Primates at the Greensboro Science Center

For our final field trip, Dr. Rodrigues took some of us to the Greesnboro Science Center in Greensboro, NC. Although it is not a huge zoo, they do have Javan Gibbons, Ring-tailed Lemurs, Red Ruffed Lemurs, and Black Howler Monkeys. The zoo, overall, did not seem to have a lot of educational or conservation information at each exhibit, and some other species did not have any species-specific information at all. Although it is a science center which theoretically encourages learning, I think that the Animal Discovery zoo seemed to be more about visitors enjoying seeing the animals rather than learning a lot about them (even scientifically).

The lemur habitat, which had both types of lemurs in the same enclosure, was fairly small for the number of lemurs there (maybe about a dozen?). We noticed one lemur that was missing an arm, which Dr. Rodrigues said may be because he got an arm stuck in the surrounding chain link fence. If this is true, they should absolutely reconsider the setup of their enclosures in order to ensure the health and safety of their lemurs who do a lot of leaping, climbing, and other acrobatics which could cause them to get their limbs caught. They did not seem to have a lot of room, but the group seemed appropriately sized for this species. I noticed some lemurs displaying dominance to others, but not being particularly overaggressive. They had a lot of different enrichment objects in their enclosure, including logs, branches, plants, rocks, hanging hammocks and pipes to jump to, and other little perches in the rocks and at the top of branches. I did like that the lemurs had a lot to interact with and that the zoo showed more than one species of lemur, since most people are mostly/only familiar with the ring-tailed lemur.

The howler monkeys also had a pretty small environment, although there were fewer individuals (about 6). They could have benefited from having a taller enclosure as howlers tend to stay high up in the trees. I remember Dr. Rodrigues noting how odd it was to see Howlers walking around on the ground and picking grass. She also seemed to think that they were being unusually active for the species, which usually are much more lazy. They had branches and a tree-like structure, as well as a hammock and ropes strung around the top of the exhibit. One female howler in particular was trying to escape, coming close to the windows so we could see her up close.

My favorite of the day were the Javan Gibbons, who are one of the rarest species of gibbon in the world. This is why it is especially cool that they were able to have a baby born in captivity in 2013 (one of only 2 babies ever born in captivity!). They had a fairly tall exhibit with some tree-like structures with branches and toys for them to swing on and interact with. They also had a small blanket for the baby, who carried it around with him and wrapped around his body. They probably would like more space, but they had a lot of room relative to all of the other primates we saw. Their group was only the two parents and the baby, small for a gibbon group but considering this species is rare and they were able to produce offspring, I would say they are making a decent effort.

One behavior that I thought was interesting was that the mother initially rejected the baby, forcing zoo staff to save and raise the baby by hand until he was old enough to be reintroduced to his parents. I was curious as to whether this is something that tends to happen more in captivity than in the wild, and whether this would be species-typical or stereotyped behavior. I wonder whether this was somehow made more likely to occur in captivity because of something in this environment. In the wild, the infant could not have fended for itself after being abandoned. In captivity, zoo staff made the quick decision to hand-rear the baby and to try to reintroduce him later in order to save the species. Now, Executive Directior Glenn Dobrogosz calls the successfully raised baby gibbon the “rockstar for promoting species conservation, showcasing the quality” of their animal care team. I think the gibbons have raised a lot of awareness and having such a rare species definitely helps with conservation.

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Javan Gibbons!


Food Availability and Fat: Second Article Review

For my second article review, I found a study that compared groups of free-ranging baboons in Kenya at the Amboseli National Park and Masai Mara National Reserve Park for serum insulin, fat, and cholesterol levels. Three of the populations they studied relied completely on foraging for food in the wild, while two populations that lived in the vicinity of areas with heavy tourist-flow often were found to supplement their diet with the waste foods from these lodges on a regular basis. Because these baboons are able to rely on human garbage in addition to their normal diet, food has become highly accessible to them. This human food also has a high caloric density, providing them with an excess of energy-rich food. Despite this increase in calories in diet, however, supplementing diet with the human waste foods was found to correlate with reduced locomotion. These baboons would eat the fresh garbage intensively and spent much less time travelling than the wild-foraging baboons.

The researchers tested the blood of sexually mature males (96+ months old) and females (4o+ months old) from each of the five populations. They excluded late-gestational and nursing females from the study. They found that the baboons that supplemented their diet with human waste foods had 2 to 3 times more serum insulin than those that exclusively foraged in the wild. They also found an overall increase in cholesterol, HDL-C, and VLDL+LDL-C levels in the garbage-supplemented diet group. They found no differences between sexes other than overall body mass (I’m assuming due to sexual dimorphism in baboons).

This article was written in the context of examining how eating habits and physical activity can greatly affect the maintenance of health, as well as the progression of disease. The authors connected their results to background research on the correlations between activity level, elevated cholesterol, lipoproteins, and insulin and related diseases, such as atherosclerosis, diabetes, coronary heart disease, and hypertension. They also discuss the connection between humans and other primates and how translational research in this field could tell us a lot about the health of humans.

