There is startling variation in the character of penises (penes) throughout the animal kingdom.
Apart from size
variation, already noted, shapes and colouring vary enormously. Insect and reptilian penises
are often equipped
with spines, corrugations, knobs, hooks, etc., to secure the female once insertion has taken
place. If a copulating
pair of insects or snakes are forcibly separated then either the male or the female may be
irreparably damaged.
The genital organs of the male may be torn off or the female may be terribly lacerated.
Disengagement, following
coitus, often needs to be a delicate business. The spines and hooks on certain animal penises
are normal for the
species and are often useful for purposes of classification. Sometimes however the penis may
have congenital
peculiarities that render coitus difficult if not impossible. One such instance is the "Corkscrew
Penis" in bulls.
Here the penis springs into a spiral just prior to coitus, preventing access to the cow.
Veterinary experts do not
seem at all clear as to why this condition occurs.