Breech delivery and birth-related behaviors in wild mantled howling monkeys

The breech birth of an infant mantled howling monkey was observed on February 12, 1990. The mother assisted the successful delivery by pulling on the infant's tail and hindleg. No other members of the social group attended the mother or demonstrated any interest in the birth process.     

Use of leaf resources by howling monkeys (Alouatta palliata) and leaf-cutting ants (Atta cephalotes) in the tropical rain forest of Los Tuxtlas,Mexico

Use of leaf resources by a troop of howling monkeys and two colonies of leaf cutting ants was studied for an annual cycle in the rain forest of Los Tuxtlas, Mexico. Howling monkeys spent half their annual foraging time feeding on leaves; leaf-cutting ants spent at least 80% of their recorded foraging time harvesting leaves. Both herbivores preferred young leaves over nature ones, and chemical analysis showed that the protein: fibre ratio of the leaves used was correlated with these preferences. Howling monkeys used 34 tree species as leaf sources. Leaf-cutting ants used 40 plant species of which 38 were trees. Eighteen species used by Alouatta were also used by Atta; species of Moraceae and Lauraceae were among the most important in their foraging preferences. The plant species used by monkeys and ants occurred at low densities (? 4.0 ind/ha). The seasonal production of leaves, the high density of leaf-cutting ant colonies at the study site, and the high amounts of young foliage harvested by the ants from tree species, and individual trees used by howling monkeys as sources of young leaves suggest that the foraging activities of Atta may represent a significant pressure upon leaf resources available to Alouatta.     

Feeding and general activity patterns of a howler monkey (Alouatta palliata) troop living in a forest fragment at Los Tuxtlas,Mexico

The feeding behavior and general activity patterns of a howler monkey troop living in a 3.6 ha forest fragment were studied at Los Tuxtlas, Mexico, for an annual cycle. Monthly samples of their feeding behavior indicated that they used 52 species of 24 plant families as sources of food. Of these, 67% were trees, which accounted for 96% of total feeding time recorded. Ten species of Moraceae, Cecropiaceae, Anacrdiaceae. and Sapotaceae contributed to 70% of the trees used and to almost 90% of feeding time. The number of plant species used per monthly record varied from 7 to 31 with an average of 19.9 species. Young leaves and ripe fruit were the principal items in the monthly diet of howlers and average percent of time spent consuming these plant parts was 46.7% and 34.8%, respectively. The use of tree species was found to be associated to their importance value and to their pattern of spatial dispersal in the study site. Availability of young leaves was fairly constant from month to month, but it presented a seasonal pattern, and there was a significantly lower number of tree species bearing ripe fruit through the year with brief pulses of production. The monthly activity pattern was found to be related to variations in the availability of young leaves and ripe fruit as well as to the values of the intermonthly overlap in plant species used. Resting and feeding presented a bimodal pattern of occurrence throughout the day that seemed to be related to variations in maximum ambient temperatures. Results are discussed in light of the small size and shape of the forest fragment inhabited by the howler troop. Am. J. Primatol. 48:167–183, 1999. © 1999 Wiley‐Liss, Inc.     

Population trends of the mantled howler groups of La Pacifica,Guanacaste, Costa Rica

A complete survey of La Pacifica in Guanacaste Province, Costa Rica was conducted in July 1984 in order to determine whether the howler (Alouatta palliata) population had declined since 1972 as a result of deforestation. During the 6-day survey, 257 howlers were located, representing 16 different social groupings and nine solitary animals. The total number of howlers, the number and location of groups, and the age-sex composition were very similar to a 1972–1976 survey of the same population. Age-sex composition of La Pacifica howler groups was similar to those of another population of mantled howlers in Costa Rica and of populations in Mexico and in Panama, although La Pacifica had a higher mean number of adult females per group. There was no evidence to support the hypothesis that the La Pacifica howler population has declined in recent times.     

Resource availability and habitat use by mantled howling monkeys in a Nicaraguan coffee plantation: can agroforests serve as core habitat for a forest mammal?

Although shade coffee plantations are potentially valuable habitats for wildlife conservation, little information exists on the extent to which they provide resident wildlife populations with resources necessary for survival and reproduction. A 14-month study of the ecology of mantled howling monkeys Alouatta palliata living in a Nicaraguan shade coffee plantation was therefore conducted. Trees were surveyed at randomly located enumeration points in the coffee plantation and monitored for phenophase production to characterize resource availability. Day-long focal animal follows were used to characterize the ranging and habitat preferences of the howlers. The study site had a diverse canopy, with over 60 tree species providing shade for coffee cultivation; high tree diversity ensured year-round availability of the howlers' preferred foods. Howlers did not avoid feeding or ranging in areas of shade coffee cultivation. However, when foraging in coffee they favored large shade trees for feeding and were less likely to use areas of shade coffee with small trees and fewer arboreal pathways. Results suggest, in conjunction with controls on hunting and protection of nearby forests, that shade coffee can serve as alternate wildlife habitat and corridors between forest fragments for howling monkeys and possibly other forest mammals. Specific management recommendations to improve the conservation value of shade coffee for primates are made and the potential role of coffee plantations in primate conservation at a regional scale are discussed.     

