IIn 2011, shocking celebrity breakups made headlines around the world. It wasn't the breakups between Ashton Kutcher and Demi Moore or Jennifer Lopez and Marc Anthony, but the sudden and mysterious split between two 115-year-old Galapagos natives, Bibi and Poldi. Turtles at Hap Reptile Zoo in Austria.
After nearly a century of living together as a couple, Vivi, the female, has had enough. One day, she bit off a chunk of Poldi's shell, drawing blood, and continued the attack until zoo staff moved Poldi to another enclosure.
The wild Galapagos tortoise is not monogamousSo it's no small feat that Vivi and Poldi's relationship lasted so long, even though their coupling never produced any offspring. Unfortunately, attempts at reconciliation were unsuccessful. “We feel like they can't stand the sight of each other anymore,” said Helga Hupp, the zoo's director. I lamented that time.
Why do breakups happen? Among humans, this question has given rise to ballads and provided rich material for novelists. And it continues to interest scientists.
Of course, before we can break up, we have to be together first. In social monogamy, animals live together and form strong bonds known as pair bonds, but sexual fidelity is a different matter. Among mammals, humans are an exception, with social monogamy observed in less than 10% of mammals.
Professor Simon Griffiths, an evolutionary ecologist at Macquarie University, said this low figure was due to differences in parental investment between men and women. In most mammals, parental care is primarily performed by females, who invest heavily in pregnancy and providing milk for their young.
“In many mammals, there is no paternal care,” says Griffiths. “He may provide some security or hold some territory, but…he can't provide that much for his descendants.
“With birds, it's completely different. In fact, fathers can be just as attentive as women when it comes to bringing food.
“That's why birds tend to form partnerships, but mammals don't.”
Professor Raoul Mulder, an evolutionary ecologist at the University of Melbourne, said evidence suggested that bird populations were mostly sexually monogamous before there was a way to establish parentage. That's what it means.
“If you look at whether certain species mate, how long they mate, and how long they stay together, and then classify all known bird species, you'll arrive at a number above 90 percent,” Mulder said. Say.
However, since genetic testing technology was developed, scientists have begun to realize that birds are not as faithful as previously believed. – Social monogamy and sexual monogamy don't necessarily go hand in hand. Mulder's research on the amazing fairy wren revealed the following: 76% of chicks Males born in the nest were fathered by other males. This astonishing cuckolding rate is rivaled only by the Australian magpie. Rates as high as 82%.
But overall, Australian birds tend to divorce less than their European counterparts, and Griffiths says they need strong partnerships to survive fickle environmental conditions. In the Northern Hemisphere, the timing of the breeding season is predictable in relation to photoperiod, but in Australia breeding decisions are also dependent on climatic factors.
“There are years when there's literally no meaningful rain and nothing grows. The birds and animals that live there can't breed,” Griffiths says of Australia's arid regions. “[Breeding] It's a much more complex decision on an individual level, but if you have a good partnership, you can optimize it together. ”
Among birds, the typical monogamous offspring is the wandering albatross, which can live up to 50 years and typically mates for life. “These birds take a very long time to form a pair bond,” says Ruijiao Sun, Ph.D., a postdoctoral researcher at the University of California, Santa Barbara. “If an individual loses a partner, it takes years to bond with a new partner before they can start breeding again.
“Wandering albatrosses only lay one egg each breeding season, but one parent must be sitting on the nest at all times to protect and hatch the chicks. But they also need to forage. So we have to take turns.
“It actually takes two people to be able to raise a chick.”
Sun suggests that long-lived species like albatross benefit more from strong pair bonds. “Each time they breed, they fine-tune their behavior. They adjust better to each other, making reproduction easier.” [over time]”
In contrast, short-lived species may be prepared to abandon partners to maximize reproductive opportunities. Still, Sun's research estimates the divorce rate among wandering albatross to be about 10%. (Compare this with King Penguin. sexually monogamous A certain percentage of people who stay together with their partner will divorce. Approximately 80%. )
Other factors that can drive animals to divorce (what scientists call mate swapping) include high mortality rates; distorted sex ratio. Both increase competition for mates and create temptations for members of minority genders to cohabit with more attractive partners.
Research suggests that the climate crisis may also be having an impact on divorce. in Snow petrel researchnest in rock crevices in Antarctica, and Sun and his co-authors found that the number of snowy days during the breeding season is directly related to dispersal rates. Too much snow will bury the nest, freeze the eggs, and cause them to fail to hatch.
“They may either abandon their previous nest or abandon their partner,” Sun said, adding that the stress of constant shoveling may lead the birds to “blame their partner more than usual.” he added.
The study predicted that reduced sea ice due to climate change would also affect future survival and skew sex ratios. “There will be more males in the population, but fewer females to mate with them,” Sun said.
In the Falkland Islands, unusually warm water temperatures are thought to be a culprit, with stress and spousal responsibilities also likely playing a role. high divorce rate Among the brown-browed albatross. Researchers suggested at the time that “environmentally driven divorce may represent an overlooked consequence of global change.”
