Ecological determinants of body mass:
insights from the group foraging bat Molossus molossus.
4th International Bat Meeting, Berlin, Germany, 13-15 March 2015.
Y. Gager (1,2,3), & D. K. N. Dechmann (1,2,4)
1 Max Planck Institute for Ornithology, Radolfzell, Germany
2 University of Konstanz, Konstanz, Germany
3 International Max Planck Research School for Organismal Biology, Department of Biology, University of Konstanz, Konstanz, Germany
4 Smithsonian Tropical Research Institute, Panamá, Rep. of Panamá
The use of public information has been proposed as an important driving force in social evolution, including in bats. Information transfer about food patches appears as a promoter of group living in male groups from the temperate zones as well as mixed groups in tropical species. By acquiring social information about food, individuals can both reduce foraging time and increase their energy intake. Over the long- term, an improved foraging efficiency can ultimately enhance fitness and promote group hunting.
Group foraging and eavesdropping has been recently observed by a telemetry study in the Neotropical bat Molossus molossus. Members of a social group fly within hearing distance to find and share patches of ephemeral insects. Our objective was to characterize the ecological parameters (sex, group size and climatic variables) influencing body mass variation as a proxy for foraging efficiency in these groups. We predicted that an optimal, but fairly small group size, should allow for most efficient information transfer and thus linked to mass gain. To test this, we monitored individually marked bats with an automated recorder – integrating a PIT-tag reader and a scale –installed at the entrance of five roosts to record activity and mass of individuals.
Analysis with GAMM models showed that bats were active predominantly just after sunset and this was linked to a significant increase in mass. Rain had a negative effect on individual mass variation while group size had a positive effect, indicating that access to information from more foraging partners increases efficiency. Our study is the first one to show a direct link between mass variation and group size in a social foraging bat, emphasizing the importance of investigating alternative explanations in order to understand the evolution of sociality
Y. Gager (1,2,3), & D. K. N. Dechmann (1,2,4)
1 Max Planck Institute for Ornithology, Radolfzell, Germany
2 University of Konstanz, Konstanz, Germany
3 International Max Planck Research School for Organismal Biology, Department of Biology, University of Konstanz, Konstanz, Germany
4 Smithsonian Tropical Research Institute, Panamá, Rep. of Panamá
The use of public information has been proposed as an important driving force in social evolution, including in bats. Information transfer about food patches appears as a promoter of group living in male groups from the temperate zones as well as mixed groups in tropical species. By acquiring social information about food, individuals can both reduce foraging time and increase their energy intake. Over the long- term, an improved foraging efficiency can ultimately enhance fitness and promote group hunting.
Group foraging and eavesdropping has been recently observed by a telemetry study in the Neotropical bat Molossus molossus. Members of a social group fly within hearing distance to find and share patches of ephemeral insects. Our objective was to characterize the ecological parameters (sex, group size and climatic variables) influencing body mass variation as a proxy for foraging efficiency in these groups. We predicted that an optimal, but fairly small group size, should allow for most efficient information transfer and thus linked to mass gain. To test this, we monitored individually marked bats with an automated recorder – integrating a PIT-tag reader and a scale –installed at the entrance of five roosts to record activity and mass of individuals.
Analysis with GAMM models showed that bats were active predominantly just after sunset and this was linked to a significant increase in mass. Rain had a negative effect on individual mass variation while group size had a positive effect, indicating that access to information from more foraging partners increases efficiency. Our study is the first one to show a direct link between mass variation and group size in a social foraging bat, emphasizing the importance of investigating alternative explanations in order to understand the evolution of sociality