Happy World Orangutan Day- A Brief Review of Recent Research and News

Happy World Orangutan Day. Orangutans, both Bornean (Pongo pygmaeus) and Sumatran (Pongo abelli), are some of my favorite primates. These orange, solitary creatures live a primary arboreal life in the country of Indonesia on the islands of Borneo and Sumatra. They are highly intelligent and one of our closest living relatives. In honor of International Orangutan Day, I thought I'd celebrate with a post on some of the latest orangutan research.

Starting off with some good news: there are more Sumatran orangutans than was previously thought. There are possibly 8,000 more, bringing the total up to approximately 14, 600 individuals. Better methods and techniques are the main reasons behind the increase in numbers with areas previously not surveyed visited and orangutans found at elevations higher than researchers previously thought it was likely they inhabited.

Sumatran orangutans have been classified as critically endangered since they were first listed on the IUCN Redlist. However, Bornean orangutans were previously listed as endangered, until it was announced earlier this year that they have slipped to critically endangered as well. Habitat loss due to palm oil and rubber plantations threaten this species as well as hunting.

Rocky, an orangutan at the Indianapolis Zoo, can reproduce grunting sounds made by humans. He is able to mimic the pitch and tone of sounds made by humans and started mimicking at age eight. When compared to a database filled with the sounds of other orangutans, Rocky is unique. This new finding raises more questions about the development and origin of language in humans and what our last common ancestor with orangutans looked (and sounded?) like.

Another zoo-based study has shown that orangutans have the ability to use past experiences to create new images in their mind about new experiences. This ability is referred to as affective forecasting. Naong, an orangutan housed at a Swedish zoo, is able to guess whether he likes a new juice flavor based on the past juices he's tasted.  Originally given four flavors of juice, once Naong was familiar with these flavors, the juices were mixed together. Naong, if he observed the mixing, was able to guess whether or not he liked the mixed flavors based on his past preferences. This is yet another way humans are not as unique and different from our primate ancestors than perhaps we thought. Although anyone who has spent a significant amount of time observing these animals at a zoo or reading up on them probably won't be too surprised.

An unsettling study shows how just aggressive female orangutans can be. For the first time, researchers have observed the death of a female orangutan due to the aggressive actions of other orangutans. A young, female, Bornean orangutan attacked an older female with the help of a male orangutan for over thirty minutes. The two attackers traded off, with one attacking and the other preventing the victim from escaping. The older female later died as a result of her injuries. While aggressive behavior on this scale is known in chimpanzees, this is the first time such extreme behavior has been observed in wild female orangutans.

To end on a lighter note, a Sumatran orangutan has released his first music single. Playing on the drums and piano while a zookeeper recorded, Kluet is on his way to international fame perhaps. You can purchase the single here. Proceeds are going towards conservation efforts.

To conserve these animals and show your support for them, consider buying sustainable palm oil, being mindful of your overall consumption and energy expenditure, and donating your time or funds to charities that support these magnificent apes, such as Orangutan Foundation International, Bornean Orangutan Survival Foundation, or the Center for Great Apes.

Bonobos focus on the positives: humans focus on the negatives

Photo: Mark Dumont

A recent study done on captive bonobos (Pan paniscus) reports that these apes focus on images that are of a more positive nature (compared to images of danger or aggression). Using a test designed to understand attentional bias in humans, researchers from various institutions in The Netherlands studied attentional bias in bonobos, our close relatives.

Four female bonobos each completed either twenty-five or twenty-six trials in total over thirteen separate testing sessions. They were briefly shown two images and then a dot appeared on the screen which remained there until the individual tapped the dot. Upon tapping the dot, the individual is rewarded with a food item. In half of the trials, the images briefly shown were of a bonobo in some sort of emotional state, such as pant hooting, playing, or in distress. In the other half, the images were of a bonobo in a neutral state.

By looking at the reaction time, Kret and colleagues (2016) were able to determine that bonobos are more captivated by images of other bonobos that are affiliative or protective rather than images with bonobos in distress or aggression, which has found to be the case most often for humans (Vuilleumier and Schwartz, 2001; Williams et al., 2004; Tamietto et al., 2005; Flaisch et al., 2009).

Images of yawning, grooming, and sexual behavior caught the bonobo's attention the most. Reaction time was longest for yawning, followed by grooming and then sexual behaviors. Yawning is a contagious behavior in humans and also for bonobos (Palagi et al., 2014). Grooming and sexual behavior are both types of behavior that reduce tension (Manson et al., 1997; De Waal, 1997; Crockford et al., 2013).

The increased attention devoted to these social behaviors suggest that they are of greater importance to bonobos than aggressive behaviors or actions associated with a threat. Given that this isn't the case with humans and what captures our attention, this study highlights another intriguing difference between the two species.

Links of potential interest:
Paper in PNAS 
Are bonobos more peaceful than chimpanzees?
IUCN page on bonobos


Works cited:
Crockford, C., Wittig, R. M., Langergraber, K., Ziegler, T. E., Zuberbühler, K., & Deschner, T. (2013). Urinary oxytocin and social bonding in related and unrelated wild chimpanzees. Proceedings of the Royal Society of London B: Biological Sciences, 280(1755), 20122765.

De Waal, F. B. (1997). The chimpanzee's service economy: food for grooming. Evolution and Human Behavior, 18(6), 375-386.

Flaisch, T., Schupp, H. T., Renner, B., & Junghöfer, M. (2009). Neural systems of visual attention responding to emotional gestures. Neuroimage, 45(4), 1339-1346.

Kret, M. E., Jaasma, L., Bionda, T., & Wijnen, J. G. (2016). Bonobos (Pan paniscus) show an attentional bias toward conspecifics’ emotions. Proceedings of the National Academy of Sciences, 201522060.

Manson, J. H., Perry, S., & Parish, A. R. (1997). Nonconceptive sexual behavior in bonobos and capuchins. International Journal of Primatology, 18(5), 767-786.

Palagi, E., Norscia, I., & Demuru, E. (2014). Yawn contagion in humans and bonobos: emotional affinity matters more than species. PeerJ, 2, e519.

Tamietto, M., Latini Corazzini, L., Pia, L., Zettin, M., Gionco, M., & Geminiani, G. (2005). Effects of emotional face cueing on line bisection in neglect: a single case study. Neurocase, 11(6), 399-404.

