Natural Instincts and Traits

Although most of the characters are anthropomorphic, they still have some natural instincts or traits of their real animal counterparts.

Lumpy

 * In Out on a Limb Lumpy mooed like an real moose when he was in pain (debatable, it could have been a muffled scream due to the object in his mouth).
 * In Snow What? That's What!, Lumpy lays on a hammock shirtless in the winter. As he was not shivering, Lumpy may have a thick layer of fur, which real moose have for protection against the cold. This could actually be proof of Lumpy embracing his immunity to the cold or simply cooling off. However, in Snow Place to Go, he is briefly seen shivering along with everyone else.
 * Lumpy is so far the only character who has been shown to be unable to climb a tree (though it's likely Mime and Lammy can't either). This is evidence in All Flocked Up in that he had to come up with more creative ways to get the bird into the tree while most other characters could have just climbed up like Flaky in Take a Hike or Mole at the end of the episode. This makes sense because real life moose can't climb trees at all. However, like most things in the show, this is inconsistent as he was able to climb a tree in Doggone It.

Sniffles

 * Probably the most well-known instinct seen on the show is that Sniffles tries to eat ants. He even uses his incredibly long tongue in order to do so, which real anteaters have for this purpose.
 * Like real anteaters, Sniffles has poor eyesight, but wears glasses to improve his vision problems.

Splendid

 * In Helping Helps he was seen harvesting acorns.

The Mole

 * Like most moles, he lives underground.
 * He is blind, the same way most moles are blind or prone to brightness.

Nutty

 * Several times he can be heard making squeaky "chittery" sounds which sound very similar to a real squirrel's chitters (though he makes a lot of strange sounds when he is on a sugar high).
 * Being a squirrel, he is able to easily to climb trees in Take a Hike even after stuffing himself with honey.

Lifty & Shifty

 * Like many raccoons, they were rummaging in a trash dumpster as seen in As You Wish.
 * Raccoons are well known for being sneaky and stealing things.

Russell

 * He eats and enjoys seafood.
 * He can swim and hold his breath for an extensive amount of time (though in Sea What I Found he was supplied with oxygen, but it may have been because he was underwater for a very long time).
 * As shown in Whose Line Is It Anyway?, he cracks open shells with his chest much like actual sea otters.

Cuddles

 * His ears flop down when he is sad.
 * In his smoochie, Hear Today, Gone Tomorrow, and A Bit of a Pickle, he seems to like carrots.

Flaky

 * She has the ability to climb trees (which is a real ability of porcupines) in Take a Hike.
 * Just like other porcupines, she uses her quills when frightened.

Lammy

 * When she talks, screams, or laughs, she bleats like a real sheep.

Flippy

 * He is shown to follow an omnivorous/carnivorous diet like real bears. He is seen drinking/eating the bloody remains of Cuddles (Flippin' Burgers), Mime (Party Animal), Shifty (Easy For You to Sleigh), and Lumpy (Remains to be Seen).
 * In Operation: Tiger Bomb, he makes growling and roaring sounds when attacking the Tiger General.
 * Most real-life bears are usually rather gentle creatures (except to their prey obviously) but are known to become extremely violent when provoked, traits which Flippy is famous for.

The Ants
Moreso than other characters, they seem to be anthropomorphic crossed with non-anthropomorphic animals (though Sniffles probably wouldn't try to eat them otherwise). Some examples include:
 * They are seen collecting fruit, crumbs, etc.
 * They live in an anthill.
 * They only let family members/certain ants enter their home.
 * They are in one episode seen milking a spider, which some ants really do.

Buddhist Monkey

 * Many times he makes monkey sounds, most notably right before he begins a fight.
 * Like other monkeys, he is very strong, flexible, and athletic.

Char Sui

 * He made snorting sounds a couple of times.
 * He squealed when he was about to die.

Sneaky

 * He can change color and camouflage his body (although this could be with the help of technology, as he becomes entirely invisible, or it may simply be a cartoonish effect.) However, the camouflaging ability in real chameleons is just a coincidence, they normally change color due to their mood (among other things).
 * He can climb on/stick to walls.

Petunia

 * In the episode Blind Date, she sprays at Disco Bear when he gets too close, just like real skunks do for defensive purposes (debatable, as it could have been pepper spray).