Primatology.net

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

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.

The study of conservation biology, and its oft-times competitor – urbanization, is increasingly relevant to the study of primatology. As a species, long-tailed macaques demonstrate a number of conflicts and potential implications of the urbanization occurring in primate-habitat countries. The long-tailed macaque (Macaca fascicularis) is the third-most common primate in the world with an extensive range across Southeast Asia covering Timor and the Philippines to the Southeast of Bangladesh (Richard, Goldstein, & Dewar, 1989). Although they are common relative to other primate species and listed as least concern by the IUCN, scientists recognize that their range and population status is declining due to habitat loss and degradation and exportation for the biomedical industry (Eudey, 2008). Whole groups are cultivated in Cambodia for trapping and sale for pharmaceutical testing based on demand from China and the United States while other anthropogenic factors, such as shipbuilding and shrimp farming negatively impact populations in Bangladesh (Eudey, 2008). They have also been introduced to areas outside their native range, including to the island of Mauritius and to China for use in medicine and consumption (Eudey, 2008; Richard, Goldstein, & Dewar, 1989).

Macaque (Photo: Kristin Abt)

While macaques are able to utilize a variety of human habitats, Malaivijitnond and Hamada (2008) suggest that anthropogenic land-use change has forced these animals to coexist in human-dominated landscapes. Long-tailed macaques are naturally found in low elevation habitats, including, seashores, swamp and mangrove forests, and river banks (Eudey, 2008). Studies have found, however, that long-tailed macaques prefer secondary, disturbed forests to the primary forests that most other primate species prefer (Richard, Goldstein, & Dewar, 1989). Macaques are commonly seen and encouraged in monkey parks, temples, monasteries, city and forest parks, and restaurants, often with individuals released as pets incorporated into the urban troops (Malaivijitnond & Hamada, 2008). This study based in Thailand found that groups averaged two-hundred monkeys per location with five locations containing upwards of one thousand individuals in a single group, including numerous subspecies and hybridized animals. These groups are locally overcrowded, which exacerbates human-wildlife conflict, especially in dry seasons and limited food supply (Malaivijitnond & Hamada, 2008). An extreme example of such conflict possible in an urban environment occurred in Malaysia where a suspected long-tailed macaque approached a house, potentially attracted by the female pet monkey, and grabbed a baby that it later dropped to the ground when it became alarmed. The child did not survive the incident and the monkey was found and shot (“Monkey snatches,” 2010).

Aggressive encounters with macaques are common in urban areas and some countries hire guards in public places to chase the animals away (Richard, Goldstein, & Dewar, 1989). Unintentionally, humans contribute to the problem by leaving garbage for them to raid (Eudey, 2008). In many cases, humans actively promote their presence for spiritual and entertainment purposes by provisioning food for the macaques, including banana, papaya, watermelon, mango, rambutan, pineapple, and coconut (Malaivijitnond & Hamada, 2008). These authors noted that local villagers in Thailand will hold “feeding parties” for the macaques and stop their cars to allow troops to cross roads, yet need to protect their buildings and houses with metal and protective guarding from the damage caused by macaques. There is also the potential for zoonotic disease transmission, including the potentially fatal herpes B simplex virus, from macaques to people. Long-tailed macaques will also commonly raid human crops, including rubber fruits, rice shoots, corn, and beans, causing some to label them as pest or “weed” species (Richard, Goldstein, & Dewar, 1989). The monkeys have been seen raiding palm oil plantations in Borneo, as well (personal observation).

Long-tailed macaques exist in the absence of humans on forest edges with suitable access to fruits and crustaceans; however, the urban environment facilitates their feeding and reproduction potential by increasing group sizes and decreasing their need to forage and seek wild habitat. Humans both promote macaque populations through provisioning and protection in some habitats and hinder through habitat fragmentation, exportation for research, human consumption, and the pet-trade.

References

Eudey, A. A. (2008). “The crab-eating macaque (Macaca fascicularis): Widespread and rapidly declining.” Primate Conservation, 23, 129-132.

Malaivijitnond, S., & Hamada, Y. (2008). Current situation and status of long-tailed macaques (Macaca fascicularis) in Thailand. The Natural History Journal of Chulalongkorn University, 8(2), 185-204.

“Monkey snatches, kills baby in Malaysia.” October 7, 2010. My Fox DC. Retrieved from www.myfoxdc.com.

Richard, A. F., Goldstein, S. J., & Dewar, R. E. (1989). “Weed macaques: The evolutionary implications of macaque feeding ecology.” International Journal of Primatology, 10(6), 569-594.

Single nucleotide polymorphisms (SNPs) are 1 base pair differences in the genetic code when compared to same sequence from another individual. Many population geneticists who study human genetics compare and contrast SNPs between different populations to understand ancestry and genaology. A new database of non-human primate SNPs, MonkeySNP, has been recently released, and was announced in the journal Bioinformatics.

