Do Chimpanzees Understand Death?


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Pansy - Illustration by Denise Nestor

Pansy – Illustration by Denise Nestor

Maggie Koerth-Baker, senior writer for Boing Boing, recently wrote an article in the New York Times reviewing the behaviors of chimpanzees around mortality. She retells the death of a chimpanzee named Pansy, who died in captivity, at the Blair Drummond Safari and Adventure Park in Scotland, about 5 years ago. The death was imminent. Many observed it, but it was James Anderson, a primate psychologist at the University of Stirling in Scotland who published the account in the journal Current Biology, “Pan thanatology.”

Koerth-Baker writes,

Pansy was probably in her 50s when she died, which is pretty good for a chimpanzee. She passed in a way most of us would envy — peacefully, with her adult daughter, Rosie, and her best friend, Blossom, by her side. Thirty years earlier, Pansy and Blossom arrived together… They raised their children together. Now, as Pansy struggled to breathe, Blossom held her hand and stroked it.

…During her last hours as Blossom, Rosie and Blossom’s son, Chippy, groomed her and comforted her as she got weaker. After she passed, the chimps examined the body, inspecting Pansy’s mouth, pulling her arm and leaning their faces close to hers. Blossom sat by Pansy’s body through the night. And when she finally moved away to sleep in a different part of the enclosure, she did so fitfully, waking and repositioning herself dozens more times than was normal. For five days after Pansy’s death, none of the other chimps would sleep on the platform where she died.

The video below documents a different death, that of a new orphaned male bonobo, Lipopo, who dies unexpectedly from pneumonia in Democratic Republic of Congo. His body is defended by Mimi, an unrelated female, the group’s alpha female. You can see her swat away flies and inspect his arm, at times seeming to pat his dead body. This footage was taken by Brian Hare, an evolutionary anthropologist at Duke.

Koerth-Baker summarizes that when the caretakers try to remove the corpse out of the enclosure with long poles, Mimi viciously fights back. She grabs, calls others, and even when the tranquilizer appears, she stands her ground and screams. This begs me to wonder why was Mimi willing to risk an encounter with a gun to protect the body of a mere acquaintance?

The results of chilling behavioral studies like these in non-human primates are humbling to us because they often call into question our anthropocentric view of the world. Is this interpretation a form of speculation is laden with epistemological issues: are the scientists guilty of anthropomorphizing their subjects? Are these just isolated events? Are they more likely in captivity?

Koerth-Baker eloquently closes her piece with this quote,

As we’re now poised to end a somewhat arbitrary regulatory distinction between wild and captive chimps, it’s worth considering how we’re protecting actually distinct groups of chimps, some of which may have developed their own cultures. When they die off, they take with them behaviors that we might not find anywhere else and that we don’t yet understand — maybe including, somewhat tragically, the extent to which they comprehend their own demise.

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The Possibility Of Full Protection For Chimpanzees Under The Endangered Species Act


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For as long as I’ve been alive, wild chimpanzees have been “endangered” under the Endangered Species Act (ESA). Captive-born chimps, however, have only been classified under the lesser class of “threatened.”

Excerpts from Japan: Nogeyama Zoological Gardens, Yokohama, from Angie G.

Excerpts from Japan: Nogeyama Zoological Gardens, Yokohama, from Angie G.

Dan Ashe, the director of the U.S. Fish and Wildlife Service (FWS), announced today that the loophole that exempted captive-bred chimpanzees from the full protections of the ESA may finally be closed. It’ll take some work, but it is a step in the right direction.

The distinction was put in place in 1990 for the purpose of those who registered with the FWS to legally import, export, re-import, sell and ‘take’ (including euthanize) their captive-bred apes as long as those activities ultimately showed an overall enhanced survival of the species. Those activities include scientific research, exhibition (a.k.a. show-biz apes) or holding and maintenance of ‘surplus’ apes. Ashe clarified that then,

“We wanted to encourage breeding of chimps at that time, believing at that time that providing additional animals in captive populations would reduce the incentive to remove animals from the wild.”

