"Two methods of placement are used. In the first, either type 
of trap is placed close to the burrow entrance. In the second 
method, the double-door trap is placed in an excavated portion 
of a main runway, usually just below ground level. During in- 
clement weather, the traps should be covered with weatherproof 
material. In fair weather, they may be covered with foliage, 
bark or sod, Covering keeps the captive animal relatively 
quiet and gives the appearance of an extension of the burrow, 
Sufficient quantity of salal, sword fern, or apples should be 
placed in the traps for sustenance of captive animals, 
Baiting 
"On larger areas baiting with poison bait is more effective 
where trapping would be impractical. The best known bait is 
fresh apple cut into l-inch cubes, dusted with powdered strych- 
nine alkaloid at the rate of 1 ounce to 16 pounds of bait. Two 
or three poison baits are placed in the burrows appearing to be 
most active, Active burrows are detected by their worn appear- 
ance or by accumulations of fresh cuttings at their entrances. 
It is advisable to prebait the active burrows to about 1 week 
before baiting with poison bait, to accustom the mountain beaver 
to the bait. Other fruits, vegetables, and pelletized baits 
have been used with little success," 
TECHNIQUES - . 
Age Determination 
The pelage of the young mountain beaver is soft and gray. As the 
animal matures the pelage becomes harsher and its color changes to brown 
or red. Pfeiffer (1958) used the degree of closure of the distal epiph- 
yseal femoral suture to determine four age classes (see Reproduction). 
He found little difference comparing pelves of the sexes. The space be- 
tween the iliac crests was more narrow in first-year animals than in 
older animals. In young the union between the pubes consisted of car- 
tilage jointed with ligament. In adults the cartilage was replaced by 
bone. 
Males -- Pfeiffer (1956) found that the baculum in juvenile males 
is about 11 mm. long; in yearling males (18 months old) about 21 mn., 
and about 30 mm. in adults. The adult baculum is deeply bifurcated at 
its distal tip. 
Females -- Pfeiffer (1958) reported that juvenile, anestrous, 
and parous females taken prior to the breeding season did not show the 
dense patches of black hairs around the nipples shown by pregnant, 
lactating, and nonpregnant females with corpora lutea, 
28 
