Primatology.net

As described in a recently published paper in Biology Letters, the Philippine Tarsier (Tarsius syrichta) has been found to communicate through extremely high pitched vocalisations in the ultrasound domain, undetectable by human ear. These presumed mute primates baffled primatologists… How can such lack of calls be observed when closely related species are clearly dependent on frequent vocal signals within the group? However the mystery was solved when upon further inspection, these little guys could be heard communicating among the highest frequency levels detected from any terrestrial mammals. It is now thought the extremes of these calls could allow conspecifics to communicate whilst remaining undetected by predators or prey and/or allow individuals to be more easily heard through background noise.

(Ramsier et al. 2012) Primate communication in the pure ultrasound.
DOI: 10.1098/rsbl.2011.1149

A paper released this earlier this week has been first to document spontaneous prosocial behaviour in chimpanzees, finally drawing a line under the question as to whether the welfare of others is considered during choice making in this species; a controversial topic, where such behaviours have been often concluded to be absent in any primate apart from humans (generally from research within the social sciences). This research was carried out at the Yerkes National Primate Research Center by Victoria Horner, and Frans de Waal.

Pairs of chimpanzees (Pan troglodytes) where placed into testing rooms, separated by a mesh barrier. One individual had access to 30 tokens, divided into two separate colours – all of which could be given to the experimenter in exchange for food. Half of these when exchanged resulted in a selfish outcome in which only the individual handing the token received a reward, whereas the other half resulted in an altruistic outcome where both individuals received an equal reward. The individual handing the tokens to the experimenter was rewarded regardless.

If chimpanzees where choosing under a system driven by selfish interests, there should be a preference towards the choice where only the individual in control of the tokens receives a reward, and if the choice was purely random, each token would be expected to be seen 50% of the time. However, it was found that pairs where significantly more likely to share a reward (displaying prosocial behaviour), than choose the selfish option.

Victoria Hornera, J. Devyn Cartera, Malini Suchaka, and Frans B. M. de Waal (2011). Spontaneous prosocial choice by chimpanzees Proceedings of the National Academy of Sciences : 10.1073/pnas.1111088108

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

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.

Reference:

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

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).

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.

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.

Reference

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 www.orangutan.org 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.

When trained Macaques were given a choice of three answers in a computer game; one of which was correct, one incorrect, and an additional option to pass – macaques where shown to choose the latter option to pass rather than risk being incorrect. The macaques were rewarded for a correct answer, but an incorrect answer initiated a pause in the game until the next question.

The “pass“ option was used in an identical fashion to that of human participants, and the macaques were observed to show self-doubting behaviour – a trait which was previously thought to be unique to us. When capuchins were faced with an identical challenge, they failed to take this third option, and seemed unaware when they are likely to make an error.

More information and Video at; BBC – Earth News

Last October, London Zoo saw the birth of a new baby gorilla? He has since been named Tiny and he’s walking now.

London Zoo's Tiny

Sexual competition can be highly disruptive of group relationships, especially if conflicts are escalated into a fight – so it is important for third-parties to “keep track” of consortship partners within a group in order to take appropriate action and possibly avoid such confrontations. De Marco et al. collected data from 2 Tonkean Macaque groups, to test whether attention from third-parties would be directed towards actively consorting group-mates and to then see if activities are modified, or if stress levels increase.

They found that the dominant male was approached more frequently when involved in a partnership with an estrous female. But also found that although females gain more attention during estrous, levels of interactions with the female during consortship did not change comparatively to the control. De Marco et al. also found that levels of sleeping and environment manipulation from bystanders were significantly reduced during times of sexual pairing; this study is the first to demonstrate a change of group behaviour in primates during times of sexual consortship.

Read more of the study at;
De Marco, A. Cozzolino, R. Dessì-Fulgheri, F. Thierry, B. 2011. Interactions between Third Parties and Consortship Partners in Tonkean Macaques (Macaca tonkeana). Int J Primatol DOI: 10.1007/s10764-011-9496-9

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 cepf.net

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.

Conclusions

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.

References

Association of Zoos and Aquariums. 1998. Lion-tailed macaque 98 fact sheet. Retrieved February 8, 2011, from Web site: http://www.nagonline.net/Fact%20Sheet%20pdf/AZA%20-%20Lion-Tailed%20Macaque%20 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: http://www.iucnredlist.org/details/12559

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.