Female reproductive success and calf survival in a North Sea coastal bottlenose dolphin (Tursiops truncatus) population.

Between-female variation in reproductive output provides a strong measure of individual fitness and a quantifiable measure of the health of a population which may be highly informative to management. In the present study, we examined reproductive traits in female bottlenose dolphins from the east coast of Scotland using longitudinal sightings data collected over twenty years. From a total of 102 females identified between 1997 and 2016, 74 mothers produced a collective total of 193 calves. Females gave birth from 6 to 13 years of age with a mean age of 8. Calves were produced during all study months, May to October inclusive, but showed a seasonal birth pulse corresponding to the regional peak in summer water temperatures. Approximately 83% (n = 116) of the calves of established fate were successfully raised to year 2-3. Of the known mortalities, ~45% were first-born calves. Calf survival rates were also lower in multiparous females who had previously lost calves. A mean inter-birth interval (IBI) of 3.80 years (n = 110) and mean fecundity of 0.16 was estimated for the population. Calf loss resulted in shortened IBIs, whilst longer IBIs were observed in females assumed to be approaching reproductive senescence. Maternal age and size, breeding experience, dominance, individual associations, group size and other social factors, were all concluded to influence reproductive success (RS) in this population. Some females are likely more important than others for the future viability of the population. Consequently, a better knowledge of the demographic groups containing those females showing higher reproductive success would be highly desirable for conservation efforts aimed at their protection.

Behavior of a solitary sociable female bottlenose dolphin (Tursiops truncatus) off the coast of Kent, Southeast England.

This article provides a report of the behavior of a solitary sociable dolphin studied on the southeast coast of England in 2007. This is the first study of its kind in which behavior of such a nonhuman animal was systematically studied. By the time of this study, this young female was highly interactive with people in the water. People accompanied the dolphin for 18.4% of the 100 hr of observation, and their presence changed her behavior. The study recorded 39 different behaviors; feeding and resting behaviors declined in frequency in the presence of people. In addition, the dolphin exhibited behavior possibly hazardous to people in the water, which included preventing swimmers from leaving the water. The dolphin received several wounds, at least one of which was life-threatening. This article discusses the welfare implications for such animals.