Coquerel’s Sifaka Born at the Maryland Zoo in Baltimore



On April 13, 2011, The Maryland Zoo in Baltimore announced the birth of an Endangered Coquerel’s Sifaka (Propithecus coquereli) making it one of only 50 individuals found in accredited institutions in the United States.

Coquerel-Sifaka at the Maryland Zoo in Baltimore, Photo: Kristin Abt

Read the press release for more information!

The Duke Lemur Center manages the United States’ Coquerel’s Sifaka population and provides more information about the species: Coquerel’s Sifaka

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Environmental Enrichment for Captive Primates: Recent Article on the Importance of Gum for Zoo Monkeys


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By: Kristin Abt

A recent article in the journal, Zoo Biology, discusses the current lack of gum enrichment for certain primate species in a captive setting that is in contrast to their wild behavior. Huber and Lewis (2011) surveyed zoos at an international scale to assess the occurrence and methods of “gum-based enrichment.”

Patas Monkey at Woodland Park Zoo (Photo: Kristin Abt)

Golden Lion Tamarin at National Zoo (Photo: Kristin Abt)

They identify numerous primates that feed on gums in varying amounts in the wild, including galagos and lorises, marmosets and tamarins, and members of Cercopithecinae.  Because enrichment aims to promote species-typical behaviors in a non-natural environment, the items that are offered should be primarily selected based on whether or not they contribute to this aim.

This study obtained responses from 46 zoos, 27 of which feed gum to at least some of their primates. The greatest disparity between wild gum-feeding and captive gum-provisioning was for cercopithecines. They identify patas monkeys as obligate gumnivores; therefore, they specifically highlight the need for the development of enrichment programs utilizing gum for this species. Also, they highlight the need to provide enrichment devices that simulate how primates feed on gum in the wild as opposed to free-feeding in dishes.

Patas Monkey Exhibit (Photo: Kristin Abt)

Huber and Lewis (2011) take a focused approach to assessing an area of enrichment within zoos that can have a marked management impact. This study shows the value of applied research to enhance the ability of zoos and other facilities to care for their collections in a manner more representative of the wild experience.


Huber, H. F. & Lewis, K. P. (2011). “An assessment of gum-based environmental enrichment for captive gumnivorous primates.” Zoo Biology 30: 71-78.

The Semantics of Vervet Monkey Alarm Calls: Part II – The Experiment

Last week, I blogged about the semantics of alarm calls in vervet monkeys. This post will focus solely on the ingenious experiment by Robert Seyfarth, Dorothy Cheney and Peter Marler (1980) to test whether vervet monkey alarm calls convey information or if these calls were just an uncontrollable auditory response to predators. Their question was simple; would vervet monkey alarm calls alone elicit different responses?

A vervet monkey. Photo from Wikipedia.

Here’s what the researchers did in the field. They used playbacks of recorded vervet monkey (subjects) alarm calls from concealed speakers. Equal amount of alarm calls for leopard, eagle and snake were used. These alarm calls were recorded from known adult male, adult female and juvenile vervet monkeys in the field. Trials were done when subjects were on the ground and also when they were in the trees. These trials were conducted in the absence of predators to eliminate visual cues from the caller.

Alarm calls were broadcasted in different amplitudes to mimic natural alarm calls. In succession from loudest to lowest amplitudes are alarm calls for leopard, eagle and snake. Subsequently, leopard calls have the lowest pitch while snake calls have the highest pitch. To control for the possible effects of amplitude, the researchers broadcasted alarm calls that do not differ significantly in the amplitudes for all three predators.

Table from Seyfarth et al. (1980). Click on illustration for its original size

The alarm call playbacks showed two types of responses. First, subjects of any sex and age looked at the direction of the speaker and spent more time scanning their environment once an alarm call was made for more than 10 seconds. The researchers believe that they might be scanning for additional cues from the “caller” and the subject’s surrounding.

Second, each alarm calls seem to elicit a distinct response from the subjects. Remember the trials were done when the subjects were on the ground and on the trees? When subjects were on ground, leopard calls were more likely to make them run up into the trees and eagle calls made them look up and run into cover (bushes) Snake calls made them look down. When subjects were on the trees, leopard calls were more likely to make them run higher in trees and to look down. Eagle calls made them look up and sometimes run out of trees. Snake calls made them look down.