Vuilleumier, P., & Schwartz, S. (2001). Emotional facial expressions capture attention. Neurology, 56(2), 153-158.

Williams, M. A., & Mattingley, J. B. (2004). Unconscious perception of non-threatening facial emotion in parietal extinction. Experimental Brain Research, 154(4), 403-406.

The latest puzzling chimpanzee behavior

Young chimpanzee. Photo credit Sabine Bresse

Of the animal kingdom, chimpanzees, Pan troglodytes, are one of the well-known tool users. All populations of wild chimpanzees studied have been observed using leaves to obtain food and some populations have been observed modifying branches to forage for termites and even fashioning spears to hunt bushbabies (Shumaker et al, 2011; Boesch, 2012).

As is the case with studying many primates, our knowledge of tool use and how it is passed from generation to generation is limited by the number of field sites where long-term research occurs. Chimpanzees must first become used to human presence (or habituated) before their natural behavior can be studied, and this can take a great deal of time.

Theorizing that the repertoire of chimpanzee behavior is much wider than what is currently known, Kühl and colleagues used camera traps to study multiple populations of chimpanzees in West Africa that are not habituated. This is when they noticed some very interesting behavior. Researchers first noted unusual piles of rocks in trees and used camera traps to determine what was behind this puzzle. They observed chimpanzees picking up rocks from piles around or in trees and then throwing them at the tree.

Through the camera trap footage, researchers were able to determine that chimpanzees would throw the stones at the trees and vocalize a long-distance pant-hoot at the same time. The stones are mainly thrown by adult males and they seem to be independent of any sort of foraging behavior. The same chimpanzee was often observed returning to the tree and engaging in the behavior. This strange accumulative stone-throwing has only observed in West Africa and was seen in four populations of chimpanzees.

Stone throwing may be a type of male display, during which the individual attempts to draw attention to one's strength and impress other chimps. Kühl and colleagues theorize that using the stones in this manner may produce a loud sound resulting in a greater display. Another theory the authors present is that this may be a symbolic behavior. In either case, obviously more data is needed. Stone-throwing chimpanzees raises more questions than it does answers in terms of behavior and possibly cognition in the case of the latter theory.
 
This work goes to show that you can still learn a great deal about a comparatively well-studied primate species even if you're not Jane Goodall and haven't been working at the same research site for decades. Kühl and colleagues have captured some truly fascinating behavior that raise a series of new questions using technology to their benefit.

Links of potential interest:
Video of behavior
Pan African Programme: The Cultured Chimpanzee
How human are chimps?
Females more likely to use tools when hunting



Works cited:

Boesch, C. Wild Cultures: A Comparison between Chimpanzee and Human Cultures. (Cambridge University Press, 2012).

Kühl, H. S. et al. Chimpanzee accumulative stone throwing. Sci. Rep. 6, 22219; doi: 10.1038/srep22219 (2016).

Shumaker, R. W., Walkup, K. R. & Beck, B. B. Animal Tool Behavior: The Use and Manufacture of Tools by Animals. (JHU Press, 2011).

Find yourself being spiteful? Blame these primate relatives.

It looks like humans aren't the only ones who make an effort to punish or act negatively towards those we believe are undeserving. Leimgruber and colleagues (2015) recently published a new study on inequality and fairness in the journal Evolution and Human Behavior. They looked at whether capuchins (Cebus apella) would punish individuals who stole food or who benefited from an unequal distribution of food. The results and how they compare to other research might surprise you.

Capuchins are a New World Monkey that are closely related to us. Humans and capuchins last shared a common ancestor roughly 30 million years ago (Fragaszy et al., 2004). These social primates live in large groups with dominance hierarchies. To learn more about this species, including their behavior, click here.

C. apella Photo: John Mittermeier

As you can probably guess, capuchins were tested in captivity to determine how they responded when a reward was not equally given and when a resource was stolen from them. Six individuals were tested. All individuals were tested against a low-ranking member of their social unit. Monkeys were tested in different enclosures but with a shared table that spanned both enclosures. Multiple conditions were tests: one where the test individual had access to the food, one where the test individual briefly had access to the food and then a researcher moved it to the low-ranking individual, and one where the low-ranking individual could steal the food outright. When the low-ranking individual gains control over a food source (due to the researcher moving the food source towards the individual), capuchins will pull on a rope that collapses the table holding the food. They will also do this when the low-ranking individual is given the ability to steal the food.

Intentions don't seem to matter if you're a scorned capuchin. Capuchins punish the low-ranking individual even when that individual was not to blame for the unequal distribution of food. As Leimgruber stated when interviewed for Phys.org, capuchin monkeys appear to have a sort of "If I can't have it, no one can"attitude.

Similar inequality studies have been conducted with chimpanzees, our closest living relatives. When we think of chimpanzees in comparison to capuchins, chimpanzees may seem more ruthless. They will kill one another and they've been observed going to "war" with other troops of chimpanzees. Yet, chimpanzees will only make an effort to punish if the other individual is responsible for the inequality (Riedl et al., 2012). Perhaps capuchins are the anomaly or maybe this spiteful behavior does have its evolutionary origins 30 million years ago, making chimpanzees the anomaly. Similar studies will need to be done in other primate species to better understand the evolutionary history of this trait in primates.

Of course, we can't actually blame capuchins for our spiteful actions (nor should we: let's not forget the power of human agency), but this study adds to our knowledge of human behavior while, perhaps, raising more questions.

Links of potential interest:

Phy.org article
Video of capuchin fairness test
Frans de Waal Ted Talk on Moral Behavior

Works cited:

Fragaszy, D. M., Visalberghi, E., & Fedigan, L. M. (2004). The complete capuchin: the biology of the genus Cebus. Cambridge University Press.

Leimgruber, K. L., Rosati, A. G., & Santos, L. R. (2015). Capuchin monkeys punish those who have more. Evolution and Human Behavior.


Riedl, K., Jensen, K., Call, J., & Tomasello, M. (2012). No third-party punishment in chimpanzees. Proceedings of the National Academy of Sciences, 109(37), 14824-14829.

