Sophisticated societies (Shore 9)

 

These posts make more sense when read in order.

Please click here for the first article in this series.

 

Willy Volk, CC BY-NC-SA 2.0 (adjusted).

[...] on the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much—the wheel, New York, wars and so on—whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man—for precisely the same reasons.

—Douglas Adams in his humorous sci-fi novel, The Hitchhiker’s Guide to the Galaxy.

If I were to guess which marine animal is the most like us, I’d say it’s the dolphin. Dolphins have qualities that many people find endearing. Like us, they are quite intelligent, friendly, brave, and they’ve been known to save the lives of people and other animals—often from sharks. But we do tend to emphasize their good attributes, while ignoring their bad.

Like us, dolphins can exhibit criminal-like behavior. They have their own personalities and some can be vicious, brutal, and deadly. Some attack young manatees, young dolphins of other species, and harbor porpoises. As with humans, they also on rare occasions commit gang rapes and infanticide. But, as with most people, they have a lot more positive attributes than negative. And they’re always a joy to see.

Marine biologist Frauke Bagusche wrote in The Blue Wonder of an incident that took place in the Maldives while she was leading a snorkel group.

We were just on our way back to the ship when the skipper frantically signaled to look behind me. A few feet away I could see a dorsal fin on the surface of the water.[...] A moment later the skipper again began gesticulating wildly and, lo and behold, a pod of dolphins had surfaced behind me. But that wasn’t all. All of a sudden bubbles appeared all around us, bubbles from deep down, and we felt as if we were in a whirlpool. Sounds from beneath the surface began to swell to a wild chirping similar to birds ashore. Suddenly we were surrounded by spinner dolphins, chirping and whistling, jumping out of the water next to us and spinning in the air.[...] We reckoned that about three hundred creatures swam past us, returning to the atoll from hunting on the open sea.

Bottlenose dolphin (top) and a spinner dolphin, along with a 1.5-foot-tall (0.5 m) chicken for size comparison. Mith, CC BY-SA 3.0 (bottlenose dolphin, modified). Liisa Havukainen, CC BY-SA 3.0 (spinner dolphin, modified).

Spinner dolphins are named for their tendency to leap from the water, spinning around up to seven times, before splashing back in. They swim well up to ten miles per hour (16 km/h), but above this speed it’s more efficient for them to leap and spin.

Spinner dolphins are much smaller than bottlenose dolphins. Spinners are four to seven feet long (1.3 to 2.1 m) and weigh up to 165 pounds (75 kg), while bottlenoses range from six to thirteen feet (1.8 to 4 m) and weigh up to 1,450 pounds (650 kg). People often confuse porpoises with dolphins. They are similar, but in general the bodies of porpoises are stubby and they have blunt noses, while dolphins are slender with long noses.

During the day, they often hangout near the shore and in sandy bays. At night they hunt for fish and squid far out at sea in deep water, sometimes reaching depths of three thousand feet, or more than half a mile (1 km), using echolocation.

With this natural sonar they make clicks and listen to the soundwaves that bounce back off of objects, most likely using this information to form pictures in their minds, since this is what happens to deaf people who have developed their sense of echolocation. The range of dolphin hearing is up to ten times wider than ours. They can echolocate landscapes, predators, and prey well out of eyesight. They can expand it or focus it like a laser-beam of sound. With higher frequencies they can perceive tiny objects and fine details. They might even be able to perceive textures as colors, since sound waves are similar to light waves.

When focused, they can use it to stun and disorient fish and squid, and they can see inside other animals to detect internal trauma. Some evidence suggests they can even send out beams of different frequencies in two directions. They are way beyond the capabilities of our best sonar.

Dolphins are very sociable and are usually seen in small groups, but when traveling or hunting they sometimes gather together in groups of several thousand dolphins of different species in what are called superpods or megapods. The groups can be five miles wide (8 km) and difficult to count since many are underwater at any given moment. They come together casually and then suddenly they take off in a stampede, with many of them leaping out of the water. Those in front send out acoustic signals telling those in the back when to turn. Marine biologists still aren’t sure what these dolphin conventions are all about.

