Born Free Foundation - Keep Wildlife in the Wild

Moray Firth Bottlenose Dolphins

© Gael Holiday Homes
©Gael Holiday Homes

New Insights into the ‘Super Mum’ Dolphins of Scotland

The Moray Firth in northeast Scotland is home to the most northerly resident population of bottlenose dolphins in the world, and one of just three resident groups in the U.K*.

Comprised of just 200 individuals, this fragile population is under threat by oil and gas exploration, marina developments, chemical pollution, accidental entanglement in fishing nets, collision with boats, and other human activities.

Effective conservation of these highly intelligent animals requires an in-depth understanding of their ecology, population dynamics, and behaviour. Although large and charismatic, surprisingly little is known about dolphins and other cetaceans. Collecting data on the intricacies of their daily lives is difficult, as they have expansive home ranges and spend their lives underwater, frequently far out to sea and in remote locations.

The Cetacean Research and Rescue Unit (CRRU), a small non-profit focused on the welfare, conservation, and protection of cetaceans, has been studying Scotland’s dolphins since 1997. With the support of Born Free, the CRRU team undertook a long-term study on the reproductive success of individual bottlenose dolphins in the Moray Firth. Such data is important for the conservation of this unique northerly population, as it helps researchers understand individual fitness levels, overall population health, and the factors affecting variation in reproductive success between individuals. However, robust assessments can be extremely time consuming; bottlenose dolphins are long-lived and have low reproductive rates, with females producing only one infant every few years. Data collection for this CRRU study therefore spanned an impressive twenty years, resulting in an in-depth understanding of individual reproductive success in these dolphins.

Factors considered when determining reproductive success of individual female dolphins are her reproductive lifespan, the pace at which she gives birth, and the survival rate of her offspring. Of the 102 female dolphins identified in Moray Firth during the study period, 74 were reproductively active. Approximately 24 individuals produced one calf during the twenty-year study, and 32 produced three or more calves. Our adopted dolphin, Muddy, gave birth to an outstanding seven calves – the maximum number produced by a known female during this study. Her calf, Hiccup, was born in 2014, and her most recent addition was born in October 2016.

Dolphin mothers in this population were between six and thirteen years old when they first gave birth, with an average age of eight years. Females had one calf every 3.8 years on average, although the time between births was significantly lower in females who had lost a calf.  Calves were born in all study months (May to October), but there were baby booms in the warm summer months of July to September, when water temperatures were at their peak.

Of the 193 calves born between 1997 and 2016, approximately 83% survived to their second or third year. Calf survivorship in the Moray Firth was found to depend on a number of factors, including maternal age and size, breeding experience, dominance, individual associations, group size, and other social factors. Calf survivorship was also lower if the female had previously lost a calf.

Overall, results of the study show that some dolphin mothers in Moray Firth have much higher reproductive success than others. Even the loss of just a few of these mothers could have a significant impact on the total population. Researchers therefore hope that these new insights will help with the development of long-term conservation strategies for the increased protection of these dolphin ‘super moms.’

*The other two resident dolphin groups in the U.K. occur off the coasts of Cornwall, England, and Cardigan, Wales.

Dolphin Adoption

Help us protect dolphins in the Moray Firth by adopting Muddy and Hiccup

Muddy & Moonshine, two of Born Free’s adoptable dolphins
Muddy & Moonshine
Born Free Foundation
Broadlands Business Campus, Langhurstwood Road
, Horsham, RH12 4QP, UK - Charity Reg. No. 1070906

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