At the Zoo: Gharials Star in the Reptile
Discovery Center and on Gharial Cam
Imagine coming face to face with a crocodile bearing more
than a hundred razor-sharp teeth in foot-and-a-half-long jaws.
Sound terrifying? It certainly would be if you met a gharial
while strolling along a riverbank in India or Nepal. But you
can safely see these crocodiles at the Smithsonian National
Zoo’s Reptile Discovery Center, and now, for the first
time, on our new underwater
Gharial Cam.
Gharials, sometimes called gavial from their scientific name, Gavialis gangeticus, are one of the world’s largest crocodiles. Adult males reach between 16 and 20 feet in length, with some reports of animals as long as 23 feet. Females are smaller, but still reach a hefty 13 feet or more. Despite their enormous size and fearsome teeth, however, gharials tend to avoid rather than attack people. Indeed, their extremely long and narrow jaws and thin teeth aren’t strong enough to grab and tear apart large prey like Nile crocodiles and some others do.
Gharials are almost exclusively fish eaters. The predator waits passively for schools of fish to swim alongside it, then, in a lightening-fast sideways swing, snaps its jaws to seize the luckless victim in those deadly teeth. The long, narrow snout offers little resistance in the water, while the puncturing teeth are adapted to hold slippery, struggling fish. Once the gharial has the fish under control, it raises its head out of the water and repositions the fish to be swallowed whole, head first.
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If
you’re lucky when you tune into the web cam, you might
glimpse a Zoo gharial catch one of the tilapia that share
their pond. These fast-moving, agile fish pose a real challenge
to the gharials’ predatory skills, however, as they
typically catch slower fish in the wild. Thus, the occasional
live tilapia meal forms a small part of their Zoo diet. Keepers
hand-feed them chunks of tilapia meat as their main sustenance.
Scientists label gharials as the strangest of all crocodilians. Twenty-three living species of crocodilians form the order of reptiles technically called the Crocodylia. The Crocodylia, in turn, is composed of three families. The family Alligatoridae includes seven species: the familiar American alligator, its close relative the Chinese alligator, and five species of caiman, all native to South America. The family Crocodilidae contains 12 species of “true” crocodiles, such as the American crocodile, Nile crocodile, and muggar crocodile. It also includes one unusual species, known as the false gharial because it too is a fish-eater with a long, slender snout.
Finally, in a family all its own—the Gavialidae—is the single species we call the gharial. It is the most aquatic member of the order and leaves the water only to bask and nest, usually on sandbanks. On land, the animal’s weak legs restrict it to pushing itself forward on its belly. Other crocodiles move on land like most mammals do, in what is called a “high walk.” Adult male gharials also sport an unusual knob, called a ghara, that bulges from the tip of the snout.
This species was not always so lonely. Long-snouted gavial ancestors first appeared in North Africa more than 25 million years ago, then are believed to have spread to India, Europe, and the Americas, diversified into various species, then became extinct everywhere except Asia. Species of Gavialis first appear in the Asian fossil record in the Miocene, which began 20 to 23 million years ago; however, all but one were gone by about two million years ago. And gharials today have a distribution restricted to the northern part of the Indian subcontinent. Most live in India and Nepal, and a few are believed to remain in Pakistan, Bhutan, Bangladesh, and possibly in Myanmar (Burma). This last surviving Gavialis is in danger of extinction.
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Only an estimated 2,500 to 3,000 individuals remain today (Editor's note: in 2004, the number is reported as less than 1,000). In 1975, conservationists believed that fewer than 100 gharials remained. The reasons for the gharial’s decline are depressingly familiar. They were hunted for sport and for skins; their eggs were collected for food and traditional medicine. Their habitat—calm parts of fast-flowing deep rivers with sandbanks for nesting—has been reduced as a result of rivers being dammed for power and irrigation. Riverbanks have been converted to farms and other human settlements. Rivers have been polluted by farm runoff and mine tailings. Gharials get caught up in fishing nets and drown or are killed by fishermen. Fishermen don’t like gharials—a net torn up by a captured gharial represents a substantial economic loss. They also believe that gharials compete with them for food. It turns out, though, that gharials eat many fish that prey upon fish species sought by fishermen. With fewer gharials eating the predators, these preferred food fish are declining.
Aggressive conservation action in India and Nepal is responsible for the gharial’s partial recovery, although its status is still precarious. Conservation breeding and restocking programs have been in place since 1975 in India and 1978 in Nepal. In fact, the Smithsonian Institution helped to establish Nepal’s Gharial Crocodile Reproductive Centre in the Royal Chitwan National Park.
These programs used both wild and captive gharials to help increase their numbers. A large percentage of the 35 to 60 eggs a female lays in the wild won’t survive to adulthood. To improve the odds, some wild eggs are also collected, artificially incubated, raised to juvenile age, and then released. Gharials are also bred in captivity so their young can be released into the wild. The process is relatively slow. Females don’t reach breeding age until they reach eight to nine feet long when they are eight or more years old; males aren’t sexually mature until they reach 13 feet long at 15 to 18 or more years of age. Recovery seems to have leveled off, however, because the available habitat is full and some small populations are not growing and must be replenished from the captive stock.
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Two gharials have been residents of the National Zoo since
1982. They hatched in 1979 from eggs taken from the wild and
incubated and raised at the Nepal breeding center, and came
to the Zoo as a gift from the then-king of Nepal. Both are
now about ten feet long and one is developing its ghara, the
knob-like protuberance on the end of its snout. According
to Michael Davenport, Zoo assistant curator and herpetologist,
this confirmed for him that this individual is a male—the
sexes are very difficult to tell apart by other visual cues.
The ghara eventually forms a lid on the nostrils. When a male
exhales, the lid flaps, creating a buzzing sound. The sound
appears to function in courtship and territorial defense.
Davenport believes the second gharial is a female. Gharials
are seasonal breeders, and, in January of the last two years,
Reptile Discovery Center staff noted some unusual interactions
between the two that might have been courting behavior. However,
they saw no matings and no eggs were hatched. The staff are
waiting to see what happens in January 2003.
Like most reptiles, gharials aren’t the liveliest of beasts. But they are still fascinating to watch, both in person and on the underwater cam. And while waiting for the gharial to move, you can follow the swarming tilapia, which often spawn in the pond. The Reptile Discovery Center’s winter hours are 10:00 a.m. to 4:30 p.m. daily. You can see gharials and tilapia on the cam.
—Susan Lumpkin
ZooGoer 31(6) 2002. Copyright 2002 Friends of the National Zoo. All rights reserved.
