Life of the Party: Dolphin Personalities and Social Structures

Díaz López, B. When personality matters: personality and social structure in wild bottlenose dolphins, Tursiops truncatus. Animal Behaviour 163, 73-84 (2020).

Smarter than they look

A pod of dolphins glide through the water. (Image Source: NOAA)

How would you describe your personality? Are you more of a life of the party type person or a wallflower reserved type? Did you ever think that non-human animals, like dolphins might have similar personality differences? Additionally, how do these personality differences impact their social structures?

Dolphins are not only extremely intelligent, but also have unique characteristics like highly developed social skills and self-awareness. Like humans, social structure is important for dolphins as it is vital for communication, reproduction and protection. Social groups also change over time when dolphins leave or join a group, a term called a fission-fusion society. Personality has also been shown to impact the life history, habitat use and behaviour of this marine mammal. However, few studies have examined wild dolphins’ particular personalities and social structures.

In this study, scientist Bruno Díaz López investigates the wild bottlenose dolphin (Tursiops truncatus), a socially and cognitively complex marine mammal. The goal was to examine the relationship between personality and social structure in this species and gain insight into the wild bottlenose dolphin social network.

The study: Do dolphins have personalities and do they impact their social structures?

To find out, Díaz López examined long-term data on a community of bottlenose dolphins located on the northeastern coast of Sardinia, an Italian island. Boat surveys were conducted year-round from 2004 to 2013, with pictures taken to determine identification, sex, and age. Dolphins were identified by comparing their dorsal fins and unique markings. Calves were not included because it was thought they would look to their mothers to decide how to behave.

There were 24 bottlenose dolphins (13 females, 11 males) identified that were distinguishable from others, lived in the study area, and were seen more than 20 times over 4 years that were chosen for the study.

The bold and the shy

The shy-bold continuum is often used in animal behaviour studies to find out if animals are more of the curious or reserved type. Díaz López examined if these 24 bottlenose dolphins were bold or shy based on their reaction in new, risky or challenging situations. If a dolphin is less likely to approach something new or that it perceives as dangerous, then it is considered shyer. Conversely, if a dolphin is quicker to approach something new, it is considered ‘bold’.

The new object used in this study was one of two potentially threatening situations. The first situation involved an acoustic harassment device (AHD) which produces an extremely loud noise for the dolphins for a maximum of 40 minutes. The second situation was the presence of an underwater observer who wore snorkelling gear (example pictured below). The scientist measured the distance between the dolphin and the object to see how quickly they would approach and how close they would get. Video recordings were taken to examine their behaviours when faced with this new situation.

A free diver swims with bottlenose dolphins. (Image Source: Wikimedia Commons, Dolphin Embassy)

The perks of not being a wallflower 

Results showed that wild bottlenose dolphins tended to have a consistent personal response to the loud noises or the snorkeler. Within each group, their personalities ranged on the shy-bold continuum. There was no difference in sex or age, but the results suggested a differentiated social system, where each member plays a role.

Specifically, the bolder dolphins who were more curious played a greater central role in the dolphin social structure than the shy individuals. Bolder individuals had deeper and stronger relationships with the other dolphins while shy individuals had fewer connections with others. Therefore, the bold individuals are more valued and can help keep the group together by promoting stability. Since these dolphins are more outgoing, they can easily spread information such as finding hot spots for feeding, consequently proving more useful.

Does it matter?

This was the first time individual personality differences, specifically on the shy-bold scale, have been noted in wild bottlenose dolphins. It allows insight into their individual personalities and what these roles play in their social structures.

A wild bottlenose dolphin emerges! (Image Source: NOAA)

An individual’s network position has been associated with mating success, connectivity, and even discovering new areas to forage. From a conservation perspective, it is important to understand these differences to better understand their life history and potential threats. For example, since bold individuals are likely to explore, they could be injured or die from contact with humans or other risky situations more often than shy individuals.

Social personalities and social structures are vital to bottlenose dolphins, as well as humans. This is because group interaction supports cohesion which increases the survival and fitness of all members. Basically, we are happier, healthier, and have a better survival chance when we are together. This has definitely proved to be difficult in the challenging time period we are currently in, as we social distance during the pandemic. However, wild bottlenose dolphins are still thriving in their social groups, whether they’re the wallflower or the life of the party.

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