Love the premise. Being able to fight/possess new animals with new attack patterns I think would be a logical next step.
I found that the dead bodies having collision made it really hard to move, especially when big waves of squirrels were attacking. I think making bodies fall behind alive entities would make the game much easier to play.
There was no cooldown on attacking, so I found that if I mashed fast enough, I could instantly kill enemies. Maybe add a cooldown to attacking? Especially if there are more animals with more abilities.
Overall, the concept of keeping dead bodies around to repossess was super fun. Great job! Would love to see this expanded!