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I just watched a documentary on PBS that featured many African mammals in the wild. One scene in the documentary showed a baby zebra that was described as "minutes old" walking next to its mother. After a brief moment discussing how the baby needed to learn to walk shortly after birth they showed a male zebra rush the baby and attack it. The mother, obviously distressed, was trying to push the male zebra off the baby without much success. After a period of the male repeatedly cycling between stomping on the baby and pulling it off the ground (by the leg or neck) with its teeth, the male zebra left the baby broken on the ground. The mother stood watch over the baby and you could see the baby struggling. Once the vultures started circling the mother started desperately calling to the baby, but the baby died soon after.

The narrator said this attack happened because the male was new and the baby was from an older male that was muscled out. They said this attack was an instinctual response by the new male to give their offspring the best chance at survival. It is probably naive of me but I was frankly a bit surprised that a zebra would act in this manner. This leads to my question. Is this an accepted social norm for zebras, or should the young male expect retribution? The mother probably couldn't win a fair fight against the male but I'm sure even zebras sleep. She could probably give him a hard kick to the head when he was asleep though and hurt him badly before he could put up much of a fight. Alternatively I'm sure a pack of female zebras could take on one male, but somehow that seems even more unlikely than an ambush by a lone female.

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    Darwin would say no. – ab2 Mar 23 '17 at 3:28
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    @ab2 if baboons can adapt why not zebras? radiolab.org/story/91694-new-baboon You can hear the baboon stuff start around 6 minutes in. Plus you can have variance in behavior in any species. I was wondering if this is abnormal zebra behavior or not. – Erik Mar 23 '17 at 3:40
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    The same thing happens with lions, by the way. There is evolutionary pressure for this behavior when the social structure is such that a dominant male stays with the group and exclusively mates with all the females. The males that did this originally left more offspring, so eventually that trait dominated and all the males now do this. Put another way, the male you see killing the offspring of another male is there because he is decended from a long line of males that all did the same thing, not the ones that sacrificed their own breeding opportunity to let offspring of other males live. – Olin Lathrop Mar 23 '17 at 12:03
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    This is radically anthropomorphizing an animal's behavior beyond all reason. – cobaltduck Mar 23 '17 at 14:07
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    @Erik Chimps are basically epitomize how brutal primates can be. They're cannibalistic, genocidal, and vicious. – ShemSeger Mar 23 '17 at 20:04
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This happens because stallions will kill foals that are not their own.

This is where things can take a dark turn. If the females in the harem have recently given birth, the new dominant male may kill their foals to eliminate any traces of his predecessor, and to bring the females into oestrus in order to further his own genetic legacy.

Source

Sometimes domestic mares will abort their pregnancy as a preemptive measure.

The high rate of failed horse pregnancies may have a simple explanation: pragmatism. Mares may simply abort because nearby stallions other than the sire could be expected to kill the foal anyway.

Bartoš argues that the results make sense in light of horses’ natural behaviour. Wild horses live in “harems” consisting of one or more mares and a stallion. A stallion can gain new mares by challenging and defeating another. If a mare becomes pregnant by one stallion but then becomes a member of another harem under another stallion, she will tend to lose the developing foal and breed with the second stallion instead, he says, because stallions often kill offspring that are not their own. “The mares are just trying to avoid wasting resources on a foal that will be killed when born,” he says.

Given that the mare will mate with the second stallion after losing the first foal, it doesn't seem like they would seek revenge.

Zebras could be different, but because they belong to the same genus I suspect that they would have the same tendencies.

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  • Is the mare mating with the second stallion consensual or forced? I always assumed animals in a harem like situation were generally forced. – Erik Mar 23 '17 at 3:04
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    @Erik I don't know, but I think that this is a perfect example of how cruel nature can be. – Charlie Brumbaugh Mar 23 '17 at 3:10
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    I agree. I know nature doesn't really care one lick either way, but some times I'm surprised when I see it. I guess I've been watching too many Disney movies with the kids recently... – Erik Mar 23 '17 at 3:14
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    We can't hold discussions with zebras, so assigning chains of reasoning or abstractions like 'revenge' to their behavior is just story telling. It may simply be that the changes to the hierarchy of the herd are stressful, and stress is known to increase the rate of miscarriage in large mammals. Animals (including humans) don't generally have sex because they want offspring, they have sex because they really WANT sex. And they really want sex because the animals that really wanted sex out reproduced the animals that were indifferent to it. – Charles E. Grant Mar 23 '17 at 3:24
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    @CharlesE.Grant sure but in general they don't want any old mate they want "the best mate" (female) or "the most mates" (male). Also we can't have a conversation but we can observe behaviors and form a hypothesis. If males that killed foals regularly got kicked in the head by the mother and males that didn't kill foals don't then it would be a reasonable hypothesis that mothers were reacting to the male killing the foal. I don't converse with apples but I'm reasonably sure they will fall to the ground if I drop them. – Erik Mar 23 '17 at 3:53

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