Suicide

Humans are very curious animals. They are also often unwittingly guilty of anthropomorphism. Since sub-humans don't really share their innermost feelings with us in a clear, unmistakeable verbal language except through ambiguous bodily gestures, all human thoughts and ideas about the so-called sub-human animal behavior, including suicide, are just speculations and conjectures. Time should be more beneficially spent on contemplating on our own death by suicide.

We have to give Freud some credit for the insight of death wish as opposed to life force (dualism is useful in explaining most of phenomenon, physical or otherwise. Unitarianism is for deeper or more knowledgeable minds. Buddha had such mind).

To my way of thinking, there are three types of (human) suicidal behavior:

1. The conscious, deliberate, attention-getting kind where the act of taking one's life is for the common good of the group/tribe/nation (kamikaze pilots, contemporary suicide bombers), assertion of human dignity or protest.

2. The quiet, slow surrender to the idea that one's life no longer has meaning and thus death is preferable to living. The idea takes hold in one's mind and proves to be irresistible: a  very interesting phenomenon/process where an irrational, harmful thought/ idea drives the mind and the mind is incapable of holding it down or keeping it at bay. Madness no longer stands at the door. It is now in the master bedroom and takes over the house. Why is it so? A failure, breakdown at the cellular level or is it a result of weak will power? What is will power, anyway? Why do some humans seem to have it abundantly while do others seem to lack?

3. The self-destructive, suicidal lifestyle either as a cry for help or a sign of lack of will power to resist harmful impulses.

Conclusion: to really live, one must have a clear purpose and mission other than just mere preoccupation with sell-preservation, otherwise one can never be more than an animal, pure and simple. To be born as a human is a privilege and an honor. One must live one's life as such.

Addendum 1:

Suicide is a fascinating subject to me. I don't pretend that I am an ethologist, but I submit that only humans commit suicide because only humans possess a conscious will that can routinely override many instincts if they so wish. One of the instincts that humans routinely think of and sometimes do override is self-preservation. Sub-human behavior is largely governed by instincts. Sometimes their instincts are overridden, especially with human interference (animal training) at an early age. I agree with you that mammals do get stressed out, and that may result in their extreme loss of appetite or some abnormal behavior resulting in death, but to say that some  mammals consciously seek their own self-destruction is to say that similar to humans, they possess a free, conscious will. I am not prepared to go that far as we don't really know what's going on in the brains of the sub-humans because there is not yet a free flow of deep info exchange between humans and sub-humans, despite some attempts to teach sign language to chimps. At least with respect to humans, some of them left written records behind to tell us that they willingly killed themselves.

To think about/come to terms with  death is to try to find a meaning of life. After all, we all have to die someday, willingly or not.

Addendum 2:

Suicide is not simply death. It is a conscious, deliberate act of hastening death, an act may or may not define or ennoble or degrade the individual, but it does raise philosophical questions about Being. A person's attitude about Being determines/has an effect on the his behavior. Albert Camus even went as far as saying that suicide is  the only true, important philosophical question. Viktor Frankl, a survivor of Nazi concentration camp, wrote  "Man's Search for Meaning" where he dwelled on the meaning of Being,  hence existentialism, despite the squalid and demeaning environment, without giving in to nihilism and suicide.

Salmons die after laying eggs and sperms at where they were spawned because of built-up toxins from the exhausting homecoming journey.They don't consciously kill themselves before their time is up as some humans do.

Cowards don't commit suicide. Nor do they really love their countries of birth or adoption. They just love themselves above everybody and everything else. I don't really know if they really possess a zest for life or they are so consumed with a desire of self-preservation that all else do not matter to them, except perhaps self-justification in order to cling to a false pride. Fear of death can drive a man to do anything, including a regression to pre-human state. That's why the image of men fighting for freedom in Libya despite being outgunned and thus facing a high probability of being killed is so beautiful and uplifting to me. It speaks of Man's inherent nobility and yearning for dignity and honor. Contrary to cowards, these men are not afraid of an early death. To them, life without dignity and freedom is not worth living whereas to cowards, life simply means to cling to self-preservation at all costs. In other words, with freedom fighters, life is quality; with cowards, life is longevity (quantity). 

Addendum 3:

Yes, suicide only has import if its meaning is understood. And I agree with you that very possibly only humans possess that understanding. Sub-humans probably also know about death, otherwise they would not flee from physical danger or predators. But I am not sure if a salmon knows it's going to die when it gets back to its spawning ground. Likewise, I don't think a dog consciously know it's going to die when it refuses to eat. Please note that I consciously use "qualifiers" in the preceding two sentences because I am neither a fish nor a dog, I cannot logically claim that I understand what and how a fish or a dog thinks or feels. Recall that I have made a comment about a penchant of most humans to engage in anthropomorphism. That is what people do when they claim and assert that sub-humans (or non-humans, if you wish to hear a nicer expression) commit suicide. It's hard enough to understand our fellow humans with whom we share a common language with clear meanings, let alone trying to understand how and what species other than humans feel and think. Of course, humans throughout ages have established some rapport with domesticated animals and pets, so some kind of mutual understanding exists, but to get into a complex subject like suicide, we need to be careful not to tread into anthropomorphism. 

As for my own penchant to drag the age-old contrast between cowardice and heroism into a discussion, I think it is germane to the subject of suicide. Also, I do think the dualism of cowardice and heroism pervades quite extensively in human conduct and affairs. We tend to paint our fellow humans in broad strokes for easy identification and assessment. Since the cowardice/heroism dichotomy is such a useful yardstick, it is widely used. In addition, I would submit that ordinarily we would like and line to associate ourselves with heroes than cowards because heroes are inspiring and can also help us when we are in danger while cowards are useless to us and can also pose a danger to us. Finally, a man constantly meditates on the cowardice/heroism dualism tends to be the one who is instinctively averse to cowardice and is open to possibilities of heroism, otherwise he would keep his mouth shut. I have belatedly concluded that Obama is not endowed with heroism. A hero is somebody who's willing to take risks-- calculated, preferably---, not someone who is cautious, deliberate, tentative when innocent civilian lives are at stake, as was the case of the situation in Libya. Good timing, decisiveness, and willingness to take risks and enduring personal sacrifice for the common good are hallmarks of heroes. I now regard Obama as an opportunistic politician who has taken advantage of the political and social situations in America to advance his personal ambitions. I am no longer sure he is willing to take on the entrenched interests to steer America back on a right course. It also seems to me  that he is not really a statesman. Nor does he seem to me that he really cares about the world at large.