Jake: *shrugs* B-because I-I'm a d-deer a-and a r-rabbit? Me: Jake you can talk properly- OoO

Jake: I dunno, ask Oli- Me: Because fox/wolf hybrids are overrated.

Scientists wanted to see what would happen if they combined two totally different species, rather than two of the same family. Jake was born from a deer, hence why he has a deer like body, who was injected with rabbit DNA. After he was born, he wasn't breathing. So, they deemed it a failure, and tossed it out. Well, the impact was enough to lodge some mucus out of this throat, allowing him to breath, and once he could walk, he ran.