Bottlenose dolphins are born into family groups headed by mothers and grandmothers. In some groups the males and females remain in the same group, but in others the males form or join groups with other males. The groups of males are called “alliances” and groups of females, “parties”. The female groups also include juvenile males.

These groups are dynamic, with some members coming and going and with the sizes of the groups changing depending on what they’re doing. Two or three dolphins usually spend most of their time together, but they’re part of a larger team of a dozen or so individuals. They may go off with another group for a while and return. Dolphin social groups are fluid, as one would expect with independently minded individuals, but they do have preferences as to who they hang out with and they do stick with their team.

Dolphins each have their own names, just as elephants, marmosets, bats, parrots, and orange-fronted parakeets do. When born, baby dolphins make putt sounds so their mothers can find them. At nine months of age, they gain the ability to make complex whistles. Some researchers say their mothers give them their names, while others say they choose their own names. Perhaps it’s a bit of both. Either way, they have their unique name by the age of one and use it for the rest of their lives. For the females it remains the same for at least a decade, but the males sometimes make adjustments to theirs to make it similar to an alliance partner.

These signature whistles are usually repeated in a short loop, but the loop tends to grow longer as the individual ages, so this might also be used to indicate how old they are. The number of loops also varies by context, and others will add loops to a dolphins name when calling or referring to them. Dolphins use their own name to tell others of their location, so the extra loops could signal that someone is calling the individual’s name.

Individuals may also alter their own name slightly to indicate their mood, motivation, or reproductive status. Their name might also indicate their family connections or the environment they live in, such as mud flats or seagrass—seagrass using high notes and mud flats using low. Small groups sometimes make up a name for their gang.

Dolphins make a lot of different sounds, but about half of all their whistles are signature whistles. Some birds also make more complex signature sounds that refer to themselves and are used by their friends and relatives to refer to them. If another dolphin calls their name or an artificial version of their name comes out of a speaker, they’ll respond. In addition, other dolphins use their name in what appears to be conversation, raising the possibility that they might gossip about one another.

When meeting a new group, one dolphin from each group introduces themselves with their signature whistles. They also use them when they become separated from the group to let the group know where they are or perhaps if the others are unable to recognize them with echolocation. And pregnant mothers whistle their own names a lot, probably so their calf will be familiar with it when they’re born.

Forming teams

The basic male teams number around a dozen individuals, but each dolphin usually hangs out with one or two close friends. When the females are in heat, a small male group might kidnap a female from her family. They will then call together the other members of the team, using each dolphin’s name, to help defend their captive from being stolen by other groups. After the females pregnant, they’re then returned to their family group.

The members of the small groups of two or three friends sometimes change, but their larger team can remain together for decades, which can be for most of their lives, since their average lifespan is twenty years, although they can live into their forties. It is these teams of about a dozen dolphins that form the core groups of male dolphin society and it is the calls from these groups that the members respond to the quickest. They appear to have more loyalty to the team, than to the friends they spend most of their time with. Sometimes teams will temporarily combine to form larger groups in order to ward off attacks.

Some scientists believe dolphin societies with their alliances are the most complex of all animal societies, except for ours. Dolphins have complex relationships with others, forming a rich network that extends their social groups. Chimpanzees form alliances to defend their territories, but dolphins do it for protection, hunting, socialization, and to retain their captive females. They don’t have territories.

Their hunting partnerships are also more complex. They hunt in packs of around six dolphins, with each having a specialized role that they play and they usually take on the same role when they’re with that pack, although they will take on elements of another’s role when hunting alone.

Orca families

An orca with a diver for size comparison. Matthew Maxwell and Pablo Alvarez Vinagre at StudioAM, CC BY 4.0 (diver, modified).

