The first sign that something was wrong was that the female hamsters were really active in their cages. These were European hamsters, a species that is endangered in France and thought to be on the decline in the rest of their Eurasian range. But in a lab at the University of Strasbourg in France, the hamsters were oddly aggressive, and they didn’t give birth in their nests.
Mathilde Tissier, a conservation biologist at the University of Strasbourg, remembers seeing the newly born pups alone, spread around in the cages, while their mothers ran about. Then, the mother hamsters would take their pups and put them in the piles of corn they had stored in the cage, Tissier says, and eat their babies alive.
“I had some really bad moments,” she says. “I thought I had done something wrong.”
Tissier and her colleagues had been looking into the effect of wheat- and corn-based diets in European hamsters because the rodent’s population in France was quickly disappearing. It now numbers only about 1,000 animals, most of which live in farm fields. The hamsters, being burrowers, are important for the local ecosystem and can promote soil health. But more than that, they’re an umbrella species, Tissier notes. Protect them, and their habitat, and there will be benefits for the many other farmland species that are declining.
A typical corn field is some seven times larger than the home range for a female hamster, so the animals that live in these agricultural areas eat mostly corn — or whatever other crop is growing in that field. But not all crops provide the same level of nutrition, and Tissier and her colleagues were curious about how that might affect the hamsters. Perhaps there would be differences in litter size or pup growth, they surmised. So they began an experiment, feeding hamsters wheat or corn in the lab, with either clover or earthworms to better reflect the animals’ normal, omnivorous diets.
“We thought [the diets] would create some [nutritional] deficiencies,” Tissier says. But instead, Tissier and her colleagues saw something very different. All the female hamsters were able to successfully reproduce, but those fed corn showed abnormal behaviors before giving birth. They then gave birth outside their nests and most ate their young on the first day after birth. Only one female weaned her pups, though that didn’t have a happy ending either — the two brothers ate their female siblings, Tissier and her colleagues report January 18 in the Proceedings of the Royal Society B.
Tissier spent a year trying to figure out what was going on. Hamsters and other rodents will eat their young, but it is usually when a baby has died and the mother hamster wants to keep her nest clean. They don’t normally eat healthy babies alive. The researchers reared more hamsters in the lab, this time supplementing their maize and earthworm diet with a solution of niacin. This time, the hamsters raised their young normally, and not as a snack.
Unlike wheat, corn lacks a number of micronutrients, including niacin. In people who subsist on a diet of mostly corn, that niacin deficiency can result in a disease called pellagra. The disease emerged in the 1700s in Europe after corn became a dietary staple. People with pellagra experienced horrible rashes, diarrhea and dementia. Until the disease’s cause was identified in the mid-20th century, millions of people suffered and thousands died. (The meso-Americans who domesticated corn largely did not have this problem because they processed corn with a technique called nixtamalization, which frees bound niacin in corn and makes it available as a nutrient. The Europeans who brought corn back to their home countries didn’t bring back this process.)
The European hamsters fed corn-based diets exhibited symptoms similar to pellagra, and this is probably happening in the wild, Tissier says. She notes that officials with the French National Office for Hunting and Wildlife have seen hamsters in the wild subsisting on mostly corn and eating their pups.
Tissier and her colleagues are now working to find ways to improve diversity in agricultural systems, so that hamsters — and other creatures — can eat a more well-balanced diet. “The idea is not only to protect the hamster,” she says, “but to protect the entire biodiversity and to restore good ecosystems, even in farmland.”