Predator-Prey Interaction, Niche Partitioning, and Eavesdropping -Ecological and Behavioral Relationships among Terrestrial Vertebrates in Madagascar

点击翻译按钮获取中文摘要

In each season, the field research was conducted from October to February, which is the rainy season of the study site, Ampijoroa dry forest. Throughout these periods, ecological studies on lizards, particularly geckos and chameleons, and snakes were made to investigate their food habits, foraging behavior, and trophic morphology based on direct observations and a mark-recapture method. Radio-telemetric study was conducted with four species of snakes that were presumed or confirmed to be predators of birds. With the aid of graduate students of Antananarivo University, these snakes were tracked over one to two years. These studies revealed that snakes are important predators of many terrestrial vertebrate species in this forest, but there are no snakes that specialized on eating birds. This implies that other animals such as sparrowhawks and lemurs may be major predators on eggs and chicks of birds. We also made several pilot tests to examine the effects of different types of snakes on the frequency of inducing mobbing of birds by presenting snake models and real snakes. On the other hand, defensive responses of lizards were investigated by presenting a model of a sparrowhawk, which demonstrated that a flying model approaching to the lizards induces a strong escape reaction of them. The tests of eavesdropping on alarm calls of birds by lizards were conducted using Madagascan day gackos, spine tailed iguanas, and plated lizards. The results strongly suggested that Madagascan day geckos change their body color in response to alarm calls of birds so as to make their body more cryptic against the background. Birds often displayed mobbing behavior to brown lemurs, suggesting that the lemurs are important predators of them. Overall, coupled with the results of our previous surveys, it is demonstrated that reptiles and birds are ecologically related through predator-prey interactions, competition, and eavesdropping.