In the discussion, the authors mention that the fatness levels of these garbage-eating baboons were similar to those in well-provisioned, group-housed captive baboons. They also mention that these fat baboons, however, were still considerably leaner than baboons singly-housed in captivity, which have richer diets and even lower activity levels. Another interesting note they make is that body mass was about the same in wild-foraging males and garbage-eating males. They believed that this could be due to females staying in their groups throughout their lives, while males likely immigrated into the garbage-eating group during or after adolescence.

I think this paper will be very helpful for my project because it gets down to the root of the problem of obesity in primates: food availability/accessibility. It more specifically addresses the effects of food accessibility and availability for these free-ranging baboons that a lot of studies of captive primates do not. Although this study was not about captive primates, it is still a comparative study between populations of the same species in generally the same area. The only major difference they mention is that the 3 groups foraged in the wild and two groups supplemented their diets with human food, making it easier to attribute differences in health to diet. This eliminates a lot of the other potential confounding factors that could become an issue in comparative studies between captive and wild primates (such as differences in environment, ranging options, and social interactions), which is why I liked this study even more. I think this article very clearly supports what I would propose to conduct research upon, which is food accessibility and availability affecting physical activity (how much effort/energy they need to expend to get food), and the interaction of these two factors affecting primate health, while bringing in an interesting social aspect suggested by fat level difference in singly-house vs. group-housed primates.

Baboon Eating Human Waste Foods



Health and Behavior of Primates in Captivity: My Proposed Paper Topic

Since I was a child, I have always been interested in why domestic and captive animals become obese and why wild animals do not. For my Student-Faculty Seminar class for senior anthropology majors, I am doing my research on food accessibility in humans and how by creating this “captive environment” for ourselves in which food is readily accessible and fairly easy to obtain, we are more likely to become obese. I am taking a biocultural approach to my research and using evidence of obesity in captive primates to support some of the larger anthropological and evolutionary theory I am basing my research off of. After talking with Dr. Rodrigues about my senior research project, she suggested some directions to take my projects and offered me some sources. Much of what we have learned in class, like the socioecological factors that can affect health, behavior, and social organization, is also very relevant to that research. This is how I became more specifically familiar with food accessibility for primates and its effects on health and behavior, more specifically in comparison between free-ranging and captive primates.

Because the focus of our senior projects is on humans, I will only very briefly be touching upon supporting evidence from non-human primates. For my proposed paper, I would like to study the health and behavior of primates in captivity, particularly in comparison to free-ranging primates. From our research on gorillas for our midterm paper and some of my own research, it is clear that there is not enough research done on animals in captivity. Although I am not 100% sure about the format of my paper, I think that I will probably approach the topic as a proposal for a research project. Some of the research questions I will be approaching include:

  • Is a captive environment detrimental to the health and physical, emotional, social, and psychological well-being of primate species?
  • What ways can zoo staff, animal behaviorists, and researchers enrich enclosures to challenge primates physically and mentally to improve their lives?
  • Why do some species thrive in captivity while others do not?
  • Are there noticeable differences in health and behavior in species between captivity and the wild?
  • What effects do food accessibility have on the health and behavior of primates?

I know that narrowing down my research topic is something that I will definitely need to do if I choose to stick with the research study proposal format. If I had to narrow it down, I would likely choose primate obesity and related health problems and changes in behavior that result from this. This is one of the primary health issues in zoos around the world (as you can see in the photo below). Some zoos have implemented changes in diet to combat the lack of energy and effort an animal needs to expend to get the food. As we have learned in class, we have discussed many species that must travel great distances to get food and therefore have high caloric requirements. In captivity, most primates must travel a matter of feet to grab the food given to them. For future research, I would propose implementing challenges or tasks for animals to get the food, not only so they expend more calories but also so they are stimulated mentally.

Obese Rhesus Macaque at the Omaha Park Zoo in Osaka, Japan


The article that I wrote about for our previous article review e-portfolio post is very relevant to my final paper. I have found several other articles on the subject, some of which discuss differences in both health and behavior based on diet and food accessibility. I am looking to find more research on how the captive environment affects their behavior outside of food accessibility.


Ange-van Heugten, K.D., van Heugten, E., Timmer, S., Bosch, G., Elias, A., Whisnant, S., Swarts, H.J.M., Ferket, P., and Verstegen, M.W.A. 2009.  Fecal and salivary cortisol concentrations in woolly (Lagothrix ssp.) and spider monkeys (Ateles spp.). International Journal of Zoology, 2009.

Fairbanks, L.A., Blau, K., and Jorgensen, M.J. 2010. High-fiber diet promotes weight loss and affects maternal behavior in vervet monkeys. American Journal of Primatology, 72(3): 234–241.

Kemnitz, J.W., Sapolsky, R.M., Altmann, J., Muruthi, P., Mott, G.E., and Stefanick, M.L. 2002. Effects of food availability on serum insulin and lipid concentrations in free-ranging baboons. American Journal of Primatology, 57(1): 13–19.

McEwen, B.S. and Wingfield, J.C. 2003. The concept of allostasis in biology and biomedicine. Hormones and Behavior. 43(1): 2-15.

Power, M.L., Ross, C.N., Schulkin, J., and Tardif, S.D. 2012. The development of obesity begins at an early age in captive Common Marmosets (Callithrix jacchus). American Journal of Primatology, 74(3): 261–270.


