Analysing the link between adaptability and species success of Elvira rat, Cutch rock rat

The fate of two native rat species: Elvira rat (Cremnomys elvira), the critically endangered and more common Cutch rockrat (Cremnomys cutchicusBy examining the status of the two species, wildlife researchers show how a species’ ability to adapt to a particular landscape affects their chances of success.

“The rocky outcrops and granite inselbergs of the Madurai region are not the places most people associate with wildlife viewing. Shrubby vegetation clings to thin soil between exposed rocks; the landscape looks almost uninhabitable, wasted in the dry months. But C. cutchicusThis is prime real estate. According to R. Brawin Kumar, a wildlife biologist who studies lesser-known faunal species in Tamil Nadu, during night transect surveys conducted over multiple evenings between 8 pm and midnight at three sites in the rocky terrain south and east of Madurai, Cutch noticed that the rock mouse was in areas with “large, jointed granite blocks presenting deep crevice systems.”

He also noted the species’ presence in Salem’s Shervaroy Hills, which is home to the Elvira Mouse, the critically endangered sister species of the Cutch Rock Mouse. Unlike its predecessor, Elvira Mouse is confined to a specific Shonkinite rock formation in the Shervaroy Hills. Shonkinite is also one of the rarest geological rock types in the world.

“Interestingly, the Cutch rock mouse has been observed in adjacent rocky areas with different lithology, suggesting that the two species may partially overlap in geographical space when separating the microhabitat by rock type, a question that warrants dedicated research efforts,” Mr. Kumar said.

The Cutch rock mouse builds nests in rock crevices and thrives thanks to the thermal stability of granite rock. “The Aravalli Range, the main stronghold of C. Cutchicus in Rajasthan, is one of the oldest geological formations in the world, formed during the Precambrian period, believed to be 1.5 to 3.2 billion years old. The rocky outcrops of Tamil Nadu, although geologically diverse (containing Archaean gneisses, granites and the rare Shonchinite of Salem), are relatively old. These mouse-only ancient rocks exist along with some of the oldest land surfaces on Earth.” “It happened,” he said.

Mr Kumar believes the relative success of the Cutch rock mouse compared to its sister species, the Elvira mouse, is due to its ability to adapt to different rock types. “The Elvira rock rat is bound to Shonkinite, an extremely rare intrusive igneous rock with small, local outcrops, found in only a few places worldwide. The Elvira rock rat is found only in Salem and nowhere else in the world. The Cutch rock rat, in contrast, tolerates a wider variety of rocky substrates, granite, quartzite, basalt, Deccan Trap formations, and therefore has a wider distribution,” he said.

Critically endangered Elvira mouse | Photo Credit: R. Brawin Kumar

However, he cautioned that although the species is found in Theerthamalai, Salem and Madurai in Harur division and other medium-sized rocky hills, the wider distribution does not mean that the species is not threatened, as the rock mouse’s primary ecosystems in the Aravalli ranges are under serious threat in the coming decades due to mining.

“The threat profile is different in Madurai and Salem, the southernmost confirmed field areas for this species based on recent observations. Here the pressure is not from mining but from urbanization expanding into the city’s rocky scrub edges and the conversion of rocky hillsides near Salem to industrial use. Southern population C. cutchicus“If it is genetically distinct from northern populations (a question not answered by any molecular studies published to date), it may represent a conservation unit of independent significance,” he said.

Mr Kumar, who received the Tamil Nadu Environment Award in 2016 and the Tamil Nadu Environment Champion Award in 2022, said: Hindu Rock shrews are the primary food source for species such as the Bengal fox, as well as some species of birds of prey. “Their preservation and presence in these landscapes is crucial to the local rocky ecosystems in which they live,” he said.