From the results, Seyfarth et al. (1980) posit that vervet monkey alarm calls alone do elicit different responses. It’s hard to tease out whether these alarm calls symbolize the predator “leopard” or a command “run up tree”. However, we can postulate that these alarm calls are rudimentary semantic signals used to warn other conspecific of impending danger. For those that are not familiar with semantics, it refers to the meaning of a symbol, sign, word or phrase. In this case, vervet monkey alarm calls are semantic signals because it conveys a specific meaning.

Here’s an interesting video by Robert Seyfarth summarizing his research with the vervet monkeys.



Seyfarth, RM. Cheney, DL. Marler, P. 1980. Monkey responses to Three Different Alarm Calls: Evidence of Predator Classification and Semantic CommunicationScience 210(4471): 801-803.


Originally posted on The Prancing Papio.

The Semantics of Vervet Monkey Alarm Calls: Part I


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Anti-predatory alarm calls are important  for social animals to alert others of approaching predators. Without the presence of “language”, some non-human primates are known to give out different predator-specific alarm calls to alert conspecific. These non-human primates include ring-tailed lemurs (Zuberbühler et al., 1999), white-faced capuchin monkeys (Fichtel et al., 2005), Diana monkeys (Zuberbühler, 1999), Campbell’s monkeys (Ouattara et al., 2009) and vervet monkeys (Seyfarth et al., 1980).

Alarm calls are typically high frequency sounds because these calls are hard to localized by predators. On the other hand, low frequency sounds are easier to localized by predators. Calls that are hard to localized by predators are selected for because conspecific can pick up on the warning but predators cannot identify the location of the caller. If an individual successfully alert its social group of approaching predator yet does not reveal its location, it will significantly decrease the chance of the caller to be detected and increase the chance of its social group to avoid predation.

Vervet monkeys. Photo from Wikipedia.

Here, I will focus on the study of predatory alarm calls in vervet monkey (Chlorocebus pygerythrus) by Seyfarth et al. (1980) in the Amboseli National Park, Kenya. Vervet monkeys are Old World monkeys that range between Eastern and Southern Africa. These monkeys are diurnal and live in closely-knit social groups. They are quadrupedal and are both terrestrial and arboreal. Like all Old World monkeys, vervet monkeys have the characteristic cheek pouches that enables them to forage and store food to be eaten later. Male vervet monkeys have blue scrotal area and a red penis. Males and females are sexually dimorphic, with males slightly larger than females.

Male vervet monkey with blue scrotal area and red penis. Photo from Something Up Her Sleeve.

Vervet monkeys are known to elicit predator-specific alarm calls. Three well-documented vervet monkey alarm calls are those for leopard, martial eagle and python. Leopard alarm calls are short tonal calls produced in a series of inhalations and exhalations. Eagle alarm calls are low pitched grunt while python alarm calls are high pitched “chutters”. Different alarm calls seem to evoke different responses to individuals that heard the alarm calls. However, the first reaction of a vervet monkey upon hearing an alarm call is to look at the direction of the caller. Looking at the direction of the caller gives them clues as to why the alarm calls were made and also where the caller is facing reveals the direction of the approaching predator. You can listen to these different alarm calls on this site.

As we said before, different alarm calls evoke different responses. Leopard alarm calls would make the monkeys run up into the tree to avoid being ambushed by the leopard. Also, these monkeys would sit on the branches further away from the tree because, even though leopards can climb trees, the branches could not support the leopard’s weight. When an eagle alarm call is given, vervet monkeys would make them look up, run for the nearest bush or both to avoid an approaching aerial attack. Python alarm calls would the monkeys stand bipedally and look down on the ground.

A martial eagle. Photo by Jacques S G from Flickr.

