A recent article in the journal, Zoo Biology, discusses the current lack of gum enrichment for certain primate species in a captive setting that is in contrast to their wild behavior. Huber and Lewis (2011) surveyed zoos at an international scale to assess the occurrence and methods of “gum-based enrichment.”

Patas Monkey at Woodland Park Zoo (Photo: Kristin Abt)

Golden Lion Tamarin at National Zoo (Photo: Kristin Abt)

They identify numerous primates that feed on gums in varying amounts in the wild, including galagos and lorises, marmosets and tamarins, and members of Cercopithecinae.  Because enrichment aims to promote species-typical behaviors in a non-natural environment, the items that are offered should be primarily selected based on whether or not they contribute to this aim.

This study obtained responses from 46 zoos, 27 of which feed gum to at least some of their primates. The greatest disparity between wild gum-feeding and captive gum-provisioning was for cercopithecines. They identify patas monkeys as obligate gumnivores; therefore, they specifically highlight the need for the development of enrichment programs utilizing gum for this species. Also, they highlight the need to provide enrichment devices that simulate how primates feed on gum in the wild as opposed to free-feeding in dishes.

Patas Monkey Exhibit (Photo: Kristin Abt)

Huber and Lewis (2011) take a focused approach to assessing an area of enrichment within zoos that can have a marked management impact. This study shows the value of applied research to enhance the ability of zoos and other facilities to care for their collections in a manner more representative of the wild experience.

Reference:

Huber, H. F. & Lewis, K. P. (2011). “An assessment of gum-based environmental enrichment for captive gumnivorous primates.” Zoo Biology 30: 71-78.

Well Wood and crew setup two sets of experiments that tested the behavioral response of over 120 primates, including cotton-top tamarins, a type of New World monkey, rhesus macaques, a Old World monkey and chimpanzees to represent the apes.

I have been confused about the design of the first experiment, which the tested the primates by presenting them with two potential food containers. One container was grasped by the scientists on purpose and the other container was accidentally grasped by flopping their hand on top of it. I probably didn’t do a great job translating the setup, so forgive me.

The most sense I can make out of what was tested here is the ability to understand or differentiate goal-oriented and accidental behavior. And the results show that in all three species, the primates picked out the the food container that was purposefully grasped more often than the container upon which the hand was flopped. This indicates that the primate inferred goal-oriented action on the part of the experimenter when he or she grasped the container, and was able to understand the difference between the goal-oriented and accidental behavior.

In the second experiment, the primates were also presented with two potential food containers but this time the researchers sought to answer if the primates can infer others’ goals under the expectation that other individuals will perform the most rational action allowed by the environmental obstacles. In one situation, an experimenter touched a container with his elbow when his hands were full, and in another scenario, touched a container with his elbow when his hands were empty. And low and behold, the primates looked for the food in the container indicated with the elbow more often when the experimenter’s hands were full.

The primates considered, just as a human being would, that if someone’s hands are full then it is rational for them to use their elbow to indicate the container with food, whereas if their hands are empty it is not rational for them to use their elbow, because they could have used their unoccupied hand.

Wood comments on his paper,

“A dominant view has been that non-human primates attend only to what actions ‘look like’ when trying to understand what others are thinking. In contrast, our research shows that non-human primates infer others’ intentions in a much more sophisticated way. They expect other individuals to perform the most rational action that they can, given the environmental obstacles that they face.

This study represents one of the broadest comparative studies of primate cognition, and the significance of the findings is reinforced by the fact that these results were consistent across three different species of primates. The results have significant implications for understanding the evolution of the processes that allow us to make sense of other people’s behavior.”

What sorta significance? Well this study kinda sorta implies that the ability to engage in this type of rational action perception evolved as long as 40 million years ago, with non-human primates, and that it is not a human only response… possibly this sort of behavior was positively selected for in the primate lineage and ultimately folds into the social brain hypothesis. Speaking of which, you may also wanna check out the evolution of the social brain, which also debuted in the latest Science, while you are at it.

“a combination of deforestation and exports for biomedical research during the 1960s and 70s left cotton-top monkeys facing extinction…”

So it news like Hampshire Zoo‘s success in breeding a set of cotton-top tamarin twins is really good news to me. From the BBC,

“The cotton-top tamarin twins were born as part of a breeding programme at Marwell Zoo, near Winchester.

They have been named Zambrono and Tol after places near the Las Coloradas Sanctuary in their native Colombia, South America.

The twins are being nursed and cared for by their mother Magdalena, while dad also shares responsibilities.”

Marwell Zoo has been very successful in rebuilding the cotton-top population (albeit they are in captivity), they have breed over 50 individuals. The twins seem healthy and are being reared by both parents.

I wish the zookeepers the best of luck, and if they happen to read this, keep up the good work!