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

CONTINUING EDUCATION

Special Topic- Intern Olivia
Capuchin Development

Capuchins go through similar stages of development as other primates. Gestation is about five months, and the newborn baby is inspected by its mother at birth and treated with cautious interest by others in the group. A phenomenon called allonursing occurs in capuchins. This is when the infant nurses from any lactating female. An infant will begin to seek out other lactating individuals more frequently as their own mother begins the weaning process.

Capuchin young must learn which foods 

are safe to eat by observing adults.  

Young Viola watches Miranda eat a fig.

As the infant grows up they begin to learn to feed themselves and manipulate objects, so just after a year old they can be weaned. The young capuchin is completely nutritionally independent by their second year. This means that they have a year between weaning and when their mother cuts them off in which to learn which foods to eat, where to find them, how to access them, and how to avoid predators. Younger capuchins do not have the same physical strength or the same mental capability for determining what to eat as adults do, and this often results in starvation of the young capuchin. Those that survive have developed faster than those that do not, and their children will be more likely to survive to sexual maturity because of their ability to forage for food. Foraging is not the only development the capuchin must go through, but it is the most essential to their survival.

Capuchin young observe and participate in play activities so that when they get older they will be prepared to defend their territories and protect their families and themselves.

There is also sexual play occurring before the time of sexual maturity. With females this begins about age four and for males around age three. This can be different sexual activities, such as mounting, where everyone participates in mounting and being mounted. Female sexual play ends at the age of sexual maturity when their interest in the opposite sex arrives, and they put the sexual play to good use.

Behavioral development is as important, or even more important, than physical development. By the time an individual is large enough that the mother is going to stop breast-feeding, he/she has to know how to forage appropriately or he/she will starve, as others in the group will no longer help them determine what to eat or how to get at good foods. They do need the jaw formation to bite into some of these foods, but as long as they have a wide range of knowledge of the different foods, they will not starve.

Other social behaviors, such as learning the difference between play and aggression and how to use brute strength to defend your food source and your family are very important as capuchin’s social structures are very complex. They need to learn the difference between sexual behavior and certain play behaviors so they know how to solicit a mate for reproduction. Play gets confused with many other behaviors, because juveniles use play to learn what these behaviors are and how they will be used in the future.

Capuchins get old, but remain active socially and physically and can live well into their forties, as long as they’re healthy. Females experience longer inter-birth intervals as they age, but there is no conclusion as to whether or not they go through menopause.

-Fragaszy, D.M., Visalberghi, E., Fedigan, L.M. (2004) The Complete Capuchin: The Biology of the Genus Cebus. UK. Cambridge University Press



Special Topic-Extern MC
Chapter 9: Social interactions, social relationships and the social system of Spider monkeys

Spider monkeys have a fission-fusion social system characterized by a constantly changing group size as subgroups merge and separate throughout a day. This social system is thought to be a means of coping with sporadically distributed food sources because it reduces feeding competition between individuals of the same community. Depending on the local availability of food, spider monkeys will forage for food in small subgroups when food is scarce, and larger subgroups when food is plentiful. However, unraveling the social relationships of spider monkeys is not so simple and researchers are just beginning to discover the complex world of their social lives.

Females are often found foraging on their own or in very small subgroups, especially if they have dependent offspring. The common theory for their preferred small subgroups suggests female spider monkeys forage this way in order to save in travel costs. Groups with more individuals must visit more feeding sites to satisfy everyone’s hunger, thus expending more energy. Smaller groups need to visit less patches of food, thus travelling less and saving in energy expenditure. This is especially important to a female carrying an offspring. A consequence of foraging alone or in small groups is the lack of development of strong social bonds between females.

Less grooming and other affiliative behaviors between females have been reported by many studies of wild spider monkeys. Interestingly, embraces and grooming interactions increase between females when one has an infant. The author suggests that because female primates are strongly attracted to other females’ infants, an individual without an infant will offer grooming to a female with an infant in order to gain access to the baby. Aggression between females is rare, though because female spider monkeys leave their natal group when they are reproductively mature, leading females sometimes show aggression to new females immigrating into their community.

Unlike relationships between female spider monkeys, relationships between males are very strong. Within a social community, interactions between males are overwhelmingly affiliative. Grooming, embracing, and pectoral sniffing (a species typical affiliative behavior) are interactions most commonly seen between males. Males often forage in larger subgroups and often travel together to the boundaries of their home ranges on “patrols.” They have even been observed walking on the ground in single file deep into territory of neighboring communities in order to carryout “raids” in which they display and often chase members of the rival group. The strong social bonds between males foster the trust and cooperation necessary to carry out such dangerous endeavors. Observations of wild spider monkey communities show very low levels of aggression between males, although lethal aggression has been witnessed and may be more widespread than originally thought.

Montana comes in close to share an embrace with his brother, Carlos

Relationships between male and female spider monkeys are described in this chapter as intermediate between male-male and female-female relationships. Grooming and instances of embraces occur more frequently between a male and female than between females, but less frequently than it does between males. However, very strong bonds are found between a mother and her adult son. The most instances of aggression in a spider monkey community are by males being aggressive toward females. A possible explanation is that because spider monkeys are not sexually dimorphic (in other words, no size difference exists between the sexes), the aggression exhibited by males to females are “intimidation displays” in which males attempt to dominate equal sized females. This chapter stresses the need for further investigation into the complex social lives of spider monkeys before more definitive conclusions on their social structure can be made. With increased conservation efforts, wild spider monkey culture will be preserved and determined primatologists can delve further into the fascinating social world of spider monkeys.

