WESTERN GHAT PLATEAUS - AN ABODE FOR FAUNAL DIVERSITY

 

BY VARAD GIRI

It was summer in 2001 and we were searching for reptiles on one of the coastal rocky plateaus in Maharashtra. The entire habitat was looking barren as these are crests of small mountains mostly covered with rocks and with scarce vegetation in some patches.

The heat was unbearable and we were turning rocks to get a glimpse of reptiles if there are any. Our meticulous efforts yielded result as we saw a small lizard under one of these rocks. On close observations it was identified as White banded viper gecko Hemidactylus albofasciatus, a lizard which is considerably rare and is only known from a few coastal plateaus in Maharashtra. Subsequently, I visited many such plateaus in the Western Ghats region of Maharashtra for the last decade and realised their distinctiveness in terms of unique biodiversity.

The coastal tract of Maharashtra and Goa, locally called Konkan is one of the major geographic divisions of western India. The geomorphology of Konkan is characterized by a coastal plain of variable altitude and width, backed by the escarpment of the Western Ghats on the east and the Arabian Sea on the west. Apart from this, the uniqueness of this region is the presence of large laterite or basaltic plateaus on the crest of mountains close to the coast and Western Ghats mountains. The forest, mostly semi-evergreen, is in the valleys. These plateaus though look barren in non monsoon season and they metamorphose into a beautiful landscape during rainy season. It is mainly due to the presence of varieties of endemic and ephemeral floral diversity. These plant species which bloom during the monsoon changes the perspective of these plateaus. Similarly, there are some interesting faunal components, mostly amphibians and reptiles, which are evident during monsoon on these plateaus. I realized this only when I visited tese plateaus during monsoon of 2002. Instead of their exclusivity, plateaus are greatly ignored, except a few studies on their floral diversity. The unique floral and faunal diversity on these plateaus is obvious for a short duration during monsoon thus there is need of a long term monitoring throughout all the seasons to understand intricacies of this unique habitat. Due to lack of proper knowledge the plateaus are highly vulnerable and need immediate attention in terms of their conservation.

I am trying to give more emphasis on diversity of amphibians and reptiles as I have personally spent about seven years studying herpetofauna of this region and the work is still in progress. Most of the amphibians and reptiles seen on these plateaus are representatives of arid habitats and their occurrence in the Western Ghats, which is considerably wet region is quite remarkable. These plateaus though vast, they are not interconnected, are like islands and thus become a best example for studies pertaining to biogeography.

Amphibians require unpolluted environment and are commonly seen during the monsoon. The plateaus though appear unsuitable for amphibians we have observed about 17 species, a few of them endemic, to these plateaus.

Caecilians are legless and burrowing amphibians and are considered rare. Traditionally caecilians are only reported from habitat having leaf litter, soil cover, forest and agriculture landscapes. Due to the lack of all these, plateaus appear to be unlikely habitat for caecilians. But we have observed about five species of caecilians on these plateaus.

One of the endemic genus of caecilians of the northern Western Ghats of Maharashtra Indotyphlus, which is represented by two species, I. battersbyi known from Lonavala, Khandala and Matheran and I. maharashtraensis only known from Koyna Wildlife Sanctuary and Kaas is the best example. I. maharashtraensis was discovered from near Koyna Wildlife

Sanctuary in 2003. This is one of the interesting species and is only known from laterite plateaus of the Koyna Wildlife Sanctuary. There are some recent reports of this species from near Kaas plateau also.

The type locality of Indotyphlus maharashtraensis is approximately 150 km south of the known provenance of I. battersbyi, and at a similar altitude. Both species are mostly seen during the monsoon season in similar habitats often under rocks in open, grassy, shallow-soiled areas within strongly seasonal, semi-evergreen or deciduous vegetation without perennial surface water. Such habitats might be considered atypical for terrestrial caecilians, which are generally known more from moist soils and litter, and they would appear to be inhospitable environments for caecilians during the long dry season.

Gegeneophis seshachari is another recently described caecilian and is apparently one of the widely distributed species in the northern Western Ghats with wide habitat preferences. This species is a most common resident of coastal plateaus in Ratnagiri and Sindhudurg districts of Maharashtra. On one of the occasions we encountered 21 individuals of this species under a small rock on a plateau in Sindudurg district.

Apart from this we have also reported occurrence of caecilians like Gegeneophis danieli and Ichthyophis sp., species from plateaus, which are predominantly confined to semi-evergreen forest.

Recent molecular phylogenetic analyses have revealed a radiation of toads with distinct adult and larval ecomorphs on the Southern parts of the Indian subcontinent. Of this one genus Xanthophryne is endemic to the Western Ghats region of Maharashtra represented by two species with a very patchy distribution. These toads are mostly seen on the plateaus, locally very common and are early and prolific breeders. These toads have a very unique breeding behaviour as they lay their eggs in small water which accumulates on the lateritic rocks. Unlike most of the other toads the eggs are not laid in the form of a chain. The metamorphosis takes place in such shallow water. Thus they require constant rainfall, otherwise if there is no rain for one or two days, the water dries up resulting in the death of their eggs or tadpoles. Due to their interesting breeding behavior and restricted habitat preference, they are vulnerable to climate change.

These plateaus are also abode to many species of frogs of the genus Fejervarya, Minervarya and Sphaerotheca. These frogs breed in small temporary rainwater puddles on these plateaus. In view of the exclusive floral and some faunal diversity on these plateaus I feel that these frogs are also interesting and their proper identification and studies on natural history may reveal some hidden secrets.

In reptiles the predominant species on plateaus are Saw scaled viper Echis carinatus and Lacertids Ophisops sp. which are commonly seen throughout the year. The other uncommon lizards seen on these plateaus are Gunther’s snake skink Lygosoma guentheri and L. lineata. The exclusive species on plateaus are White-banded viper gecko Hemidactylus albofasciatus and H. sataraensis.

H. sataraensis is an endemic species of a lizard from northern Western Ghats and is known from a patch of 30 sq. km. near Kaas Plateau in Satara District. Unlike most of its congeners, which are arboreal, this gecko is strictly terrestrial and is seen under the rocks. This species is also confined to the lateratic plateaus. As per the preliminary observations, they are mostly seen in the monsoon and winter and disappear in the summer. Very little information is available on the natural history of this species.

The other, similarly looking and ground dwelling gecko Hemidactylus albofasciatus is confined to the coastal plateaus in Ratnagiri and Sindhudurg district. Interestingly on these plateaus this species patchily distributed and is seen throughout the year.

Most of my observations about faunal diversity of plateaus in the northern Western Ghats is based on short duration surveys conducted over last decade in a few localities. Many plateaus are not visited by any researchers. These plateaus are under tremendous anthropogenic pressure recently. Due to lack of appropriate knowledge about this interesting habitat, they may become susceptible target for mining activities, which is happening in some localities in northern Western Ghats. Interestingly effort towards assessment and documentation of this loss is very meager. Thus proper conservation measures are essential to regulate this loss and if not then this unique habitat and its diversity will vanish without our knowledge.

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