Bats keep separate households
The use of different environments by males and females in the parti-coloured bat makes population estimation and thereby the conservation of the species more difficult
The use of different resources by males and females exacerbates the estimation of population sizes. However, the monitoring of population sizes, particularly for rare and threatened species, is pivotal to quick and effective conservation action. Scientists from the Max Planck Institute for Ornithology in Radolfzell investigated the ecological niches of male and female parti-coloured bats (Vespertilio murinus) and discovered that the sexes use entirely different foraging grounds. Their findings demonstrate that a finer grained view of what different demographic subsets of species do is essential for correct estimation of population trends with important implications on action plans for conservation.
Reliable knowledge of population sizes and changes thereof, which is often obtained by field surveys is essential for conservation. Differences in behaviour between demographic subsets of species, for example males and females, can lead to differences in resource use such as in diet or roost use. These differences can lead to specialisation and ultimately translate into spatial segregation within species. Reliable estimates of population sizes are however much hampered by sexual segregation. For threatened and rare species monitoring of population trends are essential for fast and appropriate conservation action.
Scientists from the Max Planck Institute for Ornithology in Radolfzell and their collaborators at the Swiss bat conservation centre now propose a novel way to obtain better estimates of population size for sexually segregating species.
They investigated the parti-coloured bat (Vespertilio murinus) in Switzerland. Although the distribution of this species stretches over a vast area reaching from the Netherlands all the way to China, the species is rare in Western Europe. Despite the fact that males and females are barely different in size and fur coloration and identical in their preferences for day roosts, at a close glance they are fundamentally different. As so often among mammals in the parti-coloured bats too, females carry the full load of parental care with no support whatsoever from males in raising their twin pups. Twinning is rather exceptional among bats and presumably leads to even higher energetic costs imposed on the females. These differences in the investment between the sexes, so the scientists argue, result in different tolerance of males and females towards the quality of their foraging areas and the amount of prey they need to sustain themselves, leading to a segregation of the sexes.
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