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Allocare in a nocturnal primate: data on the spectral tarsier, Tarsius spectrum
1Department of Anthropology, City University of New York, Queens College, New York, NY 11367, USA.
Insights
Spectral tarsiers exhibit limited non-maternal infant care, despite a high infant/adult weight ratio. Subadult females provide the most care, while males offer minimal assistance, challenging previous hypotheses.
Area of Science:
- Primatology
- Behavioral Ecology
- Evolutionary Biology
Background:
- Non-maternal infant care (allocare) in New World primates is often linked to high infant/adult weight ratios.
- The spectral tarsier (Tarsius spectrum), an Old World primate, possesses a notably high infant/adult weight ratio (20-33%).
Purpose of the Study:
- To investigate allocare behavior in spectral tarsiers.
- To test the hypothesis that a high infant/adult weight ratio predicts extensive allocare.
Main Methods:
- Observational study of spectral tarsier social interactions.
- Comparison of allocaretaking behaviors across different age and sex classes (subadult females, subadult males, adult males).
Main Results:
- Spectral tarsiers display significantly less allocare than observed in New World primate species.
- Subadult females provide the most allocare, including food sharing, transport, grooming, and play.
- Adult and subadult males engage in limited allocare, primarily grooming and play, alongside territorial defense.
Conclusions:
- A high infant/adult weight ratio may be a prerequisite for extensive allocare but is not a direct cause.
- The spectral tarsier's limited allocare suggests other selective pressures are at play.
- Further research is needed to understand the costs and benefits of allocare in this species.
Abstract:
Non-maternal infant care in many of the small-bodied New World primate species has been hypothesized by some researchers to be related to the high infant/adult weight ratio found in these species. The spectral tarsier, Tarsius spectrum, an Old World primate, has one of the highest infant/adult weight ratios of any primate, with infants weighing between 20-33% of adult weight at birth. On the basis of the hypothesized relationship between allocare and the infant/adult weight ratio, it is predicted that the spectral tarsier will also exhibit extensive allocaretaking behaviour. The results of this study indicate that although spectral tarsiers show care by male and female subadults as well as adult males, it is extremely limited compared to the extensive allocaretaking behavior observed in New World primate species such as Aotus and Callicebus. Spectral tarsier subadult females provide substantially more allocare to infants than do subadult males or adult males. Female subadults were observed sharing food, transporting, grooming, playing, alarm calling, baby-sitting and maintaining physical contact with infants more than other age/sex classes. Although the amount of allocare exhibited by adult males and subadult males was much less than that exhibited by female subadults, the data suggest that adult and subadult male spectral tarsiers do play a small part in the care and socialization of the infant. Adult males and subadult males were both observed occasionally engaging in allocaretaking behaviors such as grooming and playing, as well as frequently patrolling and defending the territory's boundaries. The results from this study suggest that although a high infant/adult weight ratio may be a prerequisite for selection to favor extensive allocare, it is not a causal factor. Additional research is needed in order to understand better the selective pressures involved and the costs and benefits of providing allocare to subadults and adult male spectral tarsiers.