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Relation between reproduction and age

  1. Jun 1, 2012 #1
    In this Article there is a remark by biologist "It's one of the basic lessons in biology: Reproduction is very costly, and if you don't use it, you can live much longer".
    Can someone give few examples of species that live longer if they don't reproduce?
  2. jcsd
  3. Jun 1, 2012 #2
    Well, there are some species, insects particularly for which reproduction will mean a very abrupt end of life, be it the male eaten by the female or the female dying while laying the eggs or giving itself as food to the little critters... :)
  4. Jun 1, 2012 #3
    How about elk? They really have to fight alot to mate, in general anyway. Helps if you got really big racks. But they're heavy and unwieldy; get caught in the bush when evading bears and all. But if an elk is to mate, big racks are better than small ones because of the competition for the females. By the time the big elks are finished, they're exhausted and that makes them easier prey.
  5. Jun 1, 2012 #4


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    The act of reproduction and the production of young ones may be costly as oli3 stated. Competition for a mate can also be costly as jackmell stated.

    A third aspect is caring for the young until they reach an age of maturity, which is evident for mammals, birds, and some species of reptiles, insects, fish etc.
    Foraging for food for extra mouths in addition to your own means that the parent is out more often from a secure place and more prone to predation.
    Incubating eggs or caring for the new young such as birds do would mean that the parent is now in one place and if found by a predator has to make the choice of fleeing and leaving behind the energy and time already spent to care for the potential young or challenging the threat with the possibility of life extinction.

    You can even relate your question to humans where before the advances of hospital and medical care that certain societies enjoy now, the female had a greater chance of dying by giving birth ( as opposed to not having children ).
  6. Jun 2, 2012 #5
    The article linked to is talking about a phenomenon whereby the butterflies actually stay younger longer when they're not in reproductive mode:

    Something like this must be in play with salmon as well, who seem to curl up and die soon after they get their mating accomplished.
  7. Jun 2, 2012 #6
    Surely there are many salmon migrating up the Columbia that never get to mate. Do these live longer than the ones that mate? How about even more drastic: suppose I corner a group of migrating salmon just before they get to their final location, after they have made the arduous trip, and I prevent them from mating. Will this group of salmon live longer than the ones that are allowed to mate?

    A correction: the ones that mate do die. So if I corner them right before they mate, and prevent them from mating will they still die? Is it the trip that killed them or some reproductive event that causes them to die?
  8. Jun 3, 2012 #7

    In the case of the butterflies, they remain immature due to short days. Becoming sexually mature and mating doesn't really seem to be the cause of their demise, it's the fact longer days cause them to age. The salmon seem to be the same: it seems it's primarily the long term exposure to fresh water that causes the changes that burn them out, not the mating itself.

    Your question remains unanswered, though. What would happen if we, say, blocked off a river and prevented the salmon from going up to spawn? Would they live indefinitely or would this cause some other problem that killed them? I don't know. The quote seems to say they'd have the choice of not reproducing and living longer thereby. I tend to doubt that: that they're capable of making any such choice.
  9. Jun 3, 2012 #8
    Ok, thanks for that. The paragraph, "The Spawning" suggest they do deteriate rapadily during the run but some survive after spawning and return to the ocean and recover.
  10. Jun 4, 2012 #9
    'Death' actually evolved as a consequence of sexual reproduction.

    Note that the dividing amobae never must die, and so it is with every asexually-reproducing organism. All sexually-reproducing organisms have a typical 'life span', which is not true for asexually-reproducing species.

