Mantled Howler (Alouatta palliata) Arboreal Pathway Networks: Relative Impacts of Resource Availability and Forest Structure

Abstract

Numerous studies have concluded that primates move about their environments in a nonrandom manner, frequently traveling between consecutive foraging sites along relatively straight-line paths. However, primates do not always take the most direct path between resources, and a number of species have been observed to travel repeatedly along a network of the same arboreal pathways. In this study, I used spatially explicit techniques to examine quantitatively what mantled howler monkey groups on Barro Colorado Island, Panama, accomplish by selecting nonlinear paths between resources and by repeatedly using the same paths within an arboreal network. Results show that chosen arboreal paths between sites where foraging occurred have higher levels of resource availability and canopy connectivity than comparable straight-line paths between the same sites. When comparing the relative importance of these factors, autologistic models of pathway choice indicate that though canopy connectivity is related to the location of repeatedly used arboreal pathway networks, the most statistically significant predictor is resource availability (both on a path and within a visual detection distance of a path). These results provide support for the hypothesis that repeated use of arboreal pathway networks aids in resource monitoring and acquisition. In addition, statistical models developed from 1 primary focal group's travel patterns had high predictive value when employed to generate likely locations for arboreal pathways in the home ranges of 3 neighboring groups. This finding has important implications for studies of primate habitat use and seed dispersal, as it suggests that different groups consistently use similar characteristics when deciding on travel paths.

Howler Monkeys

“…Studies that failed to demonstrate a positive relationship for howlers in general (among other folivorous primates) attributed this result to a weak or absent food competition and/or a reliance on alternative, fallback food items, such as mature leaves (Isbell 1991 ;Janson and Goldsmith 1995 ). A signifi cant relationship was found in four out of seven studies that evaluated this aspect at the species level, particularly in A. palliata (Larose 1996 ;Williams-Guilén 2003 ;Hopkins 2011 ), the howler monkey that forms the largest groups and presents the wider variation in group size (see . The fourth study that found this relationship involved a population of A. pigra at the Community Baboon Sanctuary (Ostro et al 1999a ).…”

“…These studies tested predictions such as (1) howlers minimize ("optimize") the distance traveled by using straightline movements to the nearest available tree of a few target species; (2) they monitor the availability of large and/or preferred food sources, and exploit the most productive trees available; (3) they repeatedly use travel pathways that include large trees that provide more food and from where they enjoy enhanced visibility of the surroundings, thereby reducing the need for memory load; and (4) they use these tall (high-visibility) trees where different routes intersect as nodes or decision points, an indication of a topological mental representation ( A. caraya : Ventura 2004( A. caraya : Ventura , 2005A. palliata : Garber and Jelinek 2006 ;Hopkins 2008Hopkins , 2011A. g. clamitans : Pereira 2008 ).…”

“…However, they used "less-direct" routes (traveled longer distances) when feeding on fruit of Ficus organensis by selecting the most productive trees and bypassing less-productive sources of the same species (Pereira 2008 ). This strategy might be related to a preference for foraging in areas with higher resource availability (trees with larger diameter at breast height), or to the selection of routes crossing areas with higher canopy connectivity (Hopkins 2011 ). This strategy can also be interpreted as evidence of spatial knowledge because these trees were usually outside the monkeys' potential fi eld of view (Garber 1989 ;Janson 1998 ;Cunningham and Janson 2007 ).…”

Anthropogenic Habitat Modification, Tourist Interactions and Crop-Raiding in Howler Monkeys

“…A. caraya has even been reported consuming wild and domestic birds' eggs (Bicca-Marques et al 2009 ). Howler monkeys appear to choose travel pathways with higher resource availability than comparable straightline paths (Hopkins 2011 ), and those living in forest fragments have been known to gather as much as 20 % of their total annual diet from outside their home patch (Asensio et al 2009 ). Therefore, while the only howler monkey species currently recognized as a crop-raider is A. palliata (McKinney 2010 ), the wide distribution and dietary fl exibility of the genus suggests that the prevalence of crop-raiding in this group is likely to be much higher.…”

Habitat structure and food resources for wildlife across successional stages in a tropical forest

“…In particular, vegetation structure (e.g. Dial et al, 2006;Hopkins, 2011;Lambert et al, 2006;Malcolm, 1997;Pardini et al, 2005), as well as the structure of the leaf litter (e.g. Naxara et al, 2009;Sayer et al, 2010;Van Sluys et al, 2007;Vonesh, 2001) and woody debris (e.g.…”