I don’t regularly announce such news, but I consider this a pretty significant tool for any researchers who are studying primate diversity. As you may know many primate species are severely endangered and any successful conservation effort requires an understanding of the genetic diversity of the surviving population. This database will help currate this genetic diversity.

But the database is rather limited right now. Only 827 SNPs are listed, and are only macaque SNPs. I’m hopeful that as the genes and genomes of more primates species and individuals are sequenced this database will grow. In the mean time, I suggest you bookmark this site and keep an eye on it.

S. Khouangsathiene, C. Pearson, S. Street, B. Ferguson, C. Dubay (2008). MonkeySNP: a web portal for non-human primate single nucleotide polymorphisms Bioinformatics, 24 (22), 2645-2646 DOI: 10.1093/bioinformatics/btn493

I’m scouring the American Journal of Primatology for a paper on gorillas using tools as weapons in the wild. National Geographic News says the paper is out, but I can’t find it anywhere in the early edition nor in the current issues. I’ll continue looking, but in the mean time here’s what we got to run on (and it ain’t much)

“Researchers [doing a three year study of Cross River gorillas (Gorilla gorilla diehli)] in Cameroon have documented three cases in which the [gorillas] threw clumps of grass or tree branches at humans.”

The people who documented the behavior suggest that the gorillas possibly learned their unusual behavior from interactions with humans. Captive gorillas have been documented picking up stone throwing from their chimpanzee neighbors, so it’s not too improbably that wild gorillas could pick up grass and branch hurling from human neighbors. How did these gorillas learn the behavior? Could it be possibly due to mirror neurons? Conveniently this is a perfect transition into an upcoming PNAS paper on tool use and mirror neurons in macaques, that was announced in this ScienceNOW news article,

“To investigate how the brain performs this sleight of hand, [the team] recorded brain activity in two macaque monkeys. Each was trained for 6 to 8 months to grasp items of food with pliers. The team documented the activity of 113 neurons in F5 and in a brain area called F1, which has also been implicated in the manipulation of objects. The researchers first established the brain’s firing sequence when the monkeys grasped only with their hands. The experiment was then repeated while the monkeys used normal pliers that required first opening the hand and then closing it to grasp the food. The same neurons fired in the same order. Remarkably, the same neurons also fired, in the same order, when the monkeys used “reverse pliers” that required them to close their fingers first and then open them to take the food.”

The research is coming from the University of Parma which seems to be specializing in this sorta research because about a year and half ago they documented mirror neurons role in mimicry. In the new paper, the researchers,

“conclude that when learning to use a tool, the pattern of neuronal activity is somehow transferred from the hand to the tool, “as if the tool were the hand of the monkey and its tips were the monkey’s fingers.” As for how the same neurons could affect both the opening and the closing of the hand, the team speculates that they may be connected with other sets of neurons that more directly control these movements. The authors also point out that area F5 is rich in so-called mirror neurons, a type of nerve cell discovered earlier… that fires both when a primate performs an action and when it observes another individual doing the same thing. Mirror neurons in F5, the authors suggest, may be involved in this transfer process as a monkey learns how to use a tool by watching others.”

The first observations of gorillas using tools in the wild was made a couple years ago, and last year we saw (albeit not too convincingly) a chimp fashioning a spear to hunt, so I’m not too surprised about this news… I just wanna see it!

With all the depressing news of gorillas being slaughtered and primates being brought closer to extinction, I wanted to share this photograph of an abandoned baby macaque, who was taken in by an animal hospital in Goangdong Province, China. He was very lonely until he made friends with a white pigeon.

In many cultures, the white pigeon or dove, is a symbol of peace and hope. It seems like this little birdy brought a lot of hope to this little macaque… two are now inseparable, and make for an awfully adorable friendship.

Read more about their heartwarming story over at the Daily Mail.

P.S. Doesn’t this remind you of the baby orangutan and tiger friendship?

From this news release, is this Science paper, “The Perception of Rational, Goal-Directed Action in Nonhuman Primates” where Justin Wood of Harvard’s Psychology department and colleagues., figure out that primates expect one another to act rationally. How?

Well Wood and crew setup two sets of experiments that tested the behavioral response of over 120 primates, including cotton-top tamarins, a type of New World monkey, rhesus macaques, a Old World monkey and chimpanzees to represent the apes.

I have been confused about the design of the first experiment, which the tested the primates by presenting them with two potential food containers. One container was grasped by the scientists on purpose and the other container was accidentally grasped by flopping their hand on top of it. I probably didn’t do a great job translating the setup, so forgive me.

The most sense I can make out of what was tested here is the ability to understand or differentiate goal-oriented and accidental behavior. And the results show that in all three species, the primates picked out the the food container that was purposefully grasped more often than the container upon which the hand was flopped. This indicates that the primate inferred goal-oriented action on the part of the experimenter when he or she grasped the container, and was able to understand the difference between the goal-oriented and accidental behavior.

