Dogs often enjoy rolling around on dead animals. This behavior, although gross to humans, is quite normal and can be attributed to several theories.
Dogs might roll on dead animals to mask their own scent, a behavior inherited from their wolf ancestors. This could help them sneak up on their prey more easily.
Dogs might want other dogs to smell the scent on them, showing off that they have found prey. This could also signal to their "pack" that there's prey nearby.
Dogs also leave their scent by rubbing against things, like a dead animal. This signals to other dogs that this is their property or territory.
Dogs are attracted to intense smells. They might roll on a dead animal, garbage, or poop because they are excited about the strong smell.
Leash training, fencing in your yard, and working on recall can help prevent your dog from rolling on dead animals.
Bathe your dog immediately if they roll on a dead animal. Use dog-safe shampoo and consider using baking soda as a dry shampoo in between baths to remove the smell.