Aspects of Reproduction of the
Fisher, Martes pennanti, in Manitoba

Richard D. Leonard

Department of Zoology, University of Manitoba, Winnipeg, Manitoba R3T 2N2

Present address: Parks Canada, Prairie Region, Confederation Building, 4th Floor, 457 Main Street, Winnipeg, Manitoba R3B 3E8

 

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Leonard, Richard D. 1986. Aspects of reproduction of the Fisher, Martes pennanti, in Manitoba. Canadian Field Naturalist 100(1): 32-44.

 

Abstract

During March and April, 1976 and 1977, aspects of reproduction of Fishers (Martes pennanti) were studied in the field by use of radio-telemetry, tracking, and track observations. Information on male and female reproduction was gathered from analysis of 195 trapper-caught Fisher carcasses collected from four areas of Manitoba during the winters of 1972-73 to 1977-78. Presence of pregnant females in the yearling age class, increased tract volume and follicular development of late-winter juveniles, and observation of-a tract of a recently-bred juvenile female indicated that first estrus of females occurred at the end of the first year of age. Winter maturation of testes followed a similar pattern for juveniles and adults. All males tested in March were spermatic, but none was spermatic earlier in winter. Weights of bacula from juveniles increased during winter and by March approached the range of bacula weights of adults. Estrus and parturition occurred in late March and April. Uniform development of early-winter juveniles suggested that a restricted whelping period and possibly a restricted mating period occurred for all ages of reproducing females. The mean and mode corpora lutea counts for pregnant females were 3.5 and 3, respectively. Age-related fertility rates appeared to exist. Indices of fertility and productivity remained relatively constant from 1972 to 1978, suggesting that no significant time-specific changes in reproduction occurred. Reproductive characteristics of Fishers from Manitoba differed little from those reported from other regions within the species' geographic range. Observations of maternal behavior and physical characteristics of captive-born and wild-born kits are presented. Radio-telemetry and tracking evidence during the mating period suggested that adult females in or approaching estrus remained sedentary. Males moved extensively to seek out females in estrus and intrasexual spacing mechanisms among males appeared to break down. No male-male physical interactions were observed in the field, but the presence of minor skull injuries in breeding-age males implied that some form of interaction could occur. All available evidence supports the presence of a promiscuous breeding system in Fishers.

Key Words: Fisher, Martes pennanti, reproduction, breeding systems, Manitoba.

 


 

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