What are they?
Thanks,
BP
Ugly Duckling
Uctopus
Unicorn
I’ll just be beating you scumbags to “urangutan”.
Any, like, REAL ones?
BP
44 posts notwithstanding, with your longevity on the board, you should have seen that coming a mile away 
I submit Urial: an upland wild sheep (Ovis vignei) of southern and central Asia which is reddish brown and the males of which have a beard from the neck to the chest (definiton from m-w.com)
Urchin
Ungulate (yeah, I know, that’s not one species, but among the responses so far, it’s better than the average!)
From the Encyclopedia Britannica:
The uakari is a South American monkey; the unau is also known as the two-toed sloth; urchin is a general name for several marine invertebrates, of which sea urchins are best known, but there are also cake urchins and heart urchins. And there’s the unique-headed bug; “as indicated by its common name, has an unusual elongated head that is constricted behind the eyes and also at the base”. (Most of these names, like many common names of animals, refer to multiple species; just as there are several species of zebra, so there are a couple of species of unau.)
And of course if you get a few drinks into Ukulele Ike…
I heard that there were only three animals that end with “gry” 
Wasn’t there a dog named Ubu?
“Sit. Ubu, sit.”
From the IUCN’s website, 57 species who have at least one common name beginning with U. Some are kind of questionable. I’m not sure if I’d count unistriped or Utah, but I dunno.
-Lil
Zyada and I ran into this question as we were driving to the Ribfest last weekend. We somehow got started on the word-chain game* (last letter of this word is the first letter of the next) and ended up stuck on ‘U’. I’m glad somebody else has the same problem.
- Yes, we are geeks. Does it show?
Uil = owl, in Dutch. 
Can we at least agree that they are Uncommon?
There’s the uintathere - but it’s extinct, sorry.
Then there’s the umber moth.
Plus, if there was a really hungry bear, it would probably start with “U” before moving on to me.