As part of a larger study of the behavioral ecology of the spectral tarsier, Tarsius spectrum, a population census was conducted. A modified form of the fixed point count and quadrat census methods was conducted within a 1-km2 area in Tangkoko Dua Saudara Nature Reserve, in northern Sulawesi, Indonesia. In 25 one-hectare plots, 14 groups were located, containing a total of 39 individuals. Therefore, the mean number of groups per ha was 0.56 and the mean number of individuals per ha was 1.56. The number of groups for the entire sampled area (100 ha) was calculated to be 56, while the total population within the sampled area was calculated to be 156 (i.e. 156/km2). Group size, defined as the number of individuals sharing a sleeping site, varied from 2 to 6 individuals. Group composition varied from 1 adult of each sex to 1 adult male and 2 adult females and their offspring. Fourteen percent of groups contained more than 1 adult female. In one of the groups with two adult females, both females gave birth to infants. The home ranges of 13 individuals, obtained using radio telemetry, were between 1.6 and 4.1 ha, with an average size of 2.3 ha for females and 3.1 ha for males. Results from this study indicate that spectral tarsiers are still relatively abundant at Tangkoko Dua Saudara Nature Reserve. Nonetheless, the limited geographic distribution of this species, the lack of information on its relative abundance in other areas of its range, as well as the high rate of habitat disturbance throughout its range, suggests that the conservation status of the spectral tarsier should be changed from indeterminate to vulnerable.
Few mammals-cetaceans, domestic cats and select bats and rodents-can send and receive vocal signals contained within the ultrasonic domain, or pure ultrasound (greater than 20 kHz). Here, we use the auditory brainstem response (ABR) method to demonstrate that a species of nocturnal primate, the Philippine tarsier (Tarsius syrichta), has a high-frequency limit of auditory sensitivity of ca 91 kHz. We also recorded a vocalization with a dominant frequency of 70 kHz. Such values are among the highest recorded for any terrestrial mammal, and a relatively extreme example of ultrasonic communication. For Philippine tarsiers, ultrasonic vocalizations might represent a private channel of communication that subverts detection by predators, prey and competitors, enhances energetic efficiency, or improves detection against low-frequency background noise.
No abstract
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 radio‐collar 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. Am. J. Primatol. 46:145–155, 1998. © 1998 Wiley‐Liss, Inc.
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