Special Collections: Dian Fossey Archives


A few weeks ago for class, we were tasked with visiting the Special Collections & Archives in the Z. Smith Reynolds library and look through the papers of Harold T.P. Hayes. Hayes had written an article on Dian Fossey and her Gorilla research for Life magazine in 1987, leading to the 1988 film Gorillas in the Mist. He was working on an extended piece on Fossey when he died of cancer at age 62. He subsequently donated all of his notes to Wake Forest which we have the opportunity to utilize as a primary resource for this e-portfolio post.

The document I chose from the folder I was given was an outline of Fossey’s Gorilla Research Project, which appears to have ended in July 1967 (there is a note written by Hayes saying “Early – but date unknown”). She breaks down the different components of her research and behaviors her team will be studying, which included play activities, deaths/injuries, range distribution, range determination, reactions and uses of surrounding objects, nesting activity, food and feeding behavior, displacement activities, communications, reactions to other animals, and study methods.

Play Activity: She notes that play activities seem to be the first activity interrupted by an observer’s presence, meaning that playing could be more common than was previously thought (just not recorded). She made observations about age-sex combinations and how all combinations usually occur except for the silverback-blackback combination. She noted that gorillas preferred certain times of day when it is most sunny: in the mornings or after a noon rest period. They also preferred open lava slide areas where their movement is uninhibited or around the base of a large, central tree where a group is gathered. Mothers begin or end grooming sessions with their infants by mock-biting, tickling, or a “teasing type of cuffing.” Infant play activity is notable for its repetition (for example, sliding). When feeding is not intensive, any member of the group can initiate play. Some other behaviors she observed were chasing, tickling with a plant, tumbling and rolling, swinging and rocking on tree limbs, and throwing plants at each other.

Deaths and Injuries:  During her 19 months of study, she noted only 3 traumatic deaths. An infant was killed when a mother interfered witha peripheral silverback attempting to enter the group. After its death, the mother dragged its body for three days before left in a used day nest. The mother of this infant received severe lacerations in the altercation, began lagging behind for six days, then disappeared, and was presumed dead. A 3-year-old juvenile was injured in a snare and was assumed dead after a sudden disappearance from the group. Two natural deaths occurred during this period, including an aged female of around 50 years who showed childish and senile behavior before disappearing, and a second dominant silverback died of peritonitis, pleurisy, and bronchial pneumonia after not being able to vocalize properly. She also noted injuries to 3 individuals. A peripheral silverback was injured after a brief altercation with the dominant silverback, a female was injured likely due to a snare, and a young blackback was bitten when two gorilla groups came together.

Personal Estimate of Present Range Distribution in Virunga Mountains:  She describes 4 sites: Mt. Mikeno, Mt. Karisimbi, Mt. Visoke, and Mt. Gahinga/Sabinio/Muhavura.

Tentative Range Determinations: She lists factors that may influence ranging behavior in mountain gorillas. For seasonal causes, she lists heavy rain leading to water barriers and prolonged dry periods which affect vegetation, although she noted little variation in range due specifically to different types of vegetation. She also included inter-group correlation, which depends on the proximity or distance of another gorilla group. She also mentioned that cattle grazers and poachers have a massive impact on gorilla occupation of saddle area, as well as her opinion that if cattle grazing and poaching continued to increase at the rate at the time, she believed that free-range mountain gorillas would become extinct in 25-30 years.

Applications and Reactions to Surrounding Objects (Natural and Introduced):  She discusses the uses of foliage(leaves, moss, bark, etc…), including aimed throwing, tossing, using stalks of lobelia as “spear object” before a running display, and for tickling in play. She mentioned leopard-killed bodies of duiker (small forest antelopes), which gorillas largely ignored when they came into contact with them. The introduced objects included gloves, a knapsack, shoelaces, and camera equipment, piquing the curiosity of a blackback adult, who stared, picked them up, smelled them, and replaced. Gorillas also used plant material for nest building.

Nesting Activities: She notes that their location may be contingent upon ease of surveillance and especially the weather, especially protection from rain. She said they rarely repeatedly use their nests, and if they did, they would add new plant materials to it. To build the nest, they often use ground foliage (60%) and occasionally moss. Some groups build elaborate nests in very specific locations while others will nest in any place. Sharing of nests is rare but has been observed in a few instances.She also noted one young adult who built a function-less canopy over his nest.

Food and Feeding Behavior: She chooses not to detail their food preferences because they were consistent with previous studies. She states that transportation of food is common, and that there are individual differences in feeding habits. Sharing has not been observed and mothers will often take food from their infants’ mouth and discard it. A crippled juvenile adapted to eating by using a gripping foot. Symbolic feeding in gorillas was found to lead to real feeding and human observer can induce feeding by pretending to feed.

Displacement Activities: Fossey discuss chestbeating, the most common means of releasing excitement and observed in all ages and sexes other than newborns. Other displacement activities that she describes are leg kicking, foliage slapping and branch breaking, ground thumping, body rocking and weaving, and cart-wheeling.

