Spectral tarsier

At the very base of the tarsier society is that they live in groups and males and females have different roles. Males tend to travel longer distances and they occupy a larger area. Females tend to hunt more efficiently and they also consume more insects. A study done by Sharon Gursky in 1998 defines group size as the number of individuals sharing a sleeping site. She goes on to say that these groups are usually composed of 2 to 6 individuals. The study was done in the Tangkoko Dua Saudara Nature Reserve and Gursky et al. found that 14% of groups contained more than 1 adult female. "In one of the groups with two adult females, both females gave birth to infants (Gursky et al. 1998)."[7] In the research done by Sabrina Archuleta, it was found that tarsiers can be both monogamous and polygynous. She found that some live in pairs or groups and some males may even live alone.[5]

A Spectral tarsier, relaxing on a tree.

A Spectral tarsier, relaxing on a tree branch.

In a study done in North Sulawesi, Indonesia in 2007, the Mackinnons found that the spectral tarsiers were monogamous and territorial. They found that families slept at the same sites each day and that they gave loud duet songs as they gathered at sleeping sites. As their study went on they found that tarsier young are quite advanced and that they start traveling alone at as young as 23 days (Mackinnon et al. 1980).[10] Hidayatik et al. did a 9-month survey in 2018 where they found that the tarsiers courtship behaviours consist of scent marking and genital marking for females and that males use genital inspection. They recorded that copulations lasted between 3 and 4 minutes and occurred only once per pair for the duration of the study (Hidayatik et al. 2018).[12]

Sharon Gursky did a study in the a northern Sulawesi rain forest in 1994 where she found that infants were alone from 40%-50% of the time. Gursky et al. found that the two subadults in the group were more regularly caring for the infant than the adult males, females or mothers were. They believe that these results suggest that subadults are actually guarding or babysitting the infants (Gursky et al. 1994).[13] Infanticide has been reported by Gursky, but only in one case and by a neighboring adult male. "The only hypothesis that could not be rejected outright, on the basis of this single observation, was the competition for limited resources hypothesis (Gursky et al. 2011)."[14]

According to the study done by the Mackinnons, tarsiers scent mark their ranges by rubbing branches with urine and special epigastric glands (Mackinnon et al. 1980).[10] It was found that the primary predators of the tarsiers are monitor lizards, civets, snakes, and diverse birds of prey. "Tarsier niches are largely as predator and prey. Their presence affects the population size of organisms that they feed on and of those who feed on them (Archuleta S. 2019)." Archuleta goes on to say that they are host to many endo- and ectoparasites, including mites and intestinal worms.[5]

A study done in 2019 by Sharon Gursky found that spectral tarsiers use ultrasonic vocalizations. These are high frequency and can only travel short distances. Gursky identifies this as echolocation and says it is used for navigation (Gursky et al. 2019).[15] "There are 5 main categories of vocalizations: chirps, twitters, choruses, doubles and whistles. Chirps, twitters, and choruses extended from the audible to the ultrasonic range, the doubles and whistles were pure ultrasound (Gursky et al. 2015)."[16]

Archuleta S. 2019 talks about how vocalizations include high pitched whistles and duets. She goes on to say that duets are like chattering melodies and high pitched whistles vary from simple calls to predator warnings; to mob, or ward off a predator.[5] "In the presence of bird predators, individuals vocalize and disperse to hide. When in the presence of a terrestrial predator, such as a snake, individuals "mob" the threat (Archuleta S. 2019)." Sharon Gursky describes mobbing as all the individuals in an area responding to a threat with vocalizations and then each repeats lunging towards and retreating from the predator (Gursky et al. 2006).[17]