This proposal is not finalized yet. It will soon appear in the government’s Federal Register, after the public will have 60 days to comment. Ashe welcomes comments on how chimps are being used in medical research, entertainment, and other fields so that those activities can be governed by the ESA. The WFS looks also to work closely with the NIH and Association of Zoos & Aquariums as well as the biotech research community to see how the new proposal will affect their ongoing work. After the 60 day period ends, the agency will have about 12 months to write the final rules.

This redefinition is reminder to us about the plight of chimps in the wild. Chimpanzees continue to face habitat loss, encroaching human populations, poaching and diseases.

“We hope this proposal will ignite a renewed public interest in the status of chimpanzees in the wild as well as an appreciation for the wild things and the wild places that sustain us all.”

Monkey Midwifery

A paper published in the journal Behavioural Processes describes a rare phenomenon, midwifery behavior among black snub-nosed monkeys in Yunnan, China. The paper is titled, “Daytime birth and parturition assistant behavior in wild black-and-white snub-nosed monkeys (Rhinopithecus bieti) Yunnan,China,” and documents this day time birth accompanied by a helper.

Black Snub Nosed Monkeys

Black Snub Nosed Monkeys

As you may know, primates have a large head to body ratio — larger than other mammals. This makes birthing a challenge as larger head has to pass through the birth canal. As a result, labor is far more laborious and risky and primate infants are born less developed than other mammals.

Assistance during labor has been seen a few time before.  In one case, a male cottontop tamarin pulled his infant’s shoulders. Another report documents the grooming of a female capped langur during birth, perhaps in trying to ease the distress. While primates offer some help during birth, it has been seen in that male Djungarian hamsters regularly assist with deliveries, pulling infants out with their front paws and incisors.

In the paper, Xiao and colleague document the 15 minute birthing of a first time mother. She climbs up a rhododendron tree, faintly calling. Her calls turn into screams within 10 minutes. An experienced female black snub-nosed monkey climbs up to this screaming mother. As the new mother began crowning, the experienced female sat beside.

The head, once fully exposed, was grabbed by the midwife, who pulled the baby out with both hands. She progressed to rip open the birth membranes. The new mother reclaimed the infant within a minute, and severed the umbilical cord. She ate the placenta as the midwife descended.

Black snub-nosed monkeys live in bands. These bands are as large as 300-400, but are often sub-divided into smaller groups of 10 individuals. These groups are often harems. The female black snub-nosed monkeys tend to stay in the group they were born in. It is likely, therefore, that females in a group are closely related and to have strong social bonds and act upon calledkin selection. Furthermore, it has been observed that juvenile females closely watching births. During this particular birth, two other females watched it happen.

Ding, W., Yang, L., & Xiao, W. (2013). Daytime birth and parturition assistant behavior in wild black-and-white snub-nosed monkeys (Rhinopithecus bieti) Yunnan,China Behavioural Processes DOI: 10.1016/j.beproc.2013.01.006

The Completed Bonobo Genome


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Pan paniscus

Two Bonobos {Pan paniscus} vocalizing. Lola Ya Bonobo Sanctuary, Kinshasa, DR of Congo, 2007

The bonobo genome is sequenced. The letter reporting was recently published in Nature, and is available openly under the title, “The bonobo genome compared with the chimpanzee and human genomes.”  Kay Prüfer from the Max Plank Institute for Evolutionary Anthropologyis the lead author. There are some interesting preliminary comparisons such as:

  • Bonobos and chimps have 99.6% sequence similarity
  • Bonobos and humans have 98.7% sequence similarity
  • The split of bonobo and chimpanzee is confirmed to have approx. 1 million years ago, with no inbreeding occurring
  • 6% of the bonobo genome has evidence of incomplete lineage sorting(when an allele does not match the population history of a species)
    • This has lead to the observation that  ~1.6% of the bonobo genome is more similar to humans than chimpanzees

a, Schematic description of ILS states and percentage of bases assigned to each state. b, Effective population sizes and split times inferred from ILS and based on a molecular clock with a mutation rate of 10−9 yr−1. Myr, million years. We note that other estimates of mutation rates will correspondingly affect the estimates of the split times. c, Overlap between predicted ILS transposons and the closest HMM ILS assignments within 100 bp of a transposon insertion. d, Proportion of ILS in exons, introns and across the whole genome, counted within ~1-Mb segments of alignment (Supplementary Information, section 8). e, Proportion of ILS dependent on recombination rates. Errors, 95% confidence interval.

