids may depend on reproductive status. For males, social status or tenure did not predict corticosteroid metabolite levels. However, males of the largest clan had the highest levels of fecal corticosteroids, possibly reflecting higher rates of social interactions in larger clans.

Maternal and social behaviour of Indian false vampire bats

Indian false vampire bats, Megaderma lyra, are carnivorous bats roosting in caves and large buildings such as hindu temples throughout India. We discovered that the sexes partially segregate when mothers rear their pups. Some mothers remove their pups from the day roost during the night and "park" them in special night roosts. Although the significance of this behaviour is not yet understood it may be part of a strategy to minimize between-litter siblicide in this species.