I Want It All: The Checkered Keelback’s Game Plan

This semi-aquatic snake is ready to pounce on almost anything, even creatures it can’t really hope to swallow

By Gerry Martin

A skittering frog (Euphlyctus cyanophlyctus) suddenly bursts into action, skimming the surface of the pond a few times before it vanishes underwater. The cause of this sudden commotionin an otherwise tranquil pond soon follows,and it is flummoxed by the disappearance of its quarry. The checkered keelback water snake (Fowlea piscator) or Asiatic water snake continues its hunt, for fish and frogs,as twilight fades to darkness.

This master of freshwater ponds, lakes, and streams is completely at home in this habitat, using reeds, aquatic plants,and crevices to live its very adaptable life. Found almost throughout mainland India, the species has made itself quite at home around humans. In cities, they are found in gardens, living in sewers, back yards and anydamp to wet place where they can find shelter and food. In rural settings, checkered keelbacks seem to love rice fields with the bounty of fish and frogs they have to offer. They’re also common in open wells, irrigation tanks, lakes, and ponds.

Checkered keelbacks hunt using their sharp eyesight. In some parts of India they have been observed occasionally hunting and mass feeding in coordinated groups. Photo: Gerry Martin
Active by both day and night, these semi-aquatic snakes are frequently seen near streams, lakes, ponds, rivers, and paddy fields. Cover Photo: Chayant Gonsalves -CC BY-SA 4.0

Checkered keelbacks are voracious feeders, responding actively to movement and ripples in water,or any visible movement on land. They strike and grab frogs and fish and will even bite off more than they can “chew”. Every so often I’ve seen a keelback struggle with a particularly large fish, frog, or toad, that they almost certainly cannot swallow. They either barely succeed at ingesting it, or just give up and leave it to other scavengers. I remember when I was in school, seeing a keelback dying on the side of the road because it had swallowed a catfish whose spines had pierced through the snake’s body!

Wet rice fields are a great place to spot these snakes. Especially, when water is being released from one field to another and there is constriction in the waterway, bringing high densities of fish to one point. Sometimes, a couple of dozen snakes can be seen congregating at these places and gorging themselves on the feast of fish, much like scaled down grizzly bears grabbing salmon. Being opisthoglyphous, checkered keelbacks have their fangs in the rear of the mouth. These enlarged teeth are mildly grooved to allow venom to trickle into their prey. It does make envenoming their prey a little more complex than for a cobra or a viper, whose fangs are in the front of their mouths. But it seems to work just fine on small prey that they can’t seem to get enough of. Although venomous, checkered keelbacks aren’t really harmful to humans.

Checkered keelbacks seem to favour ponds with sufficient vegetation, which enables them to hide from danger and hunt effectively. Photo: Myke Clarkson

Checkered keelbacks seem to favour ponds with sufficient vegetation, which enables them to hide from danger and hunt effectively. Photo: Myke Clarkson

This fact seems lost on many a snake rescuer who will back away from checkered keelbacks and seem less confident with this harmless snake than they are while handling a cobra! The species’ eagerness to feed is beaten only by their reputation as vicious biters. When first caught, checkered keelbacks try and repeatedly bite almost anything they can reach. Although this isn’t necessarily the case all the time, they have earned a special place amongst non-venomous snakes as one that can and will defend itself.

Checkered keelbacks are also prolific breeders. They start the breeding season in late winter and groups of males can often be seen with one female, vying to mate with her. Mating seems to be purely by chance, and there aren’t yet any reports of male combat in this species. Eggs are laid in March and April, with females laying upto 50 eggs in termite mounds, heaps of manure,rotting vegetation, crevices in wells and walls,or any other suitable sheltered and humid place. Then, during the summer season, they seem to vanish from most places. While small congregations can be found in wells and ponds, there is a marked absence of them through much of their landscape during the hot and dry months.

As their scientific name Fowlea piscator suggests, checkered keelbacks are primarily fisheaters. Photo: Karunakanth CC BY-SA 4.0

Young checkered keelbacks are seen just before the monsoon begins. They hide in leaf litter, bogs, grass,and any place they can find a healthy mix of feed and security. They will spend the first few months of their lives in these wet landscapes, feeding on frogs that have also just bred by the millions. From the beginning, these tiny noodle-sized predators instinctively forage actively, moving steadily through the ground cover and grabbing any tiny animal that appears in their path. Frogs, small fish, tadpoles and insects all contribute to the high protein diet they need to grow fast.

However, danger lurks everywhere when you’re that little. Juvenile keelbacks form part of the diet of a host of animals, large and small. Birds, including kingfishers, some ducks, numerous waders, jungle fowl, etc. will all happily make a quick meal of a little keelback. They are also eaten by rats, cats, monitor lizards, other snakes and ironically, even by some fish and frogs.

Being eaten is not the only danger that plagues a young keelback. They are regularly caught in fishnets and crushed under the loads of fish. Or, they get run over on roads or stepped on by people and animals because they often live in areas that are ripe for grazing. This is where a really large clutch size helps the species persist. Despite all these dangers, a small percentage, but still a significant number,of baby keelbacks make it past the first year of their lives.

The numerous recurved teeth that checkered keelbacks possess allow them to grab and hold on to their slippery fishy prey. Photo: Anurag Nashirabadkar -CC BY 4.0

Unfortunately, even this truly adaptable snake now faces a massive threat in the forms of landscape change and pollution. Many wetlands are being transformed into urban infrastructure or being built upon. Roads now crisscross through lands that were once open grassland, forest, or wetland. Waterways that were clear and near pristine a couple of decades ago are now drainage for effluents from cities and towns, killing many of the prey species that keelbacks depend on. Even agricultural spaces that used to be perfect for these snakes now suffer from extensive use of pesticides, fertilisers,and herbicides.

Walking around the rural landscape I live in, I wonder for how much longer many of these species that cohabit all our spaces,will be able to take the battering from intensive growth and production. Then, I look in the well, and see a checkered keelback water snake dive deep as soon as it sees me, and I know that we can still turn this tide.

Gerry Martin

is the founder director of The Gerry Martin Project, and has been involved with herpetological research and conservation, documentary filmmaking, education and eco-tourism over the past decade

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