. The Canadian field-naturalist. 388 The Canadian Field-Naturalist Vol. 97 1000. 15 30 45 Age (months) 60 Figure 5. Hypothetical survivorship curve of a cohort of 1000 juveniles at Luther Marsh. Until now, no one has ever quantified the propor- tions of a home range in water and vegetation stands and thus determined the composition of suitable Muskrat habitat. In this study, the average home range had a ratio of vegetation stands:open water areas of 1:1 and it is suggested that vegetation stands cannot be dissociated from water areas when one considers the composition of a suitable habitat. Ac
. The Canadian field-naturalist. 388 The Canadian Field-Naturalist Vol. 97 1000. 15 30 45 Age (months) 60 Figure 5. Hypothetical survivorship curve of a cohort of 1000 juveniles at Luther Marsh. Until now, no one has ever quantified the propor- tions of a home range in water and vegetation stands and thus determined the composition of suitable Muskrat habitat. In this study, the average home range had a ratio of vegetation stands:open water areas of 1:1 and it is suggested that vegetation stands cannot be dissociated from water areas when one considers the composition of a suitable habitat. According to previous studies (Sather 1958; Erickson 1963; Neal 1968), summer home ranges can be enclosed by a circle 45 to 60 m in diameter. In this study, such a circle would have overestimated home range sizes by including areas unused by Muskrats, such as vegetation stands isolated from water areas and thus inaccessible. Furthermore, in this study, late summer home ranges often consisted of disconnected areas, each occupied by some family members concen- trating their activities around the installations that they built. The minimum home range sizes determined in this study would appear to be realistic in that they measured areas intensively used by Muskrats and not areas traversed by animals in the re-establishment of their areas of daily activity. Home range expansions during the summer could be due to juveniles which were forced to leave the breeding lodge before the birth of the next litter (Errington 1961). In this study, home range expan- sions occurred in late July. At this time of the year, second litter juveniles started to investigate the imme- diate surroundings of the main dwelling and first litter juveniles re-established themselves in new homes. However, with a decrease in the water level in late summer 1979, several vegetation stands became inac- cessible. An expansion of the home ranges could have served to re-establish a balance of water to vegetation and to a
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