Animal Stories

The first animal story concerns one Gérard de Nerval a 19th-century French poet. He had a pet lobster called Thibault, who, it is rumoured, he took on a walk in the garden of the Palais Royal in Paris. The story is probably apocryphal, and whole thing is explored in detail in the Museum of Hoaxes website.
So:
 

The lobster he’d bought for a lark

To take it for walks in the park
It was such a shame
Just not quite the same
If only he’d taught it to bark

The next two are a sort of reflection on the human condition. The first is anon as far as I can tell, the second comes from Ranjit Bolt's book referred to in the introduction.

Said an envious, erudite ermine,
"There's one thing I cannot determine;
When a dame wears my coat,
She's a person of note;
When I wear it, they label me vermine!"

Two bugs were discusing Man's Evil
Whether it was acquired or primeval
"I've no views on that head"
The wiser one said
"I'm just thankful I'm only a weevil"

Sometimes ascribed wrongly to Ogden Nash, but actually by Dixon Lannier Merritt, an American newspaper editor, poet and humourist, this limerick is great example of the form.

A wonderful bird is the pelican 
His bill will hold more than his belican
He can take in his beak
Enough food for a week
But I'm damned if I see how the helican

The last two are a) silly and b) a tongue twister. The first comes from the Brownielocks website, the second is by Ogden Nash, the great American humourist. 

Amazingly, antelope stew
Is supposed to be better for you

Than a goulash of rat
Or Hungarian cat;

But I guess that you probably gnu.

A flea and a fly in a flue
Were imprisoned, so what could they do?
Said the fly, "let us flee!"
"Let us fly!" said the flea.
So they flew through a flaw in the flue.