Population Size and Characteristics of Alouatta pigra Before and After a Major Hurricane

Abstract

Although some environmental risks and resources are known to affect the evolution of primate social groups, we know little about the effect of major natural disturbances on primate populations. Hurricane Iris hit the Monkey River watershed in southern Belize in October 2001, presenting a unique opportunity to document the effects of a natural disaster under circumstances wherein some pre-hurricane data were available. We measured the characteristics of the population of black howlers in the affected forest 3.5 years after the storm and compared the population data with pre-hurricane data from a 52-ha study area, that may represent the larger continuous riverine forest and from which all monkeys were known. From February to May 2004, we sampled 28.77 km 2 of the 96-km 2 forest fragment via five transects walked 12 times each. From these data we estimate that the population in the watershed has dropped from 9784 to 1181 monkeys, a reduction of 88%, reflected by both a 79% drop in the number of social groups and a 38% reduction in group size. Before the storm, 75% of the social groups were multimale; after the storm, 74% of the groups were unimale. While the ratio of adult females to males improved slightly, the ratio of adults to immatures, and adult females to immatures more than doubled, indicating a much lower potential for growth. These data provide a quantitative assessment of how a major natural disturbance can affect a primate population.

Current status of the habitat and population of the black howler monkey (Alouatta pigra) in Balancán, Tabasco, Mexico

“…Returning to the issue of ecological density, in Belize Ostro et al [2001] and Pavelka et al [2007] have suggested that high densities are owing to the frequent occurrence of multimale and multifemale social units as opposed to unimale or other types of social units. However, even though this social unit was also very frequent in Balancán, ecological densities in Balancán were much lower.…”

“…Subsequently, we might predict changes in demography and distribution, including troop fission, troop migrations, expulsions of both sexes, death of both adults and immature individuals, and eventually a decrease in overall abundance [Brockett et al, 2000;Crockett & Eisenberg, 1987;Ostro et al, 2001;Pavelka et al, 2003Pavelka et al, , 2007.…”

“…In these studies, the monkeys survive and have exhibited unusual behaviors, such as feeding and ranging on the ground and drinking water from nontypical sources, including those located on the ground [A. caraya: Bicca-Marques & Calegaro-Marques, 1994; A. pigra: Pozo-Montuy & Serio-Silva, 2007; A. palliata mexicana: Serio-Silva & Rico-Gray, 2000; A. fusca : Steinmentz, 2001]. Additionally, changes in group membership and population decline have been documented in A. pigra after traumatic events such as hurricanes and translocations [Ostro et al, 2001;Pavelka et al, 2007]. However, at present we have little detailed information on specific factors that may influence the abundance and persistence of A. pigra living in fragmented habitats, such as size of the fragment, degree of isolation among fragments, abundance and composition of food sources, and distance to roads and human settlement.…”

Parasites, Primates, and Ant-Plants: Clues to the Life Cycle of Controrchis spp. in Black Howler Monkeys (Alouatta pigra) in Southern Belize

“…Cecropia peltata is widespread throughout the neotropics and, as a shade-intolerant pioneer species, is most abundant in disturbed and open areas. Cecropia peltata is particularly important in the diet of the Monkey River black howler population because the forest was severely damaged by Hurricane Iris in 2001 (Pavelka et al, 2003(Pavelka et al, , 2007.…”

Hurricanes and coastlines: The role of natural disasters in the speciation of howler monkeys

“…When a group was heard vocalising we estimated the distance in metres and direction of the group. In previous studies (Pavelka et al, 2007), we found this overestimated the distance by 0.5 to 1.0 km, therefore we took this into account in our analysis here. All spatial data (visual and vocal contacts, confirmations of presence from local informants, and track information) were entered into ArcMap software (v.10.1).…”