Grizzlies in Yellowstone National Park were trapped 

 and immobilized. Weights and measurements were 

 taken and the bears were tagged and color-marked 

 before being released. This bear weighed 565 pounds. 

 (Photo by Frank C. Craighead.) 



the close of the rutting seasonhad anaverage 

 of 1.25 fetuses each. Older does showed 1.94 

 fetuses each. Three -fourths of Iowa's doe 

 fawns breed their first fall. 



For the past 6 years the Arizona Unit has 

 carried on a program of research to gather 

 needed information on the collared peccary. 

 These studies have included work on re- 

 production, methods of aging animals, pro- 

 ductivity, food and water requirements, 

 home range and movement studies, and an 

 analysis of age structures of wild popula- 

 tions. During 1961, four Arizona Unit publi - 

 cations on this important game animal 

 appeared. 



As a result of studies onhow to determine 

 the age of peccaries, it is now possible to 

 classify the animals into known-age cate- 

 gories up to the age of 2l| months. It 

 was found that, in 1957, 2 percent of the 

 animals were in the 2- to- 10-month age 

 class compared with 6, 4, and 3 percent, 

 respectively, in this category in 1958, 

 1959, and 1960. It is believed that the low 

 percentage in the 2-to- 1 0-month age class 

 in 1957 and the low percentage in the 



10 -to -21 1 -month age class in 1958 (9 per- 

 cent in 1958, compared with 20 and 13 

 percent, respectively, in 1959 and 1960) 

 were results of the severe drought of 

 1956. There are strong indications that 

 severe drought years have adverse ef- 

 fects on the peccary populations, and that 

 their numbers, like those of so many 

 animals, are closely related to the annual 

 rainfall. 



In studies of beaver production by the 

 Maine Unit, no. significant differences were 

 noted in current reproductive rates as 

 compared with an earlier period (1947 to 

 1950); beavers in central Maine, however, 

 produced significantly more young than 

 did those of northern Maine. Also, as 

 compared with northern beavers, Alabama 

 beavers use relatively little woody vegeta- 

 tion for food, and this use occurs primarily 

 in winter. Summer feeding is more of the 

 browsing and grazing type, with much 

 herbaceous vegetation being eaten. In sum- 

 mer, dams are abandoned to a large extent, 

 and the beavers use natural waterways and 

 manmade impoundments. 



A study of muskrats on a large marsh in 

 northern Ohio revealed a higher juvenile 

 age ratio in muskrats taken from 

 controlled water level units than in those 

 from areas not under management. Data 

 from slightly over 9,000 specimens sug- 

 gest that age ratios vary because of higher 

 juvenile survival, rather than in the in- 

 herent reproductive capacity of the two 

 populations studied. Immature muskrats 

 from the managed marsh units weighed 

 significantly more than those trapped in 

 undiked units of the marsh. The presence 

 of 21 placental scars in each of 3 repro- 

 ductive tracts showed that some of the 

 female muskrats in western Lake Erie 

 marshes produce 3 litters per breeding 

 season. Three cases of probable trans - 

 uterine migration and one case of twinning 

 were noted in the specimens examined. 

 Ovaries collected from January through 

 August contained corpora lutea. 



Adult female cottontails in southeastern 

 Ohio are known to produce fewer young 

 per litter than they do in other parts of the 

 State. An attempt is being made by Unit 

 personnel to ascertain why this is so. 



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