What does it take to discover geckos?

On a warm summer evening in 2007, Dr Ishan Agarwal, a herpetologist, was scouting the hillocks of Rishi Valley in Andhra Pradesh. Eyeing his favourite creatures, the lizards, he looked for them under rocks, between crevices, and in thorny bushes. Ishan spotted several lizards—some of which he had seen before and could recollect their names. But, there were two that he could not put his finger on, and he began his quest to find out more. After 13 years of spotting them, this year, he and his colleagues described them as two species new to science—Rishi Valley dwarf geckos (Cnemaspis rishivalleyensis and Hemidactylus rishivalleyensis).

Identifying lizards is hard work. Often, it’s the presence of a certain number of scales or tiny differences in the DNA that can tell two species apart. An untrained eye can easily miss them all! “It was only through a careful examination of the lizards’ morphology and the use of molecular markers that we were able to figure out that they were two new species,” Ishan recollects about the discovery. It was also an extraordinary moment for him because Rishi Valley is where Ishan developed an interest in the natural world.

A few years ago, during fieldwork for his PhD, Ishan had collected some geckos from a rocky roadside in Sakleshpur, a hill station in Karnataka. He thought that they belonged to an already described species, the Gund day gecko (Cnemaspis heteropholis). Much later, one of his collaborators pointed out that this may be an entirely new species. Voila, it turned out that!

Why is it so hard to identify new species, you ask? In this case, scientists knew C. heteropholis only through one female specimen. Until they obtained the genetic information of males of the species, they could not confirm that the Sakleshpur individuals were, in fact, a new species altogether. They called it Cnemaspis magnifica or the Magnificent dwarf gecko and described it this year in a detailed research paper. “That’s really how the stories go most often. It can be a long and painstaking process to figure out that your new species has not been previously named,” shares Ishan.

Geckos are a type of lizard, characterised by their sticky digits, which lets them climb vertically on walls and rocks, and even upside-down! Those lizards that you see in your house are geckos too. As of today, India is home to around 320 species of lizards. In the last decade, Ishan and his collaborators have discovered over 35 new species. Just this year, the number stands at a grand thirteen so far.

Geckos are found in various habitats across the country — from the rainforests in the Western Ghats to the dry and arid Thar desert. Some are endemic to specific regions. Due to its mosaic of habitats, Tamil Nadu is a hotspot for gecko species. This year, the Nilgiri slender gecko (Hemiphyllodactylus nilgiriensis) was discovered from the deciduous habitat of the Nilgiris. The KMTR slender gecko (Hemiphyllodactylus peninsularis) was found hiding in the evergreen forest of the Kalakkad-Mundanthurai Tiger Reserve. The Sirumalai rock gecko (Hemidactylus sirumalaiensis), a rare find, was spotted in the scrublands of Sirumalai hills. It is the first endemic species and the only vertebrate discovered in the Sirumalai massif in 133 years!

Most gecko species discovered so far are restricted to a small geographic region. The Stardust dwarf gecko (Cnemaspis stellapulvis), also discovered this year, is only seen on an isolated granite hill near Yediyur in Karnataka. The Sabin’s Nellore dwarf gecko (Cnemaspis avasabinae) is found near a forest stream in Nellore, Andhra Pradesh. And the Urban bent-toed gecko (Cyrtodactylus urbanus) found in a degraded forest in Guwahati city!

The Mysore plateau, an undulating landscape flanked by the Western and the Eastern Ghats on either side, is spread across the states of Andhra Pradesh, Karnataka and Tamil Nadu. This year, three new species of geckos, the Granite dwarf gecko (Cnemaspis graniticola), Golden banded dwarf gecko (Cnemaspis bangara) and the Yelagiri dwarf gecko (Cnemaspis yelagiriensis) were found here.

Encountering so many new species is no miracle. A logical explanation would be that there are, in fact, so many species and we are beginning to understand them only now. “Reptilian taxonomy in India is undergoing a second discovery phase with our understanding of Indian herpetofauna in general, and lizards and geckos in particular, changing dramatically,” says Ishan. “There are perhaps around 100 geckos to be named in India, possibly even more. The Western Ghats, North East India, hills of South India and the Eastern Ghats are the most diverse regions, but there are new species all across.”

The tricks in a herpetologist’s hat

For herpetologists, a quick look at a gecko can be sufficient to identify its genus. However, when they see any gecko that does not look very familiar, they go about using the many tricks up their sleeves. The first is an instrument to measure the various parts of the lizard. It measures the size of the limbs, eyes, tail, the distance between the snout and the base of the tail, the body width—about 30 such measurements in all! For most geckos, the body colour and the number of scales and pores on different parts of the body act as identifiable markers.

With the advent of DNA sequencing, identification of new species is not just based on how the specimen looks. “The DNA sequence data allows you to understand if two very similar-looking geckos might represent very different evolutionary lineages and have a divergent history,” explains Ishan. Hence, herpetologists also collect tissue samples of the gecko of their interest.

The evolutionary history of geckos also provides some clues in deciphering their taxonomy. For example, the DNA analysis of the three geckos from the Mysore plateau shows that they evolved 25 million years ago in colder rainforests. While today’s Mysore plateau is predominantly warm and dry, it contains small hillocks and rocky outcrops which are colder. It is in these small refuges that we can still find those geckos. That is also the problem as these hideouts are now disappearing due to the changing climate. “Many gecko species, which are adapted to colder climates, already live on mountaintops. With increasing temperatures, they may have no other cooler places to get to,” rues Ishan.

The future is bitter-sweet for the geckos. While new species discovery is enthralling herpetologists, they are worried about the havoc climate change is wrecking on these tiny reptiles. Most geckos and lizards are also very specific about their microhabitats, and any changes to them will knock them out. “Many of their habitats in India today are reaching temperatures close to or above lethal limits for the lizards. If it increases any further, they may go extinct,” worries Ishan.

A case in point is the Ganjam slender gecko (Hemiphyllodactylus minimus), whose description was published earlier this year. This tiny gecko is known to hang out on some mango trees in a sacred grove in Odisha. Sacred groves are small patches of native forest protected by local communities. As cultures change, such groves are losing their sacred status, which might mean the end of the road for these geckos.

Enthusing the public about the exciting lives of these geckos could benefit their conservation, and community science could also help in monitoring these tiny reptiles. Online forums like the India Biodiversity Portal, and a few other Facebook groups, invite community scientists to upload photos of geckos for identification. If you are on a hunt for finding the next new species, “begin by photographing what is around you and take it forward from there,” advises Ishan.

(The writers are with Research Matters)