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Female reproductive output in a Mediterranean bottlenose dolphin (Tursiops truncatus) population

Monica Francesca Blasi,†*, Chiara Bruno,†, Luigi Boitani

*Corresponding author:

ABSTRACT: The reproductive output of wild bottlenose dolphins (Tursiops truncatus) has been largely investigated, nevertheless it remains widely unexplored in the Mediterranean Sea. This study investigated the reproductive history of female bottlenose dolphins in the Aeolian Archipelago (Italy). Thirteen years of photo-identification data were used to track the reproductive pattern of 7 females and their 16 calves. The birth period was accurately estimated within one month for 6 calves (37.5%), peaking in June/July. The mean number of calves for females was 2.3 ± 1.1 (SD), ranging from 1 to 4. The mean interbirth interval was 3.5 ± 1.6 (SD) years, ranging from 2 to 7 years. The mean weaning age was 3.2 ± 0.6 (SD) years, although one calf might have been weaned by its fifth birthday. Mother-calf postweaning associations were tracked for 9 calves ranging from 4 to 10 years of permanence in the mother group of the calf. The age of first pregnancy was 7.5 years. The number of calves was influenced by the mean group size of the mother, with more calves for females sighted in larger groups. However, the number of calves was not influenced by the strength of the association of mothers with other females. Calf mortality by age one was high (12.5%). Two juveniles also died postweaning within 6 years from their birth. Finally, 2 females may have died since they were not re-sighted at the end of the study. Our results highlight the need to implement urgent conservation actions to protect this bottlenose dolphin population.