Shakespeare's "two backed beast"?

Two beasts back to back are not likely to bear any new beasts, wwh, unless the beast is a lion.

Lions are retromingent so I assume they couple in reverse ... which could be an advantage to a lion keeping his eye out for other game.

For a lion, a bird in hand may not be worth two in the bush.

He is, after all, "the King of the Beasts".