Among some orcas, adult sons, but not daughters, could play a long-term investment, feeding them forever. Delayed payoff? Greater glory to my grandmother.
Females in a quirky population of killer whales off the Pacific Coast of North America allow their grown children to catch fish that mom catches. Biologists know that this is a lifelong crime that can last for decades. Daughters born, often feeding their own offspring, do not receive such.
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Decades of data analysis have now revealed what moms sacrifice in order to provide a lifetime of food for their child, researchers report on February 8. Current Biology. A mother’s annual success rate at weaning a calf drops by about half after she has a cub, says behavioral ecologist Michael Weiss of the Center for Whale Research in Friday Harbor, Wash.
For moms, “it’s big, and you’re taking on huge costs,” Weiss says. “It shows the uniqueness and intensity of this mother-in-law bond in killer whales.” For creatures that give birth to young in series, this discovery is “the first kind of direct evidence of any animal demonstrating parental life placement.”
These killer whales off the coast of Washington State and British Columbia are part of the “southern resident” population Orcinus orcaDo not migrate. More specifically in feeding years around the region’s fish, such as large chinook salmon.
When moms catch a fish, “they do this huge head jerk, and half of the fish stays in the mouth and the other half swims a trail behind them,” Weiss says. The son swimming with her can then take that other side. It is not the son approaching and plucking the fish from his mouth, he said.
The son’s company looks consensual to Weiss. Mothers and sons “spend a lot of time swimming together on the surface … just enjoying a kind of company with each other.” The whale police need to make interpretations of reading behavior, but his “insight to watch them is more about a mom failing to provide for her child.”
Weiss doesn’t think she’s going to decline in new births after giving birth to a son that doesn’t come from every opportunity for intercourse. “These bats are really social,” he said. “They are usually in large groups, and usually with at least one fornication around the mature sea.” When watching them from the drones, “we see that the social behavior in these whales often involves a lot of sex,” he says. However, all those halved fish can’t give mom enough nutrition for the demands of the whale’s pregnancy.
Mom’s grandchild, however, can make a tally for her limited reproduction as she pampers her children, cetacean records show. Children have no parents. They just deliver the right sperm address. Plus, the longer the males live, the better, says Weiss. A few years ago, genetics suggested that the two oldest males of the southern population would account for more than half of the new calves.
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Female orcas, however, were restrained. Orcas of the womb last for some 18 months. So Casanova the whale’s sister is worried for a long time to make just one not-so-small friendly wrinkle and then swim to freedom.
Bad killer whales have the ability to help future generations survive because the species is among the few non-human mammals that experience menopause (SN: 3/5/15; SN: 8/19/13). (Women may stop producing in their 30s or 40s, but may live into their 80s).
Whether the mother-in-law in other orca populations also claims and consequently serves dinner for the adult children is not an easy question to answer. Weiss wonders if the same whales elsewhere, perhaps with more abundant fish, would still bring their mothers back to give birth later.
No other human orca records can match the depth of those used by Weiss, says cetacean biologist Eva Jourdain of the University of Oslo. His research leads to killer whales around Norway, which follow seasonal movements of herring and other food bonanzas.
Jourdain does not remember skirts throwing fish, but he observes whales and herring swimming in balls of large fish. What they share. Therefore, other types of food-based frameworks may still be developed.
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