Communications: She notes a variety of vocalizations and their frequency, including alarm barks, screaming, changing of voice in an individual, intensive roar, whinneying when not able to vocalize due to illness, and hooting. She also describes chestbeating as a communcation of location when not for displacement. Acridness of odor communicates the emotions of a situation (fear, anger, or exceitement), while posturing is used to show intention. She felt that facial expressions, at the time did not convey much of a communicative effect.

Reactions to Other Animals: She noted that a few gorillas liked to observe elephants but did not interact with them, while they are “intolerant” of buffalo who follow their trails. They note the alarm barks and vocalizations of duiker, dogs, and birds. There is no evidence of any incidental meeting with cows.

Study Methods: She finally describes her methods. Obscured (concealed)  contacts are invaluable for observation of normal behavior but it does not promote habituation. Un-obscured (open) contacts is useful for habituation and they will slowly refer back to more normal behaviors rather than imitative behaviors. Daily contacts are beneficial for understanding routing reasons in ranging. Her positioning strategy is to be downhill (uphill makes the gorillas uneasy) and as close as possible before the observer is noticed. The effect of poachers and grazers on habituation is detrimental in some areas because this is the only human contact for some gorillas and makes it more difficult for them to be studied.




“Outline of Gorilla Research Project – Dian Fossey” from the Howard Hayes Files in the Special Collections of the ZSR Library at Wake Forest University.

Robbins, M.M. 2014. Gorillas Across Time and Space. In Primate Ethnographies. Ed. Strier, K. B., Upper Saddle River: Pearson. 163-174.

NC Zoo

Earlier this month, we had the opportunity to visit the North Carolina Zoo in Asheboro for a class field trip. Our assignment was generally to learn more about gorillas in a non-classroom environment. We experimented with three different methods of observation, including free observation, continuous focal sampling, and instantaneous focal sampling. We had two complementary assigned readings: Dian Fossey’s Gorillas in the Mist and Martha Robbins chapter “Gorillas Across Space and Time” in the Primate Ethnographies textbook. We also had the opportunity to read through some of Howard Hayes’ files on Dian Fossey and her research in the Special Collections section of the ZSR library at Wake Forest. The two readings and the files outlined these two primatologists’ research projects on free-ranging gorillas in the wild and were assigned to us so we could make comparisons between wild gorillas and captive gorillas as well as comparing our observations and findings to those of these two researchers. Finally, we were to take these readings and our observations of the captive gorillas and write a midterm paper, additionally supplemented by our own background research.

One of my favorite behaviors I observed at the zoo was the gorilla’s use of burlap. I saw each of the five gorillas using the burlap sacks for a variety of reasons. The infants would run around their enclosure, dragging a sack behind them, chewing on it, wearing it on their heads, or slamming it against the windows. The adults would carry the burlap sacks around the enclosure and lay them down to sit or nap on. I also noticed one gorilla Jamani cuddling with her baby Bomassa on two pieces of burlap lined up next to each other. She pulled it up around herself slightly and rubbed the textured material between her fingers while she slept. One zoo employee I spoke to mentioned that they believe that the burlap sacks provide a sense of comfort for gorillas in many zoos. When transferring gorillas between zoos, staff will often pack burlap with the gorillas to keep them calm and help them adjust to their new enclosures more quickly. The reminder of home through the familiar smells on the burlap might be the reason for this.

If I were given the opportunity to choose between studying gorillas or one of the other types of primates at the zoo, I think this would be a hard decision for me. Ideally, I would love the opportunity to study all of these primates to compare how effective some of these techniques are on different species in different enclosures. I think that studying some of the more active species would have resulted in completely different activity budgets. I think that there would probably be a greater difference between continuous and instantaneous focal samples for animals that change their behavior more rapidly, potentially resulting in a significant chi-square test. I still believe, however, that the gorillas were a good choice for many reasons. Because there were only 5 gorillas, it took us less time to learn how to identify and distinguish between them. Also, their body size and shape and large, expressive faces make them much more recognizable than some smaller species would have been. The size of the enclosure, their proximity to the viewing windows, and the lack of places to hide or be obscured all made it easier to pick out identifying physical features, especially with my terrible eyesight. I also think that their lifestyle and energy level allowed for a good starting point for new primatology students learning to utilize different observation techniques, as other more active and high-energy species would have been more chaotic and difficult to keep track of for our first time observing. I also think that our study of gorillas was as much about honoring the work and research of Dian Fossey as her book was meant for our benefit in researching captive gorillas. This entire project really emphasized her critical importance in the field and history of primatology.

I have always had an interest in the enclosures of animals in captivity. Because I wish to pursue a graduate degree in animal behavior, I am particularly interested in applying the research of behavior and biology of species and how they vary in captivity and the wild. I would love to be able to expand the scope of these studies and apply this research to enriching the enclosures of the animals to stimulate them mentally and physically and fostering the best possible health, social interactions, and psychological well-being.

My favorite animals that we visited at the NC Zoo were the Hamadryas baboons. Although we did not get to stay very long, I loved watching the young baboons play and compete with each other over peeling big pieces of bark off of the logs. I also liked seeing the adults’ reactions to the juveniles playing.