New research on vocalizations, grooming, and social bonds

Lemur catta Photo: author

Both grooming and vocalizing are linked to social bonds and relationships. Increases in the vocal repertoire of primates is correlated with group size and amount of time spent grooming (McComb and Semple, 2005). Previous research has shown that pairs of baboons (Papio cynocephalus) spend more time grooming one another (allo-grooming) and allo-groom more frequently if they are bonded socially (Silk et al., 2006). Dunbar first suggested that vocalizations may serve to act as a way of socially bonding when larger group sizes make grooming every member more difficult (1993; 2003; 2004).

A study published this December provides further insight into the reasons why small talk may have evolved and how it relates to social relationships. Studying ring-tailed lemurs (Lemur catta), Kulahci and colleagues (2015) examined vocalizations and grooming.  Four troops of free-ranging and semi-freeranging lemurs at the Duke Lemur Center and on St. Catherine's Island were studied. Vocalization and grooming network outdegrees were calculated to determine who each individual initiated vocalizations and grooming towards. The grooming network outdegree was simply the number of individuals the individual in question groomed. The vocalization network outdegree was   the number of individuals that the individual in question produced a vocal response towards upon hearing a call.

Kulahci and colleagues (2015) found that ring-tailed lemurs were more selective in who they vocalized to than who they chose to groom: as troop size increased, lemurs groomed more individuals but they did not vocalize directly towards more individuals. Regardless of troop size, vocalization network outdegrees were lower than grooming network outdegrees, showing that lemur are picky about who they vocalize to but less so about who they groom. Individuals responded to the vocalizations of lemurs they groomed more frequently than they did lemurs they groomed less often.

When audio playbacks were used, the same selectivity in vocalization responses was displayed. Thus, this selectivity in vocalizations is not due to olfactory or visual cues.

While this study agrees with previous work highlighting the connection between grooming and vocalizations, it does not align with Dunbar's hypothesis (1993; 2003; 2004) that vocalizations allow an individual to maintain more social bonds than grooming would. Whereas we would have expected to see vocalizations increase with group size, the opposite was true for this study. Rather than vocalize with more troop members as group size increases, L. catta selectively vocalize and groom all members. Thus, vocalizations may be a better indicator of social bonds than grooming, at least in L. catta.

Links of possible interest:
 Social grooming in primates
How the size of the neocortex and the size of grooming clusters relate
Derived vocal complexity of geladas


Sources:

Dunbar, R. I. (1993). Coevolution of neocortical size, group size and language in humans. Behavioral and brain sciences, 16(04), 681-694.

Dunbar, R. I. (2003). The social brain: mind, language, and society in evolutionary perspective. Annual Review of Anthropology, 163-181.

 

Dunbar, R. I. (2004). Gossip in evolutionary perspective. Review of general psychology, 8(2), 100.

 

Kulahci, I. G., Rubenstein, D. I., & Ghazanfar, A. A. (2015). Lemurs groom-at-a-distance through vocal networks. Animal Behaviour, 110, 179-186.

 

McComb, K., & Semple, S. (2005). Coevolution of vocal communication and sociality in primates. Biology Letters, 1(4), 381-385.

 

Silk, J. B., Altmann, J., & Alberts, S. C. (2006). Social relationships among adult female baboons (Papio cynocephalus) I. Variation in the strength of social bonds. Behavioral Ecology and Sociobiology, 61(2), 183-195.

 

 

Gregarious chimps have more grey matter in specific region of the brain

Chimpanzees with offspring, Photo credit: flickr user Valerie

As one of our closest living relatives, studying the behavior, ecology, and anatomy of chimps provides a look back in time as to what the last common ancestor of chimpanzees and humans may have been like. A recent study examined the brain structure of over one hundred chimpanzees to understand how personality and the brain are connected.

Latzman and colleagues (2015) studied 107 captive chimpanzees by using MRIs and an assessment composed of 41 questions about each individual chimp's personality that was conducted by staff members who care for the animals. The article did not state how long these staff members worked with the chimpanzees, only that they felt they could assess their personalities.

Latzman and colleagues (2015) showed that the volume of gray matter and asymmetry of various regions of the frontal cortex are correlated. Grey matter, found mainly on the outside of the brain, is composed on neuronal cells and unmyelinated axons. (To learn more about grey matter, click here.) Chimpanzees ranked as more dominant, open, and extraverted have greater average grey matter in the frontal cortex of their brains. Extraversion in this article is defined as "energetic approach orientated." Their research also shows that frontal cortex asymmetry, or lack of equality/symmetry, is associated (but not correlated) with dominance, extraversion, and unpredictability.

Source: Biological Psychology 6e via Wikipedia

There are limitations to this study, as Latzman and colleagues (2015) mention. It is impossible to determine the causal relationship. Do personality differences create these structural differences in the brain? Or do structural differences in the brain create these personalities differences? As of right now, we can't answer this question. Interpretations of these findings are also limited by our own understanding of the brain, and we have much to still learn about the structure and function of this complex organ.

Yet, because of this study we have a greater understanding of the biological bases of behavior and personality.  Latzman and colleagues (2015) are the first to study the frontal cortex of the brain and personality in chimpanzees. As we know, chimpanzees are an excellent model for human behavior and personality because they are so closely related to humans. Studies such as this one allow us to refine our understanding of the evolution of our own species.

Food for thought: Would we expect to see the same results in bonobos? Orangutans? Lemurs?



Links of interest:
Cooking chimpanzees
Female friendship in chimpanzees
Differences in tool use between males and females



Works cited:

Robert D. Latzman, Lisa K. Hecht, Hani D. Freeman, Steven J. Schapiro, William D. Hopkins. Neuroanatomical correlates of personality in chimpanzees (Pan troglodytes): Associations between personality and frontal cortex. NeuroImage, 2015; 123: 63 DOI: 10.1016/j.neuroimage.2015.08.041

Female orangutans may prefer males with large cheekpads

Dominant male named Kiko at NZP. Photo: author

Orangutans display an interesting form of sexual dimorphism in that males have large cheek pads but females do not. Males are also larger and have large throat sacs that aid them when they make long calls, which advertise to females and tell other orangutans, "I am here!" However, not all males develop this large size, cheek pads, and throat sac. The cheek pads, large size and throat sacs are characteristic of dominant males. Thus, orangutan males display bimaturism, meaning the timing of development differs. Some males develop these dominant characteristics much sooner than others.  Because adult males aren't always large and with the distinguishing cheek pads and throat sacs, it can be quite difficult to tell non-dominant males and females apart.


