Cannibalism in Moray Eels?

[scubadada]

My wife and I recently spent 2 weeks diving in Bonaire. At about 80 feet, on Bari Reef, I witnessed a large Spotted Moray devouring a smaller Spotted Moray tail first. Eventually, the smaller eel was completely swallowed. I have never seen this happen before and had not heard of it. Does anyone know more about this phenomenon? I found a few videos, but little information, when I searched online.

 

[waves_221]

I have also observed this before in the Virgin Islands. I saw a relatively small green moray eating a smaller spotted moray. Very interesting, but I wasn't surprised as they are opportunistic predators.

 

[Jcp2]

That’s Amore.

 

[Akimbo]

It makes you wonder what is going on. Devouring their young? Eliminating competition? Territorial dispute? Just hungry?

 

[tursiops]

This seems to be common enough that the science article are not surprised about it.
Here are two such pubs. One ("Revisiting...") is a review article that has some discussion of why it happens. The other specifically mentions "conspecific" cannibalism in two species of moray, with no further comment.

Regarding why, here is a relevant quote from the review:

"More than 30 years after Polis’s review, there appears to be little consensus about the commonness of cannibalism and its ecological and evolutionary importance."​

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[scubadada]

Thanks very much @tursiops

The review article is not very useful. The paper by Young and Winn identified unidentified Moray remnants in the stomach of just 1 Spotted Moray and 1 Purple Moray. I don't think this addresses species specific cannibalism. I would love to hear about other information on this topic

 

[tursiops]

Thanks very much @tursiops

The review article is not very useful. The paper by Young and Winn identified unidentified Moray remnants in the stomach of just 1 Spotted Moray and 1 Purple Moray. I don't think this addresses species specific cannibalism. I would love to hear about other information on this topic

Actually, the Young and Winn paper said the spotted ate a spotted and the purple ate a purple...."conspecific".

 

[cgills]

Yes, have witnessed it before, and like you, surprised and taken totally off guard by it as well. No photos as I was diving with nephew, who didnt tote a camera. Happened two years ago, we had just observed an eel attack on an octopus who managed to escape minus one tenacle, when I spotted Turtle Reefs/Macabuca/Grand Caymans resident monster green moray out hunting. Decided he might be worth following, proceeded to watch him grab a full size Spotted Moray mid body , fold it in half , and choke him down in less then two minutes!! Unreal!! Exciting, and very shocking! I've dived a bunch, and tons of night dives, never have I seen this behavior exhibited before.

 

[drrich2]

I saw a relatively small green moray eating a smaller spotted moray.

There's a key difference. In this case, nourishing one's self by eliminating a potential competitor from the area. Said competitor is not of the same species, and thus there is no mitigating benefit to letting it live - such as a potential future mate, or vehicle for advancing shared genetics to the next generation.

Killing your own kind can mean killing your own young or a potential future mate. This does happen with some species in nature; it's my understanding some crocodilians (aside from the mother of a recently hatched brood) engage in cannibalism of youngsters, and Komodo dragons are known for cannibalism (note adults live on the ground, young may take to arboreal habitat).

And males within a species fighting over territory and access to mates are a 'thing' - such as with hippos, lions and more. I can't 'sex' morays by looking at them (or any other way), nor do I know whether they have territories.

One potential disadvantage: it's possible another moray is more likely than most prey to have parasites or infectious diseases that can harm the devouring moray. I'm speculating, but it makes sense.

 

[scubadada]

Actually, the Young and Winn paper said the spotted ate a spotted and the purple ate a purple...."conspecific".

Thank you @tursiops The event I witness was also conspecific. One of my questions was whether this was always intra-species or also occurred between different species. The data from the article suggests that this is relatively uncommon. Have you ever witnessed this phenomenon?

Yes, have witnessed it before, and like you, surprised and taken totally off guard by it as well. No photos as I was diving with nephew, who didnt tote a camera. Happened two years ago, we had just observed an eel attack on an octopus who managed to escape minus one tenacle, when I spotted Turtle Reefs/Macabuca/Grand Caymans resident monster green moray out hunting. Decided he might be worth following, proceeded to watch him grab a full size Spotted Moray mid body , fold it in half , and choke him down in less then two minutes!! Unreal!! Exciting, and very shocking! I've dived a bunch, and tons of night dives, never have I seen this behavior exhibited before.

Thank you @cgillis that, along with the reply by @waves_221 answers the question regarding intra and inter-species, which I assume would not be called cannibalism.