An extremely rare red-haired baby Hamadryas baboon born at a Safari in Israel!


From Food to “Friends”

This week’s topic is the relationship between food and social organization. Food security and availability are especially important in determining social organization, influencing competition and defensiveness, size of groups, and range of movement. Seasonality brings changes in food availability and, in turn, changes in reproductive behavior. Carefully synchronizing gestation, birth, lactation, and weaning periods with ecological, nutritional, and social conditions is of the utmost importance for reproductive success and the survival of the mother and her offspring.

The size of food patches limit how much individuals can eat, as well as how many individuals can eat there at the same time. If a patch can feed multiple individuals in a feeding group sufficiently (enough to replenish their energy), it becomes more worth it to defend that patch. The size of these patches determine grouping patterns and sizes and how willing individuals are to cooperate and compete within or between groups. The density of these patches also creates a tough decision-making process for primates based on the time and energy of traveling from patch to patch and defending them from individuals within or between groups. If patches are close together in an area, this can be considered a larger territory that primates can defend. If these patches are too spatially spread apart, it is not economically advantageous to defend this entire area. Individuals who are more frugivorous must expend more energy to find the fruits, which are more patchily disperse than leaves. However, fruits provide more energy than leaves to the individual, and they will be able to travel farther to get them. Small territories are easier to defend, but if they are filled with mostly low-quality foods (leaves), primates will be less inclined to defend them.

Food is particularly important to female primates because of the energetically taxing responsibility of pregnancy and neonate care. Better-fed female primates can begin reproducing at a younger age, can become pregnant more frequently, and live longer to continue reproducing. Aside from a few species, most mother primates also bear most or all of the burden of caring for their infants. Some primate species “park” their young in safe hiding spots or have the help of a mate or group member, but those that don’t must support their own, fattier body (built up for nursing) as well as the ever-growing body of their baby.  Producing milk during the period of lactation requires 2-5 times more energy than at any other time of their life. To meet these high energy demands, they need to spend more time feeding and choosing foods with higher protein content.

Spider monkeys prefer to go for high-quality foods (fruit) whenever seasonally available. They have fairly fluid grouping patterns, coming together in large feeding groups at big fruit patches, splitting up into smaller groups at small patches, and even foraging alone. Because there are not enough large fruit patches in their environment, spider monkeys generally do not defend resources cooperatively, but rather acknowledge a hierarchical order of fruit patch access. Subordinates allow for dominant spider monkeys to take first dibs on the fruit and often forage on their own rather than within-group competition. This submissive cooperation with their group is more beneficial to them, especially in contests against other groups. Although extremely closely related, different species of spider monkey in different regions of the world can vary in their behavior, despite how biologically and genetically close they are. For example, fruit patches in Peru are generally larger than those in Costa Rica. Peruvian spider monkeys, therefore, are able to to cooperatively defend these patches in between-group competition, living in extended matrilines. Costa Rican spider monkeys do not cooperatively defend patches, restrict their births to the dry season, and live in extended patrilineal societies. For squirrel monkeys in Suriname, patches are small and dense, making the level of within-group competition (scramble) much higher than other spider monkey species.

Peruvian Squirrel Monkey chowing down!

Costa Rican Squirrel Monkey grabbing a snack!

Suriname Squirrel Monkey grubbing out!

A major take-away from this week’s lesson is that, in many cases, morphological traits are changing more slowly than the selection pressures on the continuously changing environment. This is largely in part to human encroachment, forcing some species to move and change their diets. Some species, such as macaques, are fairly adaptive and have learned to change along with their environments in order to survive. Other species with more specialized diets, however, may have a more difficult time adapting if their environment is threatened by change. This is a major conservation issue, and if these environments continue to change, the world may lose many of these species. These changes in environment lead to changes in diet, and as a result of this, their behavior can also change substantially. I am curious as to how much these changes in behavior due to environment could, in turn, effect the environment itself.


Strier, Karen B. Primate Behavioral Ecology. Boston: Allyn and Bacon, 2000. Print.

Peruvian Squirrel Monkey:

Costa Rican Squirrel Monkey:

Suriname Squirrel Monkey:

Sexy Bonobos

Bonobos kissing while grooming

To study the role of sex in behavior and evolution this week, we used the bonobo, our genetically closest living ancestor. We read the article “The Other ‘Closest Living Relative’: How Bonobos (Pan paniscus) Challenge Traditional Assumptions about Females, Dominance, Intra- and Intersexual Interactions, and Hominid Evolution,” (2000) which outlines the sexual and reproductive behaviors of bonobos and suggested theories to explain these behaviors. According to the research, female bonobos are very much in control of their own reproductive and social interactions, having been observed attacking males who refuse to mate with them, high-ranking males protesting a female copulating with a low-ranking male, and low-ranking males they are mating with when a high-ranking male threatens. There is some debate as to what female behavior we call “dominant” or “co-dominant,” and there appears to some bias in distinguishing between male and female behavior.

