Mantled Howler Monkey
From Costa Rica Travel Guide: Vacation and Travel tips
Mantled Howler Monkey
Costa Rica’s most common monkey is the Mantled Howler monkey. Howlers are all dark except for a mantle of light yellowish to reddish fur on the sides and a beard of fur on the chin. Adult howlers will be approximately 20 inches in height and weigh about 11 pounds, with the male a little larger than the female. The males are easily distinguishable by their conspicuous white testicles.
Howlers are diurnal, arboreal and usually travel in troops of up to 45 individuals. Howlers forage by day and when active, mostly stay in the upper levels of the forest although they will come down to the ground to cross open areas or to swim across rivers that cannot be accessed via the canopy. However, howlers are more lethargic than other monkeys and can spend as much as three quarters of the day and all night resting or asleep.
Howlers feed heavily on leaves, but about a third of their diet is comprised of fruit and flowers as well. When eating leaves they are very careful, as leaves are challenging to eat because of the toxins and cellulose they contain. Howlers will eat the leaves of dozens of different tree species, but prefer young leaves since they possess more protein and less toxins and cellulose. During the dry season when food tends to be scarce, howlers have to eat leaves that are less nutritious and more toxic and weak individuals often die at this time of year. Howlers also like figs and avocados, which tend to be infested with insect larvae, but this provides howlers important proteins that their other foods lack.
In the howler world, all males are dominant over all females. The hierarchy between the sexes is unusual especially compared with other primates and most other social mammals. The youngest adult of each sex is dominant and the hierarchy continues according to age, placing the oldest howlers at the bottom of the ladder. High ranking howlers get first choice of food and resting sites and the alpha male mates with all the females of the troop. An alpha female will be dominant for about a year before being replaced, but since there’s less males, the alpha male will be replaced about every 4 years. A new alpha male will typically kill infants less than eight months to a year old-with the majority of them being born from a rival predecessor. Mothers of the murdered young will quickly come into heat again and mate with the new alpha male, becoming pregnant with his own young.
Howler won’t really defend their territory from other howler troops; they usually just stay clear of each other. However, if by chance the two troops do happen to meet, they may contend for the area. Howlers tend to be indifferent, but can become agitated or scared by people and will frequently vent that frustration by urinating or defecating on their observers.
Howler males flick their tongues in order to impress a female, and if the female is impressed, mating takes place and lasts approximately 30 seconds. Gestation lasts about six months and results in a single young or occasionally, twins. The mother gives birth at any time of year, in the treetops, and will pull the baby out of the birth canal herself. The young will be carried, almost exclusively, by the mother and other troop members for the first four or five months. Young, lucky enough to survive the rigors of being a howler, stop nursing all together at a little over a year. Both male and female juveniles will leave their troop at various times in the first few years of life and will wander alone for up to three years until eventually rejoining another howler troop.
Howlers are renowned for their strong vocal cords, which are 25 times larger than that of other similar-sized monkeys. Howlers produce an intimidating, pulsating roar that can last several seconds. These sounds which are usually in response to either neighboring howlers or other similar sounds made by engines, thunder or even the Arenal Volcano. These roars can be heard several kilometers away.
Although deforestation and human disturbance has had a huge impact on the animal life in Costa Rica; the howler, because of its diet and being situated relatively low in the food pyramid, needs less area than most mammals their size and can survive in forest fragments where many other mammals have disappeared.