These non-dominant males aren't juvenile or infertile. They are perfectly capable of reproducing and previously have been shown to produce about half of all wild orangutan offspring (Utami et al., 2002). These two forms of adult males have different strategies when it comes to mating. The dominant males defend their territory. Their homerange is very large and includes multiple females. Non-dominant males are able to gain access to females when the dominant male isn't around.

Bonnie(female) at NZP. Photo: author

A new study resulting from eight years of field research at Tanjung Puting National Park on the island of Borneo found that females prefer dominant males with cheek pads. This is the longest study to have been done at one site in a single population of individual orangutans in terms of orangutan paternity. Banes and colleagues (2015) determined parentage for orangutans inhabiting the homerange used by Kuasasi, a dominant male. They determined he produced far more offspring once he achieved dominance and that he fathered the majority of offspring in the area. This is in contrast to what Utami and colleagues found in 2002 in Sumatra in which unflanged males produced half of the offspring.

This more recent study is arguably limited by the fact that researchers determined the parentage of orangutans in one dominant male's range (Kuasasi). It is possible this is just one very successful male. Or, females are in fact choosing dominant, flanged males over unflanged males. The authors also point out that their study site may affect their results. Camp Leakey is characterized by both wild orangutans and individuals that were once captive but released to the area in the 70s. Orangutans at this site also receive medical treatment, which may mean that dominant males are surviving attacks that they otherwise would not, affecting the population.

Conducting studies on paternity and life history variables on orangutans is very difficult given that, other than humans, orangutan offspring take the longest to reach adulthood of any primate. Females will reproduce every eight years (Gladikas and Wood, 1990), thus answering these types of questions remains difficult.

Links of interest:
Encyclopedia of Life Page on Bornean Orangutans
 IUCN Redlist Page on Bornean Orangutan
Monopoly of the male orangutan
Orangutan long call


Sources:

Galdikas BMF, Wood JW (1990) Birth spacing patterns in humans and apes. Am J Phys Anthropol 83:185–191

Graham L. Banes, Biruté M. F. Galdikas, Linda Vigilant. Male orang-utan bimaturism and reproductive success at Camp Leakey in Tanjung Puting National Park, Indonesia. Behavioral Ecology and Sociobiology, 2015; DOI: 10.1007/s00265-015-1991-0

Utami, S. S., Goossens, B., Bruford, M. W., de Ruiter, J. R., & van Hooff, J. A. (2002). Male bimaturism and reproductive success in Sumatran orang-utans. Behavioral Ecology, 13(5), 643-652.

Chimpanzee populations in Uganada greater than previously thought

 Chimpanzees (Pan troglodytes) are currently listed as endangered by the International Union for the Conservation of Nature (IUCN) due to threats from habitat loss and degradation causing a decrease in population numbers that will likely continue (Oates et al., 2008). However, a recent study examining chimpanzee numbers in Uganda gives us reason to hope for our close primate relatives. In the open access journal BMC Ecology, McCarthy and colleagues report that 15 months of data collection has lead them to determine that over two hundred and fifty chimpanzees live in a corridor that was previously assumed to hold ~seventy individuals.

Chimpanzees with offspring, Photo credit: flickr user Valerie

The Budongo and Bugoma Forest Reserves in Uganda are two large areas of protected land separated by an unprotected area that contains villages, agricultural fields, along with grasslands and forest. It's not your typical, ideal chimpanzee habitat. This corridor is dominated by humans, with 107 humans per square km (NPHC, 2014). Yet, studies like this one have obvious merit as we lose more and more pristine habitat.

Researchers collected fecal samples and genotyped those samples from 2011-2013. They then used models to determine the number of individuals. This noninvasive method is more accurate than counting the number of nests chimpanzees make at night in order to determine the number of individuals. (Chimpanzees make nests out of branches and forest materials every night that they sleep in. See a video here.) Using this method, they were able to determine that there are at least nine communities, each with anywhere between eight to thirty-three individuals. Because not all areas of the unprotected corridor were not sufficiently sampled in this study, it is possible this is a conservative estimate, and numbers may be even higher.

McCarthy and colleagues point out that chimpanzees exhibit a great deal of behavioral flexibility, which likely accounts for how they've coped with a less-than-ideal environment. Chimps are omnivores and can adapt their diet if they need to, including human-cultivated foods. Provided a lack of pressure from hunting, it is worth considering these stretches of land that previously may have been overlooked as viable areas worthy of conserving. The next steps will be understanding just how the chimps are doing so well in this habitat. What behavioral changes are they making?

Links of interest:
IUCN Redlist page on chimpanzees 
Map showing current range of chimpanzees 
The fate of western lowland gorillas and chimpanzees over the next decade
How human are chimps?

Works cited:
Maureen S McCarthy, Jack D Lester, Eric J Howe, Mimi Arandjelovic, Craig B Stanford, Linda Vigilant. Genetic censusing identifies an unexpectedly sizeable population of an endangered large mammal in a fragmented forest landscape. BMC Ecology, 2015; 15 (1) DOI: 10.1186/s12898-015-0052-x
NPHC 2014 provisional results report. Uganda Bureau of Statistics, Kampala; 2014.
Oates, J.F., Tutin, C.E.G., Humle, T., Wilson, M.L., Baillie, J.E.M., Balmforth, Z., Blom, A., Boesch, C., Cox, D., Davenport, T., Dunn, A., Dupain, J., Duvall, C., Ellis, C.M., Farmer, K.H., Gatti, S., Greengrass, E., Hart, J., Herbinger, I., Hicks, C., Hunt, K.D., Kamenya, S., Maisels, F., Mitani, J.C., Moore, J., Morgan, B.J., Morgan, D.B., Nakamura, M., Nixon, S., Plumptre, A.J., Reynolds, V., Stokes, E.J. & Walsh, P.D. 2008. Pan troglodytes. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. 

Olive baboons can be democratic when it comes to troop movement

Olive baboons (Papio anubis) live in a world where social rank matters. They live in troops that can have over one hundred individuals, with females remaining in their natal group and males dispersing. Males are dominant over females but females have a strict linear dominance hierarchy, meaning who your mother is matters. A lot. Related females groom each other and have each others backs in agonistic meetings.

Photo credit: Nevit Dilmen

A new study out in Science by Strandburg-Peshkin and colleagues shows that, much to everyone's surprise, olive baboons are democratic when it comes to troop movement. Yep, these primates, which can be known for their aggression (just look at those canines), don't bully when it comes to choosing where to go.