Adult vervet monkeys are more discriminatory when eliciting alarm calls. Infants and juveniles calls however, are less discriminating as they attribute most terrestrial mammals with leopard calls, flying birds with eagle calls and stick-like figures with snake calls (although, compared to infants, juveniles are more discriminant when making alarm calls). In spite of that, adult vervet monkeys seem to elicit eagle alarm calls to different species of raptors and non-raptors (see illustration below). We can infer that adult vervet monkeys attribute eagle alarm calls to birds with the same silhouette as martial eagles. As vervet monkeys get older, they seem to have a better association between predator species and types of alarm calls. Vervet monkeys generally pay more attention to adult alarm calls than those of juveniles or infants.

Alarm calls made by infant, juvenile and adult vervet monkeys in response to sightings of birds of prey (raptors) and non-raptors. The number of calls cited for each age group refers to the total number of calls that were analysed (Gould & Gould, 1999). Click on illustration for larger view of the image.

The study of vervet monkey alarm calls by Seyfarth et al. (1980) laid an important ground work to better understand the complexity of animal communications. By showing that vervet monkeys make different alarm calls to different predatory species, we can posit that vervet monkeys have the ability to categorize different species. The ability to discriminate between terrestrial mammal, flying birds and snake-like objects starts during infancy in vervet monkeys. As they get older, they are better at associating predators with specific alarm calls.

An infant vervet monkey with its mother. Photo by Lip Kee from Flickr.

The ability to over generalize during infancy is evident in both vervet monkeys and humans. For example, upon learning the word “dog”, human infants would refer to quadruped mammals they see as “dog”. As the infant grows, so does the ability to associate the semantic meaning of words they learned. However, the acquisition of alarm calls in vervet monkeys is different than the acquisition of speech (language) in humans. Alarm calls in vervet monkeys are instinctual and not learned. Humans, however, have to learn their language. Failing to do so during the “critical period” generally will result in the inability to learn language in later years. Feral child are examples of human infants that lack linguistic input during their critical period of language acquisition.

Most of us interpret animal alarm calls as an uncontrollable auditory response to fear or pain, akin to humans yelping if we had our finger caught in a door. While this is not entirely false, some animal calls actually convey information from the caller to the listener. Seyfarth et al. (1980) posit that vervet monkey alarm calls are actually basic semantic signals or symbolic signals because each alarm calls seem to mean something to these vervet monkeys. While we don’t know if these alarm calls actually mean “leopard” or “run up to the tree”, we do know that it conveys specific information to their conspecific about approaching predators.

I will be blogging Part II of this post later this week, where I will explain in details the experiments done by Seyfarth and Cheney on vervet monkey alarm calls.

Cawthon Lang KA. 2006 January 3. Primate Factsheets: Vervet (Chlorocebus) Taxonomy, Morphology, & Ecology. Accessed 2011 March 9.

Fichtel, C. Perry, S. Gros-Louis, J. 2005. Alarm calls of white-faced capuchin monkeys: an acoustic analysis. Animal Behaviour 70(1): 165-176. doi: 10.1016/j.anbehav.2004.09.020.

Gould, JL. Gould, CG. 1999. The Animal Mind. Scientific American Library.

Ouattara, K. Lemasson, A. Zuberbühler, K. 2009. Campbell’s Monkeys Use Affixation to Alter Call Meaning. PLoS ONE 4(11). doi:10.1371/journal.pone.0007808.

Seyfarth, RM. Cheney, DL. Marler, P. 1980. Monkey responses to Three Different Alarm Calls: Evidence of Predator Classification and Semantic CommunicationScience 210(4471): 801-803.

Zuberbühler, K. Jenny, D. Bshary, R. 1999. The Predator Deterrence Function of Primate Alarm Calls. Ethology 105: 477–490. doi: 10.1046/j.1439-0310.1999.00396.x.

Zuberbuhler, K. 2000. Referential labelling in Diana monkeys. Animal Behaviour 59(5): 917-927. doi: 10.1006/anbe.1999.1317.

Free conservation biology textbook

Free conservation biology textbook

Sodhi, N. S. and P. R. Ehrlich (Eds.). 2010. Conservation Biology for All. Oxford University Press.
Available online at:

“The authors published Conservation Biology for All in a free and open access format in an effort to make conservation knowledge available to as many people as possible.”

