Deforestation sponsors local langurs on a demolition derby
source: DM/Friday, July 06, 2007
By Rashmini de Silva
With the end of the last ice age, all non-human primates encroached and over shadowed the entire human population in this world. Gradually that phenomenon took a reversing deform as development of agriculture and technology rigged against our most adjacent cousins when we humans started to rapidly obtrude upon every niche of the earth. Humans pervasively colonized, dwarfing the other primate populations, ensnaring them to dreadful vulnerability. While human inhabitants expanded, their needs and requirements escalated in parallel with it, which resulted in forests haphazardly being obliterated and utilized in order to comply with their ever-rising necessities. Discounting the repercussions of depleting the natural habitats of these fascinating primates, disregarding the evolutionary similitude, humans are now blinded by technological advancements and are unfortunately prepared to overlook the severe eradication of their closest cognates. Umpteen amounts of primate species all over the world are being impelled towards extinction, focusing on Sri Lanka; the Purple-faced Langur (Trachypithecus vetulus) is certainly a prominent endangered primate contender who is suffering form the misconducts of us, human beings.
Spanning from the dry zone to the wet zone and even to high elevations over 2000m the Purple-faced Langurs thrive where ever there’s ample forest coverage. Depending on their locale, a group comprises of 4-21 individuals and they mainly feed on various fruits and leaves. This hefty diurnal arboreal primate has a pelage diverging from grey to black and their facial skin consists of a purplish black undertone, where it is more prominent in infants. The wispy grey coloured rump patch is one of the Purple-faced Langur’s most distinct traits along with the beige coloured cap of hair and white whiskers outlining the side sections of the face and chin.
At present there are four sub species of the Purple-faced Langur identified with slightly different coat tints and other characteristics, who occupy various ranges in our island. The Northern Purple-faced Langur (Trachypithecus vetulus philbricki), the montane Purple-faced Langur who is more commonly referred to as the bear monkey (Trachypithecus vetulus monticola), The Lowland wet zone Purple-faced Langur (Trachypithecus vetulus vetulus) and the western Purple-faced Langur (Trachypithecus vetulus nestor) are the four sub species who are in a constant rival for existence due to the drastic declination of habitat loss in Sri Lanka.
The northern Purple-faced Langur (T.vetulus philbricki) dwells in the forests of the dry zone and is fairly large bodied like the bear monkey comparing to the other two sub species. The rump patch of this langur is insipid and not that conspicuous though the lower limb areas are covered in black. Residing in the wet zone in montane areas of 1200m-2000m altitudes, is the bear monkey. The significant difference of this langur that separates it from the other sub species is the thick long fury coat. There are frequent sightings of T.vetulus monticola in the Horton planes. The southern lowland wet zone Purple-faced Langur (T.vetulus vetulus) lodge in the lowland and midland rain forests in the island. The whitish rump dapples are blatantly visible in its black fur coat. This sub species along with the western purple faced leaf langur (T.vetulus nestor) are relatively small in size in contrast with the other sub species. The smallest of the sub species is the western Purple-faced Langur (T.vetulus nestor). These langurs inhabit in forests in the vicinity of western low lands and its range spreads out to the inlands as well. The coat of this sub species is dull grey and the fur covering the rump area is silvery grey.
Apart from the above mentioned four sub species, as times passed there was a discovery of a fifth sub species (T.vetulus harti) in the dry zone from the areas of Tantirimale, Tunukkai and Illavankulam. According to researcher, Dr. Jinie Dela, doubts had been expressed at first whether T.vetulus harti was a variant of T.vetulus philbricki rather than a definite sub species. This had been fuelled by the fact that there had not been any records of this sub species since 1954 and because its range has been inaccessible for the past 20 years (for security reasons) for the verification of its presence. And significant colour differences are evident between this and the other sub species because the yellowish scalp hair shades down to chocolate brown at the shoulders.
As a result of being imposed to various threats the whole species of the Purple-faced Langur fall into the endangered species category of the IUCN redlist. The Purple-faced Langur being predominantly arboreal is very vulnerable to habitat change through loss of tree cover. Forest populations appear wholly arboreal and rarely range into the surrounding villages. The loss, degradation or fragmentation of forests will directly affect them, mentioned Dr. Dela when inquired about the rationale for the minimization of these fascinating creatures. According to environmental lawyer, Jagath Gunawardhana, under section 30 of the fauna and flora protection ordinance, killing, injuring, buying, selling, keeping in captivity or keeping body parts (skin, skull) of the Purple-faced Langur is considered as a serious offence. Despite the numerous rules, regulations and laws implemented, illegal lumbering, hunting these langurs for skin to make traditional drums and for food still haunts even conservation forests.
Dr. Dela also emphasized on the enormity of the destructive impact habitat loss can lay upon this species, habitat loss for the purple face langur is inflicted critically in the dry zone by forest clearance for chena cultivation. A serious negative derivation elicits along with the spreading of chena cultivation because farmers deem these monkeys as pests and kill them brutally. In regions where forests have been expunged and replaced, constituting numerous usage of land, these langurs have suitably adapted well to a stable beneficial life style in home gardens as well as in rubber and coconut plantations, where they devour on the fruits and leaves available. During the past two centuries deflation of forest areas in wet lowlands within the island was indorsed by cash crop cultivations and human accommodations, at present a substantial amount of Purple-faced Langurs live and contend with humans for food sources. As the human populations enlarged and expanded, the demand for land ascended along with it, boosting the deprivation of habitat of these primates.
Amongst the sub species who are struggling to subsist, the Western Purple-faced Langur (T.vetulus nestor) population is suppressed and subdued and is restricted to minuscule areas where food and shelter is intensely scarce. This sub species is declared as critically endangered imputable to the decreasing diminutive population. “A fairly large portion of the western Purple-faced langur is enclosed within the western province, where urbanization disseminates at a hasty rate inducing forest patches, rubber plantations and even home gardens to exhaust and minify. Due to the lack of tall trees and a steady supply of food, the western Purple-faced Langur is exposed to countless obstacles varying from threats from poachers and predators to territorial conflicts. Although proper evaluations haven’t been done yet, the fifth sub species (T.vetulus.harti) could be encountering worse circumstances ascribable to the on going war in its range of existence.” stated Dr. Dela pointing out the current scenario of two immensely periled sub species of the Purple-faced langur.
Although the entire species of this primate is endangered, any sort of formal conservation project hasn’t been endorsed yet. Proper city planning, public awareness programs and insitu conservation projects should be commenced immediately to deflect the western Purple-faced Langur along with all the other species from fading into extinction.