Other lines from Vance Randolph, Ozark Folksongs:
The elephant a-leanin on the kangaroo
Polecat a-talkin' to the bumblebee.

The oldest version in Higginson, 1867, doesn't mention animals. It is a boat song.

Lyr. Add: ONE MORE RIVER

O, Jordan bank was a great old bank!
Dere ain't but one more river to cross.
We have some valiant soldier here.
Dere ain't etc.
O, Jordan stream will never run dry,
Dere ain't etc.
*Dere's a hill on my leff, and he catch on my right,
Dere ain't but one more river to cross.

"Dat mean, if you go on de leff, go to (de)'struction, and if you go on the right, go to God, for sure." T. W. Higginson, Atlantic Monthly, June, 1867, song X. From http://xroads.virginia.edu/~HYPER/TWH/Higg.html.
Negro Spirituals