Orangutan Behavior during the Rehabilitation Process


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By Kristin Abt


Orangutan at Sepilok (Photo: Kristin Abt)

A recent article “Fostering Appropriate Behavior in Rehabilitant Orangutans (Pongo pygmaeus)” published online in the International Journal of Primatology discusses research on the behavior of rehabilitant orangutans (Pongo pygmaeus and P. abelii) at the Orangutan Care and Quarantine Centre in Pangkalan Bun, Kalimantan (Indonesian Borneo). Much past research has focused on postrelease behavior of rehabilitated orangutans and on the behavior of wild individuals; therefore, this research is especially timely and useful for the number of centers currently attempting to rehabilitate the ever-increasing number of displaced great apes and other fauna (Descovich et al., 2011).


Curious Orangutan in Sabah, Malaysia (Photo: Kristin Abt)

Orangutans (n=40) in this study included males and females, mass classes ranging from 5 to 25 kg, and good, moderate, and poor health distinctions. Individuals were observed continuously for a period of 5 hours during 3 separate forest excursions each.  A number of behaviors relevant to postrelease success in the forest habitat were recorded (type of locomotion, social behavior, such as play, human caretaker interaction, point of height in tree or on ground, feeding and food choice, grooming, etc.).

Results from this study showed that rehabilitant individuals’ masses were associated with the amount of time spent at the centre. Authors note this finding as a result of the early age of admittance to the centre for most individuals. Further, orangutans in better health spent an increased amount of time consuming food and less time resting than other categories. In terms of locomotion (>30% of overall time), quadrupedal movement in trees was the dominant method (again, with orangutans in better health doing so more often). Individuals who had been at the Care Centre longer spent more time on the ground rather than swinging or other locomotion. As the day in which focal individuals were observed continued, human interaction increased.

Orangutans at Sepilok Rehabilitation Centre (Photo by Kristin Abt)

As rehabilitation of orphaned individuals is a component of the long-term species survival of orangutans, research regarding the behavior of these individuals is important for increasing the chance of postrelease survival and success. Additionally, as their habitat is lost as a result of a number of conservation threats, land protection is necessary to provide habitat in which the released individuals and their wild conspecifics can live.


Descovich, K. A., Galdikas, B. M., Tribe, A., Lisle, A., & Phillips, C. J. 2011. Fostering appropriate behavior in rehabilitant orangutans (Pongo pygmaeus). International Journal of Primatology. doi:10.1007/s10764-011-9491-1

Orangutan Foundation International (a 501(c)3 nonprofit organization) supports the work of the Orangutan Care and Quarantine Centre and other crucial efforts to promote orangutan conservation, including land protection, research, and education. Visit to donate directly to OFI. If you would like to donate items specifically to enhance the lives of individuals at the Care Centre, visit this wishlist to select items that orangutans, such as those in this study, will greatly benefit from. If you would like to learn more, look for the upcoming IMAX© movie Born to Be Wild to be released in theaters April 8, 2011.

Habitat Fragmentation’s Effect on an Endangered Indian Primate, the Lion-tailed Macaque


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Woodland Park Zoo Lion-tailed Macaque (Photo: Kristin Abt)

By: Kristin Abt

The Lion-tailed Macaque (Macaca silenus) is an endangered cercopithecine primate native to the Western Ghats region of India, described as one of the primary hotspots of biodiversity in the world (Kumara & Singh, 2004).  IUCN (2010) estimates a mere 2,500 mature individuals with a total population size of 4,000 individuals.  Furthermore, these monkeys (LTMs) exist in an estimated 47 subpopulations in 7 locations.  Their serious status merits continuing intense and collaborative research on their demographics, current pressures, and the effects of habitat fragmentation, which appears to be the primary concern for their long-term survival in the wild.

Ecology and Distribution

These Old World monkeys have cheek pouches with simple stomachs, long, non-prehensile tails, an opposable hallux and pollex, hardened ischial callosities, and close, downward facing nostrils.  They are diurnal with complex, matrilineal social systems normally with one adult male and one subadult male to multiple females and their offspring.  Males disperse and females display estrus swellings to advertise their reproductive status.  They have an average group size of 18 with a range of 7 to 40 individuals (Umapathy & Kumar, 2000b).  Compared to other macaque species, Umapathy and Kumar point out that they have a slower life history with females reproducing first at 6.6 years and having a birth rate of 0.31 infants/female/year thereafter.  This overall low prolificacy with delayed sexual maturity, long interbirth interval, and low population turnover presents an additional challenge when groups must respond to external survival pressures.