What we'd expect in a primate with such a strict social system is that the group would go where dominant individuals want to go. Those lower on the social totem pole aren't going to act against a more dominant individual's decision nor are they going to attempt to make these decisions themselves. However, using GPS technology, researchers found that the troop tends to go where multiple initiators want to go and individuals who move in a directed manner are more likely to be followed.

When two groups within a troop are moving in different directions, the larger group is more likely to win, and this likelihood grows as the difference in size between the two groups of initiators grows. The authors failed to clarify if, of those decisions with multiple initiators, the number of dominant individuals within groups of initiators made a difference. I'd like to know if five low-ranking individuals could top two high-ranking individuals, when determining which direction to go. Does social rank really have no effect? I'm not sure I'm entirely convinced that it doesn't, but I also don't study baboons.

Now, this study was conducted by studying 33 out of 46 members of one baboon troop over nine days, so it'd be interesting to see if results differ in other troops, in troops of differing sizes, or during different times of the year (for example, when food resources are low). It'd also be interesting to see if this finding holds true for other species of baboons. For example, previous research has shown chacma baboons (Papio ursinus) do pay attention to social relations when deciding which patches of food to target (Marshall et al., 2012).

Food for thought:
Strandburg-Peshkin and colleagues didn't find any differences based on sex when it came to an individual initiating troop movement. Why is this surprising?
Why might this system (in which the troop is democratic in deciding where to go) be adaptive to baboons? When might it not be?

Links of potential interest:
Olive baboon behavior and social organization
Chacma baboon study


Literature cited:
Ariana Strandburg-Peshkin, Damien R. Farine, Iain D. Couzin, and Margaret C. Crofoot. Shared decision-making drives collective movement in wild baboons. Science, 19 June 2015 DOI: 10.1126/science.aaa5099

Harry H. Marshall, Alecia J. Carter, Tim Coulson, J. Marcus Rowcliffe, Guy Cowlishaw. Exploring Foraging Decisions in a Social Primate Using Discrete-Choice Models. The American Naturalist, 2012; 180 (4): 481 DOI: 10.1086/667587

Rank affects a female's likelihood to seek out "friendships"

Photo: Chris Allen

Chimpanzees (Pan troglodytes) are social creatures, living in a fission-fusion society, meaning one large group often breaks into smaller ones to form feeding parties. In the chimp world, males outrank females and there is a strict linear hierarchy to male relationships (Goldberg & Wrangham 1997). Whereas males can remain in their natal group, females migrate around the time when they reach adolescence (years 9-14) (Nishida et al. 2003). Thus, females eventually need to make new friends, whereas males have the benefit of life-long buddies. In most chimpanzee populations, females spend a lot of time by themselves (Williams, Liu, and Pusey, 2002). At Gombe, the famous site where Jane Goodall first went to the wild and studied chimpanzees, females spend the majority of their time alone or with a few other family members (Wrangham and Smuts, 1980; Goodall, 1986).

Gombe National Park in Tanzania, Google Earth

A study due to be published next month in the journal Animal Behaviour reports new insights into the "friendships" of female chimpanzees. (Friendship may very well be too strong of a word. Acquaintance or association is likely more accurate.) Foerster and colleagues used thirty-eight years of data from Gombe National Park and show that female chimpanzees aren't just bonding randomly with each other. Unsurprisingly, mothers, daughters, and sisters form the strongest bonds. However, among unrelated females, those of a low rank were more likely to seek out other females than were mid or high-ranking females. They also sought out other low-ranking females. 

There are multiple reasons low-ranking females might seek out others of the same rank. As Foerster and colleagues suggest, perhaps having an additional low-ranking pal makes competing for food easier or perhaps they seek others to dissuade higher-ranking members from bullying. The reason for their increased likelihood to seek out other female friends remains unknown at the time. It would be interesting to know how long these partnerships last. If they're temporary, why? What circumstances or events cause the end of the partnership?

 Finally, the presence or absence of offspring affects the likelihood a female will seek out other unrelated females. Females with young female offspring associate with other females less than expected, but females with young male offspring seek each other out. This may because it is especially important for males to interact socially with each other and bond, given that those bonds have the potential to last a life time. The same cannot be said for young female chimpanzees because they will eventually leave and find a new troop. Thus, it apparently is worth forming relationships with other young females within the troop.

Food for thought: What are the benefits and disadvantages to spending time with others (if you're a chimpanzee)?
How might this study differ if the study species had been bonobos? Remember, they have a very different social system!

Links of interest:
ScienceDaily article
Chimpanzee social systems
Chimps create traditions video clip
IUCN Redlist page on chimpanzees
Female chimps more likely to use tools
How human are chimps?


References:
Foerster, S, McLellan, K, Schroepfer-Walker, K, Murray, CM, Krupenye, C, Gilby IC, Pusey, AE. Social bonds in the dispersing sex: partner preferences among adult female chimpanzees. Animal Behaviour, 2015; 105: 139 DOI: 10.1016/j.anbehav.2015.04.012
Goldberg TL, Wrangham RW. 1997. Genetic correlates of social behavior in wild chimpanzees: evidence from mitochondrial DNA. Anim Beh 54: 559-70. 
Goodall J. 1986. The chimpanzees of Gombe. Cambridge (MS): Belknap Pr.
Nishida T, Corp N, Hamai M, Hasegawa T, Hiraiwa-Hasegawa M, Hosaka K, Hunt KD, Itoh N, Kawanaka K, Matsumoto-Oda A, et al. 2003. Demography, female life history and reproductive profiles among the chimpanzees of Mahale. Am J Prim 59(3): 99-121. 
Williams, J. M., Liu, H. & Pusey, A. E. 2002. Costs and benefits of grouping in female chimpanzees at Gombe. In: Behavioral Diversity in Pan. (Ed. by Boesch, C., Hohmann, G., and Marchant, L. F.) pp. 192-203. Cambridge: Cambridge University Press.
Wrangham, R. and Smuts, B.B. (1980). Sex differences in the behavioural ecology of chimpanzees in the Gombe National Park, Tanzania. Journal of Reproduction and Fertility. Supplement, 28, 13-31.

