People who eat a diet dominated by corn can develop a deadly disease: pellagra. Now something similar has emerged in rodents. Wild European hamsters raised in the lab on a diet rich in corn showed odd behaviors. These included eating their babies! Such behaviors did not show up in hamsters that ate mostly wheat.
Pellagra (Peh-LAG-rah) is caused by a shortage of niacin (NY-uh-sin), which is also known as vitamin B3. The disease has four major symptoms: diarrhea, skin rashes, dementia — a type of mental illness characterized by forgetfulness — and death. Mathilde Tissier and her team at the University of Strasbourg in France never expected to see something similar among rodents in their lab.
As a conservation biologist, Tissier studies species that may face some risk of going extinct and how they might be saved. Her team had been working in the lab with European hamsters. This species was once common in France but has been quickly disappearing. There are now only about 1,000 of the animals left in the whole country. These hamsters also may be on the decline throughout the rest of their range in Europe and Asia.
These animals play an important role in local ecosystems by burrowing. That turning over of the soil as they excavate tunnels can promote soil health. But more than that, these hamsters are an umbrella species, Tissier notes. That means that safeguarding them and their habitat should give benefits to many other farmland species that may also be declining.
Most European hamsters still found in France live around corn and wheat fields. A typical corn field is some seven times larger than the home range for a female hamster. That means the animals that live on a farm will eat mostly corn — or whatever other crop is growing in its field. But not all crops provide the same level of nutrition. Tissier and her colleagues were curious about how that might affect the animals. Perhaps, they guessed, the number of pups in a litter size or how quickly a pup grew might differ if their moms ate different farm crops.
So Strasbourg and her colleagues launched an experiment. They fed lab-reared hamsters wheat or corn. The researchers also supplemented these grains with with either clover or earthworms. That helped the lab diet better match the animals’ normal, omnivorous diets.
“We thought [the diets] would create some [nutritional] deficiencies,” Tissier says. But instead, her team witnessed something quite different. The first sign of this was that some of the female hamsters were really active in their cages. They also were oddly aggressive and didn’t give birth in their nests.
Tissier remembers seeing newly born pups alone, spread across their moms' cages. Meanwhile, the mothers ran about. Then, Tissier recalls, some hamster moms picked up their pups and placed them in piles of corn they had stored in the cage. Next was the really disturbing part: These moms proceeded to eat their babies alive.
“I had some really bad moments,” Tissier says. “I thought I had done something wrong.”
All female hamsters had reproduced fine. Those fed corn, though, behaved abnormally before giving birth. They also gave birth outside of their nests and most of them ate their young the day after they were born. Only one female weaned her pups. But that didn’t end well either: The two male pups ate their female siblings.
Tissier and her colleagues reported these findings January 18 in the Proceedings of the Royal Society B.
Confirming what went wrong
Hamsters and other rodents are known to eat their young. But only occasionally. This tends to happen only when a baby has died and the mother hamster wants to keep her nest clean, Tissier explains. Rodents do not normally eat live, healthy babies. Tissier spent a year trying to figure out what was going on with her lab animals.
To do this, she and the other researchers reared more hamsters. Again, they fed the rodents corn and earthworms. But this time they supplemented the corn-rich diet with a solution of niacin. And that seemed to do the trick. These moms raised their pups 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 cause pellagra. The disease first emerged in the 1700s in Europe. That was when corn first became a dietary staple there. People with pellagra developed horrible rashes, diarrhea and dementia. Vitamin deficiency was identified as its cause only in the mid-20th century. Until then, millions of people suffered and thousands died.
(The meso-Americans who domesticated corn usually did not suffer from this problem. That’s because they processed corn with a technique called nixtamalization (NIX-tuh-MAL-ih-zay-shun). It frees up the niacin that is bound in corn, making it available to the body. The Europeans who brought corn back to their home countries didn’t bring back this process.)
