146 THE BEAVER 
SIGN HEAPS 
A means of communication used by the beaver, perhaps 
more especially if it is traveling about the country and wishes 
to leave some indication of its presence, is what we may 
call for want of a better name, the “‘sign heap.” Seton 
calls these things mud pies. 
Sign heaps are little cakes or piles of mud near a stream or 
pond on which the castoreum is deposited. One which it 
was my good fortune to find on Lost Creek, Yellowstone 
Park, was placed in shallow water close to the shore, and 
was a little more than a foot in diameter and three inches 
thick. It had been made either the preceding night, or 
the night before that, as we had been there two days pre- 
viously. It was merely a round cake of mud, but so placed 
that it stood apart from its surroundings and was really 
quite conspicuous and easily seen. I could detect no odor 
about it. 
Morgan gives an account of something similar: ‘‘After 
selecting a suitable place upon dry ground near the pond or 
stream, they void their castoreum here and there upon the 
grass, and, in the musky atmosphere thus created, spend 
some hours at play or basking in the sun. The trappers 
call these playgrounds ‘musk bogs.’”’ 
Nuttall, in speaking of trapping beavers, says: “‘Scarcely 
anything is now employed for bait but the musk or cas- 
toreum of the animal itself. As they live in community, 
they are jealous and hostile to strangers of their own species 
and following the scent of the bait, are deceived into the 
trap” (Fig. 78). 
ENEMIES 
The arch-enemy of the beaver, as of all other wild life, 
is of course man. ‘The list of other enemies is short. Cou- 
gars, bobcats, lynxes, wolves, coyotes, bears, wolverenes, 