They explain a few different viewpoints and hypotheses to explain this behavior and different interpretations of it. The first is the “Traditional View,” in which they suggest that patterns of dispersal are predictive of patterns of bonding. Chimpanzees have much stronger male-male relationships, believed to based off of evolutionary fitness, and females are also the dispersing sex, avoiding one another and the aggression of males. In bonobos, females are the dispersing sex, there is less male-male sociality than in chimpanzees (despite inter-relatedness), and males and females groom each other continuously (regardless of reproductive state). The “Revised View” holds that the relationships between dispersal pattern, bonding, and relatedness may not follow theoretical predictions. Some female chimpanzees have a reproductive strategy in which their infants are sired by males from other communities, which is desirable because they often don’t disperse as much as previously believed. This also means male-male relationships are not based on relatedness or fitness. They use extra-group paternity as an example against the theory of the bonding-philopatry relationship. Bonds between males and females are actually weaker than previously believed (besides mother-son bonds). The strongest unrelated relationships are between females, and grooming reflects social ranking within these female-female relationships. Studying female-female relationships, according to the authors, are key to understanding bonobo social organization.

Something interesting they mention early on in the article is the variability in behavior within the species of chimpanzees and bonobos (by population). A major take-away from this week is that, although it creates less cognitive dissonance for us to be able to neatly classify entire species (also meaning all of the populations and sub-species within a species) into different group social structures, it is not always accurate or pragmatic to do so. It is exclusive, all-or-none classifications like these that led to the biases in interpreting observed behavior that we have today. They prevent primatologists from approaching observation with a more open mind, as a major bias in research is the self-confirming bias. Rather than “species-typical” characteristics, most primatologists now believe that behavioral differences between chimpanzees and bonobos can be attributed to both ecological opportunities and constraints, leading to diverse selection pressures. Although somewhat in opposition to this theory, it is also worth mentioning that a study done on chimpanzees and bonobos living in identical captive environments still exhibited distinct behavioral characteristics. Bonobos engaged in co-fishing and sex when fishing for termites, while chimpanzees did not eat together and did not engage in sex while fishing for termites. Something even more interesting is that bonobo behavior observed in this specific captive environment reflected behavior in other captive environments and data collected from wild bonobos in the field.

I think that studying bonobo sexual behavior can tell us a lot about our own sexual behavior. Having taken the psychology course Human Sexuality, I know that studying human reproduction and sexual behavior has always been something both fascinating and important to us. The Parish and De Waal (2000) article emphasizes the need to expand our own models for human evolution based off of bonobo research to include some of the unique relationships that they share. I believe that by studying bonobo sexuality and by comparing and contrasting their behaviors to those of our own, we can take a step into the evolutionary past and perhaps track where certain behaviors developed and what factors (social, cultural, ecological, etc…) pushed for some behaviors to make us more adaptive. Perhaps we can even make speculations about the sexual behavior of Australopithecines and early Homo species from which we evolved and which link us to the bonobo.


Parish, A.R. and De Waal, F.B.M. (2000), The Other “Closest Living Relative”: How Bonobos (Pan paniscus) Challenge Traditional Assumptions about Females, Dominance, Intra- and Intersexual Interactions, and Hominid Evolution. Annals of the New York Academy of Sciences, 907: 97–113.

Strier, K.B. (2011) Primate Behavioral Ecology, 4th Edition, Pearson/Prentice-Hall. (PHOTO)

Obesity in Captive Marmosets: Article Review

For my ANT 390 Student-Faculty Seminar course, I am planning on doing research on how food security and accessibility affects primates’ health and behavior. On the one hand, the theory of cultural ecology supports the idea that the easier it is for a group to get food, the more time they have to advance socially, technologically, and culturally. On the other hand, many animal behavior studies show that animals in captivity are at an increased risk of obesity because they are not as challenged to find food (just walking over to a food bowl) as they would be in the wild. However, not very much research has been done on obesity in infant primates. This is why I chose Power, Ross, Schulkin, and Tardif’s article, “The Development of Obesity Begins at an Early Age in Captive Common Marmosets (Callithrix jacchus).”

This article studied the patterns of fat mass gain in 31 marmosets from birth to 12 months old (15 considered normal, 16 considered fat). The original subject pool was 33 marmosets, but one was stillborn and another died of “trauma.” The normal condition necessitates that marmosets have less than 14% fat compared to lean muscle, and marmosets with fat content higher than 14% were placed in the fat condition. I thought that the sample size was appropriate for captive baby marmosets (small pool to choose from) and also because they were able to maintain almost the same number in each condition. They chose marmosets because they develop fairly quickly, making longitudinal studies easier, tracking fat content and obesity from infancy into adulthood. These marmosets were fed either a normal diet or a special high-fat mix after being weaned after 30 days.

They measured weight and fat content at 1, 2, 6, and 12 months of age. They were unable to take initial weight and fat content measures of neonates because they did not want attachment issues with the mothers but took these measures from the two marmosets that died within the first 36 hours of their life. I thought that this was actually a pretty creative way to deal with unexpected circumstances and to make up for data that would have otherwise gone unrecorded. The marmosets were divided into normal and fat conditions based on their fat content at ages 6 months and 12 months.

