Fleas do tend to live on just one particular type of host. There are cat fleas and dog fleas, for example, that live in the fur of these animals. Rabbits, porcupines, and beavers have their own fleas. "Human" fleas on the other hand, are shared with foxes and pigs. If they are hungry enough, most fleas will take blood from any animal. Human fleas are now rare in houses, and genuine dog fleas are not very common in Britain. Most fleas around now are cat fleas.