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Banded Sea Krait

BANDED SEA KRAIT (Laticauda colubrina)

Image modified from wikipedia.
Original photograph by Bernard Dupont
The banded sea krait is a type of sea snake - I'm not 100% clear on what the difference between a snake and a krait is, if there is one - that lives in tropical climes and has a somewhat unfounded reputation for being deadly to people. I think they're neat because they look like a pair of socks I own.

Appearance

Sea kraits are super weird because, unlike regular snakes which hunt on the land, they hunt on the sea. To do this with any degree of success, they have to have a whole bunch of adaptations for functioning underwater. Probably the most striking is their paddle shaped tail which they use to swim quickly through the water. But, because they mate and shit on land, they have to still be adapted to move through the dirt. So they are creatures of two worlds, like Aquaman.

The banded sea krait specifically hunts around the coral reefs in the Indo Pacific, so, like reef fish, it has fun colouration to camouflage in the corals from prospective prey and predators. The result is that it looks like that worm snake or whatever from Beetlejuice.

Points: 1/1

Behaviour

Like I said earlier, sea kraits have to come on to land to mate. A lot of snakes do group mating which can last for a few hours, but sea kraits are known to spend literally days getting their fuck on in a mating ball.

Despite being called a marine reptile, they're a lot less marine than, say, sea turtles, which do pretty much everything except lay their eggs in the water. Sea kraits lay their eggs on land, shed their skin on land, and digest their food on land - so even though they hunt in water, they have to come up out onto the shore to digest and, presumably, shit. Really, they shouldn't be considered marine reptiles at all, anymore than fishermen should be considered marine humans.

Points: 0.5/1 for being misleading

Distribution

A lot of marine and semi-marine animals have osmoregulatory adaptations - that is, they can drink seawater and excrete the excess salt. Sea kraits can't do that, so one of the factors determining where they can live is whether or not they can access fresh water to drink. This is yet another thing they have to come onto land for, and it means they can't live off the coast of just any rock out in the sea, but have to live near actual islands that have lakes and rivers and stuff so they can have a little sippy sip of H2O when they come on land.

Although the banded sea krait is the most widely distributed of all sea kraits, they still are restricted to living places where the sea is relatively warm because they are snakes. I have one thing to say about that, and that's diversify, you dicks. How cool would it be if marine snakes were found all over the world? And why stop at marine snakes? Why not have river snakes? Lake snakes?

Points: 0/1 for being narrow minded

Ecology

The main component of sea kraits' diet is eels, which makes a lot of sense. Nevertheless, there's something intensely disturbing about a snake eating another snake, and snakes eating eels falls into the same category. It's just like... God doesn't want that to happen, ya know? And that's why we get hurricanes.

Like a lot of marine animals, sea kraits have extremely potent venom which can stop a fish dead in the water. This is because trailing injured prey is really hard under water, so they need enough venom to kill the absolute shit out of something instantly. The sea is a harsh kingdom.

The snakes themselves have been observed being eaten by birds, fish, and, get this, sea anemones. I managed to get through 28 years of life without knowing that sea anemones sometimes eat snakes, and yet here we are. I guess I'm going to have to just... live with the nightmares now. Anyway, things don't generally eat them though because they have aposematic colouration (warning colours). Except sea anemones don't have eyes so they're still fucked on that front.

Points: 0/1 for creeping me out twice in one section

Evolution

Let's think about the evolution of vertebrates over the last 400 million years or so. 400 million years ago, all of the vertebrates were fish. They had gills, and fins, and all that good stuff, right? Then a group of lobe-finned fish came along and started sporting some really sophisticated lungs for extended stays out of water. Around 350 million years ago, some of them switched out fins for legs, and most of them lost their gills, moving onto land entirely. Fast forward 250 million years and snakes were like, "fuck legs, we don't need 'em." Finally, sea kraits decided to just hop back into the water. Make up your goddamn mind, you weirdos.

Points: 0/1 for being worse than whales for flippy flopping about what they want to do with their lives

Life History

Banded sea kraits are pretty secretive, so not a whole lot is definitively known about their reproduction and life history. Because of the warning colour thing I talked about earlier, they don't have a whole lot of natural predators, so they can get away with laying pretty small clutches of eggs. Most snakes do basically fuck all for parental care, only going so far as incubating eggs before they hatch, but since only a couple of nests have been found in the wild, we don't even know if they do that. I've got to give them props for being sneaky and not letting humans in on their secrets.

Points: 1/1

Interactions with Humans

Banded sea kraits are one of the more venomous species of snakes, with an LD50 of 0.45 mg/kg. For those among you who aren't completely obsessed with venom, LD50 means the lethal dose for 50% of mice in a trial. If that seems like a weird and imprecise way to measure something, it kind of is but it's the best way we have right now to compare how venomous things are.

Anyway, banded sea kraits encounter humans fairly regularly both on land and in fishing nets, but they don't really get off on biting people. Not very many people get bitten by these things, and most bites are non-fatal. The sad thing is that they get harvested for their skin, and if they would only fight back they could probably avoid this fate.

Points: 0.5/1 for having decently potent venom but not using it to literally save their skins

Final Score: 3/7
As much as I love snakes, banded sea kraits are just okay

Further Reading

  • Bryner J. 2009. "Two-headed" snake fakes predators. Livescience. [Link]
  • Clinical Toxicology Resources. Laticauda colubrina. [Link]
  • Ghergal I, Papes M, Brischoux F, Sahlean T, Strugariu A. 2016. A revision of the distribution of sea kraits (Reptilia, Laticauda) with an updated occurence dataset for ecological and conservation research. Zookeys. 569: 135-148
  • Heatwole H, Grech A, Monahan JF, King S, Marsh H. 2012. Thermal biology of sea snakes and sea kraits. Integrative and Comparative Biology. 52(2): 257-273 [Link]
  • Lane AM, Shine R. 2010. When seasnake meets seabird: ecosystem engineering, facilitation, and competition. Austral Ecology. 36(5): 544-549
  • Levey HA. 1969. Toxicity of the venom of the sea-snake Laticauda colubrina, with observations on a Malay "folk cure". Toxicon. 6(4): 269-276
  • Palermo E. 2013. What are the world's deadliest snakes? Livescience. [Link]
  • Shetty S, Shine R. 2002. The mating system of yellow-lipped sea kraits (Laticauda colubrina: Laticaudidae). Herpetologica. 58(2): 170-180
  • Shukla P. 2018. Why fatal sea snake bites are unusual. Forbes. [Link]
  • Slanders KL, Lee MSY, Leys R, Keogh JS. 2008. Molecular phylogeny and divergence dates for Australasian elapids and sea snakes (Hydrophiinae): evidence from seven genes for rapid evolutionary radiations. Journal of Evolutionary Biology. 21(2): 682-695 [Link]
  • Snake venom. [Link]

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