Reproduction and population growth in free-ranging mantled howling monkeys

Free-ranging mantled howling monkey (Alouatta palliata Gray) females experienced a regular estrus cycle averaging 16.3 days, demonstrated sexual skin changes, and participated in multiple matings before becoming pregnant. Gestation averaged 186 days. The average interval between births was 22.5 months. Sexual maturity occurred at approximately 36 and 42 months for females and males, respectively. Female age at first birth was about 3½ years. Births were scattered during some years and clustered during others. The age, rank, and parity of the females affected infant survival. More female than male infants survived to one year of age. Increased population size was the result of immigration rather than births.     

Patterns of mineral lick visitation by spider monkeys and howler monkeys in Amazonia: are licks perceived as risky areas?

Mineral licks--also known as \"salados,\" \"saladeros,\" or \"collpas\"--are specific sites in tropical and temperate ecosystems where a large diversity of mammals and birds come regularly to feed on soil. Although the reasons for vertebrate geophagy are not completely understood, animals are argued to obtain a variety of nutritional and health benefits from the ingestion of soil at mineral licks. We studied the temporal patterns of mineral lick use by white-bellied spider monkey (Ateles belzebuth) and red howler monkey (Alouatta seniculus) in a lowland rain forest in Amazonian Ecuador. Using camera and video traps at four different mineral licks, combined with behavioral follows of one group of spider monkeys, we documented rates of mineral lick visitation by both primate species and the relative frequency and intensity of mineral lick use by spider monkeys. On the basis of 1,612 days and 888 nights of mineral lick monitoring, we found that A. belzebuth and A. seniculus both visit mineral licks frequently throughout the year (on average ～14% of days for both species), and mineral lick visitation was influenced by short-term environmental conditions (e.g. sunny and dry weather). For spider monkeys, the area surrounding the lick was also the most frequently and most intensively used region within the group's home range. The fact that spider monkeys spent long periods at the lick area before coming to the ground to obtain soil, and the fact that both species visited the lick preferentially during dry sunny conditions (when predator detectability is presumed to be relatively high) and visited simultaneously more often than expected by chance, together suggest that licks are indeed perceived as risky areas by these primates. We suggest that howler and spider monkeys employ behavioral strategies aimed at minimizing the probability of predation while visiting the forest floor at risky mineral lick sites.     

Some observations on the present distribution and conservation of Alouatta and Ateles in Southern Mexico

Some information on the past and present distribution of Alouatta and Ateles in southern Mexico and on the impact of habitat destruction on their future existence is presented. Three surveys of primate populations and forest habitats were carried out between 1981 and 1983 in southeastern Mexico. Rapid destruction of the forest is reducing the number of forested areas where Alouatta and Ateles can exist and co-occur. Illegal hunting of the two primates also contributes to their rapid decline. Alouatta and Ateles live a precarious existence in a few large and small islands of forest, and efforts are needed to set aside some of these areas as reserves so that their future survival is ensured.     

Brief report: Infant-killing and infant disappearance following male takeovers in a group of free-ranging howling monkeys (Alouatta palliata) in Costa Rica

Events surrounding an infant-killing following a male takeover are described for a group of free-ranging howling monkeys in Costa Rica, and additional evidence is presented for infant disappearances following three previous male takeovers. Infant-killing is best interpreted in this context as a male reproductive strategy, as infant-killing did effectively shorten the interbirth interval, and only infants of high-ranking females died or disappeared following a male takeover. Due to the exclusive access of the dominant male to high-ranking estrous females, an incoming male who had lived as a peripheral male before taking over the group would run little risk of eliminating his own offspring in the course of killing the offspring of high-ranking females.     

Risk factors connected to gastrointestinal parasites in mantled Alouatta palliata mexicana and black howler monkeys Alouatta pigra living in continuous and in fragmented rainforests in Mexico

In this study we document the prevalence of gastrointestinal parasites (helminths and protozoans) found in fecal samples of populations of Alouatta palliata mexicana and of A.pigra in Los Tuxtlas and in Palenque,southeast Mexico,and its relation to habitat condition,sex/age and season.Nineteen parasite morphotypes were detected in the fecal samples from populations of the two howler monkeys,of which 58％ were shared by both species.When considering all parasite species,populations of the two howler species were more likely to be parasitized in fragmented habitat compared to continuous habitat.Individuals of both howler monkey species that lived in fragmented habitat had a higher prevalence of Controrchis biliophilus.A.p.mexicana individuals had a higher prevalence of Trypanoxyuris minutus than A.pigra,probably the result of the larger group sizes found in the former species,and T.minutus was more likely to be found in A.palliata individuals that lived in fragmented habitat.Adult A.p.mexicana males had a higher risk of being parasitized compared to adult females,but these differences were not detected in A.pigra.Parasite species such as Entamoeba sp.,Nematoda sp.28.Nematoda sp.B and Parabronema sp.where only found during the wet season m both howler monkey species.Populations of both howler monkey species had a higher prevalence of Nematoda sp.A in the wet season and Ascaridae eggs were only detected during the wet season in A.pigra.Other parasites detected displayed no clear seasonal pattern.