    ref: a lecture by Dr. George Wald, at B.U. in the 1970's
  11. Jun 6, 2012 #10
    Hey, thank you all for the information.
  12. Jun 7, 2012 #11
    All those animals whose parents die immediately after reproduction.
    I am not sure this is exactly what you meant. However, a lot of animals die immediately
    after the act of reproduction. One of the selective advantages of such behavior is that
    the parent won't eat the child. Another reason is that the act of child care uses up
    the parents resources.
    Sometimes, the parent provides nourishment for the child or other parent. This is
    an example of resource competition. Males often get eaten because the act of
    laying eggs weakens the mother.
    Here are some examples.
    1) The octopus mother stops eating after laying her eggs, tends the nest and dies of starvation.
    -She would eat the eggs if she didn't lose her appetite.
    2) Salmon stop eating and die soon after laying their eggs.
    -The mother guards here eggs and stops eating.
    -She would probably eat the eggs if she didn't lose her appetite.
    3) The male large mouth bass stops eating for two weeks after fertilizing his eggs.
    -The male guards the nest during his fast.
    -He starts eating about 2 weeks after the eggs are left, if he is still alive.
    However, he is badly weakened by his fast. He has an increased chance of being killed
    after he mates.
    4) The male of most species of spiders are killed by the female immediately after
    -By eating the male, the female gets enough strength to raise another brood.
    5) The female of many species of spiders dies immediately after laying eggs.
    -Again, she would probably eat them if she didn't die.
    6) The male preying mantis is beheaded by the female during mating.
    -By eating the male, the female gathers enough strength to raise another brood.
    7) Human females have a high chance of dying during childbirth.
    -The rate of dying during childbirth was a lot greater before the advances in
    modern medicine.
    -In primitive societies, a woman can seriously reduce her life expectancy
    by having children.
    8) Venereal diseases of all animal species can only infect a host if the host
    indulges in reproductive behavior.
    -Syphilis, gonorrhea, HIV, SIV, etc.
  13. Jun 7, 2012 #12
    I don't know either. Probably not. Anyway, they would need instincts to survive
    the world after the trip. Natural selection may not have provided them with such
    instincts, since reproduction reliably kills them.
    A salmon in the wild that doesn't reproduce may wonder what to do next!
    A salmon that whose body doesn't make eggs or milt may be very strong after
    the mating season. Further, he may be asking himself the following question.
    Should I stay in the river and risk the winter, or try to make another go round and
    risk the trip? Mutations that do that do either are not likely to leave progeny.
    This possibility is irrelevant. The answer to your question is that reproduction kills the salmon that survive the trip. Reproduction does use up resources that could have
    been used for long term survival.
  14. Jun 8, 2012 #13
    Good to know all these examples.

    Wondering whether any plant dies after releasing seeds?
  15. Jun 8, 2012 #14
    How about Harpy eagles:

    These eagles prey upon the local monkey population. Yum. But when they have offspring, the parents, in one study at least, didn't go after the local ones but rather far away to get them. The biologist studing this phenomenon suggested they were saving the local ones or "desensitizing" them in preparation for their offspring to more easily predate them: the act of reproduction causes strain in the adult, in this case by causing them to expend more energy to obtain food.
  16. Jun 8, 2012 #15
    I have given several examples. However, I skipped premating combat.
    A lot of animals fight over mates. Usually, it is the male that fights over mates. The male often gets killed. If a male didn't try to fight the other males, it is more likely to live long. However, if it doesn't fight it has less of a chance of reproducing. Thus, the initiation of mating behavior shortens the average lifetime of the male.
    I read someplace that a male lion in wild Africa has a four out of five chance of being killed by another male lion. Thus, looking for a mate is very risky for a male lion. A male lion
    that doesn't even try to mate can live much longer. For a wild lion male, combat with other males is necessary to initiate reproduction.
    Again, that biologist should have said that "Initiating reproduction is very costly." Just because an animal skips one small part of the reproductive process doesn't mean that it
    is going to live longer. Usually, the very initiation of reproductive activity is costly. With this caveat, the biologist is right.
    If you decide not to look for a sex partner and not raise a family, your average lifespan will go up. However, your chance of propagating yourself into the next generation goes way down.
    Of course, lots of animal species have mixed strategies. Different individuals have different strategies for survival. Statistically, the population can take full advantages in
    the trade off between lifespan and birthrate. However, mixed strategies are another matter.
  17. Jun 8, 2012 #16


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    As a parent of two, I'll just say anecdotally that expending resources to raise humans is expensive on time, resources, energy, etc. You luckily get a set of hormones (or something) that BS your into enjoying it though, but my grey hair conversion rate is multiplying.

    And your kids aren't going to survive if they don't get raised by an intelligent enough mammal, so you could arguably associate raising costs to reproductive costs.
  18. Jun 11, 2012 #17
    It's interesting to note too that many parasites have evolved to render their hosts infertile increasing the host lifespan and therefore their own. I'm not sure what species of parasite have evolved to do this specifically as they have such complicated life cycles and can alter the hosts hormones for their benefit anyway.

    I believe in history human eunuchs have been very large and also suffer from weight problems probably gained from the extra energy saved. So I started to wonder about animals that were born sterile such as cross-breeds but it seems to be a complicated issue with genetics and hormones. Mules are said to live longer according to one aficionado on Wikipedia. Also I suppose being sterile doesn't mean your not expending the energy to produce sperm and eggs. Then again, from reading forums, some guys have mentioned that after they lost their virginity they began to produce more semen and would thus expend more energy. So it will be interesting to note how reputed virgin Sir Cliff Richard lives. I hope I haven't meandered too far.
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