Primate Update E-Newsletter, Vol. 2, Issue 6, Part 3

CONTINUING EDUCATION

Special Topic- Erin: Diets of Wild Spider Monkeys: Chapter Summary
Spider Monkey, Behavior, Ecology, and Evolution of the Genus Ateles

Spider Monkeys are highly frugivorous, it is estimated that up to 90% of their diet
consists of fruit or nuts. Typically they swallow ripe fruits whole, ingesting the seeds
along with the fruit. Spider Monkeys are known to eat over 250 different species of
plants! They also eat plant parts such as flowers and leaves, which typically makes up
about 10% of their diet. They eat very little animal matter, mostly just caterpillars,
bees and termites. The caterpillars are eaten during a short time period each year,
when they hatch in large quantities. In some places Spider Monkeys have been seen
eating soil at mineral licks, and they are also known to eat decayed wood.

Although Spider Monkeys typically live in large groups, they usually travel and feed
together in small parties. These smaller feeding groups allow the monkeys to eat
higher quality food that is typically found in smaller patches. They can then reunite in
the evenings for the protection of the larger group. Spider Monkeys get the majority
of their fruit in the upper levels of the forest, with 77% coming from the upper
canopy, and less than 1% from the understory.

Spider Monkeys have a simple, unelongated digestive tract. This means that foods
pass very quickly through it (it makes them great seed dispersers). This fact is
important to us in providing the best diet possible to the Spider Monkeys at Pacific
Primate Sanctuary. There is very little processing of foods that goes on in the
digestive tract because of its small size. The carbohydrates and lipids are quickly
extracted, because they are easily absorbed, while the rest is quickly passed through
the system. It is important that Spider monkeys eat fruits/veggies with high
nutritional quality to get the most out of their food!

Some fruits Spider Monkeys are known to eat in the wild:
The Cherimoya and Sour Sop family,
A variety of cactus fruits,
Legumes (peas and beans),
Avocado,
Fig and mulberry family,
Sapote family (egg fruit).

-2008. Campbell, C.J. (ed.). Spider Monkeys: Behavior, Ecology and Evolution of the
Genus Ateles. Cambridge University Press.

Special Topic- Robin: Neighbor Effects in Marmosets: 

Social Contagion of Agonism and Affiliation in Captive Callithrix jacchus
CLAIRE F. I. WATSON AND CHRISTINE A. CALDWELL
Behaviour and Evolution Research Group, Department of Psychology, University of Stirling,
Stirling, Scotland, Scottish Primate Research Group, University of Stirling, Stirling, Scotland


This study elaborates on studies done on chimpanzees, and investigates whether the
“neighbor effect,” or “social contagion” generalizes to marmosets. In a nutshell, these
phrases refer to the effect of members of a group being more likely to demonstrate
affiliatve or aggressive behavior if their neighbors are demonstrating these behaviors.
The authors looked at three areas: intragroup (within a group) aggression, intergroup
(between different groups) aggression, and affiliation. The study group was
composed of a total of 121 individuals of differing ages who were housed in a
research facility in Scotland.
The authors looked at certain behaviors, and recorded frequencies of these behaviors.
They then looked at whether there was an increase in behaviors when one member of
the group displayed. For example, if one monkey “bristled,” were the other monkeys
more likely to do so as well? Or if one monkey was grooming another, would the
others in the group be more likely to groom? Would monkeys be more likely to emit
certain vocalizations if they heard another group member do so?

The study found that not only are marmosets more likely to emit the same behaviors
as their neighbors, but they are also more likely to engage in affiliative behaviors (e.g.
grooming) if their neighbors are emitting chirp vocalizations. The authors were not
able to show that this was the case for intragroup aggression, as the sample size for
the data was too small. Furthermore, the authors point out that while the results
were significant, they do not suggest a causal link. What is clear from the study,
however, is that the chirp vocalization is very important in marmoset social groups.

Anyone who has been in the corridor at Pacific Primate Sanctuary can attest to the
verity of this study. When one monkey gets upset about something, sometimes the
whole corridor will become upset with him! And conversely, it is very common to see
the entire corridor being calm and happy, emitting chirp vocalizations. This is an
important study for marmosets in captive situations, because it shows that agonistic
behaviors (behaviors that are associated with competition and fighting) in one room
of monkeys affects the entire group. For monkeys in captivity to have the best life
possible, it is important to limit the amount of agonistic behavior, which thereby limits
stress. Further study is needed in this area to continue to uncover ways to improve
captive life.

We hope you have enjoyed this issue of Pacific Primate Sanctuary’s E-Newsletter.
Your support makes our work possible. Because of compassionate people, the
Sanctuary can continue to provide a place of peace and happiness for 74 primates
saved from research laboratories, animal dealers, and smugglers. Here they can heal,
regain some of their birthright, and live free from exploitation.

“Never doubt that a small group of thoughtful, committed citizens can
change the world; indeed, it's the only thing that ever has.”
— Margaret Mead


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