New consequence of grooming discovered

Macaca fuscata grooming, Photo: Noneotuho

When primates groom each other, they improve their health and hygiene by removing parasites, dirt, and dead skin. This practice is also known as allogrooming. If a primate lives in a group, you'll likely observe allogrooming. (Note: this is not a term restricted to primates: other animals allogroom as well.)

The benefits of allogrooming extend beyond hygiene though, as evidenced by a study on mangabeys (Cercocebus torquatus lunulatus) that found difficult to reach areas were not groomed as often as one would expect if hygiene were the sole purpose of grooming (Perez and Baro, 1999). The practice also maintains and betters affiliative bonds (Seyfarth and Cheney, 1984; Stammbach and Kummer, 1982). Allogrooming promotes cooperation over food in Japanese macaques (Ventura et al, 2006). It reduces tension in Macaca fascicularis (Schino et al., 2005) and M. mulatta (Aureli, Preston, and de Waal, 1999).

During allogrooming, the primate doing the grooming is obviously focused on another individual, thus it is not entirely surprising that there's a tradeoff between allogrooming and vigilance. Macaque mothers that engage in allogrooming glance at their infants significantly less and those infants are the victim of harassment more often than when mothers are present (Maestripieri, 1993). In general, the costs of allogrooming are less well understood than the benefits. Energetic, cognitive, and other opportunity costs have all been suggested to exist (Russell and Phelps, 2013).

Brown spider monkey, Photo credit: Fir0002

A new study by Rimbach and colleagues describes a previously unknown consequence of allogrooming in the critically endangered brown spider monkey, Ateles hybridus. Studying sixteen individuals, Rimbach and colleagues found that the more connected monkeys had a greater richness of gastrointestinal parasites than monkeys that were less connected. This relationship is based on physical contact, as when the authors examined proximity alone, there was no such relationship. The authors concluded that the largest parasite risk to this particular community of brown spider monkeys is in fact social grooming.

Given that this species is critically endangered due to habit loss and hunting, identifying other potential threats to their health and survival is crucial. I'm not positive what the applications of this new study would be though, as it's impossible to stop primates from grooming each other, thus parasite transmission will continue to occur. If these monkeys aren't negatively affected by their parasites in a significant manner though, the threat posed may be small. One of the parasites found in this study, Strongyloides, has cased moderate to severe disease in grey wooly monkeys though (Lagothrix cana) (Mati et al., 2013), so it seems reasonable to assume a negative effect in brown spider monkeys as well. 

Food for thought: How might the adaptive benefits of allogrooming counter the effects of increased gastrointestinal parasites? Is it possible allogrooming no longer acts as a benefit to this particular primate population given their low numbers?

Further reading:
Sciencedaily article
IUCN Redlist page on Brown spider monkeys
What are they picking at?
Baboons groom in the morning to reap benefits in afternoon


Sources:
Aureli F, Preston S.D, de Waal F.B.M. Heart rate responses to social interactions in free-moving rhesus macaques (Macaca mulatta): a pilot study. J. Comp. Psychol. 1999;113:59–65. doi:10.1037/0735-7036.113.1.59 

Maestripieri, D. (1993). Vigilance costs of allogrooming in macaque mothers. American Naturalist, 744-753.

Mati, V. L. T., Junior, F. C. F., Pinto, H. A., & de Melo, A. L. (2013). Strongyloides cebus (Nematoda: Strongyloididae) in Lagothrix cana (Primates: Atelidae) from the Brazilian Amazon: aspects of clinical presentation, anatomopathology, treatment, and parasitic biology. The Journal of parasitology, 99(6), 1009-1018.

Pérez Pérez, A., & Josep Veà Baró, J. (1999). Does allogrooming serve a hygienic function in Cercocebus torquatus lunulatus?. American Journal of Primatology, 49(3), 223-242.

Russell, Y. I., & Phelps, S. (2013). How do you measure pleasure? A discussion about intrinsic costs and benefits in primate allogrooming. Biology & Philosophy, 28(6), 1005-1020.
Rimbach, R., Bisanzio, D., Galvis, N., Link, A., Di Fiore, A., Gillespie T.R.,. Brown spider monkeys (Ateles hybridus): a model for differentiating the role of social networks and physical contact on parasite transmission dynamics. Philosophical Transactions of the Royal Society B: Biological Sciences, 2015; 370 (1669): 20140110 DOI: 10.1098/rstb.2014.0110
Schino G, Scucchi S, Maestripieri D, Turillazzi P.G. Allogrooming as a tension reduction mechanism: a behavioral approach. Am. J. Primatol. 1988;16:43–50. doi:10.1002/ajp.1350160106
Seyfarth, R. M., & Cheney, D. L. (1984). Grooming, alliances and reciprocal altruism in vervet monkeys. Nature, 308, 541-543.

Stammbach, E., & Kummer, H. (1982). Individual contributions to a dyadic interaction: an analysis of baboon grooming. Animal Behaviour, 30(4), 964-971.

Ventura R, Majolo B, Koyama NF, Hardie S, Schino G (2006). Reciprocation and interchange in wild Japanese macaques: grooming, cofeeding, and agonistic support. Am J Primatol 68:1138–1149

Are the famous, sex-loving bonobos really more peaceful than their chimpanzee relatives?

Juvenile bonobo eating

Bonobos (Pan paniscus) are often referred to as the peaceful apes or the "make love, not war" apes. Previously known as the pygmy chimpanzee, they're thought of as more gentle and peaceful than their closely related cousins, the chimpanzee (Pan troglodytes). These two species are very closely related: 99.6% of their genome is the same.  Many people are aware that chimpanzees hunt other primates. You may even have heard that they will go to war against other chimps, brutally killing members of their own species, wiping out another group of chimpanzees.  With 99.6% of their DNA identical to chimpanzees, do bonobos really deserve this wholesome image?

Bonobos are only found in the Democratic Republic of Congo. They're smaller in body statue than chimpanzees but otherwise they look very much alike. In chimpanzee social systems, the males are dominant over the females. In bonobo groups, its the females who are dominant over males. Females remain in their natal unit and develop strong bonds with other females. Bonobos also play more as adults, engage in sexual activity more, and display less severe aggression than chimpanzees. So far, it looks like bonobos are living up to their reputation as the more peaceful primate.

