Two by Two

The animals went in two by two.
A couple of hippos, a pair of gnu,
Two spectacled bears from Lima, Peru
And even, it's said, a push-me-pull-you.

But, right at the back of the very long queue
Stood a herd of wild young caribou.
The bouncers looked angry, 'Hey you, Yes You'
'No stag parties allowed, so off with you, SHOO!'