Orcas are classified as toothed whales—as are dolphins and porpoises—but they are actually the largest species of dolphins. They’re popularly known as killer whales, but labeling them as killers is a bit harsh and doesn’t seem to be representative of their lives. They can be brutal when feeding, but so can lions and feral dogs. Pet dogs might be too if they had to hunt and kill their own food. As an apex predator, orcas can pretty much do as they like and don’t usually have to worry about being eaten or killed, as other animals do. Likewise, when free of constraints, some humans become extremely brutal.

Still, I don’t think that would warrant calling us “killer humans”, although some animals might disagree with that—particularly sharks, since people are killing them at alarming rates out of fear and for food. Millions of those harvested only have their fins cut off for shark’s fin soup, then they’re thrown back into the sea to slowly die. The fins, by the way, don’t add any flavor to the soup and have no nutritional value. They’re purely a status symbol that costs up to $2,000 a bowl and is usually ham and chicken soup with thin strips of fin providing a noodle-like texture.

Orcas make similar sounds to bottlenoses, but they are more limited and they stick with the calls of their group. They live in family groups and those groups that live in a particular geographic area are part of a clan. While comparing orca groups, researchers noticed that clans have their own dialects. The pitch, duration, and pulse patterns of orcas’ sounds vary from group to group, giving each clan its own characteristic sounds.

Minette Layne, CC BY 2.0 (adjusted).

Like bottlenose dolphins, orcas each have distinct personalities. SeaWorld trainers and staff compiled a list of thirty-eight personality traits, from playfulness to stubbornness and sensitivity to bravery in captive orcas. Researchers at the University of Girona in Spain then compared this with similar lists for humans and chimpanzees and found that while orca personality traits are similar to humans, they’re even more similar to chimpanzees, particularly in agreeableness, such as being peaceable, patient, and non-bullying, and in conscientiousness, as in being protective, constant, and stubborn. Except for stubbornness, these are not traits we normally attribute to killers. Orcas and chimps also shared some characteristics related to dominance—not surprising since their social groups are hierarchical.

There are some indications that orcas might even experience grief, particularly in mothers who have lost a calf. Naturalists have also seen this in other animals that live in small, highly social groups, such as elephants, giraffes, and chimps. Behavioral biologist Toni Frohoff told The New York Times, “We do have compelling evidence of the experience of grief in cetaceans [whales, dolphins, and porpoises]; and of joy, anger, frustration and distress and self-awareness and tool use; and of protecting not just their young but also their companions from humans and other predators.”

Orca family groups are led by older females—who can live into their nineties—and their sons. The older females are dominant, despite being smaller than the males. Adults males average twenty to twenty-six feet in length (6 to 8 m), but can reach thirty-two feet (9.8 m) and weigh up to ten tons (9 tonnes). One key feature is their tall dorsal fin, which in older males is up to six feet high (1.8 m). Females are smaller, averaging sixteen too twenty-three feet and weighing 3.3 to 4.4 tons (3 to 4 tonnes).

Males remain with their mothers for life and the mothers do whatever they’re able to do to help their sons. Even when the mothers can still have offspring, caring for their adult sons is so intensive that it reduces the number of additional children they have each year by more than half. After going through menopause, they really dote on their sons.

The mothers do everything for them from obtaining food to finding them mates, and they’re also very protective. Those sons end up with fewer tooth-mark scars, but the researchers aren’t sure what she’s doing to help. She might be mediating for him in arguments or warning him when he’s getting into dangerous situations. Or perhaps her dominating presence keeps others away, since sons tend to stick near their mothers.

Mothers don’t do this for their daughters or grandchildren. The researchers at the University of Exeter in the U.K. suggest this might be because if her sons have children, another pod has to care for them, while she’ll end up providing for her daughters’ calves. That explanation seems a bit limited to me. Perhaps there are also other reasons.