As we learn more and more about bonobos, at least one of our original ideas about them has been proven wrong. Originally, only chimps were thought to hunt and eat other primates, but this isn't true. Surbeck and Hohmann (2008) published the first account of wild bonobos hunting other monkeys. Both males and females were active in the hunts and red colobus monkeys, black mangabeys, and other primate species were on the dinner menu for bonobos.  Seems like we've busted that myth.

Bonobos sharing food

However, a study compiling over fifty years worth of data on chimpanzees and bonobos seems to suggest that there is quite a difference. Studying 18 communities of chimps versus 4 communities of bonobos, scientists reported 152 killings by chimpanzees compared to just one killing by bonobos (Wilson et al., 2014). It is thought that differences in the brain between these two great apes may be the underlying cause behind the increased violence and aggression seen in chimpanzees. The brain of a bonobo seems to be better adapted to impulse control, perceiving stress in others. Rilling and colleagues (2012)  state that their neurology "...allows them to more strongly represent distress of both self and others compared with chimpanzees. This translates into greater empathy, as well as reduced aggression." The Rilling article is a great read, as it includes not only their findings but also a thorough overview of the behavioral differences between chimpanzees and bonobos.

To summarize, while there may not be much separating these two species in terms of their DNA, how their DNA is expressed does appear quite different. At first, scientists wondered if we simply had less data available to us on bonobos, and that lack of data meant we were missing behaviors in bonobos that are seen in chimps. (The chimpanzee population is far larger than the bonobo population.) As we study them more and more, chimpanzees come out on top in terms of aggressive behaviors.  It's important to remember through that all of these aggressive behaviors don't make up the majority of a chimpanzee's day. It's quite the opposite. Social behaviors make up a small amount of any primate's day. Feeding and resting take top priority. That said, I think the conclusion that bonobos are more peaceful than chimpanzees stands for now.


Food for thought: I think it's most surprising that bonobos will share first with strangers before they share with friends or associate bonobos (Tan and Hare, 2013). This isn't something we see with chimpanzees (and arguably something we don't see in all humans). Why would a bonobo share with a stranger first? How is this an adaptive behavior?

Check out this incredible BBC video explaining the hunting tactics of chimpanzees. (Yes, they really do have tactics.)

Read NOVA's interview with the well-known primatologist, Frans de Waal, about studying bonobos.

Journal articles referenced:
Surbeck, M., & Hohmann, G. (2008). Primate hunting by bonobos at LuiKotale, salonga national park. Current Biology, 18(19), R906-R907. doi:10.1016/j.cub.2008.08.040
Wilson, M. L., Boesch, C., Fruth, B., Furuichi, T., Gilby, I. C., Hashimoto, C., . . . Wrangham, R. W. (2014). Lethal aggression in pan is better explained by adaptive strategies than human impacts. Nature, 513(7518), 414. 
Rilling, J. K., Scholz, J., Preuss, T. M., Glasser, M. F., Errangi, B. K., & Behrens, T. E. (2012). Differences between chimpanzees and bonobos in neural systems supporting social cognition. Social Cognitive and Affective Neuroscience, 7(4), 369-379. doi:10.1093/scan/nsr017
Tan J, Hare B. Bonobos Share with Strangers. PLOS ONE, 2013; 8 (1): e51922 DOI: 10.1371/journal.pone.0051922

Orangutan called a "Non-Human Person," one that can be freed Part II

Yesterday, I wrote a post about an orangutan in Argentina that was recently freed by the courts after being declared a "non-human person." I found this interesting for more than one reason, and I wanted to share the second one today.

In response to this ruling, the head of biology at the Buenos Aires Zoo stated, "When you don't know the biology of a species, to unjustifiably claim it suffers abuse, is stressed or depressed, is to make one of man's most common mistakes, which is to humanize animal behavior" (see article here)  and I think this is an excellent and often overlooked point! I can't speak for this zoo because I've never been and I don't know anyone who has been. I can speak to my experiences at the Smithsonian National Zoo where I interned for several months as an undergrad.

Orangutan named Kiko crossing the O-Line at NZ

I would often hear guests complaining that the gorillas were just sitting there. "Why aren't they doing anything?!" Well, when you consider that gorillas are large herbivorous animals that spend much of the day foraging on leaves and another significant portion of the day resting and digesting those leaves, it makes sense that they're not always climbing trees and playing. Most primates spend very little time playing in the wild. I know the primates at National were extremely well cared for. They have enrichment time to keep them from getting bored, they have keepers who really care about them and have worked there for years, and they eat better than most humans do. Should apes be kept in zoos? Well, that's a hard question to answer.

I don't believe apes should be kept as pets or in the entertainment industry. They're not for our entertainment purposes and the idea of keeping a highly intelligent, huge, and strong animal in a home is absurd. Remember Charla Nash? Keeping apes in zoos may or may not be different though.

Zoos allow people to see and hopefully learn about many different types of animals they otherwise might never really learn about unless they can afford to travel. Watching a television program isn't the same as seeing a zebra in a zoo which isn't the same as seeing one in the wild. I saw a lot of children's eyes open wide when running up to see the gorillas feeding outside or the orangutans crossing on the O-Line, a series of long ropes and towers (electrified at the base so they won't want to climb down). Click here for a video of orangutans using the O-Line. I'd like to think these children (and adults) really enjoyed their time at the zoo but also learned a thing or too, including an appreciation for nature and wildlife. There's something magical about seeing an animal in the flesh.

Brown bear at National Zoo-Thankfully exhibits have improved greatly.
Historic Images of the Smithsonian

Now,  not all zoos are created equally. Some animals do live in very small confined spaces or receive inadequate care. I don't think large animals such as orcas should be kept in captivity at all. Just watch the movie Blackfish if you haven't already. That said, animals in zoos do tend to live longer than those in the wild. They receive medical care and lots of healthy food. They're also studied in a way that may not be possible in the wild. We know their lineages, we know exactly what they eat, we can watch them 24/7, and we can use cognitive tests as enrichment to understand their brains. There are definitely advantages to having zoos. Some zoos are centers of genetic or cognitive research. A few zoos even have excellent conservation science programs, funding scientists who study wild animals and initiatives that support the protection of wild animals and ecosystems.

