Mathilde Tissier, evolutionary biologist at the University of Strasbourg, did not to set out to create cannibal hamsters. As Marlowe Hood at the Associated France Presse reports, Tissier's research was simply focused on determining the impacts of diet on the common hamster, Cricetus cricetus.
The species is disappearing quickly in western Europe, though populations seem stable in the eastern side of the continent. So scientists have been digging into the causes. Based on a study in the lab, Tissier thinks that the problem could be diet. When the animals eat primarily corn, they turn into cannibals. She and her team published their results in the journal Proceedings of the Royal Society B.
Tissier and her team fed groups of wild hamsters four different diets: wheat plus a clover supplement, wheat plus an earthworm supplement, corn with a clover supplement and clover with an earthworm supplement. The nutritional content of the diet seemed similar and the hamsters gave birth to similar numbers of pups. But while the wheat-fed hamsters succesfully weaned around 80 percent of their pups, the corn-fed animals weaned only five percent of their progeny.
Instead, they were eating their babies.
The mothers on the corn-based diets did not seem to develop maternal behaviors. "[T]hey did not gave birth in the nest (pups were spread out in the cage) and then placed their pups on top of their hoard of maize grains before eating them," the researchers wrote in the paper.
But that was not the only concerning behavior. The hamsters also ran in circles, pounded on their feeders and showed other signs of dementia. Their tongues also swelled up and turned black. All of these signs point to a deficiency in vitamin B3 and tryptophan (a B3 precursor), the researchers write.
In humans, such a deficiency causes the disease known as pellagra, which was a problem in the American South in the early 20th century due to crop failures and poor nutrition. As Mark Essig at Atlas Obscura reports, corn meal (often in the form of cornbread) was the main dietary staple in the region. Many claimed Midwestern farmers were sending them tainted or spoiled corn. But once researchers discovered the B3 connection and regulations required the vitamin B3, also known as niacin, be added to corn meal, the pellagra outbreaks stopped.
When Tissier and her team gave corn-fed hamsters a B3 supplement along with the corn diet, their symptoms went away. There is no evidence that the hamsters are cannibalizing their children in the wild. But Chloe Farand at The Independent reports more and more cropland, the primary habitat for the hamster in France, is being turned into corn monoculture, and researchers have found many of the hamsters feed exclusively on corn.
“There’s clearly an imbalance,” Gerard Baumgart, president of the Research Centre for Environmental Protection in Alsace and hamster expert, tells Hood. “Our hamster habitat is collapsing.”
In fact, Rhett Jones at Gizmodo reports that France has already come under fire for its disappearing hamsters. In 2011 the high court of the European Union ruled that the country must change its policies to protect the rodent or face large fines.
The solution, Baumgart and the researchers suggest, is breaking up some of the monoculture. “Knowing that these species already face many threats, and that most of them are in danger of extinction, it is urgent to restore a diverse range of plants in agriculture schemes,” Tissier and her colleagues write in their paper.