Western Tarsier

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Figure 2.1 Illustration of a tarsiers leaping

Source: Natural Science Illustration and Art, 2015

- Communication

Tarsiers, in general, communicate using vocalization, making sound as one of its communication channel. All tarsiers with an exception of Western tarsiers perform ‘duet’ vocalization with their mates. Western tarsiers rather perform a vocalization in the form ‘calling concert’, in which several tarsiers call together in the events of territory defense and advertisement, predation and mating. Whereas Philippine tarsiers have 15 types of vocalizations, Western tarsiers only produce 4 types of vocalization purposely for territorial defense, mating call, warning call and infant’s distress call.

Another channel of communication used by tarsiers is odor. Tarsiers bear scent glands in their faces, abdominal and genital regions, where these glands are rubbed against trees or even against other con-specifics to mark and advertise territory, as well as, to locate and secure mates. In addition, tarsiers do genital inspection, where male sniffs and/or licks the female’s genitalia to know whether the female is on estrus (Flannery, 2007; Gron, 2010; Endangered International Species Inc., 2011).

- Feeding and Foraging Behavior

Tarsiers are carnivorous primates that fed on mainly insects and small vertebrates like, small birds, lizards, frogs and even snakes. Western tarsiers, particularly, C. b. borneanus are reported to consume fruit bat. As for small vertebrates, tarsiers eat almost every part of its preys including bones and feet. Relative to insects, small vertebrates are considerably larger than the tarsiers themselves. However, tarsiers have strong jaws and teeth, as well as, wide mouths to adapt the larger-sized preys. Since tarsiers’ long hind legs and anklebones enable them to leap greater distances of about 4 times their entire body length, they are reported to have the ability to even catch birds in flight, enhanced by the sticky pads on their finger tips.

As discussed earlier, tarsiers are nocturnal animals and their foraging activities occur actively during night. Foraging behavior of tarsiers involves mainly sharing information about food location with con-specifics. For example, when threatened with a predator snake, tarsiers will produce ‘calling concert’ and individual tarsiers in a group will mob the snake, consequently, killing the snake. The predator snakes, hence, becoming their preys (Gron, 2010; Endangered International Species Inc., 2011, McKeighan, 2011).

- Social Behavior

C. b. borneanus is a territorial animal, with an average group size of three consisting of a mated pair and sometimes and additional one male (Endangered Species International Inc., 2011). They usually share a sleeping site and only occupy a small home range (WIldscreen, 2015). This pair would mark their scent with urine and a secretion from a gland on their chest and aggressively chased out any intruders. Some tarsiers are found to be solitary, only coming in contact with other members only for mating, and establishing territories. They often return to the same general area to sleep. There are two types of marks done by the species (Flannery, 2007).

Urine mark: this mark is performed by both sexes and the individual will urinate on a substrate (pole or vine) while scratching the surface of its hindlimb toe claws. The female first does this then the male follows after it.

Scent mark with the epigastric gland: males than females use this more often. This is also done to demarcate territories and was done on the trees.

Besides that, they also involved in social grooming but only between the mother and the infant. The grooming is usually done to remove dead skin and parasites. There were no social grooming observed between the father and infant as it was discussed earlier that the father tend to kill their youngs.

- Mating System and Parental Care

Cephalophachus bancanus borneanus was originally thought to be monogamy where one male and one female formed a mating pair together (Flannery, 2007; Endangered Species International Inc., 2011; McKeighan, 2011). However, recent suggestion was that the mating system generally depends on the prey availability (McKeighan, 2011). C. b. borneanus would be monogamy if the food source is abundance and would be polygyny if the food source is limited. The mating pair would keep their territories with some overlap (Endangered Species International Inc., 2011) in which the males’ territories usually overlapped with some females but neither females’ territories overlapped each other (Flannery, 2007).

Based on the mating system discussed above, it is clear that the parental care is only done by females. Males don not participate in the care of the young, instead it was found that the females guard their offspring from males (Flannery, 2007) as it was seen that captive males have been known to kill their young (McKeighan, 2011).

Females signal their readiness to mate both chemically and visually. During estrus, the females’ labia swelled and become pink, turgid, and shiny (Flannery, 2007; McKeighan, 2011). Besides that, the females would rubbed her vulva against a pole or vine near her territorial borders that are shared with the male. The females did this to secrete vaginal or glandular secretions to communicate the state of their estrus with the male. This behaviour usually lasts for about three (3) seconds. Courtship call would be performed by the male in which he emitted two to three chirrups (very high-pitched sound). This occurred within five minutes of looking at the female. This behaviour is done after the female had displayed her genitals to the male. Each call lasts on average for one second with an interval between each call is on average of three seconds (Flannery, 2007).

Acoording to Flannery (2007), the breeding season for this species was from October to December and the females give birth from January to February, however, recent findings shown that there are no exact period for the breeding season, in short the breeding of this species occurs throughout the year (McKeighan, 2011; Wildscreen, 2015). The gestation period of C. b. borneanus is around 178 to 190 days. It has only one offspring per mating in which its offspring is precocial-born with eyes open and full coat of fur. Its offspring also able to climb trees at only a day old and the leaping ability can be seen after one month of birth. The species can sometimes have