Foraging in a social setting: a comparative analysis of captive gorillas and chimpanzees.

This study was designed to investigate the foraging behavior of zoo-housed western lowland gorillas (Gorilla gorilla gorilla) and compare it with that of zoo-housed chimpanzees (Pan trogloydytes) tested previously in a similar paradigm. Specifically, we aimed to document how a group of zoo-housed gorillas foraged within a familiar environment to discover novel food sources and whether they sought out more preferred foods, even if they had to travel further to reach them, as they do in the wild. Gorillas were provided plastic tokens to exchange with researchers at two locations-at the same location as the tokens (close) for carrot pieces and another 6.5 m away (far) for grapes. Over the course of 30 sessions, a single individual-the silverback male-accounted for 96% of the 1546 tokens exchanged, all of which took place at the far location. Inter-individual distance measures collected during each session, as well as during matched control sessions, showed that while both gorillas and chimpanzees express similar patterns of social association across the two conditions, the average dyadic association for chimpanzees was stronger than that for gorillas. Together, these findings provide an example of the value of employing identical methodologies to compare cognition and behavior across species as well highlight the importance of the social context in which studies take place.

Assessment of behavior and space use before and after forelimb amputation in a zoo-housed chimpanzee (Pan troglodytes).

Primates possess great manual dexterity, and their limbs are integral to many aspects of normal functioning (e.g., climbing, feeding). As such, the loss of a limb carries the risk of significant disability and potentially harmful impairment of species-typical functioning. Limb loss is known to occur in some wild primate populations due to entanglement in hunting snares, but can also occur in captive settings due to injury that necessitates therapeutic amputation. In this study, we conducted a detailed evaluation of the behavior, travel, and space use expressed by a female zoo-housed chimpanzee (Pan troglodytes) before and following surgical amputation of her right forelimb. Overall, our results suggest that the injury did not substantively affect her daily activities. She showed no change to her vertical space use, spending equivalent proportions of her time on the ground and high in the enclosure. There was a decrease in the frequency of locomotion on the ground (P = 0.006) but also a significant increase in the overall distance travelled (P = 0.0015) following the removal of the limb. This case study provides evidence that individual chimpanzees are able to successfully adjust to significant anatomical changes when provided adequate environments in which to stay active, and highlights the importance of an effective post-surgical monitoring period-a comprehensive recovery evaluation that includes input from both veterinary and behavioral research staff is likely to provide the most holistic assessment of animal health and long-term wellbeing. Zoo Biol. 36:5-10, 2017. © 2016 Wiley Periodicals, Inc.

Behavioral research as physical enrichment for captive chimpanzees.

In this study, we evaluated the potential for a behavioral research study, designed to evaluate chimpanzee decision-making behavior, to also encourage increased activity in a group of zoo-housed chimpanzees. For the behavioral study, the chimpanzees had to carry tokens to different locations such that they always had to travel farther to obtain a more-preferred reward. We recorded the distance travelled by each subject in each of the three phases of the 15-month study. By the final phase, the chimpanzees' rate of travel during test sessions was significantly higher compared to their baseline activity. Importantly, the chimpanzees' increase in locomotion was not dependent on their participation in the study; rate of travel was not correlated with number of tokens exchanged. However, the chimpanzees' activity returned to baseline within 2 hr of the 30-min test sessions. This study emphasizes the role that research can have in providing enrichment, the importance for long-term enrichment plans, and the essential need to evaluate the impact of research on animal participants, just as we evaluate the efficacy of enrichment strategies. Zoo Biol. 35:293-297, 2016. © 2016 Wiley Periodicals, Inc.

Daily travel distances of zoo-housed chimpanzees and gorillas: implications for welfare assessments and space requirements.

The degree to which the relatively smaller area of artificial environments (compared with natural habitats) has measureable effects on the behavior and welfare of captive animals has been debated for many years. While there is little question that these spaces provide far less opportunity for natural ranging behavior and travel, less is known about the degree to which captive animals travel within their environments and what factors influence these travel patterns. We intensively studied the movement of zoo-housed chimpanzees and gorillas using a computer map interface and determined their mean daily travel and found they travelled similar distances each day when restricted to their indoor areas, but when provided additional outdoor space, chimpanzees tended to increase their travel to a greater extent than did gorillas. Both species travelled shorter distances than has been recorded for their wild counterparts, however, when given access to their full indoor-outdoor exhibit; those differences were not as substantive. These findings suggest that while large, complex naturalistic environments might not stimulate comparable species-typical travel patterns in captive apes, larger spaces that include outdoor areas may be better at replicating this behavioral pattern than smaller, indoor areas.

The birth of an infant decreases group spacing in a zoo-housed lowland gorilla group (Gorilla gorilla gorilla).

Changes in group composition can alter the behavior of social animals such as gorillas. Although gorilla births are presumed to affect group spacing patterns, there is relatively little data about how these events affect gorilla group cohesion. We investigated how members of a western lowland gorilla group (n = 6) at Lincoln Park Zoo (Chicago, IL, USA) spaced themselves prior to and after the birth of an infant, to investigate changes in group cohesion. Gorillas were housed in an indoor-outdoor enclosure in which access to the outdoors was permitted when temperatures exceeded 5°C. We recorded spatial locations of each group member using 30-min group scans on tablet computers with an electronic map interface, as well as noting their access to outdoor areas. Data from the 4 months following the birth was compared to a control period corresponding to early pregnancy. We measured distances between all possible group dyads for each scan and subsequently calculated a mean distance between all group members. An ANOVA revealed that access to the outdoors had no effect on group spacing (F(1,56) = 0.066, P = 0.799). However, the presence of an infant resulted in a significant reduction in inter-individual distance (F(1,56) = 23.988, P = 0.000), decreasing inter-individual spacing by 12.5%. This information helps characterize the behavioral impact of a new birth on captive gorilla social structure and could potentially inform future management of breeding gorilla groups.

Loss of homeostatic strain alters mechanostat "set point" of tendon cells in vitro.

Tendon cells respond to mechanical loads. The character (anabolic or catabolic) and sensitivity of this response is determined by the mechanostat set point of the cell, which is governed by the cytoskeleton and its interaction with the extracellular matrix. To determine if loss of cytoskeletal tension following stress deprivation decreases the mechanoresponsiveness of tendon cells, we cultured rat tail tendons under stress-deprived conditions for 48 hours and then cyclically loaded them for 24 hours at 1%, 3%, or 6% strain at 0.17 Hz. Stress deprivation upregulated MMP-13 mRNA expression and caused progressive loss of cell-matrix contact compared to fresh controls. The application of 1% strain to fresh tendons for 24 hours inhibited MMP-13 mRNA expression compared to stress-deprived tendons over the same period. However, when tendons were stress-deprived for 48 hours and then subjected to the same loading regime, the inhibition of MMP-13 mRNA expression was decreased. In stress-deprived tendons, it was necessary to increase the strain magnitude to 3% to achieve the same level of MMP-13 mRNA inhibition seen in fresh tendons exercised at 1% strain. The data suggest loss of cytoskeletal tension alters the mechanostat set point and decreases the mechanoresponsiveness of tendon cells.