There is no reason that deer cannot be domesticated and toilet trained, does have been taught to nurse from a human woman:
Baby shares Mom's teats with a baby doe
Evidently, somebody has already taught wild deer to use the toilet, I saw this deer toilet seat in a store last week:
Toilet training for cats
Most folks never housebreak their cats because of leash laws, but cats can be taught to scratch at the door just like dogs.
Instead, people have cats piss indoors, in a littler box, lovely:
Cats should live outside, IMHO
I had a cat one who, at age 20, became senile and would sit in the edge of the litter box and piss all over the floor . . .
The high-top litter box for cats with senile dementia
For those who don't think that cats are gross enough already, you can teach these disgusting beasts to take a dump in your toilet bowl.
Watch this whole video and watch kitty fall into the bowl:
And they have "kits" to teach kitty to take a crap in your toilet, simply delightful.
BTW, cats use the toilet naturally, smelling the odor, and figuring it out on their own . . . .
I once had a Siamese cat starting peeing in my toilet, but she would never flush . . .
Toliet training for horses
Janet’s claim to fame is being the first person in history to successfully housebreak a horse.
Scout will defecate on command (the command is “bombs away”) but we never could teach him to use the toilet.
Scout take s whiz in a Manhattan park