Normal Common Marmoset

Obese Common Marmoset

There were no effects found for sex or litter size (some were raised in twin pairs, others as singletons). The studies found that fat mothers produced larger babies (weight), maternal adiposity and diet each independently having a significant effect on infant birth weight. However, maternal adiposity did not have an effect on infant adiposity at any age. Infant diet had a significant affect of adiposity (fat content) of babies at 6 months, gaining more weight in both lean and fat mass, but before 6 months and after 12 months diet no longer had a significant effect. Obesity in captive marmosets appeared to start at 1 month of age, and although mass was similar, growth patterns between the fat and normal conditions varied (fat to lean tissue ratio). The presentation of the results was not entirely clear, and wording at times was somewhat confusing. If I was not comfortable with reading statistical analysis of data, it would have been almost entirely unclear.

The authors also mention that this study could be helpful in the study of obesity in human infants. Previous animal and primate research in obesity did not seem to make particularly good translational models for humans because it is believed that human infants have substantially more body fat, peaking at 25% fat at around 6-8 months (the point just before weaning off of breast milk). This high fat content in comparison to infants of other primates and animals is likely due to the energy demands of the large developing brain of human infants. One interesting finding of this study was that neonatal marmosets, unlike most other nonhuman primates and other mammals, were born with a relatively high fat content at birth. This means that infant marmosets may resemble human infants in adiposity more closely than other anthropoid primate models, although humans still differ in the type of fatty tissue and amount. They also found in previous research that female adult marmosets are more likely to become obese than adult males, as is also true with humans. In this study, they found that there were no significant differences between the sexes in obesity. Their previous studies also showed that obesity in marmosets is associated with lipid and glucose metabolism, resembling that of humans. This implies that obesity in marmosets may experience similar metabolic consequences to humans.



*Sorry for the late post! I completely lost track of the e-portfolio’s because of the snow storm. 

Hybrid Primates

This week we read Strier’s chapter on primate evolutionary history and the Cortes-Ortiz et al. article “Hybridization In Large-Bodied New World Primates.”

One of the major issues raised with hybridization is classification and taxonomy. It really comes down to how we define and differentiate between”species” and “sub-species” and how restrictive or loose these terms can be. Most people define a species as  individuals of a population that are capable of interbreeding and producing fertile offspring. There are several different theories behind speciation (the process by which new species are formed), called “species concepts.” However, some of these species concepts present a lot problems, especially when considering hybridization. The recognition species concept states that individuals of a species will recognize other members of the same species for potential mates. This is problematic because sometimes species will try to breed outside of their own species in certain situations, sometimes even resulting in hybrid offspring (mules, ligers, wholphins, etc…). The ecological species concept defines a species as a set of individuals exploiting a single niche. However, populations of the same species could be capable of adapting to different niches (humans, for an obvious example!). Also, two species could theoretically occupy the same niche and simply maintain different social behavior (olive and hamadryas baboons?). The evolutionary species concept states that a species evolves from its own separate lineage. It is believed that hybridization could lead to new recombinant lineages, which complicates this species concept even further. In the distant future, if no documentation is recovered, will biological anthropologists be able to distinguish the recombinant lineages of today’s hybrids clearly?

Strier uses the example of the hybrid baboons to make these taxonomic issues clear. The olive baboon and hamadryas baboon were originally defined as two of several different species of baboon. However, it has been found that olive and hamadryas baboons living in close proximity in Ethiopia will occasionally interbreed, producing fertile offspring! They can interbreed with other olive-hamadryas hybrids or from one of the two parent species. This must mean, by the definition of a species, that these two types of baboon must be the same species, and are now considered two “subspecies” of hamadryas baboon. This is difficult for many primatologists to imagine due to their significant differences in social behavior and appearance. The olive baboon lives in matrilineal multi-male, multi-female groups. Hamadryas baboons live in patrilineal groups made up of one-male units who herds a few females into his unit. Male hamadryas baboons will try to collect and heard female olive baboons, but they do not respond to the same cues, leading to short attachments. Male olive baboons are used to sharing females and would not fight off a male hamadryas. This is where interbreeding occurs, because if the tables were turned and an olive male tried to mate with a female hamadryas, he would be scared off by the protective hamadryas male and the female would be committed through her attachment to her male unit leader. The behavior of the hybrid offspring is distinct of the species of either parent, and hybrid sons more closely resemble hamadryas baboons and hybrid daughters more closely resemble olive baboons. These “cultural” differences, if you will, could also make it difficult for these hybrids to socially interact with potential mates.

The Cortez-Ortiz article uses howler monkey hybrids to make the same point that in some cases, biases in the direction of hybridizations exist and could have morphological, behavioral, genetic, and cytogenetic consequences for the population. They state in this study that these results could also give some insight into the speciation process, which implies the possibility that these hybrids could become species in the future. This article brings to mind the point that haunts many primatologists and taxonomists: that if hybridization is occurring and blurring lines of classification now, could this have played a major part in primate evolutionary history as well? Could some of the specimens discovered in the past have been hybrids, making their taxonomic classifications incorrect?

