Effects of radio transmitter weight on a small nocturnal primate.

An increasing number of primatologists have begun using radio telemetry to study the behavioral ecology of nocturnal prosimian primates. Radio telemetry has enabled the collection of data on these nocturnal and cryptic prosimians that was previously difficult or impossible to otherwise obtain. A critical assumption of studies employing radio telemetry is that the radio transmitters have no appreciable negative effects on the study animals and the data being collected are not being biased by the presence of radio transmitters. This assumption is made because comparable data from a non-radio-collared control group are impossible to obtain. In an attempt to determine the tolerable weight limit for radio collars for a small nocturnal primate, the spectral tarsier, Tarsius spectrum, a comparison of the behavior and body weight of individuals wearing collars of two different weights was conducted. This study was conducted in Tangkoko Dua Saudara Nature Reserve in Sulawesi, Indonesia. A total of 16 individuals from seven groups were trapped in mist nets, radio-collared, and observed using focal follow sampling between April 1994 and June 1995. Each individual was observed for 4-6 months depending on the life span of the radio-collar battery. The two radiocollar weights appeared not to affect spectral tarsiers differentially. Average body masses in neither set of subjects differed between the days collars were attached and 6 months later, when they were removed. No differences in activity patterns, home range size, or prey capture rate were detectable between subjects wearing the different transmitters. These results suggest that the heavier radio collars used in this study did not have any appreciable effects on the behavioral patterns of this primate.