-Campbell, Christina J. Spider Monkeys: The Biology, Behavior, and Ecology of the Genus Ateles (Cambridge Studies in Biological and Evolutionary Anthropology). UK. Cambridge University Press. 2008.


Special Topic- Intern Simon
Habitats, feeding ecology, and home range size in the genus Callithrix; by Anthony B. Rylands and Doris S. de Faria

**NOTE** The taxonomic classification has changed since the writing of this article. The genera Mico and Callibella were once considered to be part of Callithrix, but are now classified as distinct. Please note that when this article speaks of the genus “Callithrix,” it is actually referring to all three of the different genera. For the purpose of this summary, I shall simply use the term “marmoset,” but exclude the pygmy marmoset (of the genus Cebuella) from this usage.

Introduction
Marmosets are found in Brazil, the northeastern tip of Paraguay, and eastern Bolivia. The relatively wide distribution of the various marmoset species is indicative of the wide variety of habitats that they occupy. Each species is unique—a result of their adaption to their own specific habitat—but there are strong similarities as well. This article gives a general summary of these similarities and differences.

Habitats
The various habitats that marmosets live in include evergreen forests, seasonal semi-deciduous forests, Amazonian-type savannas, white sand forest patches, tall forests with dense undergrowth along waterways, lowland forests, and highland forests. Some live more inland and some are coastal. Clearly, these are all very different kinds of forests. But although they occupy this wide range of habitats, one similarity among all the different marmoset species—regardless of the type of habitat they live in—is their preference for secondary forests.

A secondary forest is a forest that has been regrown after a major disturbance (for example, after a fire or after severe logging). In a secondary forest, the effects of the disturbance are no longer noticeable. So why would marmosets choose to live in a regrown forest rather than an old-growth primary forest? It all has to do with the fruit types and fruiting patterns of the “pioneer plants” that only grow in secondary forests. Also, secondary forests are denser than primary forests, providing better shelter. Not to mention the fact that secondary forests are loaded with tasty creepy-crawlies that the marmosets can munch on…which brings us to the next point.

Feeding Ecology

Davis and Cordelia search for ants and sweet nectar 

among the petals of this pink ginger flower

Bugs might sound like an unpleasant choice of food, but they are high in protein. Marmosets also hunt other small prey as well, such as spiders, snails, frogs, lizards, and even small birds on rare occasions. In fact, animal prey makes up about 25% of most marmosets’ diets. The other 75% depends on the species. In addition to being insectivores, they are all fruit eaters (frugivores) and gum and sap eaters (exudativores) as well. But some marmoset species rely predominately on exudates, with a supplemental fruit here and there, and others are just the opposite. For example, White-tufted and Black-tufted marmosets are predominately gum and sap eaters, eating very little fruit in the wild, while Weid’s marmosets (such as PPS’s own Davis) are highly frugivorous. But regardless of how often they eat saps and gums, all marmosets are evolutionarily adapted to do so. In fact, marmosets are the only primates that have this adaption. Their long lower front teeth and their intestinal shape are specifically designed to gouge tree trunks, branches, and vines and digest the gummy goodness. But because extracting sap is an energetically costly activity for these little marmosets, fruit is often preferred when it is available. But remember, different marmoset species live in different habitats, and some of these habitats are more bountiful with fruit than others. Going back to the example of Weid’s marmoset: they are highly frugivorous, probably because they are predominately found in evergreen forests where fruit is plentiful. White-tufted marmosets, on the other hand, tend to live in highly dry thorn scrub where gums abound but fruit is scarce. So while marmosets all consume the same things, the percentage of the food items consumed depends on the availability of that food in the habitat where the species is found in.

Range Size
The ranging distance of marmoset species corresponds to the presence (or absence) of fruit. For example, recall that White-tufted marmosets usually do not have an abundance of fruit in their habitat so they mostly eat gums and saps. Well, because gums and saps are ever-present, White-tufted marmosets do not have to travel far, and therefore have a small range (only .5 between 6.5 hectares), as does the Black-tufted marmoset (1.25 to 4.5 hectares). In contrast, Weid’s marmoset has a range about twice that (between 10 to 12 hectares). This is because, the Weid’s marmoset prefers fruit, and fruit tends to be more widely dispersed than gums. Marmosets of the genus Mico have relatively smaller lower incisors and so are biologically less adept at extracting gums and saps than Callithrix marmosets and subsequently have a much wider home range.

Conclusion
As we have seen, habitat, diet, and home range are all inter-related. For example, since the White-tufted and Black-tufted marmosets excel at gouging saps (their diet), they are able to thrive in the most unfavorable environments (their habitat) and they travel less (their home range) because the gums are found everywhere. How the different marmoset species have reconciled these three factors of habitat, diet, and home range has created differences and diversity among them.

But while marmosets vary greatly from species to species, they share common features. Regarding their habitat and diet, the common features include their dependence on secondary growth or disturbed forest; their ability to extract gums when faced with permanent or seasonal shortage of fruits, and their methods of foraging for animal prey. These shared traits, contrasted with their differences, create an appreciation for the diversity among marmosets.

-Rylands, A.B. Marmosets and Tamarins. Systematics, Behavior, and Ecology. Oxford, U.K.: Oxford University Press, 1993.

Animals are not brethren, they are not underlings; they are other nations, caught with ourselves in the net of life and time. 
— Henry Beston



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