4 BULLETIN 1078, U. S. DEPARTMENT OF AGRICULTURE. 



GENERAL PHYSICAL CHARACTERISTICS. 



Beavers are compact, heavy-bodied, strongly framed animals (PI. 

 II, Fig. 1) with powerfully developed bones and muscular systems, 

 broadly flattened naked tails, and dense coats of fine, soft, water- 

 proof unci erf ur, hidden by coarse outer or guard hairs, generally of 

 some shade of dull or rusty brown. The hind feet are large and 

 the five long toes fully webbed for swimming, the two inner toes 

 on each foot being provided with unique and remarkable combing 

 claws; the front feet are small and unwebbed, and are used mainly 

 as hands. The eyes are small, with very limited range of vision ; the 

 ears are short, fur lined, valvular (closing under water), and very 

 keen of hearing ; the nostrils are small and valvular, with large and 

 complex nasal cavities lying back of the openings, and have an un- 

 usually keen sense of smell. The mouth also is valvular, with hairy 

 lips closing perpendicularly back of the long protruding, chisellike 

 incisors, so that the water does not enter the mouth when the incisors 

 are used in cutting or tearing up roots or sticks under water. The 

 genital organs also are well protected from the water, being con- 

 cealed under the skin and opening into the general anal cloaca, so 

 that the sexes are not easily determined by external examination, 

 except in adult females, which have four conspicuous teats, two on 

 each mammary gland. A pair each of large musk and oil glands 

 lie under the skin of the belly just in front of the anal opening. 

 The stomach and intestines are very large to accommodate the large 

 quantity of coarse food consumed. 



MEASUREMENTS AND WEIGHT. 



A fair-sized, probably 3-year-old, female beaver, caught near Ash- 

 land, Wis., measured in total length 42.5 inches (1,080 millimeters), 

 naked portion of the tail 11 inches (280 millimeters), the hind foot 7 

 inches (180 millimeters), and the length of the ear 1J inches (34 mil- 

 limeters). The weight was 50 pounds. Two young about 2 weeks 

 old weighed 1J and 2 pounds, respectively; yearling beavers weigh 

 apparently 25 to 30 pounds; two-year-olds about 40 or 45 pounds; 

 and three-year-olds probably 50 pounds. Old and large beavers 

 reach a weight of 60 to TO pounds, and there are records of old and 

 very fat beavers weighing from 100 to 110 pounds. 



INTELLIGENCE. 



Beavers are widely famed woodcutters and builders, and while 

 not endowed with the degree of human intelligence often ascribed to 

 them, they are wonderfully expert along their own lines and quick 

 to learn and apply new methods or to take warning from new 