Prüfer, K., Munch, K., Hellmann, I., Akagi, K., Miller, J., Walenz, B., Koren, S., Sutton, G., Kodira, C., Winer, R., Knight, J., Mullikin, J., Meader, S., Ponting, C., Lunter, G., Higashino, S., Hobolth, A., Dutheil, J., Karakoç, E., Alkan, C., Sajjadian, S., Catacchio, C., Ventura, M., Marques-Bonet, T., Eichler, E., André, C., Atencia, R., Mugisha, L., Junhold, J., Patterson, N., Siebauer, M., Good, J., Fischer, A., Ptak, S., Lachmann, M., Symer, D., Mailund, T., Schierup, M., Andrés, A., Kelso, J., & Pääbo, S. (2012). The bonobo genome compared with the chimpanzee and human genomes Nature DOI: 10.1038/nature11128

A New Primate Species From Myanmar Points To “Out Of Asia”


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In the current early edition of the journal PNAS a new paper raises a suggestion that the common primate ancestor originated in Asia and not Africa through the discovery of a new species. This new 37-million-year-old fossil was discovered in the Pondaung sediment at Thamingyauk locality in Myanmar.

Pondaung sediment

Credit: © Mission Paléontologique Franco-Myanmar (MPFM) The Pondaung sediment at Thamingyauk locality, Myanmar.

The species has been named Afrasia djijidae based upon 4 teeth recovered from the site. Afrasia pays homage to the ancestry of these early anthropoids who are now found intercontinentally, between Africa and Asia. And djijidae refers to memory of a young girl from village of Mogaung in central Myanmar. In comparing the teeth to other primates an remarkable discovery was made…

Afrasia‘s teeth closely resemble those of the 38-million-year-old Afrotarsius libycus. The shape of the Asian Afrasia and the North African Afrotarsius fossils shows both species survived off insects and weighed around 100 grams or so, about size of a modern tarsier. A. libycus was recently discovered in the Sahara, where it was more ecologically diverse and suggesting that they actually originated elsewhere. The close similarity in dentition between Afrasia and Afrotarsius raises the possibility that early anthropoids colonized Africa from Asia.

 Leaving Asia

Credit: © Mission Paléontologique Franco-Myanmar (MPFM) The close similarity between Afrasia (right) and Afrotarsius (left) now suggests that early anthropoids colonized Africa from Asia.

 Close Resemblance

Credit: Mark A. Klinger, Carnegie Museum of Natural History  Shown here, Afrotarsius (top left), Karanesia (top right), Biretia (bottom left), and Talahpithecus (bottom right) reconstructions shown feeding along the shoreline forest.

A open question that remains is just how was Africa colonized from Asia? Around 38-37 million years ago the Tethys Sea separated the two continents. The authors write how the primates could have island hopped by swimming and using logs as rafts. I think this is an outlandish idea. But they supplement this hypothesis by stating how such as Asian rodents and extinct piglike animals known as anthracotheres colonized Africa.

Another open question is how come the Afrasia species and other ancestral primates did not lead way to their lineage of primates, much like the African counter parts? The authors address this question by stating that a glacial event 34 million years ago, dramatically cooled the climate. This drop in temperature affected Asia more than Africa, leading to the disappearance of Asian anthropods. And for anthropoids like gibbons and orangutans in Asia now, such as gibbons and orangutans immigrated from Africa some 20 million years ago.

Chaimanee, Y., Chavasseau, O., Beard, K., Kyaw, A., Soe, A., Sein, C., Lazzari, V., Marivaux, L., Marandat, B., Swe, M., Rugbumrung, M., Lwin, T., Valentin, X., -Maung-Thein, Z., & Jaeger, J. (2012). Late Middle Eocene primate from Myanmar and the initial anthropoid colonization of Africa Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1200644109

Gorilla Baby Talk


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Eva Maria Luëf and Katja Liebal of the Free University of Berlin have published in the American Journal of Primatology a new paper documenting the occurrence of motheresein 24 captive lowland gorillas.

