article: A new species of monkey has been discovered after scientists learned to distinguish it by the appearance of its penis. The white-cheeked macaque was discovered in the remote highland forests of south-east Tibet after researchers set up camera traps. The monkey has a distinctive rounded penis rather than the arrow shaped genitalia found on other species in the area. Scroll down for video . The white-cheeked macaque, from Tibet, China, has a distinctive rounded penis compared to other macaques . Officially named Macaca leucogenys, it earned its common name due to the pale whiskers on its chin and the side of its face. Videos have also revealed that the animal has a distinctive alarm calls compared to other macaques in Tibet. Human males may be preoccupied by the size of their penis, but it is one of the largest in the primate kingdom. An evolutionary biologist has compared the sizes of genitals of humans to gorillas and apes to look at why there is such a discrepancy between the species. He concluded the human penis may have grown so long to make it more conspicuous to potential partners, or even as a way of cooling the body down. The relative size of the male reproductive organs across these species was discussed by evolutionary biologist Darren Curnoe in his latest 'How Did We Get Here?' video series for the University of New South Wales, Australia. Gorillas have small penises and small testicles, while chimps have medium-sized penises and large testicles. By comparison, human males have the longest penis and medium-sized testicles. 'Amazingly the size of the reproductive organs, especially the testicles, are a reflection of how the apes are organised socially,' explained Professor Curnoe. 'Why the difference? Well for the testicles it's pretty straight forward. 'It all comes down to the amount of competition the chimps, and their sperm, have when they mate with females.' But he said there wasn't a discernible reason why there is so much variation in penis size between humans and great apes. Dr Pengfei Fan, one of the researchers who discovered the new species and a biologist at Dali University, Yunnan, in China, said the new macaque had long been misidentified as another species. He said that due to the remoteness of the location in Medog County of Tibet, few biologists had been there. He said: 'Medog County is surrounded by snow mountains and so far away from the centre of science. 'Furthermore, it locates in southeastern Tibet and close to McMahon line which is a political sensitive area. Very few have people studied primates there. 'This species has long been identified as Assamese macaque (Macaca assamensis) because no clear photos or good specimens are available.' In an attempt to better study the animals living in the region, Cheng Li, a photographer with the Imaging Biodiversity Expedition in Beijing, set up camera traps in the area's remote tropical and evergreen mountain forests. They captured 685 photos of macaques and Mr Li was also able to follow a group of macaques allowing him to obtain close up images. When the researchers, whose work is published in the American Journal of Primatology, examined the images they started to notice some monkeys that had different features. They the animals hd relatively short hairless tails and almost white hairs around their face. They also had long thick hairs on their neck. But the most distinctive feature was the creatures genitalia. Most macaques from that area have arrow shaped penises. However, Macaca leucogenys had far more rounded penis and a dark hairy scrotum. Scientists noticed some of the macaques captured on by the cameras looked different with shorter tails (like those above) and light coloured markings around their face, leading them to identify a new species of primate . The images above show the more usual 'arrow-shaped' genitalia that macaques in the area have . Videos also revealed that Macaca leucogenys produced a far higher frequency squeal when threatened compared to the low pitched bark used by Macaca assamensis as an alarm call. Dr Fan said the species seemed to inhabit a diverse range of habitats and was found living in tropical forests at 1,395 metres, evergreen broad-leaved forests at 2,400 metres and a mixed broad leaf and conifer forest at 2,700 metres. However, the researchers, who also included Choa Zhao from the Southwest Forestry University in Kunming, China, warned that the new species may be under threat. They said: 'The white-cheeked macaque is threatened by illegal hunting and the construction of hydropower stations. The white cheeked macaque was discovered in the mountain forests of Medog in south east Tibet, China . The researchers say the whiskers on the side of the face of Macaca leucogenys become paler and more prominent with age. Infants can be seen in the images A and B while a juvenile is labelled C. Adult females are in the image D and adult males are seen on the far right of image E. Adults have few dark hairs on their faces . 'Discovery of this new primate species further highlights the high value for biodiversity conservation of southeastern Tibet and calls for more intensive surveys, studies, and environmental protection in this area.' Dr Fan added that it was possible there could be other species of primate still to be discovered in the area. He said: 'This area has been little studied. 'Although primates have been intensively studied for decades, two new macaque species (Macaca munzala and M. leucogenys) were discovered and described in this area in the past 10 years. 'As for other species groups that received less attention, We believe there are still some species remain undiscovered. 'It is highly possible that some primate species still remain undiscovered.' Adult Macaca leucogenys (above) have long hair on their muzzles simiarl to another species Macaca thibetana .
highlights: Macaca leucogenys long mistaken for Macaca assamensis say scientists .
  New macaque has a distinctive rounded rather than arrow shaped penis .
  Researchers say the remote highland forests of Medog, in south east Tibet, could be hiding many other new species that are waiting to be discovered .
  They warn new macaque is threatened by hunting and habitat destruction .
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