Reducing the ecological impact of field research.

Researchers and students at biological field stations, especially in remote areas, are subject to leaving "footprints," as we conduct research, work, and live in sensitive ecosystems. These footprints include travel, personal trash and waste, and field equipment (e.g. flagging, tree markers, plot markers, trail markers, monitoring devices, etc.). In this commentary, we argue that the field of primatology's commitment to minimum impact research should be more explicitly and visibly integrated into our ethical protocols with regard to field research and instruction in sensitive environments. We review current ethical codes and potential solutions to reducing our "researcher footprints" while conducting fieldwork. Using Costa Rica as an example, we address how sustainable fieldwork differs among varying cultural contexts and argue that researchers should be made responsible and accountable for how our presence, research, and teaching might impact the environment. We conclude by recommending a set of guidelines to be added to ethical protocols regarding research design, station policies, and the conduct of research and teaching in the field.

The ontogeny of prehensile-tail use in Cebus capucinus and Alouatta palliata.

A study of the platyrrhine prehensile tail provides an opportunity to better understand how ecological and biomechanical factors affect the ability of primates to distribute mass across many different kinds of arboreal supports. Young individuals experience ontogenetic changes in body mass, limb proportions, and motor skills that are likely to exert a strong influence on foraging strategies, social behaviors, support use, and associated prehensile-tail use. In this research, I examine ontogenetic patterns of prehensile-tail use in Cebus capucinus and Alouatta palliata. I collected behavioral data on activity, positional context, support size, and prehensile-tail use in five age categories of white-faced capuchins and mantled howlers during a 12-month period at Estación Biológica La Suerte in northeastern Costa Rica. Infant and juvenile howlers and capuchins were found to use their prehensile tails significantly more often than adults during feeding, foraging, and social behavior. Prehensile-tail use did not show predictable increases during growth. In both species, adults used their prehensile tails in mass-bearing modes significantly less often than juveniles. Despite differences in tail anatomy in Cebus and Alouatta, prehensile-tail use was observed to follow an increasing trajectory from infancy, peaking during juvenescence, and then decreasing in older juveniles and adults. In both species, it appeared that adult patterns of prehensile-tail use reflected the demands placed on young juveniles.

Technical note: tree truthing: how accurate are substrate estimates in primate field studies?

Field studies of primate positional behavior typically rely on ground-level estimates of substrate size, angle, and canopy location. These estimates potentially influence the identification of positional modes by the observer recording behaviors. In this study we aim to test ground-level estimates against direct measurements of support angles, diameters, and canopy heights in trees at La Suerte Biological Research Station in Costa Rica. After reviewing methods that have been used by past researchers, we provide data collected within trees that are compared to estimates obtained from the ground. We climbed five trees and measured 20 supports. Four observers collected measurements of each support from different locations on the ground. Diameter estimates varied from the direct tree measures by 0-28 cm (Mean: 5.44 ± 4.55). Substrate angles varied by 1-55° (Mean: 14.76 ± 14.02). Height in the tree was best estimated using a clinometer as estimates with a two-meter reference placed by the tree varied by 3-11 meters (Mean: 5.31 ± 2.44). We determined that the best support size estimates were those generated relative to the size of the focal animal and divided into broader categories. Support angles were best estimated in 5° increments and then checked using a Haglöf clinometer in combination with a laser pointer. We conclude that three major factors should be addressed when estimating support features: observer error (e.g., experience and distance from the target), support deformity, and how support size and angle influence the positional mode selected by a primate individual. individual.

Life history and locomotion in Cebus capucinus and Alouatta palliata.

As an individual matures from birth to adulthood, many factors may influence the positional repertoire. The biological and behavioral changes that accompany a growing individual are expected to influence foraging strategy, social status and interaction, diet, predator avoidance strategies, and ultimately positional behavior as a behavioral link between anatomy and the environment. In this work, positional behavior is considered as an important feature of life history in juvenile and adult white-faced capuchins (Cebus capucinus) and mantled howling monkeys (Alouatta palliata) inhabiting the same tropical forest in Costa Rica. During growth and development ontogenetic changes in body size, limb proportions, and motor skills are likely to influence locomotion and posture through the arboreal canopy. I collected data on positional behavior, activity, branch size, branch angle, and crown location during a 12-month period at Estación Biológica La Suerte in northeastern Costa Rica. Life history timing and differences in rates of growth did not predictably influence the development of adultlike positional behaviors in Cebus and Alouatta. Young Cebus resembled the adult pattern of positional behavior by 6 months of age while howlers exhibited significant differences in several positional behavior categories through 24 months of age. The positional repertoire of both species revealed similarities in the types of modes used during feed/forage and travel in juveniles and adults. Data presented here suggest that the environment exerts different pressures on growing Cebus and Alouatta that may relate to diet, energy expenditure, foraging skill, and/or social learning.