New publication – Oxytocin in Dolphins

Link to article: here

Download the paper for free until the 9th January: here

Or read the abstract on this site here

Bottlenose dolphin mother with a young calf in Scotland

I spend a lot of my time working on a hormone called oxytocin, it’s fascinating to study as it can act on many different kinds of social and parental behaviours in all kinds of animals (see this amazing reveiw for more information). However, most of the research done on the hormone so far is on laboratory animals, or captive individuals in zoos, and little is known about how the hormone functions in completely natural environments and populations. I have been trying to change this with my work on oxytocin in breeding grey seals here in Scotland, and I have also started to work on oxytocin in other wildlife species with the help of many wonderful collaborators. My new paper is all about the first of these new studies, where we detected oxytocin levels in a wild population of Bottlenose dolphins.

The aim of the study was to firstly see if it was possible to detect dolphin oxytocin, but also to see if there were any differences between age groups or different types of social groups. We worked with the Sarasota Dolphin Research Program (SDRP) in Florida, USA to collect samples from wild bottlenose dolphins over 3 years, and this enabled us to study adult males in breeding alliances, lone individuals and mothers with calves. The SDRP has studied the bottlenose dolphins living in and around Sarasota Bay since the 1970s and conducts occasional health checks on small portions of the population. This means that wild dolphins can be safely briefly captured so that measurements and samples can be collected, and any obvious injuries can be treated by vets. For example, one of the dolphins in our study had sting ray barbs in his head, which the vets were able to remove before he was released. The SDRP has enabled all kinds of research on dolphins to take place, from measuring aspects of their physiology to understanding dolphin cognitive abilities, and you can read more about the health checks and the research that comes from them on the SDRP website here.

Mother – calf pair of Bottlenose dolphins in Sarasota Bay, Florida. Photo courtesy of the Sarasota Dolphin Research Program, taken under NMFS Scientific Research Permit No. 20455

We found that we could use a test called an ‘enzyme linked immunosorbent assay’ or ELISA, to successfully detect dolphin oxytocin. By passing all the quality control checks to see if an ELISA is working properly with a new sample type, we know the values we are detecting are accurate and can be used in future studies. Most of the dolphins we studied had oxytocin levels that were comparable to other mammal species, and were relatively low. This surprisingly included the mothers that we sampled, in contrast to what we know about seal mothers who have high oxytocin levels up until they wean their pups. However, dolphin calves had much higher levels than other age classes, and these high levels were present across all ages that we studied (2-4 years old). Previous work on oxytocin in young mice, seals and humans have also showed that young infants have really high oxytocin levels compared to adults, but all these prior studies covered much shorter time frames (days or weeks). Our results suggest that the dolphin calves have elevated oxytocin levels for several years, covering the timeframe that they are still with their mothers.

This is important as oxytocin stimulates individuals to seek out and stay close to others that they share a bond with. Dolphin calves have to deal with regular separations from their mothers while they grow up, especially as mothers have to be able to shoot off in pursuit of prey while rearing calves. Previous studies indicate that dolphin calves must be able to cope with these separations or they will not survive, and that calves play an active role in reuniting with their mothers at sea. Elevated levels of oxytocin in this age class could be indicators of calves with strong bonds with their mothers and high motivation to re-unite with them when separated. In contrast, dolphin mothers may not have constantly elevated oxytocin because they must separate to successfully feed regularly. Continual hormonal stimulation for mothers to stay with a calf could therefore be completely inappropriate for this particular species. As dolphins have advanced cognitive and communication skills, oxytocin release in adults may instead be tied to specific signals from other individuals they share a bond with.

Bottlenose dolphins with a young calf in Scotland. One of the adults is likely the calf’s mother.

This study is just the first step in understanding how oxytocin works in socially complex dolphin species. It is important to understand hormone dynamics and how they impact on individual behaviour and survival as physiological mechanisms that act on these processes are often present across entire species. Oxytocin release and the behaviours this triggers to keep socially or maternally bonded individuals together can only happen if bonds can form in the first place. Bond formation relies on communication and interaction causing oxytocin release, often during critical time frames within an individual’s life. All wildlife species are facing increasing disturbance from human activities, and if individuals cannot form strong bonds or communicate to reinforce them via oxytocin release it could make life much harder for species that rely on group living like dolphins.

Many dolphin species have to live and rear their calves in areas that are increasingly disturbed by human activities, like this mother calf pair off the coast of a major tourist destination on Ibiza, Spain.

MEANWHILE: This month has been pretty hectic as I submitted my first ever fellowship application. Fingers crossed that my application will get to the interview stage, although the odds are low unfortunately with only about 1 in 10 applications being successful. In more positive news, I’ve also been working on the final version (aka the publisher proofs) of another oxytocin paper. This is a big review article that I worked on with a number of great oxytocin scientists. We met at a conference in 2018 and all work on different animal species to study various aspects of how the hormone works. We have joined forces and written a review about all the model animal species that have been used to study neuropeptide hormones. This should be out soon so watch this space!