These animals sacrifice themselves for their species

“Their lives are not that complicated,” the neuroscientist explains. ‘So they potentially survive just long enough to do what they have to. »

And even if they developed these pathologies, no one would know. “There is no behavioral scale for musk oxen. We can therefore not say whether they are losing their memory a bit or not,” she adds.

Ackermans now wants to study different species of woodpeckers to see if the headaches they give cause brain trauma. The only other study that looked at birds’ brains found traces of tau protein, but “not really in any specific logic,” she says.


In some ways, the musk ox represents an interesting parallel to certain marsupials, says Diana Fisher, a mammalian ecologist at the School of Biological Sciences at the University of Queensland, Australia.

Small and carnivorous, the antechinus is a genus of marsupials native to mainland Australia and Tasmania. In recent years, they have made headlines for the way men practice semel parity, which is one major cycle of reproduction followed by a planned death. The females can live two to three years or more, but the males rarely last longer than eleven months.

“They’re having a very hectic mating season,” Fisher says. Mating can last twelve to fourteen hours, after which the male tries to mate with as many other females as possible, leading to his death.

“The collagen in their skin is broken down, their intestines are broken down, and they bleed internally,” says Fisher. “They become very susceptible to parasites and diseases, and their immune system is broken down. In a few weeks they will be dead.

“All of this is pretty unusual for mammals,” Fisher says, because mammals tend to survive long enough to experience multiple mating seasons.

Suicide breeding is more common in insects, fish, plants and spiders: when another species native to Australia, the red-backed black widow, mates, the male places himself in the mouth of it after the action.

“This discourages the female from continuing to mate as she is busy eating,” Fisher adds.


In large colonies of social insects a similar but slightly different dynamic arises.

When a European bee stings a soft-skinned aggressor, such as a bear, it dies when its sting gets stuck in the victim’s skin. An explosive ant can tear its stomach in two to defend its nest against attackers. And in some species of termites, the elderly can turn into suicide bombers.

But what explains such a willingness to kill oneself, from the point of view of evolution?

“It’s pretty simple,” replies Thomas Seeley, a Cornell University biologist and author The lives of the bees, in an e-mail. “Workers achieve genetic (evolutionary) success not by reproducing themselves, but by helping their mother, the queen of the colony, to do so. This help can be especially aimed at defending the colony,” he explains.

“Some researchers call it a ‘superorganism,'” Alice Laciny, an entomologist working on explosive ants at the Natural History Museum in Vienna, said via email. “A colony of ants or a hive is thus more like a single large animal, of which the queen represents the reproductive organs. Workers are numerous and need only small amounts of resources to grow so that they resemble cells in a body in a way. »

As with musk oxen, what strikes us as violent, self-destructive behavior on the part of the working ants seems worthwhile as long as it leads to reproduction.

“In this system, by protecting its queen and its sisters, it goes so far as to sacrifice itself if it is necessary for a working ant to be able to protect and transmit its genes,” Laciny explains.


The distance that some mothers are willing to travel to give their young a chance represents another form of sacrifice found in the animal kingdom.

After birth, some species of amphibians, boneless, literally eat the top layer of their mother’s skin as their first meal. African social spiders Stegodyphus dumicola go even further: some females let their cubs practice matrifagia, that is, she lets them kill and eat her.

Giant Pacific octopuses are perhaps the most self-sacrificing mothers. The females can look after their eggs for an impressive four years, where they do not even eat.

“Inevitably, females deplete all of their body reserves and die while guarding their eggs,” says Fisher.

“It’s bound to be painful for them, but that’s how many species achieve the greatest success in ensuring the next generation’s survival.” »

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