Testosterone (T) concentrations often covary strongly with mating activities in temperate-zone vertebrates. Recent studies suggest that males of tropical species experience lower and year-round constant T levels. Here we studied plasma T concentrations in a tropical mammal with a seasonally
invariant social system, the greater sac-winged bat (Saccopteryx bilineata (Temminck, 1838)). Colony composition remains almost stable throughout the year, although mating is restricted to only a few
weeks each year. Males follow one of two mating strategies: they either defend a territory with a female group (harem) or live peripheral without females. First, we compared T within the same individuals between seasons, asking whether T levels are higher during mating season. Second, we tested
whether T levels are related to social status, and third, whether T correlates with parasite infection because of an immunosuppressive effect. We found high individual T variations. Testosterone was elevated during the mating season only in harem males and was, on average, higher than in peripheral
males. We found no correlation between T and parasite infestation. Although reproduction is seasonal in S. bilineata, T concentrations showed no pronounced seasonal pattern, probably because colony members form long-term relationships and live in a year-round stable social system.
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Document Type: Research Article
Evolutionary Ecology Research Group, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Straße 17, 10315 Berlin, Germany.
Reproduction Biology Research Group, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Straße 17, 10315 Berlin, Germany.
Publication date: 2011-12-16
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