In the second experiment, the primates were also presented with two potential food containers but this time the researchers sought to answer if the primates can infer others’ goals under the expectation that other individuals will perform the most rational action allowed by the environmental obstacles. In one situation, an experimenter touched a container with his elbow when his hands were full, and in another scenario, touched a container with his elbow when his hands were empty. And low and behold, the primates looked for the food in the container indicated with the elbow more often when the experimenter’s hands were full.

The primates considered, just as a human being would, that if someone’s hands are full then it is rational for them to use their elbow to indicate the container with food, whereas if their hands are empty it is not rational for them to use their elbow, because they could have used their unoccupied hand.

Wood comments on his paper,

“A dominant view has been that non-human primates attend only to what actions ‘look like’ when trying to understand what others are thinking. In contrast, our research shows that non-human primates infer others’ intentions in a much more sophisticated way. They expect other individuals to perform the most rational action that they can, given the environmental obstacles that they face.

This study represents one of the broadest comparative studies of primate cognition, and the significance of the findings is reinforced by the fact that these results were consistent across three different species of primates. The results have significant implications for understanding the evolution of the processes that allow us to make sense of other people’s behavior.”

What sorta significance? Well this study kinda sorta implies that the ability to engage in this type of rational action perception evolved as long as 40 million years ago, with non-human primates, and that it is not a human only response… possibly this sort of behavior was positively selected for in the primate lineage and ultimately folds into the social brain hypothesis. Speaking of which, you may also wanna check out the evolution of the social brain, which also debuted in the latest Science, while you are at it.

According news bite of a long term study of Tibetan macaques (Macaca thibetana) in the Mount Huangshan Scenic Area of China’s Anhui Province, ecotourism is doing more harm than good. In the October edition of the International Journal of Primatology, the results of a 19 year long study will show that skyrocketing infant mortality coincided with an influx of ecotourism.

From National Geographic News,

“[Tibetan macaques] regularly compete for corn in a small open area within view of spectators. [Which] likely triggered adult aggression toward each other and toward their young… As a result, less than half of the infants survive into adulthood.

The results suggest that ecotourism can be deadly when not managed properly, said study co-author Carol Berman…

Berman’s team studied the Tibetan macaques for six years before ecotourism began in 1991.

They also collected data while tourists visited the animals between 1992 and 2004, including a span in 2003 when tourism was suspended.

Infant mortality had been low prior to ecotourism and was primarily caused by disease, the team found.

But exposing the monkeys to tourism was linked to high death rates caused by aggressive behavior among adults and toward infants. Although they didn’t witness all the attacks, many of the infant corpses Berman’s team found had bite wounds indicative of adult macaques.”

The National Geographic news piece on this publication goes on to interview Frans De Waal on his thoughts about ecotourism. He agrees with Berman that ecotourism works when it is managed properly.

The article goes on to cites that ecotourism for gorillas in Rwanda has helped out their case, but I beg to differ. We are seeing an influx of gorillas die from human acquired diseases. Many of these diseases like E. coli are not directly due to ecotourism, but other diseases… specifically communicable ones, take the common flu, can do serious damage to primate populations without acquired immunity to these pathogens.

In both of these cases, we see ecotourism not panning out to be what it was intended for — to spread awareness and help the conservation of primates. On the contrary ecotourism has serious side effects that we have no way of really calculating nor controlling.

There’s new research coming out from Nature that shows us rhesus macaques are really tuned into statistics and probabilities, they may even have neurons specialized to calculate probabilities. But don’t get your hopes up too high… these monkeys will not be your bookies or be crunchin’ gout some gnarly ANOVA tests with p-value significance.

What you can expect, and this is all paraphrased from a New Scientist news article on this research, is what authors Tianming Yang and Michael Shadlen from Howard Hughes Medical Institute and the University of Washington have reported. They tested the reasoning capabilities of two rhesus macaques,

“By showing them a series of abstract shapes on a video screen, the monkey saw a sequence of 4 of 10 possible shapes then, had to choose which target to look at. The probability that the red target would give the reward was the sum of the probabilities for each of the four shapes; otherwise, the green target yielded the drink… both macaques learned to match their choices closely to the actual probabilities revealed by the shapes they saw, choosing the correct target more than 75% of the time.

This is the first time monkeys have been shown to make such subtle probabilistic inferences.”

Yang and Shadlen observed neurons responding to the first shape,

by firing at a rate proportional to the probability suggested by that shape. As each successive shape was shown, the firing rate changed to match the probability determined by all the shapes seen so far.

“We’re seeing neurons that are making computations,” says Shadlen. In particular, the neurons appeared to be computing the log likelihood ratio of red versus green rewards – exactly the sort of computation a statistician might do.

Like I said above, the results are published in Nature, “Probabilistic reasoning by neurons.” Hat tip to Afarensis for pointing this study out in his blog.