General Characteristics

Behavior

Social Structure

Mating Systems

References

Web Links

General Characteristics

Biological Status

The mantled howler monkey (alouatta palliata) is currently on the lower risk status according to the Convention of International Trade in Endangered Species (CITES) guidelines.

Countries of existence

Mantled howlers are located through southern Mexico, southern Guatemala, and south through the rest of Central America to the west coast of Colombia and Ecuador (DeVore 1965; cited in Broekema, 1999)

Physical Characteristics

Alouatta palliata are dimorphic animals. The male howlers are large and stocky with black fur and usually have long, yellow-brown fur saddles on their sides. The face is mostly hairless and accompanied by a thick beard, which gives reason for the name "mantled." When males reach maturity, they finish developing their prominent white scrotums and usually have a much longer beards than the females. During estrus the female usually experiences color changes in her genital area from white to pink (Glander, 1980). Adult females typically weigh less and have a smaller body frame than males.

Male howlers usually weigh around 4.5 - 8 kilograms, while females weigh 3.1 - 6 kilograms. The head and body length for males varies from 508 - 675 mm, while the female head and body length ranges from 481 - 632 mm. Both male and females have a prehensile tail- the tail is able to grasp things by wrapping around them- that ranges from 545 - 655 mm (cited in Broekema, 1999).

Habitat

The alouatta palliata is an arboreal animal, which means that they are adapted to a life in trees. Howlers utilize many different levels of their rainforest environment, but most often maintain positions in the middle to upper canopy (Mittermeier, 1988). Mantled howlers live in a large variety of forests that includes- evergreen rainforest, cloud forest, dry lowland deciduous forest, and coastal mangrove forest (cited in Broekema, 1999).

Diet

Mantled howlers eat a varied diet consisting of mature and young leaves, petioles, pulvini, buds, flowers, fruits, seeds, stems and twigs (cited in Broekema, 1999). At certain times during the year, fruits can constitute up to 95% of their total diet, but this is mainly during the wet season, or when the group is located near a fruit tree. Leaves, however, are the principle source of protein, and fruits offer the principle source of easy energy for howlers. Fruits are seasonal so most of the feeding time for howlers is spent consuming leaves. Estrada et al. reported that trees (leaves) accounted for 67 % of their total diet and 96 % of their total feeding time, while the other 33 % consisted of vines and fruits. He also observed that howlers displayed a preference for young leaves over mature leaves (1999). Yet, a study performed by Katherine Milton (1980) shows evidence that howlers prefer to eat a balanced diet of both leaves and fruits, yet this rarely occurs because of the seasonal nature of most fruits they consume (cited in Broekema, 1999). Young leaves eaten by howlers are richer in protein content per dry weight; contain a higher proportion of digestible nutrients that possess more digestible energy and less fiber than mature leaves.

Alouatta palliata have long colons and a slow passage rate of food through their intestines to permit sufficient fermentation by celluloytic microorganisms. Adaptations to leaf-eating in this species are mainly behavioral. These behavioral adaptations include a selective diet, preferably a mixture of fruit and immature leaves, using a wide range of species which are not the most common ones in the groups home range, and activity patterns that optimize the use of their resources. This explains why much of their behavior is concentrated on conserving energy. It takes a long time for them to process food and the food is still low in nutritional value. They also have to store enough energy to compensate for the days they cannot travel enough to find healthier foods. These days are more likely to result from periods of drought in the dry season.

Alouatta palliata eat a wide range of plant life. They need to consume up to 15 % of their total body weight in leaves and fruits everyday to satisfy their nutritional needs. Estrada et al. observed a troop of howlers using 52 species of plants (24 plant families) as their source of food. Ten species of Moraceae,Cecropiaceae,

Anacrdiaceae, and Sapotaceae contributed to 70 % of the trees used and to almost 90 % of their total feeding time. The number of plant species used per month varied from 7 to 31. This monthly pattern is also related to seasonal effects in their environment. Most of the feeding was related to the area the howlers traveled in that particular day or month. If there was an abundance of one resource, the howlers would remain in this area until they satisfied themselves with this resource. Estrada et al. note that the increase in the number of plant species howlers will consume is most likely related to the increasing depletion of their natural habitat, the rainforest, by humans. Howlers are forced to adapt and eat food species they may not normally consume (1999).

R. A. Mittermeier's study on alouatta palliata observed that howlers tend to search for resting places with lots of food resources near by, because they do not like traveling in the rainy or windy weather that accompanies many months of the rainforest wet season. One of the biggest problems howlers have with their poor nutritional level doesn't always come from the lack of available food resources, but the lack of available (optimal) feeding times during bad weather (1973).

Holwer monkeys obtain most of their water from their food or by licking rain from the leaves that eat. Yet, when water is scarce, they will drink from arboreal reservoirs of collected rainwater (1973).

Life Development

Howler monkey infants are completely dependent on the care and protection from their mothers for at least six months. Young infants are in constant contact with their mothers during this period. Once the infant reaches six months old, it can usually start moving around without the supervision of its mother. This is the juvenile period for the infant . Both male and female juveniles are allowed to remain with the troop until they are gradually weaned from the group's care and assistance(Mittermeier 1973).

This sub-adult period that follows weaning is usually when male howlers form into solitary groups as they disperse from their own troops. The female sub-adults do not always disperse as early as the male howlers. It depends on the relatedness of the alpha male to that young female during that time. The females disperse quickly if the alpha male is related to them. This way, the female will not come into estrus around her father. They do this to protect against any possibility of inbreeding in their group. Usually, the alpha male's tenure is so short that it never gets the opportunity to mate with one of it's own offspring. When females disperse, they are usually picked up by another troop nearby. Males need to wait for their sexual maturity before they can create or take over their own group, and this usually occurs at around three years of age; whereas, the females usually have their first birth by four years of age. Although the mortality rate for males is much higher for females, the observed life span is longer for males than for females. Howlers have an estimated life expectancy of 16.6 years for males and 15.5 for females (Froehlich et al. 1981). This is probably a result of the strongest male surviving all the earlier predators and dangers and thus becoming the foremost howler.

Locomotion

Alouatta palliata use all four limbs for movement (quadreupedal walking and climbing). They can use their prehensile tail to hang from tree branches while feeding or traveling. This tail enables howlers to save a lot of energy when resting on branches and feeding. When feeding, the tail serves to provide another, longer, hand to grab food with while supporting the rest of its body with limbs.

Howlers walk almost 70 % of the time during their movement, using their front and rear limbs. In some instance they can run through the canopy, but they usually try to conserve energy. On the ground, howlers appear uncomfortable because their limbs are unstable on the flat ground. They rarely come on the ground, usually only to cross an open area in the forest or obtain water (cited in Broekema, 1999).

Predators

Currently, alouatta palliata's main predators are the humans destroying thousands of acres of rain forest everyday to raise beef cattle or get wood supplies. They are also subject to many bot-fly parasites that destroy their health gradually, but dangerously. Leopards and other various cats of the rainforest are also a big predating factor. Birds of prey are able to attack and kill the young, but not the older howler. Still, forest depletion and bad nutritional health, which is a result of the forest depletion in most case, are the main concerns for the howler right now.

If you have any questions or concerns about this page, please contact Lucas Spivey at Davidson College or Dr. Verna Case at Davidson College. This website is only meant to be a collaboration of other researchers findings to describe the natural history of mantled howler monkeys (alouatta palliata) to a Davidson College Animal Behavior Class, Psych/Bio 323. I am no expert on alouatta palliata and do not intend to claim that any of this information is from my own research.