Baby gorilla sleeping on his mother, by bartdubelaar

Baby gorilla sleeping on his mother, by bartdubelaar

During a 4 month observation of these gorillas, it was observed that elder gorillas used different gestures to start and stop play. To engage in play, the older gorillas would typically slapp others while making a “play face” or somersault. And to end play, these gorillas would place hand on the other gorilla’s head. But when engaged with infants, each older gorilla used repeated touch-based gestures more. As explained in the abstract,

Infant-directed speech is a linguistic phenomenon in which adults adapt their language when addressing infants in order to provide them with more salient linguistic information and aid them in language acquisition. Adult-directed language differs from infant-directed language in various aspects, including speech acoustics, syntax, and semantics. The existence of a “gestural motherese” in interaction with infants, demonstrates that not only spoken language but also nonvocal modes of communication can become adapted when infants are recipients. Rhesus macaques are so far the only nonhuman primates where a similar phenomenon to “motherese” has been discovered: the acoustic spectrum of a particular vocalization of adult females may be altered when the addressees are infants. The present paper describes how gorillas adjust their communicative strategies when directing intentional, nonvocal play signals at infants in the sense of a “nonvocal motherese.” Animals of ages above infancy use a higher rate of repetitions and sequences of the tactile sensory modality when negotiating play with infants. This indicates that gorillas employ a strategy of infant-specific communication.”

A video of this behavior is provided by the New Scientist.

I used to work with two gorillas who both extensively used gestures to relay communication. So, I assume all who have taken care of these great apes would appreciate that it is is vital for all gorilla infants to identify different signals, similar to how human infants gain expertise spoken (an non-spoken) language. In both great apes, simplifying these forms of communication into baby talk, and repeating possibly help in solidifying associations.

LUEF, E., & LIEBAL, K. (2012). Infant-Directed Communication in Lowland Gorillas (Gorilla gorilla): Do Older Animals Scaffold Communicative Competence in Infants? American Journal of Primatology DOI: 10.1002/ajp.22039

Foresight & Innovation in a Devious Chimpanzee


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A chimpanzee in at the Furuvik Zoo in Sweden is documented to store various projectile object to be thrown at zoo visitors at a later time. The results of this study has been published in PLoS One, “Spontaneous Innovation for Future Deception in a Male Chimpanzee.”

I think its a pretty fascinating discussion of foresight, deception and innovation. This male chimp had the foresight to identify projectiles and story them for later use. He deceived caregivers by hiding them projectiles in innovative hay stacks… All of which indicated premeditated thoughts. What do you think?

Maternal Infanticide and Cannibalism in Moustached Tamarin

Infanticide and cannibalism are two extreme behaviors seen in primates. Though extreme, the persistence of these behaviors in primates suggest that they are adapted for and had evolved to serve different purposes. Infanticide and cannibalism can be considered as both reproductive and survival strategies. Infanticide has always been associated with males killing off the progeny of former dominant males to make females more sexually receptive and to shorten the birth interval. Cannibalism, on the other hand, is not as sinister as it has always portrayed to be but just a coping mechanism. Ingestion of body parts, usually own offspring, is a response to cope with food scarcity. Lack of food resources would inevitably result in the death of the offspring thus cannibalization returns the caloric investment back into the mother. A new paper by Culot et al. (2011) has documented a case of infanticide and cannibalism in a wild female moustached tamarin (Saguinus mystax).

Moustached Tamarin (S. mystax) from The Bronx Zoo, New York City. Photo from Wikipedia.

S. mystax belong to the Callitrichid family, and like all Callitrichids has an interesting reproductive strategy unlike those of other primate families. Callitrichids form multimale-multifemale group and has a polyandrous (one female, multiple male) mating system. Callitrichids are the only primate family that consistently give birth to twins. The gestation period for S. mystax is 6 months. Usually, only one dominant female is reproductively active and shares offspring rearing responsibilities with multiple males in the group. However, an unstable dominance hierarchy among females might lead to multiple births within the group and will compromise the survivability of both the group and the offspring from stress, less parental investment and lack of food resources.