The LTM differs from other macaque species additionally through its primarily arboreal nature.  Menon and Poirier (1996) emphasize this characteristic through the documentation of 3 falls and one subsequent death from tree gaps.  In places with incontiguous canopy cover, individuals exhibited a strong preference to exert considerable effort to cross large holes in the canopy without descending to the ground.  Ramachandran and Joseph (2000) discuss the conservation and sustainability implications of this in that LTMs failed to range into adjacent areas disrupted by fire or eucalypt and teak plantations in order to exhaust nearby resources in neighboring forest fragments.

Individuals are found only in the Western Ghats region in the three states of Kerala, Karnataka, and Tamil Nadu and have been studied extensively in such national and private evergreen forests as Silent Valley in the Palghat district (Ramachandran & Joseph, 2000), the Indira Gandhi Wildlife Sanctuary in Anamalai Hills (Umapathy & Kumar, 2000a & b), Brahmagiri-Makut and Sirsi-Honnovara (Kumara and Singh 2004), the Puthuthotam Cardamom Forest (Menon & Poirier, 1996), and the Kudremukh Forest Complex (Kumara & Singh, 2008).  Within these locations, it has been found that the LTMs prefer habitat primarily between 300m asl – 900m asl (Kumara & Singh, 2008).  It is estimated that almost 40% of the remaining population exist as small groups found in isolated, highly fragmented forests in these areas (Umapathy & Kumar, 2000a).  As one goes from South to North within their range, group size has been shown to increase (Kumara & Singh, 2004).

Woodland Park Zoo Exhibit for Lion-tailed Macaques (Photo:Kristin Abt)

Within their habitat, LTMs serve as “one of the most important habitat specialist primates in India” (Ramachandran & Joseph, 2000).  Sushma and Singh (2006) found that compared to other arboreal mammals, such as bonnet macaques (Macaca radiata), Nilgiri langurs (Semnopithecus johnii), and the Indian giant squirrel (Ratufa indica), LTMs have the narrowest niche breadth with some overlap with bonnet macaques, which indicates a degree of competition where these animals must coexist.  Ramachandran and Joseph (2000) point out that they seldom range outside of their evergreen forest even into the deciduous areas.  They also reported that LTMs feed primarily (91%) on plant matter with the remainder consisting of invertebrates, which is a higher amount than other macaque species (Sushma & Singh, 2006).  Ramachandran & Joseph (2000) found that they formed significant associations with 6 major tree species, especially Cullenia.  These are needed in the proper abundance in order to sustain the primates; however, some flexibility is present.  Menon and Poirier (1996) note that, in times of food scarcity, individuals supplement their diet with Artocarpus and Coffea trees in nearby forested plantations. Because they are highly frugivorous and consume large amounts of figs (Sushma & Singh, 2006), they must range significant distances in order to find sufficient food for the group.  Fruit, as a seasonal and patchy resource, offers a lot of carbohydrates, but not a good amount of protein.  As a result, invertebrates comprise a relatively large amount of their diet in order to provide the necessary nutrition for successful reproduction (Umapathy & Kumar, 2000a). Juveniles spend a significantly larger amount of time feeding on these, suggesting their importance for proper growth and development, as well.

Western Ghats, India Map from

Conservation Threats due to Habitat Fragmentation

When primate groups are found in highly fragmented habitat, this presents serious survival pressures for themselves and for those individuals in neighboring forests without the opportunity for gene flow.  McGarigal and Cushman (2002) define habitat fragmentation as a “landscape level process in which a specific habitat is progressively subdivided into smaller and more isolated fragments.”  They further discuss how it encompasses a change in landscape composition, structure, and function.  Because habitat fragmentation, along with habitat loss, is considered to be one of the main influences causing the incredible mass extinction of species that is currently occurring, studying the effects of this in order to produce urgent and important management strategies is paramount.

