The dolphin that bit the person may have just been friendly.

The dolphin that bit the person may have just been friendly.

Anna Igarashi & Nature magazine

Dolphin attacks have been on the rise on a quiet beach in Japan’s Fukui Prefecture. According to the Tsuruga Coast Guard, as of August 26, 18 people have been injured this year, bringing the total number of deaths and injuries over the past three years to 29. Injuries range from bites to the hand to broken bones.

The researchers believe the culprit was a male Indo-Pacific bottlenose dolphin (Tursiops aduncusThe species was named “black-tailed gull” based on the pattern on its fins captured in photographs and video footage. Nature We spoke to Tadamichi Morisaka, a dolphin ecologist at Mie University in Tsu, Japan, about dolphin behavior and ways to prevent further attacks.

Why does this dolphin bite beachgoers?

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Gentle biting is a common behavior among male bottlenose dolphins in the wild. They do it to maintain relationships, so in this dolphin’s mind, he may already have a friendly relationship with the human.

We have seen this dolphin repeatedly appear on the beach, bite people, then walk away. From my perspective, he seems to be looking for some kind of interaction with people. If he really wanted to attack, he might have gone all out and tried to bite. However, he has a gentle bite by dolphin standards, so he is probably just being friendly and not attempting a full-blown attack.

How does this behavior relate to the social structure of Indo-Pacific bottlenose dolphins?

Bottlenose dolphins generally live in groups, with males forming lifelong partnerships with other males. Pairing up gives them greater access to females, as two dolphins are stronger than one.

These pairs spend hours playing together, which can include chasing, rubbing their pectoral fins against the other dolphin (thought to be a sign of affection), and even sexual behavior such as penis pressing against each other.

Gentle biting is one such social behavior, meaning the Fukui dolphins behave as if they are playing with male mating mates, but with humans.

Is it unusual for a dolphin to be alone?

This is a mystery and an area that requires further research. Individuals are occasionally seen leaving their pods alone in Japanese waters. However, sometimes it is just females who leave, and other times they leave in groups of several individuals. The closest population to the Fukui coast is near Noto in Ishikawa Prefecture, but it has not yet been determined whether the individual that made the attack belonged to that population.

How might attacks change in the future?

We know that there are stages in human-dolphin interactions. At first, humans and dolphins just share the same space. But as the interaction deepens, dolphins hurt humans. That’s the current situation in Fukui. When the interaction progresses to the next stage, dolphins can start asserting dominance with aggressive behavior, such as tackling or jumping on humans. We saw a little bit of this last summer, and it was very worrying. Dolphins are about 2.5 meters long and weigh about 200 kilograms, so if they come charging at you at 20 to 30 kilometers per hour, it’s like getting into a traffic accident. If they tackle you, you might break a bone.

What has been done to prevent further attacks in Fukui?

Local authorities have installed underwater acoustic devices that play a variety of random sounds. This is not intended to elicit any particular response from the dolphins and can sound strange and annoying. However, bottlenose dolphins may become accustomed to this. Bottlenose dolphins are a particularly inquisitive species, so if they see something that interests them, they will head to the beach regardless of the sound. In fact, we have seen dolphins return to beaches that have these devices.

I want to develop an early detection system that can detect echolocation, which dolphins use for navigation. An alarm will sound as soon as it detects that a dolphin is approaching. If we can get people out of the water in time, the dolphins will realize that there is nothing interesting on the beach and will eventually return to their original environment. But most importantly, we need to raise more awareness about what wild dolphins look like.

Still wondering about dolphin behavior?

A lot of my research focuses on dolphin acoustic communication, and I notice a lot of strange things about dolphins when I watch them, and part of my mission is to give scientific interpretations of their behavior. For example, I know that dolphins yawn and have wet dreams just like we do.

Lately, I’ve been interested in how dolphins perceive the world. Dolphins “see” using echolocation, but there are many unanswered questions about the role of their eyes. Dolphins’ eyes move independently, and each eyeball has two veins that enhance vision. Humans only have one high point of vision. What and how do dolphins see with those eyes? How is visual information integrated with echolocation and other auditory signals? Understanding their perception helps us understand their society, because it forms the basis of how they communicate and shapes their social structure.

This article is reprinted with permission. First Edition August 28, 2024.