Does the combination of embryonic diapause and superfoetation occur in the stoat Mustela erminea? A reinterpretation of existing data

Superfoetation is when ovulation and fertilisation occur during pregnancy. Coupled with embryonic diapause, superfoetation presents an intriguing female reproductive advantage in terms of cryptic choice of males. Unfortunately, few studies have identified species possessing both superfoetation and embryonic diapause. We aim to reinterpret existing data on reproductive physiology in the stoat Mustela erminea and suggest it may be a previously overlooked species that possesses this combination. By increasing our knowledge of such reproductive systems, we can further our understanding of a cryptic sexually selected function and better explain the evolutionary gain and loss of embryonic diapause in mammals.     

Movements and home range of ferrets (Mustela furo) at Pukepuke Lagoon,New Zealand

Abstract

Ferrets at Pukepuke Lagoon were live-trapped during the periods November 1970 to August 1973 and January 1976 to July 1977. Although the sex ratio of the 75 trapped ferrets was equal, there was a strong bias towards male captures in the earlier period (58.4%) and towards female captures in the later period (68.7%). Habitat modification and changes in the trapping programme for the later period probably resulted in the increased abundance and capture rate of females. Between consecutive captures 58.2% of male movements exceeded 250 m, as against on1y 39.7% of female movements; the mean distance between consecutive captures was 435 m for males and 285 m for females. Mean monthly movements varied from 700 m in January to 315 m in June for males, and from 360 m in March to 150 m in September for females. Juveniles of both sexes moved similar, intermediate distances. Dispersing juveniles were trapped from January until April; males tended to appear in traps earlier in the year than females. Only 4 of 14 juvenile males setNed as residents, hut 15 of 28 juvenile females did so. Male and female home ranges overlapped extensively, but within each sex individual ranges were usually separate. Resident males maintained a well defined spacing pattern, adjusting their boundaries if a juvenile settled or a neighbouring range became vacant. In 1976 six females had overlapping ranges in an area of albundant food. Female ranges (12.4 ha) were on average smaller than male ranges (31.3 ha); home ranges of both sexes were smaller during the breeding season (August-February) than at other times.