The researchers were studying how help from male moustached tamarins in the same group and the absence of female competition ensure the survival of offspring when they observed a female cannibalizing an infant. Necropsy and genetic analyses were used to rule out diseases and to determine paternity. They found that the infant has no diseases and did not die from trauma (falling from tree). Instead, it was a healthy infant and was being cannibalized by its own mother.

The mother was seen biting and then eating the head of its own infant during a period when another female was pregnant and gave birth just 1 month later. Before that, the perpetrator had given birth to twins three times successfully when four to five adult and subadult males were present in the group. Although we do not know for certain that the infant was alive when the mother started biting it, our field observations preceding the event suggest it probably was. The possible infanticide case and the two cases of births and early death of the infants occurred while only two to three adult males were present in the group. This could be the second case of maternal infanticide reported in the genus Saguinus and the similar circumstances suggest a common pattern. Culot et al. (2011).

Five common hypotheses proposed by Hrdy (1979) were used by the authors to try to explain maternal infanticide and cannibalism in this scenario. These hypotheses are resource competition, sexual selection, social pathology, exploitation, and parental manipulation.

The resource competition and sexual selection hypotheses were rejected because it was maternal infanticide, and not infanticide from another female. The social pathology hypothesis was rejected because it predicts infanticide restricted in areas that are disturbed by humans. The study group was habituated and had many successful births, therefore social pathology was ruled out. The exploitation hypothesis was also reject because the mother did not kill her infant to exploit its meat. Observation shows that the mother only consumed the brain and parts of the infant’s neck.

The parental manipulation hypothesis was accepted because the authors think that it best explains the scenario. The offspring was not pathological nor did it fell from the tree. Instead, it was a healthy infant that was killed by its own mother. According to Hrdy (1979), victim of parental manipulation does not necessarily have to be defective but also born “at the wrong place in the wrong time”.

The authors concluded that parental manipulation is the best explanation for this possible maternal infanticide scenario. Parental manipulation strategy can happen in a group with poor capacity to raise the offspring from multiple breeding females, birth intervals that are shorter than 3 months, and low infant survival probability due to physical injuries or weakness.


Culot, L. Lledo-Ferrer, Y. Hoelscher, O. Lazo, FJJM. Huynen, C. Heymann EW. 2011. Reproductive failure, possible maternal infanticide, and cannibalism in wild moustached tamarins, Saguinus mystaxPrimates 52(2): 179-186.

Hrdy, SB. 1979. Infanticide among animals: A review, classification, and examination of the implications for the reproductive strategies of females. Ethology and Sociobiology 1(1): 13-40.

Originally posted on The Prancing Papio.

New adapiform species discovered in West Texas

Do you know that fossil primates once roam North America? I didn’t know either so this discovery was a shock and a “d’oh” moment at the same time.

Lingual view (side that touches the tongue) of Mescalerolemur horneri partial mandible.
Scale bar equals 2 mm. Photo from Kirk & Williams (2011).

Anywho … A fossil primate from the Eocene Epoch was discovered in Devil’s Graveyard badlands of West Texas by Anthropologists Christopher Kirk and Blythe Williams. Named Mescalerolemur horneri, this new fossil primate lived about 43 million years ago is a member of the extinct group, adapiforms, that are found all over the Northern Hemisphere. Mescalerolemur looked like a modern-day greater dwarf lemur and weighs about 370 grams.

Interestingly enough, Mescalerolemur are more closely related to Eurasian and African adapiforms than those from North America. Darwinius masillae, famously known as Aunt Ida, was a Eurasian adapiform. Another interesting fact to point out is that Mescalerolemur had unfused mandibular symphysis, similar to those of Strepsirrhines (lemurs, lorises and galagos). The authors posit that this is definitive evidence that adapiforms are more similar to Strepsirrhines than Haplorrhines (humans are Haplorrhines). Kirk &Williams (2011) published their findings on Journal of Evolution: New adapiform primate of Old World affinities from the Devil’s Graveyard Formation of Texas (PDF). You can also read more about the discovery at EurekAlert: Anthropologist discovers new fossil primate species in West Texas.

Originally posted on The Prancing Papio.


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