Fruit seems to make up an important part of the wolves’ diet — much more important than previously thought.

Wolves (Canis lupus) can eat a lot of things. They are, of course, hunters — but their chances of catching prey are much higher when they’re a group. They’re also scavengers, not being particularly picky about food. They also complement their diet with fruits and berries. For centuries, scientists have made notes of this, and many farmers can attest that wolves will sometimes come to their fields.

This was thought to be only a complement in their diet — a way to compensate for poor hunting, accounting for a small amount of their caloric intake. That may not be the case.

In 2017, biologist Austin Homkes of Northern Michigan University in Marquette noticed some unusual behavior. He was following the GPS signal from previously installed wolf collars. It seemed like a gathering where several wolves met up — indicative of a hunt, he thought.

It’s common for wolves to hunt something and then bring the pups to the carcass to feed. But this wasn’t the case. It was, indeed, a rendezvous site. Homkes watched from a distance, observing as pups gathered around an adult wolf. They started licking its mouth, which stimulates adults to throw up. Then, Homkes thought, it must be still some meat the adult wolf had previously consumed.

But this wasn’t the case here. Homkes watched in shock as the wolf regurgitated piles of partially chewed blueberries, which the pups munched on.

Premastication (the act of pre-chewing food for the purpose of feeding it to babies) is not uncommon. Humans still do it sometimes, though we don’t consume and regurgitate the food. Several species of animals are known to do it as well, either with or without the regurgitation — that’s not the surprise. The surprise is that the wolves would go to such lengths to provide berries to their pups, even when hunting is not unsuccessful.

“It’s a pretty big part of wolf ecology that was right under our noses that we didn’t see,” Homkes says.

This also raises some interesting questions: how much nutritional value do berries carry for wolves, which are thought to be primarily carnivorous? Homkes is also curious to know what happens when blueberries are not available to a pack that relies on them.

But this is not just a biological curiosity, it could be important in conservation.

“Given the dearth of information on the role of berries in wolf ecology, we think considerable research is needed to understand the importance of wild berries to wolves. Such research could, for example, illuminate how forestry practices that dramatically increase berry abundance might affect wolf pup survival,” the study reads.

The study has been published in Wildlife Society Bulletin.