Eat their young when they are in a confined space that appears to not support the population.

In a sense, we make them eat their young by putting them in cages and breeding them.

But it is behavior learned in the wild - keep alive only the babies you can actually support, or else everyone dies.

I used to work in a pet store.

There were two white with black spot "teddy bear" hamsters that had "wet tail"(diarrhea) and they were being kept in the back together while they were given antibiotics to get them well so they could be sold. They had it when they came in, unfortunately very common for factory farm raised hamsters.

After a day or two of them being there I came in to open for the day and give them their meds. I flipped over the plastic igloo they were nesting in and there was only one there. I closed the store the previous night and had given them their meds, I knew there was two in there 12 hours prior. I was standing there looking at the 5 gallon aquarium they were in and was trying to think through the early morning brain fog as a bloody hamster face poked out from under the singular fur ball.

I then understood that the one hamster has eaten the other and hollowed it out to make a cow pattern meat igloo out of its sickly cage mate. Hamsters may be cute, but they will upcycle a friend into eco-friendly housing and a midnight snack. They are adorable monsters and we pretend they aren't and give them to kids in brightly colored habitats, as if they are different than Gacy in a clown costume.

Eat their own kids