The European hamsters fed a corn-rich diet showed symptoms similar to pellagra, Tissier says. And that might also be happening in the wild. Tissier 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 now are working to how to improve diversity in farming. They want hamsters — and other wild creatures — to 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.”
aggressive (n. aggressiveness) Quick to fight or argue, or forceful in making efforts to succeed or win.
behavior The way a person or other organism acts towards others, or conducts itself.
biodiversity (short for biological diversity) The number and variety of species found within a localized geographic region.
colleague Someone who works with another; a co-worker or team member.
conservation The act of preserving or protecting something. The focus of this work can range from art objects to endangered species and other aspects of the natural environment.
conservation biologist A scientist who investigates ways to help preserve ecosystems — and especially species that are in danger of extinction.
dementia A type of mental disorder caused by disease or injury that causes people to gradually lose all or part of their memory. It may start out temporary and build to a permanent condition where the ability to reason also is impaired.
diet The foods and liquids ingested by an animal to provide the nutrition it needs to grow and maintain health.
diversity (in biology) A range of different life forms.
domestication (v. domesticate) The process of turning a wild plant or animal species into a tame version, which can take many generations. A domesticated animal is one that has been bred in captivity for food or as a pet. A domesticated plant is one usually farmed or used for landscaping.
earthworm A type of worm that lives in the soil. As it moves through soil, an earthworm creates burrows. These allow air and water to move more readily through the soil. The worms feed on decaying organic matter, which helps improve soil fertility.
ecosystem A group of interacting living organisms — including microorganisms, plants and animals — and their physical environment within a particular climate. Examples include tropical reefs, rainforests, alpine meadows and polar tundra.
endangered An adjective used to describe species at risk of going extinct.
extinction The permanent loss of a species, family or larger group of organisms.
habitat The area or natural environment in which an animal or plant normally lives, such as a desert, coral reef or freshwater lake. A habitat can be home to thousands of different species.
Meso-America A region that spans from central Mexico through Belize and Guatemala into El Salvador, Honduras and Nicaragua. The term is usually applied to the Native cultures that emerged in this region prior to its colonization by the Spanish.
niacin A micronutrient also known as vitamin B3. In humans, a niacin deficiency can cause a potentially fatal disease known as pellagra.
nixtamalization A process for treating corn or other grains with an alkaline solution — often containing ash or lye. The process makes the grain easier to grind. It also can free up nutrients and improve flavor.
nutrient A vitamin, mineral, fat, carbohydrate or protein that a plant, animal or other organism requires as part of its food in order to survive.
nutrition (adj. nutritional) The healthful components (nutrients) in the diet — such as proteins, fats, vitamins and minerals — that the body uses to grow and to fuel its processes.
omnivorous An adjective for animals whose diets include foods from both plants and animals.
pellagra A disease caused by a lack of niacin (vitamin B3) or its precursor (tryptophan) in the diet. People with this disease may experience diarrhea, mental problems, skin problems or even death.
population (in biology) A group of individuals from the same species that lives in the same area.
pup A term given to the young of many animals, from dogs and mice to seals.
range The full extent or distribution of something. For instance, a plant or animal’s range is the area over which it naturally exists.
rodent A mammal of the order Rodentia, a group that includes mice, rats, squirrels, guinea pigs, hamsters and porcupines.
sibling An offspring that shares the same parents (with its brother or sister).
solution A liquid in which one chemical has been dissolved into another.
species A group of similar organisms capable of producing offspring that can survive and reproduce.
staple (in nutrition) A food that serves as a dominant source of calories for a community or species. In people, for instance, just three plants — rice, corn (maize) and wheat — account for roughly 60 percent of calories eaten (according to the United Nations Food and Agricultural Organization). That makes these staples.
symptom A physical or mental indicator generally regarded to be characteristic of a disease. Sometimes a single symptom — especially a general one, such as fever or pain — can be a sign of any of many different types of injury or disease.
umbrella species A species used for making decisions about conservation. If one of these species is to be protected, its habitat will need protection. Such protection will have benefits for many other species within its community, or ecosystem.
vitamin Any of a group of chemicals that are essential for normal growth and nutrition and are required in small quantities in the diet because they either cannot be made by the body or cannot easily be made by the body in sufficient quantities.
wean (adj. and v. weaning) The process in young mammals of transitioning from a diet of mother’s milk to other foods.
Journal: M.L. Tissier et al. Diets derived from maize monoculture cause maternal infanticides in the endangered European hamster due to a vitamin B3 deficiency. Proceedings of the Royal Society B. Published online January 18, 2017. doi: 10.1098/rspb.2016.2168.
Journal: J. Hegyi, R.A. Schwartz and V. Hegyi. Pellagra: dermatitis, dementia, and diarrhea. International Journal of Dermatology. Vol. 43, January 2004, p. 1.