Gastrointestinal parasites of Howler monkeys (Alouatta palliata) inhabiting the fragmented landscape of the Santa Marta mountain range,Veracruz, Mexico

In recent years populations of howler monkeys (Alouatta palliata) in southeastern Mexico have decreased substantially due to the transformation and loss of natural habitats. This is especially evident in the Santa Marta mountain range, Veracruz, Mexico where several studies have evaluated the impact of fragmentation on howler monkey populations in order to propose management programs for their conservation. The conditions generated by fragmentation likely change the rates of parasitic infection and could decrease howler survival. In this study, gastrointestinal parasite species richness, prevalence, and egg density of infection were determined in howler groups inhabiting five forest fragments at the Santa Marta mountain range. Two hundred and seventy‐eight fresh fecal samples were collected between October 2002 and April 2003. Three parasite species were found during the dry and the wet season in all forest fragments sampled: one unidentified species of Eimeriidae; Trypanoxyuris minutus (Oxyuridae); and Controrchis biliophilus (Dicrocoeliidae). Both the prevalence of T. minutus and infection density for all parasites differed between seasons and fragments (the largest fragment consistently differed from other fragments). Host density, distance to the nearest town, fragment size, fragment shape, and total basal area of food trees explained parasite prevalence, but each species had a different pattern. Although parasite richness was lower, prevalence and density were higher than values reported for howlers in conserved forests. These results suggest that the establishment of biological corridors and animal translocation programs must take into account the parasite ecology of each fragment to avoid higher infection rates and preclude potential consequent mortality. Am. J. Primatol. 72:539–548, 2010. © 2010 Wiley‐Liss, Inc.     

Differences in diet and activity pattern between two groups of Alouatta palliata associated with the availability of big trees and fruit of top food taxa

The threat that forest fragmentation and habitat loss presents for several Alouatta taxa requires us to determine the key elements that may promote the persistence of howler monkeys in forest fragments and to evaluate how changes in the availability of these elements may affect their future conservation prospects. In this study we analyzed the relationship between the availability of both big trees of top food taxa (BTTFT) (diameter at breast height>60) and fruit of top food taxa (FrTFT) in the home ranges of two groups of Alouatta palliata mexicana occupying different forest fragments in Los Tuxtlas, Mexico, and their diet and activity pattern. Both study groups preferred big trees for feeding and the group with lower availability of BTTFT in their home range fed from more, smaller food sources. Furthermore, both study groups also increased the number of food sources when their consumption of fruit decreased, and the group with lower availability of FrTFT in their home range fed from more food sources. The increase in the number of food sources used under such conditions, in turn, set up a process of higher foraging effort and lower rest. In summary, our results support other studies that suggest that the availability of big trees and fruit may be two important elements influencing the persistence of howler monkeys in forest fragments. Am. J. Primatol. 71:654–662, 2009. © 2009 Wiley‐Liss, Inc.     

Are howler monkey species ecologically equivalent? Trophic niche overlap in syntopic Alouatta guariba clamitans and Alouatta caraya

According to the principle of competitive exclusion, niche differentiation allows the stable coexistence of closely related species. We analyzed dietary profile and diversity, and dietary overlap between syntopic brown howlers (BR; Alouatta guariba clamitans) and black and gold howlers (BLG; A. caraya) in the Atlantic Forest of NE Argentina, with the objective of evaluating the degree of trophic niche overlap and potential interspecific competition for food. During 12 months, we collected data on feeding behavior of two groups of each howler species using the scan sampling method, together with data on food availability. Both at the group‐ and species‐level, we analyzed feeding behavior in terms of monthly percentages of time spent feeding on each food type and specific food item, dietary diversity (Shannon index H′), and we estimated dietary overlap using the percentage index and the Morisita–Horn index (C_H). Across months, both howlers showed species‐specific preferences for certain food items, and BLG had a more diverse diet (mean±SE, H′=2.77±0.08) than BR (H′=2.39±0.09). However, diets of both species overlapped extensively (percentage index=45.64±2.97%; C_H=0.6±0.05) and diets of conspecific groups did not overlap more than diets of groups of different species. Given their high degree of trophic overlap, syntopic BR and BLG meet one of the conditions necessary for interspecific food competition to occur. Although at present we lack direct evidence for interspecific competition in these howler species, we conclude that high levels of niche overlap may have an important role in maintaining the essentially parapatric distribution of howler species throughout the Neotropics. Am. J. Primatol. 72:173–186, 2010. © 2009 Wiley‐Liss, Inc.     

Growth of Mantled Howler Groups in a Regenerating Costa Rican Dry Forest

We examined population dynamics in mantled howlers (Alouatta palliata palliata) in a regenerating tropical dry forest in Santa Rosa National Park (SRNP), Costa Rica. The population has grown at a rate of about 7% per annum during the past decade. The growth in numbers from 342 in 1984 to 554 in 1992 reflects an increase in the number of groups (from 25 to 34) and a slight increase in their average size (from 13.6 to 16.3). Population density has increased from 4.9 to 7.9 individuals per km ². Santa Rosa's population density and group compositions are similar to those at several other mantled howler sites, but densities of mantled howlers are much higher at two other well-studied sites: La Pacifica and Barro Colorado Island (BCI). We relate the low density of howlers at Santa Rosa to local historical and ecological factors. Howler populations at high and low densities differ in average group size and sex ratio. At high population densities, groups are larger and include more adult females. The number of male howlers per group appears to be more strictly limited and less variable than the number of females is. However, there is greater variation in male group membership at Santa Rosa than at La Pacifica or BCI, and at Santa Rosa there are more generating forests available into which males and females can disperse and form new groups. We present case studies describing two ways in which new howler groups are formed, and we suggest that, compared to females and compared to males at high density sites, males are relatively advantaged in the uncrowded habitats at Santa Rosa and other low density sites.     

