Siblicide

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Siblicide
Murdering a sibling, or siblicide, may seem
cruel. Fortunately it's not the most common
behavior in the animal kingdom. In fact, many
animals have amicable sibling relationships. But
when there's a short supply of food, some birds,
insects, fish, and mammals snare their share by
killing their closest competitors -- their
sibling

• Definition
• the death of an individual by its close relatives
  may occur directly between siblings or indirectly
  across the parent-offspring relationship and is
  seen to have beneficial indirect results for the
  genetic viability of a population or direct
  results for the recipient individuals.

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How does it work?
Siblicide occurs because the rations of food are
scarce in the area. Without enough food, the
parents cant feed more than one offspring. The
dominant offspring of the hatch / litter kills
the others.
This ensures that one offspring will get what it
needs nutritionally to survive. With only one
young surviving (normally the strongest
individual) it will flourish and become a strong
adult which in turn will produce healthy, strong
offspring itself.
This is a basic evolutionary process that occurs
to ensure that generations of the animal are to
come. It is simply passing on good genetics.
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Examples

• In Spotted Hyenas, pups of the same sex exhibit
  siblicide more often than male-female twins.
• It is thought that siblicide is far less common
  than proposed, and it only occurs when resources
  are insufficient to sustain two cubs.
• A study done on the Masai Mara National Reserve,
  Kenya, found in a 10-year period that spotted
  hyenas in same sex litters routinely engage in
  siblicide.

Laura Smale, Departments of Psychology, Michigan
State University Kay Holekamp, Departments of
Zoology, Michigan State University Paula White,
Department of Integrative Biology, University of
California, Berkeley
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Great Egrets

• Egrets lay a clutch of 2-3 eggs. Usually only one
  or two of the offspring survive.
• The oldest or first to hatch will peck the others
  in the head until it dies then eat it or kick it
  out of the nest.
• This is of course if it hatches, they have been
  known to kick eggs out of the nest.
• Some cases the two oldest gang up on the third
  and kill it, this in turn also helps the mother
  feed the mouths of only two.

As we see in this picture, one offspring looks
larger than the other and may eventually kill the
smaller.
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Examples Continued

• Sand Tiger Shark
• Diet consists mainly of large ad small bony fish,
  small sharks, rays, squid and crustations.
• The sand tiger is ovoviviparous, bearing 2 live
  young after a gestation period of 9 to 12 months
  each is approximately 1 meter long. In each of
  the two separate uterine chambers the first
  embryo to hatch obtains its food by eating the
  other developing eggs.
• Although, in some cases the larger (usually the
  first developing) embryo will eat its bother or
  sister inside the mother.

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Swallow-Tailed Kites

• Same as in the Egrets, Kites also lay eggs where
  the young will kill off the smaller of the
  siblings to ensure the survival of the strongest.

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Pros and Cons

• Pros
• The strongest will survive.
• More food for one.
• More parental care for one.

Cons If the one offspring dies, all is
lost. Clutch usually has two or more eggs, energy
is spent and lost. Not always the strongest
individual survives. Could be just the first to
hatch. Genetic trait for siblicide will be passed
on.
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Why does this happen?!
Survival of the Fittest Instinct Reproductive
Success Food Scarcity Success of the
Species Producing only the strongest individuals
From the time of antiquity field biologists have
observed that some organisms tend to exhibit
strategies that favor the reproductive success of
their relatives, even at a cost to their own
survival and/or reproduction.
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Related Topics
Kin Selection This refers to some organism to
exhibit strategies that will put themselves in
greater danger to ensure another individual of
their family will survive. This is exhibited in
squirrels, where one will make an alarm call to
others near by that there is danger, in turn
putting themselves in the direct line of danger
because they are making themselves more
obvious. Again this is a way that will increase
the survival of all others in the species.
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