On the reproduction biology of otters (Lutra lutra) from Denmark

The reproduction in Danish otters was inferred from examination of reproduc tive organs from 242 carcasses collected between 1982 and 1996. Estimated m onths of birth of collected cubs and evidence of breeding, determined in fe male reproductive organs, showed distinct seasonal patterns. 82 % of the cu bs were born during summer and autumn months from June to November, althoug h litters were born throughout the year. Mean litter size at birth was 1.7 +/- 0.9 cubs per litter. Adult male otters showed continuous mating prepare dness. No seasonal variation in paired testes weight for adult males was de termined and males with high density of spermatozoa in testes smears occurr ed throughout the year. Adult males with spermatozoa present had a signific antly higher body condition index compared to males without spermatozoa. As the imminent factor determining the breeding chronology, fish densities pe aked in autumn, coinciding with maximum energetic demands on reproductive a ctive females during the lactation period.