Vox alouattinae: A preliminary survey of the acoustic characteristics of long-distance calls of howling monkeys

This survey of the acoustic characteristics of howling monkey loud calls, covering six of the seven members of the genus Alouattaand presenting audiospectrograms of roars from two species for the first time, suggests that the genus consists of at least two groups: a monotypic palliatagroup, including all subspecies, and a non-palliatagroup, including belzebul, caraya, fusca, pigra,and seniculus.The non-palliatagroup vocalizes continuously for sustained periods of time;their loud calls exhibit a wide bandwidth relative to the calls of the palliatagroup, with emphasized frequencies generally in the range 300- 2000 Hz. The palliatagroup does not vocalize continuously, their vocal bouts being significantly shorter than those of the non-palliataforms. The emphasized frequencies are normally restricted to 300- 1000 Hz, with little acoustic energy in higher frequencies. This bipartite classification places pigrawithin the non-palliatagroup father than with parapatric palliata,which may have important phylogenetic implications. Further, the classification suggests two modes of employing the highly derived howler vocal tract to produce loud calls within the portion of the ambient noise spectrum favorable to long- distance transmission of sound. Finally, I discuss the constraints placed by environmental acoustics on strategies for long- distance communication, hypothesized modes of vocal production, and the use of acoustic studies for phylogenetic reconstruction. Each discussion suggests projects, some already under way, that could elucidate the determinants of variations in communicative patterns within specific social and physical environments.     

Activity pattern of the brown howler monkeyAlouatta fusca,Geoffroy 1812, in a forest fragment of southeastern Brazil

A group of six brown howlers was studied during a year in the Santa Genebra Reserve, a 250ha-forest fragment near the city of Campinas, State of São Paulo, southeastern Brasil. On average, the group rested for 64% of the daylight hours and feeding and moving occupied 18% and 13% of this period, respectively. A greater proportion of time was spent feeding during dry season (24%) than the wet season (15%), and the reverse observed for time spent resting (59% and 69% of the group's daylight hours during dry and wet seasons, respectively). The increase of resting and decrease of feeding during wet season were related to the percentage of leaves in the group's diet, high even during the fruiting season (wet season). However, additional data of other groups are necessary to draw conclusions about the effects of habitat disturbance on this population.     

Adoption in free-ranging red howler monkeys,Alouatta seniculus of Venezuela

This report describes three cases of infant adoption in red howler monkeys (Alouatta seniculus) of Venezuela. In one case, a lactating female adopted her infant granddaughter after the infant's mother disappeared and the infant survived for the next 25 months. In the second case, an adult female adopted her infant granddaughter for nine days while the infant's mother was still a group member. In the third case, a nulliparous female temporarily adopted an infant from a neighboring group. The details and the possible reasons for these adoption are described.     

Skeletal Pathologies in a Population of Alouatta palliata: Behavioral, Ecological, and Evolutionary Implications

We examined the pathological conditions in a sample of 200 skulls of Alouatta palliata recovered from Barro Colorado Island (BCI), Panama, to investigate the prevalence of disease and injury in a free-ranging monkey population. Forty-five individuals (22.5%) have some type of nondental pathological condition, indicating that illness and injury are relatively common in this population. Ten individuals, all older adult males, exhibit clear signs of antemortem trauma in the form of healed fractures. We attribute the trauma primarily to fighting, and its frequency (16.4% of adult males) contradicts previous assertions that BCI howlers are nonaggressive. Nine of the 37 scorable immature individuals (24%) have signs of a larval infestation, supporting the suggestion that ectoparasites play an important role in BCI howler mortality. Other pathological conditions in the sample include shifted muscle attachments, periostitis, arthritis, neoplasm, periapical abscesses, and facial deformity, as well as various dental abnormalities.     

Infant hybrids in a newly formed mixed-species group of howler monkeys (Alouatta guariba clamitans and Alouatta caraya) in northeastern Argentina

Natural hybridisation between species has been reported in several primate taxa. In the Neotropics, there is increasing evidence of this phenomenon in howler monkeys (genus Alouatta) in contact zones between species. We describe the first known case of formation of a mixed-species group, and two cases of putative infant hybrids between the brown howler (Alouatta guariba clamitans) and the black howler (A. caraya) in Misiones, Argentina. For 2 years, we followed a group consisting of one adult male and two adult female brown howlers and one adult female black howler. The adult female black howler was observed to copulate twice with brown howler males, and never with black howler males. In December 2006, this female was carrying an infant with a hybrid morphotype. This infant died at approximately 1.5 months of age. In November 2007, the same female had another putative hybrid newborn. This infant male died together with all members of his group during a yellow fever outbreak in early 2008. The lower frequency of mixed-species groups and hybrids at our site compared with other contact zones reported in the literature, suggests that the incidence of natural hybridisation between howler species differs depending on local factors such as population demography and landscape fragmentation.