The Descent of Man

tes; and Brehm states that after a troop of the
Cercopithecus griseo-viridis has rushed
through a thorny brake, each monkey stretches
itself on a branch, and another monkey sitting
by, "conscientiously" examines its fur, and extracts
every thorn or burr.
Animals also render more important services to
one another: thus wolves and some other beasts
of prey hunt in packs, and aid one another in
attacking their victims. Pelicans fish in concert.
The Hamadryas baboons turn over stones to
find insects, etc.; and when they come to a large
one, as many as can stand round, turn it over
together and share the booty. Social animals
mutually defend each other. Bull bisons in N.
America, when there is danger, drive the cows
and calves into the middle of the herd, whilst
they defend the outside. I shall also in a future
chapter give an account of two young wild
bulls at Chillingham attacking an old one in
concert, and of two stallions together trying to