Honey, I covered the kids in mud! The curious case of a night-frog from the Western Ghats

bats
Mudpacking Kumbara Night Frog in Kathalekan. Picture Credit: Priti Gururaja

By: Priti Gururaja

Species: Kumbara Frog (Nyctibatrachus kumbara)
Habitat: Wet evergreens of the Western Ghats

Deep inside the evergreen forests of the Western Ghats, the calls “Tok… tok ..tok” reverberate amidst the flowing streams. After months of chasing the calls, batrachologist Dr Gururaja KV found the males, calling along the edges of the stream. The frogs were much larger than the other known species from the same sites and he suspected that it could be a new species. He was studying a species belonging to Nyctibatrachus, a genus endemic to the Western Ghats, India.
He was keen to observe the behaviour of this species. To his surprise, he found that the frog displayed a unique reproductive behaviour and parental care. During the monsoons, at dusk, the male would start calling a single note, “tok”, along with the edges of the stream. As a female approached the calling male, the calls would become double notes, “tok, tok”.

However, there is a twist. Before the female mounted the male, the male would inspect twigs a few centimetres above the stream with his forelimbs; probably to locate a place for laying eggs! The female would also perform the same inspection. Next, their courtship would begin. They would do a handstand, then amplect (male grasps the female) in axillary position (at the armpit) for some time and then rotate, do another handstand and then would position their cloacae on the twig that they had inspected together earlier. After vigorously shaking its hindlimbs, the male would release the female; the female would lay her eggs on the twigs and move away.

frogs
Figure 1 a. Male and female in courtship (male and female are marked with symbols); b. Axillary amplexus in the pair; c. Amplected pair standing upright on their hindlimb before oviposition; d. Female doing a handstand at the time of releasing eggs. Picture Credit: Priti Gururaja

The male would then visit the twig where the eggs had been laid. Standing on its hindlimbs, the male would collect the mud from the stream and carefully apply it on the eggs to cover them.

frogs
Figure 2a. Male approaching the eggs; b. Male standing upright locating the egg clutch; c. Male covering the egg clutch with sand gravels and mud from the stream bed; d. Male leaving the place after covering the egg mass with sand and mud. Picture Credit: Priti Gururaja

New studies on behaviour

This is the first record of a frog putting mud to protect its eggs. This form of parental care could be for two reasons: to avoid predation of the eggs or to avoid desiccation. But more observations and experiments would be needed to draw a definitive conclusion.

Besides this behavioural observation, genetic analyses were also carried out to ascertain whether the species was indeed new and to ascertain its phylogenetic position, and evolutionary history. The analyses established that it was indeed a new species and based on the mud packing behaviour, it was named as Nyctibatrachus kumbara (kumbar in Kannada means potter, a person who shapes mud into pots).
The discovery of this species with its unique behaviour from the Western Ghats reiterates the fact that the Western Ghats are a treasure trove for amphibians and there could be many more discoveries still waiting to happen.

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