Males breed with females of other pods, but each of them remains with their own family. The dominant female leads her pod to good fishing spots and have been measured sharing fifty-seven percent of what they catch. Some orcas travel in pods of three to seven individuals, while other pods number ten to fifty.

Dolphin cultures

Passing knowledge down through generations is considered to be culture and that’s what dolphins are doing. Certain mothers off Australia are teaching their young how to use sponges when hunting for food. Oddly, it’s mostly the young females that pick this trick up. The young males aren’t really interested. They usually just wait at the surface for their mothers to return.

Over a twenty year period, Australian scientists monitored nineteen young dolphins and eleven females that belonged to the same family, all but one picked up the trait. Out of eight males, only two became spongers. Spongers are usually loners, spending eighty percent of their time alone or with one calf. They also forage in deeper water than non-spongers.

Another study reported that out of thirty seven males, twenty four of them were non-spongers. The researchers suggested that since males spend so much time forming alliances, they don’t have time for mostly solitary, time-consuming activities, like sponging. They also noticed that the male spongers hung out with other male spongers, while the male non-spongers usually stuck with non-spongers, prompting them to suggest that dolphins might choose their friends based on similar interests.

Dolphins can get pretty creative. One dolphin killed a scorpion fish and, holding it in its mouth, poked the spiny fish into a crevice to force an eel out into the open, using the fish as a tool.

Orca mothers train their young how to hunt. Since the juveniles normally remain close to their mother’s side, they watch her hunting behavior close up, but lately researchers have spotted them apparently using baby porpoises as training tools. These babies are about the same size as the salmon they hunt, which can grow to nearly five feet (1.5 m) in length and weigh 126 pounds (57.2 kg). The young orcas toss a baby porpoise around and let it escape, then they’ll wait for a bit before charging off after it. They don’t bite it, but gently grab it with their teeth, and toss it around some more. They’ll do this for quite a while. The baby usually ends up dying from the abuse, but the orcas never eat it.

Trained dolphins tail walking. Steward Holmes, CC By-SA 2.0 (adjusted).

Here is another example of dolphins passing along knowledge. At dolphin shows, one of the tricks is for the dolphins to tail-walk by rising vertically two-thirds out of the water and shimmying backwards. This is not natural behavior. It’s taught to them by trainers. But tail-walking has spread into the wild where one group near Adelaide, Australia has begun doing it.

One of the dolphins—a female—in the group spent time at a dolphinarium twenty years earlier while recovering from an illness and though she wasn’t taught the trick, she may have picked it up there and is now teaching it to other female dolphins. This, too, would be a form of cultural transmission. There doesn’t seem to be any practical advantage to this behavior, but it might just be fun, like dancing.

Dolphins do seem to enjoy having fun. The noted German-American marine biologist Bernd Würsig is quoted in Tim Cahill’s Dolphins as saying:

Then there is what I call the dolphin’s impish nature. I’ve seen duskies [dusky dolphins of the Southern Hemisphere, such as along the coasts of Argentina and New Zealand], after sating themselves on southern anchovy and when in a highly social mood, nosing v-e-r-y s-l-o-w-l-y toward a gull or black-browed albatross sitting at the ocean surface, digesting, preening, oblivious to what is going on below. Then they, woosh, pull the creature underwater by gently mouthing one or both of the bird’s feet hanging enticingly below the surface. The dusky tugs hard, and the bird may be dragged down twenty inches or so. It flails its wings and feet to get free. The dolphin opens its mouth and the hapless waterborne avian bobs to the surface like a cork, but a particularly aggravated, soggy, and frantic one. The dusky slowly cruises off with an enigmatic smile that seems to say, “Hee-hee, I got another one but good this time!”

The birds are no doubt annoyed by such practical jokes, but apparently the dolphins get a kick out of it. Of course, dolphins always have that smile, even when they’re angry.

 

Since people don't seem to be reading these in order, future posts in the ocean series will be on random topics.

 

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