White-bellied Sea Eagles catch sea snakes

“The White-Bellied Sea Eagle (Haliaeetus leucogaster) is one of the largest raptors in Southeast Asia. Its distinct image can even be found (printed) on the $10,000 Singapore note. This eagle is a good hunter and feeds mainly on fish and sea snakes.



“These magnificent eagles were often seen with fish caught in their powerful talons. Before today, I have never (personally) seen these eagles with snakes in their talons. Hence, I’m pleasantly surprised that this morning, in the space of 10 minutes, two different birds were seen successfully catching different species (presumed; based on different colour and body sizes) of sea snakes from the surface of the sea.



“The images attached show Eagle A in the sequence of diving down (top) and catching a sea snake and then flying away without much fanfare (above). Eagle A was seen soaring at great height while looking for prey. Once it found its target, it extended its feet and descended at speed by folding its wings and then gradually opening its wings to “parachute” gracefully to the target. Its aim at the targeted prey was perfect and its talons caught the snake in one strike. Immediately, it flapped its huge wings to ascend and fly away; probably to a perch to enjoy its catch.



“The hunting technique was similar for eagle B. However, there is a bit of drama for eagle B as the sea snake it caught put up a struggle and coiled itself around its leg (above). It cannot be ascertained whether the snake managed to bite the eagle. The eagle must have felt uncomfortable as the sequence of pictures captured eagle B in spectacular manoeuvres defying gravity in its attempts to disentangle the snake’s coiling around its leg. In mid-flight, the eagle was seen using its beak as well as its free leg to handle the snake (below). The eagle was even observed diving low in an attempt to free the snake’s strangle hold. After much effort, the eagle managed to subdue the snake with both talons gripping firmly onto the snake before it flew away from sight.



“Sea snakes being poisonous, I’m curious what could have happened to the eagle if it was actually bitten? Could it survive?

”

Kwong Wai Chong


Singapore
27th December 2009

7 Responses

  1. KC: Waaah! Ini bagus lah! KF

  2. My suspicion is that being rear-fanged, the sea snake just can’t get its fangs past the feathers. If it could, I don’t think the raptor will survive. That brings up the question: does the Crested Serpent Eagle have any immunity to snake venoms?

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  4. No raptors are immune to snake venom, or so it seems from the literature. The scales on snake eagles’ legs help protect the birds from snake bites. Beyond the scales are feathers, and any strike will only result in a mouthful of feathers.

  5. Slow: True sea snakes (Elapidae) are front-fanged, like their terrestrial cousins the cobras, kraits and coral snakes. However, there are other seagoing snake species, such as the nonvenomous file snakes (Acrochordidae), as well as the rear-fanged mildly venomous water snakes (Homalopsidae).

    I suppose the scales on the legs provide some measure of protection, and as YC mentioned, if the snake strikes at the bird’s body itself, it is more likely to end up with a mouthful of feathers.

    We need more observations of the dedicated snake specialists, such as the snake eagles and secretary bird.

  6. Lee Chiu San

    Those were fascinating shots. As I have some interest in snakes, I enlarged them to the maximum possible on the computer screen. In the case of Eagle B, it is very likely that the snake in question is the Sea Krait (Laticauda colubrina). This snake is indeed venomous, but is surprisingly reluctant to bite. Professor Roland Sharma, formerly of the Zoology Department of NUS and myself have captured and handled a number, and found them generally inoffensive. Of course, if in danger of being eaten by a sea eagle, even the most mild-mannered snake may protest.

    In this case, the scales of the eagle’s leg might afford protection. There are also not that many blood vessels close to the surface on bird legs to allow easy access for venom.

    To add to what was said by Hai Ren, yes, there are many snakes that can be encountered in the coastal waters of Singapore, but not all of them are sea snakes. I would say that the commonest is the Dog Faced Water Snake (Cerberus rhynchops) which is rear-fanged but effectively harmless and is often found in pure marine water. It is far more common than any of the true sea snakes.

  7. A higher resolution image of the eagle with the snake in its talons was sent to Chiu San and this is his take:

    “With the clearer picture, I have to admit that my first guess was wrong. The snake is definitely not a Sea Krait. In fact, I doubt that it is even a sea snake.

    “This is the sequence of deduction that I followed. In the picture with less resolution, the snake’s body looked grey, and there were two distinct stripes. The Sea Krait is banded throughout its length.

    “In this better picture, I can see clearly that the two stripes are injuries, not part of the snake’s natural colour.

    “The snake is clearly cylindrical, whereas most sea snakes, (but not the Sea Krait) are noticeably laterally compressed.

    “This snake is olive-brown. Locally I know of no sea snakes of that colour. It also appears smooth. The Homalopsine water snakes have keeled scales and do not appear glossy.

    “I would hazard a guess that it is a terrestial, non-venomous colubrine snake that got washed out to sea, and was already in distress, trying to keep from drowning, when the eagle picked it up.

    “Since sea eagles are known scavengers, it is possible that they pick up land animals that accidentally get washed out to sea after heavy rains.”

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