Thus far, a number of studies of the LTM have discovered relevant consequences to the habitat fragmentation continually occurring within their range.  In reference to the demographics of social groups, the effects of habitat fragmentation have been to significantly change the composition naturally found in contiguous and undisturbed sections of forest.  Specifically, Umapathy and Kumar (2000b) found near significance with smaller fragments containing larger group sizes compared to larger fragments.  Also, it appears that there is more likely to be two adult males in a social group of a small fragment than the typical one male: multiple females found in larger fragment sizes.  Significantly, there is a positive correlation between fragment size and the number of immatures and birth rate.  The authors cite possible factors for this as increased predation pressures and resource shortages.  Kumara and Singh (2004) classified health of a population by a high overall presence of groups with the modal group size, favorable sex ratio, and a large percentage of immature individuals; therefore, the findings from the previous study provide further support to their criteria as valid to use when investigating the demographics of LTMs in fragmented areas.

Studies have also investigated how vegetation status in relation to level of fragmentation affects these primates.  Umapathy and Kumar (2000a) found that individuals spent significantly less time feeding on invertebrates, a key component to their diet, in smaller fragments.  Additionally, the least disturbed fragments contained the highest plant abundance.  In areas with colonized species, such as mangos and guava, the macaques added these to their diet, which might slightly compensate for the loss in space and flora diversity; however, it could also contribute to human-wildlife conflict.  Furthermore, these researchers (2000b) also demonstrated a positive correlation between the quality of vegetation and the amount of fragmentation.

Along with demographic and dietary changes, significant changes occur in disturbed populations with respect to the groups’ overall behaviors and activity patterns.  Menon and Poirier (1996) studied individuals in a private forest that experienced selective logging and clearing for planting on the floor and found that the primates used the ground often for ranging and foraging out of necessity, but still much preferred the trees – even when travelling in such a manner presented serious and mortal danger due to the lack of sufficient canopy continuity.  They were also forced to cross roads and raid fruit in neighboring plantations, which resulted in human-wildlife conflict and deterrence measures implemented.  Furthermore, the individuals needed to increase their time ranging, which seriously impacted their ability to feed and engage in necessary social behaviors.  Especially relevant to small, isolated populations is the inability to disperse naturally, which Debinski and Holt (2000) discuss and, consequently, suggest corridors for landscape connectivity, especially for highly mobile animals.  Without proper gene flow and the opportunities for appropriate social groups to form, the long-term survival of this species is severely threatened, which is already evidenced by the results of lower numbers of juveniles in these fragmented groups.

In addition to the restriction of available habitat and isolation of existing groups, human-wildlife conflict has placed significant pressure on their survival.  Along with plantations cultivated for teak and eucalypt and areas that are clear felled for tea and coffee, humans also use the forest areas for wood gathering, logging, and hunting of the LTMs and other fauna (Kumara & Singh, 2000b; Menon & Poirier, 1996).  Fragments also increase the likelihood of the macaques coming into human contact and the likelihood that humans will disturb the forest.


As with so many conservation stories, this one can greatly benefit from increased attention, education, and priority at numerous levels. Over recent years, the LTM has featured less prominently in North American zoo collections despite its endangered status, declining populations, charismatic appearance, and active nature (Association of Zoos and Aquariums, 1998). Additionally, few conservation and education efforts are currently in place to support its population (AZA, 1998). While research into its populations and its behavioral ecology are important to further understand the species, additional efforts to increase gene flow between populations, protect its forest habitat, and address conflicts with agriculture are needed for this macaque species to persist.


Association of Zoos and Aquariums. 1998. Lion-tailed macaque 98 fact sheet. Retrieved February 8, 2011, from Web site: Species%20Survival%20Plan.pdf

Debinski, D. M. and R. D. Holt. 2000. A survey and overview of habitat fragmentation experiments. Conservation Biology 14: 342–355.

IUCN.  2010 IUCN Red List of Threatened Species.  Retrieved February 8, 2011, from Web site:

Kumara, H. N. and M. Singh. 2004. Distribution and abundance of primates in rain forests of the Western Ghats, Karnataka, India and the conservation of Macaca silenus. International Journal of Primatology 25: 1001–1018.

