. The Canadian field-naturalist. 1980 Parker and Maxwell: Muskrat Population, New Brunswick I6n i 14- 0 w 01 12- e o V 10- HI 8- z Ml > 6- 4- 2-. MAY »- •- W «SI J U N I JULY AUO U t T Figure 3. Estimated birth dates for juvenile Muskrats (< 800 g) live-trapped and weighed in the summers 1976 and 1977, based upon calculated rates of daily weight gain. than several hundred metres from the site of tagging and all were within the expected cruising distance. The tagging and recovery program, however, showed that there was a distinct seasonal shift between habitat types by many Muskrats. Most
. The Canadian field-naturalist. 1980 Parker and Maxwell: Muskrat Population, New Brunswick I6n i 14- 0 w 01 12- e o V 10- HI 8- z Ml > 6- 4- 2-. MAY »- •- W «SI J U N I JULY AUO U t T Figure 3. Estimated birth dates for juvenile Muskrats (< 800 g) live-trapped and weighed in the summers 1976 and 1977, based upon calculated rates of daily weight gain. than several hundred metres from the site of tagging and all were within the expected cruising distance. The tagging and recovery program, however, showed that there was a distinct seasonal shift between habitat types by many Muskrats. Most Muskrats remained with the same habitat type, and within a relatively confined area throughout the summer and fall seasons. All recaptures (n = 162) during the summer and fall (June-October) of 1976 were from the same habitat where first captured. In 1977 when there were 141 recaptures, no emigration occurred from the natural marsh or impoundments, but 4 of 46 Muskrats tagged in the channel were subsequently captured that summer in adjacent impoundments. Only seven ear-tagged individuals were harvested in the fall of 1976; all were trapped in the channel where they had been tagged. Only 1 of 30 Muskrats tagged during the 1977 summer and reco- vered from the 1977 fall harvest, had moved out of the habitat type where it had been originally captured. Movement of Muskrats among habitat types seems to occur most readily between the fall and spring periods, probably in early spring when high water forces them from winter lodges and flooded burrows. Nine of 24 (37%) Muskrats tagged in the summer of 1976 and recovered by trappers in the spring of 1977 had moved from the habitat type where they had been tagged. This movement was distributed equally among all three habitat types, and among Muskrats of all sex and age classes (adult male, 1; adult female, 3; imma- ture male, 3; immature female, 2). Population Estimates Several methods of population estimation were used to calculate t
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