The intro of a paper on animal suicide:
It is commonly assumed that suicide is a distinctly human act. Lacking the capacity to visualise and enact their own deaths, animals are seen to be driven by an instinct of self-preservation. However, discussion over the existence of the self-destructive animal has been long been central to debates over the nature of suicide. By granting animals the capacity to take their own lives, they were granted emotion, intelligence, consciousness.
By transgressing boundaries between animal and man, scientists and activists in the 19th century were united by a determination to ensure the welfare of both. For their critics, these boundaries were to be maintained animal acts of self-destruction were not intentional, but accidental and instinctual responses to stimuli. Nevertheless, reflections on the suicidal animal have continued, less a means of granting consciousness to the non-human, but as symbols and analogies for human acts of self-destruction devoid of thought or intention.
(Hat tip: Mind Hacks)