Kumara, H. N. and V. R. Singh. 2008. Status of Macaca silenus in the Kudremukh Forest Complex, Karnataka, India. International Journal of Primatology 29: 773–781.

McGarigal, K. and S. A. Cushman. 2002. Comparative evaluation of experimental approaches to the study of habitat fragmentation effects. Ecological Applications 12: 335–345.

Menon, S. and F. E. Poirier. 1996. Lion-tailed Macaques (Macaca silenus) in a disturbed forest fragment: Activity patterns and time budget. International Journal of Primatology 17: 969–985.

Ramachandran, K. K. and G. K. Joseph. 2000. Habitat utilization of lion-tailed macaque (Macaca silenus) in Silent Valley National Park, Kerala, India. Primate Report 58: 17–25.

Sushma, H. S. and M. Singh. 2006. Resource partitioning and interspecific interactions among sympatric rain forest arboreal mammals of the Western Ghats, India. Behavioral Ecology 17: 479–490.

Umapathy, G. and A. Kumar. 2000a. Impacts of the habitat fragmentation on time budget and feeding ecology of lion-tailed macaque (Macaca silenus) in rain forest fragments of Anamalai Hills, South India. Primate Report 58: 67–82.

Umapathy, G. and A. Kumar. 2000b. The demography of the Lion-tailed Macaque (Macaca silenus) in rain forest fragments in the Anamalai Hills, South India. Primates 41: 119–126.

Crested Gibbons: Song Structure as Indication of Phylogenetic Relatedness

By Raymond Ho

The genus Nomascus are one of the four genus that occurs in the Hylobatid family. Males have erect crown hair thus giving this genus its common name, crested gibbons. Crested gibbons are sexually dichromatic; males and females of the same species have different fur coloring and markings.The males tend to have black fur while females have orange to yellow fur. All species of Nomascus are either endangered or critically endangered. Like all gibbons, their trademark is their species-specific songs that they sing to communicate to each other. These songs, unlike those from song birds, are instinctual and are not learned (Thinh et al., 2011). Gibbons are the only monogamous ape.

Nomascus leucogenys mother and male offspring.

A new study, published this month on BMC Evolutionary Biology by Thinh et al. (2011) found that crested gibbons have species-specific song that can be used to differentiate the Nomascus species and also predict the phylogenetic relatedness of this genus. In this study, 6 Nomascus species were used as analysis: N. nasutusN. concolor, N. leucogenysN. sikiN. annamensis and N. gabriellae. The researchers used 92 out of 175 song recordings for acoustic analysis, analyzing 440 great calls (duets between males and females) and 447 male calls from 92 gibbon groups at 24 locations to confirm the relationship between song structure and phylogeny in Nomascus.

Video of Cao Vit gibbons (N. nasutus) singing. Notice the sexual dichromatism that occurs in males and females.

The researchers were able to tell the 6 Nomascus species apart by just listening to their song acoustics, albeit some with greater difficulties than others. N. nasutus and N. concolor could clearly be identified from their song acoustics. N. leucogenysN. sikiN. annamensis and N. gabriellae on the other hand, have songs that are similar in structure but with minute differences. They also found a significant correlation between song structures and genetic similarity, which means that Nomascus species that are more closely related have similar song structures. This would account to N. leucogenysN. sikiN. annamensis and N. gabriellae having same song structures but with minute differences in them because they are very closely related.

Map shows the distribution of all 7 Nomascus species. Illustration from
The authors also found that song similarities among species correspond to geographic location. They found a large difference in song structures between the most northern species and the most southern species, and a gradual difference when compared from the northernmost species to the southernmost species. This gradual difference in song structure, from the most northern species to the most southern species, supports the hypothesis that the genus originated from the north and successively migrated to the south. N. hainanus (omitted in the study) and N. nasutus are basal among crested gibbons (Nomascus). Together, these two species form a cladeN. concolor branched off first, then following by the rest of the Nomascus species; N. leucogenysN. sikiN. annamensis and N. gabriellae.
The cladogram of the genus Nomascus. Illustration from  Thinh et al. (2011).

