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Is there any documented evidence for suicide among vertebrates other than humans? Lemmings not accepted !

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Does whales beaching themselves count as suicide? Wikipedia defines suicide as "the act of intentionally causing one's own death", but, in my opinion, it's hard to determine intentions of non-human creatures. –  aland Sep 8 '12 at 19:34
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Supposedly Tarsiers will commit suicide when in captivity by banging their heads against a wall. But I think it is difficult to distinguish between "that animal went crazy and lost its sense of self preservation" from "that animal committed suicide". –  Salain Sep 10 '12 at 1:13
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He said the L- word ... –  Poshpaws Sep 20 '12 at 16:28
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I would be curious to check if unicellular organisms commit apoptosis. –  Gianpaolo R Sep 21 '12 at 15:37
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Here's a short piece about animal suicide from Time: time.com/time/health/article/0,8599,1973486,00.html –  Bitwise Sep 27 '12 at 3:46
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3 Answers 3

Well, there are certain behaviors that may qualify. The clearest example I know of would be sexual cannibalism, and more specifically (source):

The redback spider is one of only two animals to date where the male has been found to actively assist the female in sexual cannibalism. In the process of mating, the much smaller male somersaults to place his abdomen over the female's mouthparts. In about two of three cases, the female fully consumes the male while mating continues. Males which are not eaten die of their injuries soon after mating.

That sounds pretty suicidal to me...

A less flagrant but commoner example is that of mothers dying to nourish their offspring. Again often seen in spiders, the best example I know of is the giant pacific octopus (Enteroctopus dofleini). The female will chose a den and lay her eggs. She will then spend her last weeks tending her young, never leaving the lair to hunt. Eventually she dies of hunger and her body nourishes her young. My source here is the wonderful BBC life documentary series.

Neither of these are vertebrates of course but still, I thought the suicidal little spider was interesting.

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is right - basically animals care less about their lives when they have reproduced or when there are lots of near relative (like a bee hive, an ant colony or a clutch of cockaroaches or guppies). They may not overtly be committing suicide, but they will defend their nests to the death or take what would seem to be tremendous risks just for some food. –  shigeta Oct 24 '12 at 22:16
    
@shigeta, yes this question got me thinking about social insects. I would have mentioned it but for the fact that the question asks for vertebrates (and I already mentioned two invertebrates :) ) and that, for hive insects, it might be more correct to see the hive as the individual. That raises other questions of course... –  terdon Oct 24 '12 at 22:33
    
I did say vertebrates since that was the original discussion I had, but evidence for "suicide" in any organism is interesting.. –  Poshpaws Oct 25 '12 at 8:31
    
Ostensibly, its the conditions of selection that cause this not as much the branch of the family tree you come from. On the other hand there are fewer animals whose lives are cheaper than insects. Lizards will eat their own eggs... that's not suicide tho. –  shigeta Oct 25 '12 at 16:28
    
There's a cool new paper that documents for the first time a male spider (dark fishing spider) whose physiology causes death upon mating. its a one time deal for these boys. rsbl.royalsocietypublishing.org/content/9/4/20130113 –  shigeta Jun 24 '13 at 5:22
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The problem is that committing suicide, using the commonplace definition of it, would require an understanding of death. I am sure that an animal can have a basic understanding of the death of others, so far as they realise the difference between a living companion and it's dead body. But if they understand that this lifeless body will never go "back to normal" again and that there is also future death for themselves, I am not convinced. So, without the understanding of the own, irreversible death, there is (following the definition) no suicide.

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According to this article whales could kill themselves by swimming to the beach and even when pushed back to the water, they return or dogs can drown in the water when suffer a lot.

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