Dispersal Patterns in Tarsius spectrum
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abstract
One of the most widely accepted explanations for the difference in the sex bias between mammals and birds is that male-biased dispersal in mammals is due to the preponderance of polygynous mating systems exhibited by this class, whereas birds are predominantly monogamous. Spectral tarsiers (Tarsius spectrum) are unusual in that they exhibit variation in its mating system. Although the majority of spectral tarsier groups are monogamous, ca. 15% are polygynous. If mating system influences dispersal, then I predicted that the polygynous groups would exhibit male biased dispersal whereas I predicted that the dispersal patterns of the monogamous groups would be analogous to that exhibited by birds, specifically female biased. Alternatively, I hypothesized that ecological variation may influence dispersal habits in this species. Specifically, I predicted that polygynous groups would exhibit greater habitat quality than monogamous groups. The 2 hypotheses are not mutually exclusive. On the basis of 14 individuals birdbanded between 1994 and 1999, I determined that individuals of both sexes were equally likely to disperse (males, n = 5; females, n = 9). Males dispersed twice as far as females did. The mean dispersal distance for males was 660 m, and for females it was 266 m. Females (77%) were more likely to form a territory adjacent to the parental territory than were males (20%). Individuals exhibited relatively high amounts of site fidelity (86%) that were related to physical characteristics of the sleeping site. Adults that dispersed a second time (n = 4) initially resided in trees that were shorter and had a smaller diameter-at-breast height than the trees of individuals that exhibited site fidelity. The results of my study partly support the parental mating system hypothesis and also support the habitat quality hypothesis. Springer Science+Business Media, LLC 2009.