Thinh, V.N. Hallam, C. Roos, C. Hammerschmidt, K. 2011. Concordance between vocal and genetic diversity in crested gibbons. BMC Evolutionary Biology 11: 36 DOI: 10.1186/1471-2148-11-36

Originally posted on The Prancing Papio.

Rehabilitation and Release: West African Chimpanzee Conservation Success


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By: Kristin Abt

Recently published online in the International Journal of Primatology, an article by Humle, Colin, Laurans, and Raballand (2010) discusses the release of a group of 12 chimpanzeees into the High Niger National Park in Guinea, West Africa. Through the efforts of the Chimpanzee Conservation Center, 9 chimpanzees remain in natural habitat at the time of publication. The conservation benefits of this substantial undertaking are numerous:

  • While the park already has a viable population of chimpanzees, this effort adds reproductively mature individuals and genetic material to the endangered wild population.
  • Additionally, with over 1000 chimpanzees in sanctuaries and other facilities rather than in the wild, the need to address their long-term management is acute. Not only is the individual welfare of the released chimpanzees enhanced, this scientific study of the release process will also aid conservation practitioners in the implementation of future chimpanzee rehabilitation.
  • As the authors point out, the conservation status and role of the release area is promoted to the government and general public, which will hopefully bolster its future capacity to serve as suitable habitat for many species.

Previous reintroduction efforts have led to the adoption of an overall chimpanzee reintroduction plan that emphasizes adequate rehabilitation training for individuals and substantial monitoring following release. In order to determine an appropriate area for release, the authors cite numerous components, including habitat suitability (food, other resources, terrain, etc.), level of and proximity to human pressures, and the overall ability of chimpanzees to thrive in the absence of human involvement. Further, in order to monitor the activities of the chimpanzees, researchers used radiotracking collars on released individuals.

Chimpanzee (Photo: Kristin Abt)

The release site was chosen in part due to its strict protection as a core area within the park and its minimal roads. The demographics of the released individuals were 6 males and 6 females ranging from 8 to 20 years of age. Information included in the article details the social familiarity of the group, survival skills possessed by the individuals, and the number of years each had access to formative “bush-outings” with caretakers and expansive, naturalistic enclosures. Additionally, the researchers verified the genetic appropriateness of the subspecies (Pan troglodytes verus) and the overall health of each chimpanzee. The article also provides a 20 month timeline of events relevant to the release process including group dynamics, deaths, births, and sightings with wild chimpanzees.

Humle et al (2010) discusses the ranging patterns and habitat use of the released chimpanzees to obtain an overall picture of their behavior compared to typical wild chimpanzees in the area. Released males traveled significantly further than released females as measured by maximum mean distance travelled. They also remained significantly further from the release site than the females. Overall, the chimpanzees preferred forested areas over open space. Within the mixed forest-savanna habitat where the chimpanzees were released, the individuals remain independent of human provisioning. Additionally, two chimpanzees have been born to released females. Humle et al (2010) suggests that part of the success of the released chimpanzees could be due to the lower population densities of wild chimpanzees in the mixed habitat type along with their relatively larger ranges.

A number of agencies and professionals will ultimately contribute to the conservation efforts of a given species, as noted by the authors. This paper attempted to combine data on behavior, ecology, conservation, and wildlife management in order to approach the multi-faceted undertaking of chimpanzee rehabilitation. As with many conservation projects, communication and an interdisciplinary approach are needed to successfully achieve targeted goals.

The Chimpanzee Conservation Centre (CCC) is a member of the Pan African Sanctuary Alliance (PASA) that aims to promote the welfare and conservation of primates in African countries. It unites sanctuaries together to train professionals at the facilities about animal management, veterinary care, and education. PASA accepts donations at its website to continue its primate care and conservation efforts.


Humle, T., Colin, C., Laurans, M., & Raballand, E. (2010). Group release of sanctuary chimpanzees (Pan troglodytes) in the Haut Niger National Park, Guinea, West Africa: Ranging patterns and lessons so far. International Journal of Primatology. doi: 10.1007/s10764-010-9482-7


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