However, my question is whether this is truly what primatologists should be focusing on, when there appear to be more critical pragmatic issues raised by hybridization. Strier uses an example of the Florida panther to show how interbreeding threatened their status on the U.S. Endangered Species Act because hybrids were not technically included on the list. In the future, these taxonomic issues must be clarified for policy work to protect animals and species from extinction. Taxonomists and policy makers must consider the following question: Is it more important to us to preserve “pure” species and to allow for hybrids to fall through the cracks of protection and conservation or for us to protect all animals, whether “pure” or hybrid? Another major aspect of hybridization that we must consider is the influence of human activity. Our expansion into new areas forces some species out of their habitats and into niches already occupied by closely related species, resulting in forced hybridization. One example Strier gives is the hybrid offspring of olive and yellow baboons, which has been shown to yield early maturation in hybrid males. This could greatly affect the genetic composition of populations. If certain populations are reproductively isolated for long enough in certain areas, this could even lead to new species. Also humans releasing non-native species into the wild creates potentially unwanted breeding and hybridization. Another issue Strier mentions is the use of squirrel monkeys in labs for biomedical research. When breeding lab monkeys, taxonomic status is largely ignored or not taken into serious enough consideration, resulting in different kinds of hybrids being tested. We already know from the example of the baboons that different species and their hybrids have vastly different appearances and social behavior. These differences could actually be creating skewed results and it is therefore critical to take this into account when interpreting findings.

Howler Monkeys – Black x Mantled hybrid


Cortes-Ortiz, L., Duda, T. F., Canales-Espinosa, D., Garcia-Orduna, F., Rodriguez-Luna, E., & Bermingham, E. 2007. Hybridization In Large-Bodied New World Primates. Genetics176(4), 2421-2425.

Strier, K. B. 2011. Primate Behavioral Ecology. Upper Saddle River: Prentice Hall. (PHOTO)

Lar Gibbon

Lar gibbons, sometimes called “White-Handed Gibbons,” belong to the genus Hylobates, which means “forest walker”, one of four genera for all gibbons. Lar gibbons are apes, although they are often confused with monkeys due to their appearance. However, the major difference between apes and monkeys still holds true: gibbons do not have a tale, and instead have ischial callosities (sitting pads), which are leathery patches of skin where the tail would be. The average male Lar gibbon is weighs about 11-17 pounds and average females weigh 10-15 pounds, while both males and females are usually about 17-23 inches tall. Gibbons can range from a cream color to brown or black, determined not by sex or age but by genetic inheritance. The dominant allele in pelage color is dark, although the proportion of light to dark gibbons varies largely between populations. These gibbons appear to have no preference between light and dark when choosing a mate. They have a white ring of fur around their faces and white hands and feet.

Gibbon Mates!

Lar gibbons have proportionately very long arms and long hooked fingers, allowing them to swing hand over hand from branch to branch, known as brachiation. They can even swing from tree to tree, clearing distances of up to 33 feet! Their short legs can be tucked under to make it easier to maneuver quickly while swinging through branches. They are considered the fastest of all tree-dwelling, non-flying animals! Although specifically adapted for arboreal locomotion, they can also walk, hop, run, climb, swing, bridge, and leap, choosing bipedal, tripedal, or quadrupedal gaits. When moving bipedally, they hold their long arms out by their sides to help balance.

Lar gibbons primarily live in lowland forests in Southeast Asia and a small part of South Asia, in Indonesia, Laos, Malaysia, Myanmar, and Thailand. They are believed to be completely extinct in China, but still thrive in Thailand, where 15,000-20,000 of them live today. The Lar gibbon has the greatest north-south range of any species of gibbon.

A gibbon casually sunbathing

Lar gibbons eat mostly fruit, especially figs which are their favorite (figs make up 27-50% of their whole diet!).They also eat leaves, shoots, vines, flowers, insects, and even bird’s eggs. An interesting fact is that Lar gibbons eat parts of over 100 different species of plants. They also drink water that collects in holes in tress by cupping their hands and sipping it out of their hands. They have also been known to beg for food from other members of their group when food is scarce. Lar gibbons spend almost all of their time high in the tree canopy in feeding trees.

Everyone loves ice cream…even gibbons!

Lar gibbons almost always live in serial monogamous pairs, although in some populations, social relationships are more flexible, allowing for polyandry in females (mating with multiple males) or extra-pair copulations. They spend about 1/5 of their time engaging socially within their group, grooming, playing and other social contact. Within-group aggression is rare, and interactions between different groups can either lead to physical altercations or sometimes between-group playing or grooming. Between-group altercations are most times between males over territory and are just vocalizations 20% of the time. However, Lar gibbons can put their money where their mouth is when it comes down to it, and fights can lead to serious injury or death. Lar gibbons have 7 basic vocalization note types which are lumped together into “phrases,” which could mean anything from singing, alarm calls, and contact calls. Once they wake up in the morning, gibbon couples will sing a duet before going about feeding and travelling.

Lar gibbons have a lot of natural predators, including several species of big cats, pythons, eagles, and are therefore very sneaky about where they go to sleep. Usually members of a group of gibbons will sleep one to a tree in close proximity with each other. They also have been known to mob predators to chase them off. An even larger threat to gibbons is human activity (hunting is #1 and forest clearance is #2). They are hunted for both food and the exotic pet trade and are now an endangered species.

Singers and Swingers:



IMAGES/VIDEOS (in order) (BBC)