Ducks do, too. Male ducks sometimes hold other male ducks under water and rape them, it’s a dominance thing.
I was fishing off the bank one night by lantern light. I heard something behind me (thought I was gonna be Shanghied!) and it was a big ol’ beaver. Just came waddling up. I thought I’d be friendly and scratch it’s back with a stick. Bad move! That sucker hissed at me and bared those big yellow teeth, then just cruised off.
I belive you are referring to Nectophrynoides.
Another weird frog is Rheobatrachus, which broods its tadpoles in its stomach, giving birth to live little froggies - from its mouth.
Some biologists theorize that bigger brains evolve in animals mostly in relation with larger and more varied diets (man included).
The koala bear used to have a diverse diet, but at some recent point in its evolutionary history, it switched to a monotonous diet of eucalyptus leaves.
So the koala bear has a tiny brain floating around in a large brainpan. Forty percent of their heads is just fluid. They are the only mammal whose brain doesn’t fit its skull.
Aren’t they marsupials?
I can confirm this from personal experience.
My brother’s GF owned a pet bat. It would indeed “purr” when stroked - its little body would vibrate, very much like a cat’s purr.
It was a lot of fun to play “toss the bat”. 
The bat appeared to enjoy this too.
They actually make very good pets. They spend most of their time sleeping, which can be an advantage.
The only problem was that bats can’t be house trained - and they would tend to crawl up under your clothes and then do their business. Blech.
Boy, that would really make me want to vomit!
Marsupials are mammals. So are monotremes.
I’m not sure about the definitions you are using, but I feel that humans might be the only animal that has sex for non-recreational reasons. All other animals have only recreational sex, that is, not for procreation. Other animals don’t “know” that offspring will occur, they are just having sex because at that moment, when thier hormones are raging, sex is pleasurable and relieving.
From the News of the Weird:
"A landmine-detection outfit in Mozambique has upgraded from explosives-sniffing dogs to giant African Hamster rats, according to a December Agence France-Presse dispatch, because the lighter, more plentiful rats have noses that are just as sensitive and don’t suffer dogs’ need for affection and constant reassurances. "
The American Bison has only one pleural cavity. (This is the cavity in the chest that contains the lungs) This makes them relatively easy for a hunter to kill. Human’s have two pleural cavities, one for each lung, and the two spaces do not communicate. If you punch a hole in one side of the chest the lung on that side will collapse but the other lung still functions fairly well. If you punch a hole in a bison’s chest both lungs will collapse and the animal can’t breathe.
Now, unfortunately, believed to be extinct.
Yes, as in “Good luck getting all the gecko poop off your window sill.”
To me, it sounds more like chirping, but perhaps you had happier geckos. 
Male lamas have a pair of sharp fang like teeth they use in fighting other males.
Mother prarie dogs regularly eat their pups when under any kind of stress.
Naked mole rats are the only eusocial mammal.
Giant 10 foot tall, half ton carnivorous birds that could bite a human in half were once the top predators in south america
Sorry.
I have personally witnessed a gecko lose its tail as I was trying to catch it to put it out of the house. It released its tail. The tail wiggled about for several minutes afterward.
Oh, and this.
From here. Can you imagine being out in the woods at twilight and suddenly a twig snaps behind you and you turn around and there’s an 80 lb nipple-eatin’ beaver walking up behind you with a rock in its paws?
(You’re going to have to take Jeff Foxworthy’s word for the nipple-eating thing.)
hippos, according to our very own Cecil, are “said to mark jungle trails by excreting a lethal mixture of urine and feces while twirling its tail like a propeller,” which “…may explain the historically sluggish market for pet hippopotamuses.” XD