Do these advantages outweigh the disadvantages of keeping animals in captivity? I'm undecided. Most zoos are aware of the problems they face. They want larger exhibits for their animals. They're trending towards creating the most natural environment possible. I hope this work continues and I hope zoos do more to ensure that visitors are actually learning when they come to the zoo. Do you stop and read the signs telling you all about a species or an issue? I'm not sure many people do, but creating more interactive displays, having keeper talks, and using technology may make the visit memorable and change perceptions. If the focus is on educating the public, conservation, and raising awareness about issues rather than making money, then zoos might be worth it.

How human are chimps? The differences and similarities between chimpanzees and humans.

The state of New York recently ruled that chimpanzees are not entitled to the same privileges and rights as humans. Chimpanzees have long given humans plenty to think about when it comes to defining what exactly is human. Jane Goodall, when she observed chimpanzees using tools in the wild stated, "Now we must redefine tool, redefine Man, or accept chimpanzees as humans." I decided to look at some of the ways chimps are just like us and some of the ways they're not at all like humans.

Young chimpanzee. Photo credit Sabine Bresser

Like humans:

1. Chimps taken from their mother at a young age suffer long-lasting behavioral consequences. Specifically, chimps raised by humans rather than other chimps groom each other less frequently than chimps raised by their chimpanzee mothers, and they also engage in sexual behaviors less frequently. Read the study done by Freeman and Ross at the Lincoln Park Zoo here. Looks like each species should probably raise its own young.

2. Chimps can cooperate and do so spontaneously. In a study where chimpanzees were given access to a task in a larger outdoor area, as opposed to a small, controlled area where most testing typically occurs, chimpanzees had the choice to use the apparatus and try the task or avoid it entirely. Surprise! Chimpanzees chose to use the apparatus, which required cooperation and choosing a partner chimpanzee to achieve the task, meaning chimps don't just work together when there's nothing better to do. These chimps sought cooperation out. Check out the article by Suchak and others here.

3. Chimps display different cultures, as shown by separate populations of chimpanzees using tools in different ways despite seemingly the same ecological conditions. A 2010 study examined how two populations obtain honey (a real treat for a chimpanzee) and found one population using sticks while another used wedges of leaves to soak up the delicious and highly coveted food item.

Unlike humans:

Photo credit Sergio Morchon

1. Chimpanzees may be able to communicate, but they have yet to display a mastering of complex language and grammar. While yes, chimps and other apes have a grasp of sign language and some even use computers and symbols to communicate with humans, are they capable of knowing the difference between sentences such as, "I bit the dog" and "The dog bit me?" The answer appears to be no. For a great film that I highly recommend, watch Project Nim. It's thought-provoking, heartbreaking, informative, and definitely worth a watch if you're interested in language or even more broadly interested in chimps.

2. Chimpanzees don't teach their young. Now, this might be a somewhat controversial claim since teaching in animals is hard to study (how do you determine if one it is one individual's intent to share knowledge with another?). Chimps certainly learn by watching other chimps and new behaviors are socially transmitted, but does one chimpanzee purposefully and knowingly teach another? Even if you disagree with me, you must admit that humans take teaching to a new level. With our creation of schools and our ability to guide and help others in a hands-on way, we take teaching to a level definitely not seen in chimps.

3. Finally, chimpanzees are not nearly as adaptive as humans when it comes to geography. Homo sapiens, or humans as we know and love ourselves today, weren't even the first to leave Africa and travel to other continents. Our earlier humans ancestors did that first, but the fact remains, humans love to travel. We have blogs dedicated to traveling, the desire to know what's just over that mountain or on the other side of the lake. We seemingly need to go everywhere and we're on every continent if you include the research done in Antarctica. We've adapted to all of these different climates through tools and clothing and behavioral adaptations. I don't think anyone can argue chimps have caught the travel bug quite like humans have.

Food for thought: Does learning these facts about chimps change the way you view what it means to be human? What is the most important difference between chimps and humans? What is the most important similarity?

Female Chimps and Male Attention

Everything is connected. More time spent resting means less time spent grooming. Less time spent grooming may mean greater chance of parasites and thus a greater chance of illness. Illness means greater chance of mortality. This is just one example of how everything is connected and one aspect of life affects another. The same is true whether one is a chimpanzee or a human. If you spend more time playing soccer with your friends, you will need to spend less time doing your homework. Or maybe you will compensate for that time lost doing your homework by working late into the night and sleeping less.

Chimps grooming, Photo credit flickr user Tambako the Tiger

One would think that receiving male attention would be a good thing, if one is a female chimpanzee. The more males seeking your attention, the more choice you have, right? The more opportunities to mate, and since an individual's fitness is a measure of the number of offspring one produces that survive to maturity, mating is an important part of life. So it's straightforward then. The more male attention, the better. Right? Not so fast...

A recent study led by Melissa Emery Thompson of the University of New Mexico found that male attention comes with costs. In the world of chimpanzees, males do indeed compete to mate with females. (Chimpanzees live in groups of multiple males and females and males are dominant over females.) A female will give birth to an offspring and then raise that offspring for five to seven years, which is a pretty long time in the animal kingdom. In part because female chimps raise their young for so long, males compete seriously for access to females. It's not as though the guys always have a chance with that type of reproductive schedule. Females will mate with multiple males, some of whom will then guard her to prevent other males from mating with her, so she can receive quite a bit of attention, whether she wants it or not.

For eleven years, researchers observed chimpanzee behavior and collected their urine to analyze or study hormones (naturally occurring substances that affect or regulate the activity of other cells or organs), such as estrogen and progesterone, which are two female sex hormones important for female sex characteristics and for reproduction. Emery Thompson and colleagues also collected urine to look for C-peptides, a byproduct of insulin. Declining levels of C-peptides indicate a female is spending more energy than she is currently consuming, which is not good.

Chimpanzees with offspring, Photo credit: flickr user Valerie

What they found was that females with more males surrounding them had lower levels of C-peptides and lower levels of those reproductive hormones. Thus, females with all of this attention are not consuming enough energy and are producing fewer hormones than needed. It appears that all of this male attention could very well stress out the females. Perhaps all of that attention from males means that females are less efficient at foraging and obtaining the food they need. Or perhaps they feel a need to keep an eye on those males, as males are dominant, and this extra vigilance is taxing or stressing. Whatever the exact connection is, it appears there are costs to having a lot of males around when cycling or lactating.


Food for thought: Why might female chimpanzees mate with multiple males? Hint: do some research into infanticide and think about how this might protect against it.