A dog caring for her litter of puppies may look like the ultimate altruist—especially if she’s malnourished and living on the streets of India. But beneath her heart-of-gold image lurks a dark side, scientists say, one that comes out instantly if someone offers her a bit of meat. Growling and snarling, she’ll snatch the meat from her pups and devour it alone, researchers report today. The findings, the team says, bolster the idea that the ancestors of dogs first joined humans as scavengers, not as puppies stolen from a wolf’s den.
“We didn’t expect to see this kind of behavior from a mother,” says Manabi Paul, a behavioral ecologist at the Indian Institute of 24小时娱乐在线 Education and Research (IISER) in Kolkata, India, and the lead author of the study. “Sometimes, a mother fought and bit her own pups to keep the meat for herself. She was telling them, ‘No, I will not give you any!’”
Paul and her colleagues discovered the behavior while studying parental care in free-ranging dogs—that is, domesticated dogs that live on the streets. Such canines are common in India, where they’ve been part of city and village life since at least 2000 B.C.E., says study co-author Anindita Bhadra, a behavioral ecologist also at IISER.
Despite the dogs’ long history with humans, scientists know very little about them. They are unsupervised by people, but they are still dependent on us for food—either through hand-outs or trash. “They do not see humans as part of their pack, but as a resource,” Bhadra says.
?The mothers are known for their parental care. Paul notes that juvenile puppies often stay with their moms even after they’re weaned, at about 7 weeks of age. But as the scientists observed the dogs, they spotted signs of classic parent-offspring conflicts: The mothers sometimes refused to suckle their pups or would fight with them over food. Behavioral ecologists say that such conflicts arise because although the mother wants her pups to survive, she also needs to restore her health so she can have another litter—thus maximizing her reproductive success.
To find out whether human-provided food led to more mother-pup conflicts, Paul and her colleagues devised two experiments, each spanning the 5 weeks after most pups are done weaning. In one, twice a day over three consecutive days, Paul tossed biscuits to dogs in 15 different litters with one to seven puppies each. In the second experiment, she threw pieces of raw chicken to another 16 litters, again doing this twice a day for 3 days in a row for 6 weeks.
Street dogs in India
From Paul’s videos of these feedings, the scientists calculated the amount of sharing and conflict within each litter, and quantified each mother’s level of conflict for each week. They found that in every litter, the mothers rarely let any pup have a scrap of meat. In the first week, when giving the litters biscuits, the mothers’ level of conflict was only 25% on the scientists’ scale. But the mothers’ conflict level over meat started at 80%, the scientists report. Some mothers were “so needy for meat, they would jump over their pups to grab each piece, and wouldn’t share a bit,” Paul says. But as the puppies matured, their mothers’ generous behavior with the biscuits also declined, the team reports online today in Royal Society Open 24小时娱乐在线. When mother dogs no longer share any food with their pups, the youngsters are considered fully weaned and are on their own.
The mothers’ desperate play for the meat stems from their nutritional needs, the scientists say. Although dogs, unlike wolves, can digest carbohydrates, they still need protein. Lactating mothers and pups require a diet comprised of at least 28% protein.
It’s that need for protein that may have led the ancestors of today’s dogs to separate from their packs and attach themselves to humans, Bhadra says. “Instead of leading to more cooperation among the ancestral wolf groups, the rich resources of human hunters may have induced them to split apart,” she says, a division that in time produced the dog. There was, thus, no need for people to take wolf puppies from their dens to domesticate; the canids joined people on their own, the authors speculate.
Such a scenario is plausible, says ádám Miklósi, a behavioral ethologist at E?tv?s Loránd University in Budapest. But he points out that when this “decline of cooperative tendencies” in dogs took place “is still an open question.”
Miklósi and others nevertheless say the study sheds light on the little known lives of free-ranging dogs, especially their maternal behavior. “That behavior has not been studied in detail,” he says, “and it may be the key to understanding these dogs’ success.”
“This study reminds us that dogs don’t live in a Disney-like fantasy world of doting moms and offspring,” adds Julie Hecht, an applied ethologist at City University of New York in New York City. “The conflict between mother dogs and their pups is real and complex.”
This conflict may not be limited to street dogs, points out Monique Udell, a behavioral ecologist at Oregon State University, Corvallis. “It may be no coincidence that puppies are adopted into new homes at around 8 weeks of age,” she notes—the same age that the free-ranging mother dogs in India will bite their own offspring to grab a bit of meat.