Can post copulatory sexual selection occur after conception?
Yes. Competition over who leaves descendants continues.
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How?
Sexually selected infanticide.
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Example of animal that does this?
Hanuman Langurs.
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Why?
Live in troops with 1 dominant reproductively active male, females and offspring. Intense male-male competition for access to harem. Dominant male monopolises who gets access.
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What is a tenure?
Male's residency time.
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How long does a tenure last for?
Anything from days-years.
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When does sexually selected infanticide tend to happen?
When new resident male takes over/start of their tenure.
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How can newcomer male's increase their reproductive success?
Through killing offspring present from previous resident male. Female cannot ovulate while lactating. Killing infant means she can reproduce.
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Benefits of killing offspring?
Speeds up process of returning to fertility, meaning offspring can be born to new resident male. Increase reproductive success.
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SEXUALLY SELECTED INFANTICIDE IS A MODE OF...
Post copulatory competition
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When does sexually selected infanticide occur?
Post conception.
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Sexually selected infanticide includes killing young already alive and...
Those still unborn.
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What are the explanations for sexually selected infanticide?
Sexual competition. Cannibalism. Social Pathology.
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What are the claims Sexual Competition makes?
Male will kill other male's infants. If you replace dominant male with replacement male, infanticide still occurs.
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What are the claims Cannibalism makes?
Males will consume infants. Will kill infants from other male's. Will occur under abnormal circumstances e.g. human interference.
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What are the claims Social Pathology makes?
Infanticide occurs due to abnormal conditions e.g. human interference. Male will kill other male's infants.
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Another example of animals that do this?
Lions.
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How long is tenure of lion?
24 months approx.
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Why must lion inseminate female quickly?
Tenure is only 24 months and cubs remain vulnerable for 9 months. Ensures cubs survive.
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Why do animals such as this kill infants?
Female will come back into estrus.
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How much quicker do male lions sire cubs if they kill infants?
8 months earlier.
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Evidence for sexual competition theory in animal study?
African Leopards - highest rates of infanticide. Should find they are unrelated. This was indeed found.
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In birds, replacement mate will exhibit what 3 things?
Parental care (brood adoption), indifference, or infanticide.
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Counter strategies to infanticide in lions?
Avoidance and aggression to new males.
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What behaviours can lion females do to minimise takeover?
Grouping, Optimal pride size, Attracting a large male coallition.
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Counter strategies to infanticide in Langurs?
Pseudoestrus. Elicite copulations during takeover if pregnant at the time - causes paternity confusion.
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Other strategies?
Horses abort after copulation with new male.
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What is the Bruce Effect?
If males are infanticidal, females will abort offspring. Prevent wasted resources.
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Why do mice become aggressive towards pups 3 weeks after mating?
Gestation period. Assumes pups aren't his before 21 days.
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What is the proximate mechanism for the switch?
Can tell by day and night cycles. Can be tricked in tests which alter light and dark in mice.
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