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Subordinate Males in Harem Groups of Jamaican Fruit-Eating Bats (Artibeus jamaicensis): Satellites or Sneaks?

Authors


Héctor T. Arita, Instituto de Ecología, Universidad Nacional Autónoma de México, Apartado Postal 70-275, 04510, México, Distrito Federal, Mexico. E-mail: arita@miranda.ecologia.unam.mx

Abstract

In the caves of Yucatan, Mexico, the Jamaican fruit-eating bat, Artibeus jamaicensis, forms harems consisting of four to 18 females and a dominant male that defends the group against foreign males. Large groups (>14 females) contain an additional subordinate male. In theory, subordinate males can associate with harem groups either as satellites, if they provide at least some benefits to the dominant male, or as sneaks, if they only impose costs on the dominant male. We assessed the costs and benefits of subordinate males in three removal experiments. In the first experiment, when a dominant male was removed from its group, its role was occupied by the subordinate male (in large groups) or by a foreign male (in small groups). Former subordinate males took less time to gain control of the harems and stayed longer with the groups than foreign males. In the second experiment, when a subordinate male was removed, the rate of visitation by foreign males and the number of agonistic displays by the dominant male both increased. In the third experiment, when the number of females in large groups was reduced, subordinate males spent less time with their groups and the rate of visitation by foreign males increased. However, the frequency of agonistic displays by dominant males towards subordinate males did not change. Dominant males invest large amounts of energy in defending the harems, but obtain direct and immediate benefits from the presence of subordinate males in the form of access to a larger number of females, and suffer no obvious costs. Subordinate males apparently invest little energy in defending the harems, obtain no obvious immediate benefit, but gain long-term benefits by having priority access to vacant positions left by dominant males. Subordinate males in harem groups of the Jamaican fruit-eating bat can be considered satellites because their presence brings immediate benefits to the dominant males.

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