DT
PT
Subscribe To Print Edition About The Tribune Code Of Ethics Download App Advertise with us Classifieds
search-icon-img
search-icon-img
Advertisement

What it takes for a male gharial to be born, and survive

A fluctuation of a mere 1.5ºC is enough to seal the fate of a gharial embryo as a male or female
  • fb
  • twitter
  • whatsapp
  • whatsapp
featured-img featured-img
An adult male has a bulbous knob called the ghara that sits atop the tip of its long, narrow snout. Photo courtesy: Anish Andheria
Advertisement

At first, I couldn’t grasp the significance of what my colleagues at the Wildlife Conservation Trust were telling me. I couldn’t comprehend why a few sightings of male gharials along the Gandak river (that originates in Nepal, and flows through Bihar and Uttar Pradesh) during a routine river survey warranted such excitement. I didn’t realise then what it took for a male gharial to survive and reproduce in the wild. Or what it took for a male gharial to simply be born.

Turns out, it takes a lot!

Adult male gharials are exceptionally rare and sighting them is rather special for conservationists for very good reasons. The gharial (Gavialis gangeticus) is one of the world’s most critically endangered crocodilians, and being a highly sensitive species, it needs an undisturbed habitat to survive and breed successfully. Only a few thousand individuals of this fish-eating crocodile species remain in the wild. Odds in the form of anthropogenic threats are already stacked tall against the species and its riverine habitat in this human-altered world. And thanks to their reptilian reproductive biology, the sex ratio is rather skewed in favour of females.

Advertisement

Sex determination in gharials, like in certain other reptiles, depends on the incubation temperature of the eggs. A fluctuation of a mere 1.5ºC is enough to seal the fate of a gharial embryo as a male or female. A narrow window of temperature of approximately 32ºC is when males take birth. Cooler or warmer than that, and much higher are the chances of females being born. Furthermore, experts believe that rising global temperatures could perhaps be skewing the sex ratio in gharials all the more. This is yet to be proven.

Many things have to go just right for a male gharial to be born. And it only gets more challenging from there on for this slow-growing, late-maturing species. Males reach sexual maturity at 15 to 18 years of age. They need to grow to considerable size and proportions to achieve true mating success. Gharials are some of the largest crocodilians alive and can grow up to 6 metres in length! An adult male has a bulbous knob called the ghara that sits atop the tip of its long, narrow snout. Gharas, it is believed, play a crucial role in mating rituals, and are used by males to emit acoustic signals underwater during courtship and mating. To successfully mate, the ghara of a male has to be big enough. But, tragically, according to researchers and conservationists, the bulbous gharas could also be leading to more males getting entangled in fishing nets, leading to greater injuries and casualties.

Advertisement

There have to be enough number of adult males and females for a gharial population to be viable. When male numbers fall below a critical threshold, the populations become unviable and prone to extinction, especially smaller sub-populations. The present situation of gharials in India is rather grim. Surveys reveal that out of a handful of Indian rivers where gharials are found, they breed only in five. Most gharial-inhabited rivers have very few adult gharials, and most do not harbour even a single mature male! The gharial populations in rivers sans males are obviously incapable of reproducing.

Gharials were once widespread in the Ganges river and its tributaries flowing through the river plains of India, Nepal, Pakistan, Bangladesh and Bhutan. Today, they are found only in India and Nepal. Remarkably, the Gandak river is not protected formally across most of its length in India, and yet holds the third largest gharial population for any Indian river, after the Chambal and Ghaghra — where most gharials occur in the protected areas of the National Chambal Sanctuary and Katarniaghat Wildlife Sanctuary. Even in these rivers, adult male gharials may just be 5 to 10 per cent of the population.

To a river ecologist or gharial researcher, the sight of a 5 to 6-metre-long, sexually mature male gharial tells the story of survival against all odds. It means the conditions had to be favourable at birth, and proper nutrition had to be available to grow. It would have had to successfully navigate major bottlenecks in its most vulnerable years and survive predators, fishing nets, hunters, floods, or even sudden water releases by dams built on rivers. It would have had to be a survivor.

Now I understand why the sighting of even just a few adult males lends hope and holds promise for the population of this enigmatic and fascinating reptile.

— The writer works with the Wildlife Conservation Trust

Advertisement
Advertisement
Advertisement
Advertisement
tlbr_img1 Home tlbr_img2 Opinion tlbr_img3 Classifieds tlbr_img4 Videos tlbr_img5 E-Paper