Life barier on the western ghats of india

Birds

There are 508 species of birds found in the Western Ghats, out of which 16 species are endemic to the region. The Laughingthrush are amongst the most prolific ones sighted here. The two main species of the Laughingthrush found in the region are the Kerala Laughingthrush and the Black-chinned Laughingthrush; the former found principally in the region south of the Palakkad Gap whereas the population of the latter is confined to the Nilgiri region in the Ghats. Dr P O Nameer of the Centre for Wildlife Studies, Kerala, adds that species differ morphologically and are allopatric in their distribution, meaning that their ranges do not overlap each other ensuring that each species have their distinctive characteristics preserved. “While the two species may share their home in the high altitude regions of the southern Western Ghats, their behavioural activities are different,” he says. The bird calls of the Kerala Laughingthrush consists of high-pitched series of steeply ascending notes ‘pee-koko… pee-koko’ while the Black-chinned resort to making birds calls in ascending and descending sounds of ‘kek’, heard during early morning and afternoon periods. Another distinction between the species is their diet preferences. With the species in the Nilgiri region feast on flowers, fruits and insects, their counterparts in the south of the Palakkad Gap remain steadfastly vegetarian by feasting on fruits and flowers. Within the regions of the Palakkad Gap, home to the Kerala Laughingthrush, there are two distinct zones. Here the sub-species of the Kerala Laughingthrush – the Palani Laughingthrush is found to the south – and the Banasura Laughingthrush is found in Coorg and Wayanad region, which lies to the north of the Gap.

Fish

Almost all the rivers in the southern part of India have their origins in the Western Ghats. A total number of 102 species of fishes reside in these rivers and hill streams of the Ghats, of which 11 species belonging to the Garra genus are endemic in various isolated areas of the southern Western Ghats. As majority of the rivers of the Western Ghats empty out into the sea, these fresh water fish have developed a peculiar characteristic to help adapt to the conditions. “The fishes of this genus have a disc protruding on the ventral side near its mouth. It is known as a sucker and is used by the species to attach their bodies physically to either the roots of the trees, small tennis sized pebbles or boulders and rocks near the river banks,” elaborates Dr M Arunachalam, professor at the Sri Paramakalyani Centre for Environmental Sciences, Tamil Nadu. This, he states, “allows the fish to avoid getting washed out into the sea while maintaining their velocity in the rapid river current.” The Garra gotyla stenorhynchus belonging to this genus is found, thanks to its limited distribution pattern, only in the tributaries of the Kaveri basin. Another species called the Tunga Garra (Garra bicornuta), found only in the Tunga River in Karnataka, has two distinct horn like structures on the dorsal side of its head, near its mouth, which are made of keratin and in some cases are often used as a defence mechanism by them,” says Arunachalam. The Kalakad Garra (Garra kalakadensis), found in the Pachayar River in Kalakad Mundanthurai Tiger Reserve region is characterised and identified by its physical appearance. “In order to survive in the cold waters of the Western Ghats, the Kalakad Garra, has undergone an evolutionary adaption, thereby ridding its body of scales and having a naked ventral side.”

Elephants

The elephant population is focused mainly in the Nilgiri, Anamalai Hills and the Periyar regions in southern Western Ghats. There are a number of elephant corridors in the Ghats including the Nilgiri-Mysore-Wyanad Elephant Reserves that are spread over Tamil Nadu, Karnataka and Kerala. Another critical corridor lies in the Tirunelli region of Kerala that links the elephant population of Wyanad and Nagarahole with the Brahmagiri hills. A third critical corridor is in the Kollegal region, near the settlement of Bailur in Karnataka. Recent studies have discovered a genetic differentiation in the elephants found in north and south of the Palakkad Gap based on analysis of their mitochondrial DNA. “The elephant population found in the Nilgiri region, which is spread over 15,000 sq km, north of the Gap, can be traced to a single matriarchal lineage,” says Prof Raman Sukumar, an ecologist from the Centre of Ecological Studies at the Indian Institute of Sciences, Tamil Nadu. On the other hand, research further showed the Nilgiri population of elephants to be genetically distinct from those found in the Anamalai Hills and Periyar regions, separated by the 40 km Palakkad Gap. “Here, three mitochondrial haplotypes (which in genetics is a combination of alleles (DNA sequences) at adjacent locations (loci) on the chromosome that are transmitted together) have been discovered among the elephants living in the south of the Gap. Though these differences among these haplotypes maybe small, as they all belong to the Beta elephant clade common in southern and east-central India,” he concludes. While the reason behind this genetic disparity is still elusive, it is indicative of the Gap acting as a biogeographic barrier in the past.