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Howler Monkey Species (howler + monkey_species)

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Life Sciences100%

Selected Abstracts

Impact of yellow fever outbreaks on two howler monkey species (Alouatta guariba clamitans and A. caraya) in Misiones, Argentina

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 6 2010
Ingrid Holzmann
Abstract Two yellow fever outbreaks (YFOs) ocurred in northeastern Argentina between November 2007 and October 2008, seriously affecting populations of two howler monkey species: the brown howler Alouatta guariba clamitans and the black howler Alouatta caraya. Both howlers live syntopically in El Piñalito Provincial Park, Misiones, where four groups (36 individuals) were studied since January 2005. The first dead howlers were found on January 20, 2008, in El Piñalito. Systematic searches found 14 dead howlers within the area (12 from the study groups and two from neighboring groups), with only two young seen on January 25, 2008, and none found since up to December 2008. In October 2008, another YFO hit howler monkey populations from El Soberbio, Misiones. Overall, 59 howlers were found dead in Misiones from November 2007 to December 2008. Thanks to the alert of the howler's death in El Piñalito, a prompt human vaccination campaign started in the area. Wild howler monkey populations from both species are in a delicate situation in Misiones, especially the brown howler, an already endangered species in Argentina and endemic to the Atlantic Forest. If we add the recurrence of YFOs to the reduction of suitable habitat to small fragments, it could be only a matter of time until howler populations disappear from the Upper Paraná Atlantic Forest in Misiones. Am. J. Primatol. 72:475,480, 2010. © 2010 Wiley-Liss, Inc. [source]

Are howler monkey species ecologically equivalent?

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 2 2010
Alouatta caraya, Trophic niche overlap in syntopic Alouatta guariba clamitans
Abstract 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 (CH). 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%; CH=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. [source]

Seed Dispersal and Ingestion of Insect-Infested Seeds by Black Howler Monkeys in Flooded Forests of the Parana River, Argentina

BIOTROPICA, Issue 4 2008
Susana Patricia Bravo
ABSTRACT All howler monkey species (Alouatta spp.) have a folivorous,frugivorous diet. Howler monkeys are reported to be seed dispersers in several areas, including black howlers (Alouatta caraya), which are important seed dispersers in northern Argentinean forests. The goal of this work was to study the three-way interaction between insects, seeds, and black howlers, and assess the functional significance of this tri-trophic interaction for seed dispersal. I determined through direct observation that fruits of species with a high proportion of insect infestation were important components of howler monkey diet. Ocotea diospyrifolia seeds from fresh faeces of black howlers contained dead larvae, but seeds were still able to germinate. Seeds in which larvae had reached an advanced stage of development did not germinate. Larvae of infested Eugenia punicifolia fruits were killed by digestion when they occurred in the pulp early in the fruiting season, but were dispersed alive with seeds later in the season. Banara arguta fruits contained both healthy and infested seeds; infested seeds were destroyed during digestion, while healthy seeds were dispersed. Black howlers' ingestion of infested fruits could result in the: (1) killing of larvae and dispersion of healthy seeds; (2) spread of larvae; or (3) destruction of infested seeds. This will depend on the relationship between the time at which fruit is consumed by black howlers, the time at which insect infestation occurs, and also probably on the hardness of the seed coat and the seed,insect size ratio. RESUMEN Todas las especies de monos aulladores (Alouatta spp.), poseen dietas folívoro-frugívoras. Los monos aulladores han sido reportados en varias ocasiones como dispersores de semillas, incluído Alouatta caraya, el cual es un importante dispersor de semillas en las selvas del norte de Argentina. El objetivo de este trabajo fue estudiar la interacción triple insectos,semillas,Alouatta caraya y determinar su significado funcional para el proceso de dispersión de semillas. Se determinó por observación directa que el consumo de frutas de las especies que poseían una alta infestación por insectos representaba una alta proporción de la dieta. Las semillas de Ocotea diospyrifolia colectadas de heces frescas de A. caraya contenían larvas muertas y su capacidad germinativa intacta. Las semillas en las cuales las larvas habían alcanzado un avanzado estado de desarrollo ya no podían germinar. Al principio de la estación de fructificación las larvas que infestaban las frutas de Eugenia punicifolia se encontraban en la pulpa y morían al ser ingeridas por A. caraya, pero cuando, avanzada la fructificación, las larvas se movían hacia las semillas, eran dispersadas vivas dentro de las mismas. Las frutas de Banara arguta contenían tanto semillas infestadas como sanas; las infestadas fueron destruidas por la digestión mientras que las sanas eran dispersadas. La ingestión de frutas infestadas por parte de A. caraya puede llevar a: (1) la muerte de las larvas y la dispersión de semillas sanas, (2) la dispersión de larvas o (3) la destrucción de las semillas infestadas. Esto depende de la relación entre el tiempo en que es ingerida la fruta por A. caraya y el tiempo en que se produjo la infestación, probablemente también sea importante la dureza de la cubierta de la semilla y la relación entre el tamaño de la semilla y el de la larva. [source]