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Five Fascinating Facts About Bottlenose Dolphins

Bottlenose Dolphins
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KCETLink is kicking off its environmental summer lineup with Earth Focus Presents, a series of seven of the hottest current environmental documentaries, as part of KCET and Link TV’s “Summer of the Environment.” We’re pleased to present this article to accompany our presentation of the documentary "The Cove."

Perhaps the most familiar of all the planet's dolphins – and there are about 40 of them – is the bottlenose dolphin. Yet many of us are unfamiliar with some of the most fascinating facts that make them unique. These streamlined, grey-and-white predators are found in temperate and tropical seas around the world, and yes, they adorned the Lisa Frank-inspired notebooks belonging to just about every elementary school student in the 1990s. It is universal knowledge that bottlenose dolphins – the common name generally applied to all three species of the genus Tursiops – are clever critters, but even the dolphin performances at marine parks and the entire series of “Flipper” miss some of the most interesting facets of their biology and behavior.

Here are five things you might not already know about bottlenose dolphins:

1. Be My Dolfriend?

Dolphin society is carefully organized in much the same way that chimpanzee and elephant societies are. Scientists use the term "fission-fusion" to describe the social order of these and other creatures, which is a fancy way of saying that over time the size and composition of their social groups change. Occasionally smaller sub-groups combine to form larger aggregations (fusion) and sometimes those larger groups break apart (fission). 

While chimpanzees and elephants and other social species are have complex social alliances, only humans and bottlenose dolphins are known to have social hierarchies at this level of complexity.

Biologists studying the bottlenose dolphins of Shark Bay, Australia have described dolphin groups in even greater detail. Groups of two or three related males form what they call "first-order alliances." These small families work together to guard one or more females from other families. Sometimes, first-order alliances work together with other first-order alliances usually in the task of "stealing" females from other groups. These teams are called "second-order alliances." And then there are the aggregations that these biologists refer to as "second-order super-alliances." These occur when multiple second-order alliances cooperate or team up to carry out some task.

These groupings are observed by dolphin researchers over and over again across multiple years, which means that dolphins pay close attention to who their friends and enemies are.

While chimpanzees and elephants and other social species are have complex social alliances, only humans and bottlenose dolphins are known to have social hierarchies at this level of complexity.

False killer whale swimming with bottlenose dolphin
False killer whale swimming with bottlenose dolphin. | Daiju Azuma/CC BY-SA 2.5

2. Interspecies Interactions
That bottlenose dolphins establish long-term close relationships (something we might think of as friendships) is fascinating enough. But it turns out that in some places, dolphins also make friends outside of their own species.

In the waters off the coast of northern New Zealand swims the elusive false killer whale (Pseudorca crassidens), which, despite its common name, is actually classified as a dolphin. Because they're so rarely observed in the wild, over the course of 17 years one team of wildlife biologists recorded every sighting. Most of the times that they spotted false killer whales, they saw them swimming alongside bottlenose dolphins. Remarkably, some of the inter-species pairings lasted quite a long time. Individual pairs were spotted together at different locations up to 400 miles apart over the course of as many as 5 years.

It's not clear why the two species form these relationships, and because false killer whales are so elusive it's difficult to study them to understand why. One guess is that the two marine mammals have learned to work together to detect and avoid predators. And while each species hunts different prey, their prey species tend to be found together. So they may benefit from foraging alongside each other.

Still, it's got to be something more than simply practical. After all, they choose to spend time with specific members of the other species, rather than randomly mixing in an opportunistic fashion.

3. Complex Communicators
Dolphins might even have individual names, like we do. When groups of bottlenose dolphins meet on another in the wild, they exchange what dolphin biologists have termed "signature whistles." They're unique to each individual, much like our own names are, and they seem to be part of the formal rituals of dolphin meetings. 

Signature whistles have been studied since the 1960s, but there's little we actually know about them. They're developed within the first few months of life and stay static for decades, though sometimes when males form new alliances they may occasionally modify their signature whistles a bit to blend in with their new crowd. Captive bottlenose dolphins emit their signature whistles when separated from their pods, suggesting that they could use them to maintain social contact.

On the other hand, they're not exactly like human names. For one thing, the dolphins seem to invent their own signature whistles, rather than having them granted by a parent. They also seem to convey more than just a name; signature whistles seem to have a component that transmits some information about the caller's emotional state or mood. And one study found that a fair proportion of signature whistles produced during dolphin interactions belong to individuals who aren't around. And nobody knows why. Are they calling to friends they can't find?

Dolphins at Chanonry Point, Scotland
Dolphins swimming at Chanonry Point in Scotland. | Shirehorse / CC BY-SA 3.0

4. Language Learners
Bottlenose dolphins Akeakamai and Phoenix lived at the Kewalo Basin Marine Mammal Laboratory in Honolulu, Hawaii. A famous marine biologist named Louis Herman worked with these animals for many years as he attempted to understand their communication. He wondered if they might even be able to understand grammar. 

Herman and his colleagues gave the dolphins instructions constructed entirely of familiar words, but in combinations that would only be understood by knowing the grammar. For example, "Phoenix Akeakamai Over" was an instruction for Phoenix to swim to Akeakamai and jump over her. "Akeakamai Surfboard Fetch Speaker" instructed Akeakamai to retrieve the surfboard and bring it near the speaker. These instructions are trickier than they might seem. For example, does "fetch" apply to the surfboard or to the speaker? In the rudimentary grammar used at the lab, it applied to the word that came before, not after: something that Akeakamai had clearly figured out.

While Phoenix and Akeakamai lived in a captive setting and had hundreds of hours of experimental participation, the results of this study and others like it suggest that even if wild bottlenose dolphins do not communicate with such complexity, their biology is such that they are at least capable of learning to comprehend fairly complex sentences.

5. Death Rituals
For animals with such close social ties, it probably isn't surprising that they have some sort of ritualized behavior upon the death of their friends and family members. Death rituals are remarkably difficult to observe, but a few researchers have gotten lucky. 

In 2000, a dead female dolphin was spotted on the sea floor of the coast of Japan. Researchers watched as two males remained with the body at all times – even chasing off human divers attempting to retrieve the body for study – only returning to the surface long enough to breathe. For two days, divers remained unable to approach. By the third day, the carcass had disappeared, ostensibly having drifted into deeper waters.

Something similar was seen in 2001. A young male was spotted dead, wedged between two large boulders on the sea floor. He was attended by at least 20 other dolphins, both males and females. Once again, when divers attempted to approach, male dolphins reacted with defensive posturing, intercepting the swimmers. In this case, the attending dolphins were seen nudging and pushing at the carcass with their heads and beaks. This time, divers did manage to retrieve the body for study, and the other dolphins continued to swim around the boat until it reached port. 

Another 2001 observation, this time near the Canary Islands, involved a deceased dolphin calf floating on the surface, accompanied by several other adult dolphins, one of which was presumed to be the mother. Not only did they chase away humans who got too close, they even chased off seabirds that attempted to approach.

As with so many similar behaviors in other social species, the reasons for these odd behaviors aren't well understood. It could be that dolphins spend time attending to the dead in an effort to learn something about death itself. Since dolphins maintain long-term relationships, it could be that they somehow feel the loss of their comrades. Whatever the case, it's hard to imagine this sort of behavior and not see something human-like reflected back at us.

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