Common dolphins toothed whales

From Dolphins to Sperm Whales: Meet the Toothed Whales

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It’s nearly time for World Whale Day, an event that takes place every year on the third Sunday in February. The aim is to highlight how important these incredible mammals are and the threats they face. Last year I celebrated by exploring the world of the baleen whales, those true giants of the ocean. This year it’s the turn of their relatives the toothed whales. This is a diverse group of species, which includes dolphins, porpoises, sperm whales and the mysterious beaked whales. Most are smaller than baleen whales. Although there are some shared characteristics, some of them have very different strategies for coping with life at sea from their baleen cousins. Like them, however, we are only just beginning to understand a fraction of their complex lives.

Long in the Tooth

After returning to the water from a life on land around 50 million years ago, the ancestors of modern whales split into two groups approximately 16 million years later. The baleen whales, or Mysticeti, began taking advantage of an explosion in tiny marine life. To do this, they gradually developed large plates fringed with bristles to help them filter small animals like krill out of the water. The toothed whales, or Odontoceti, meanwhile, continued to use teeth to catch larger prey such as fish and squid. Today, the exact number and shape of those teeth is related to their chosen food. Most dolphins have large numbers of conical teeth which help them to hold firmly onto their fish prey. The long-beaked common dolphin has the most teeth at a whopping 240. The bottlenose dolphin has about 100.

Bottlenose dolphin feeding
Bottlenose dolphins use their 100 or so teeth to grasp fish

Sperm whales have the largest teeth of any whale but only have them on their narrow lower jaws. The conical structures, numbering between 40 and 60, fit into sockets in the upper jaw when the mouth is closed. While earlier, now long extinct sperm whales certainly used their teeth to catch prey, modern sperm whales are thought to use them solely for aggression between males. They can easily suck up their squid prey without the need for teeth. Some toothed species have very few teeth at all. This includes the narwhal which, like the sperm whale, sucks up prey rather than grasping it. Males, and a few females, of this Arctic species instead have an enlarged canine that spirals to form a long, extremely sensitive tusk while the only other tooth remains embedded in the jaw. Scientists are still unsure of the tusk’s exact purpose.

Harbour porpoises have approximately 60 small, spade-shaped teeth

Into the Deep

Another major difference between toothed and baleen whales is the Odontoceti’s use of sound. Most baleen whales are certainly able to produce a huge range of sounds, sometimes called ‘songs’. These are largely for communication with each other. Many toothed whales also communicate frequently but use a series of clicks and whistles rather than the long, drawn-out notes of their cousins. However, toothed whales also use sound in a different way, using echolocation to find food and navigate. Echolocation involves bouncing high frequency sounds off objects and surfaces to determine their position and distance. To do this, scientists believe that the whales use a fatty structure in the head called the melon to help them focus the soundwaves before emitting them. A fat-filled hollow in the lower mandible receives the returning soundwaves once they have bounced off an object. This then sends the signals to the inner ear and then brain for processing.

Sperm whale tail
Sperm whales dive to great depths to find their squid prey

Echolocation means that toothed whales don’t need to rely on sight to find food. This in turn means they can hunt at much greater depths, where limited light penetrates from the surface, than baleen whales. Sperm whales, for example, spend a large amount of time at depth hunting squid and other deep-water species. The beaked whales, a group of about 24 little-studied species, also hunt squid and fish at great depths, sometimes up to two kilometres from the surface in almost complete darkness. Whereas marine species use echolocation to hunt in deep water, freshwater dolphin species use it to overcome the often silty, murky conditions of the South American and Asian rivers they live in. In fact, because sight is so useless in these conditions, they now have only tiny eyes and hardly any vision at all.

Pacific white-sided dolphins
Like all dolphins, these Pacific white-sided dolphins use echolocation to hunt
Pacific white-sided dolphins
A pair of Pacific white-sided dolphins in full flow

High Society

Toothed whales are extremely intelligent, and their complex social lives reflect this. While baleen whales are also sociable to a large extent, they tend to only group together, if at all, at certain times of year. The majority of toothed whale species, though, spend all or most of their time in family or clan groups. Orcas, the largest member of the dolphin family, live in close-knit family pods led by an older female, or matriarch. These groups spend a huge amount of time together travelling and hunting. Older animals pass vital skills down to young members of the clan. Some dolphin species even form ‘super pods’ thousands of animals strong. Recent research shows that sperm whales live in large clans of up to 20,000 animals. These are also female led, with mature males much more solitary in nature. Each group has a distinct culture and language, and they may even make democratic decisions together. Unsurprisingly, sperm whales have the largest brains of any living animal.

Common dolphins can sometimes travel in huge ‘super pods’

Although the benefits of social living, such as being able to pass on information, are huge, there are some drawbacks. Mass strandings are much more likely to affect toothed whales than baleens because they more often travel together. We don’t fully understand why species such as long-finned pilot whales or various dolphin species mass strand. One theory, though, is that if one animal is sick and heads too close to shore, the rest of the pod is compelled to follow. Excess noise may be another cause, more of which later. Occasionally, lone animals become isolated from their pods. Some then spend years alone, although whether this is always accidental or sometimes by choice isn’t known. Famous examples include Fungie, a bottlenose dolphin, who spent decades on his own around Dingle in Ireland, and Luna, a young orca who lived for five years near Vancouver. More recently, a lone beluga whale spent a few days in Shetland waters.

Fungie the dolphin
This photo shows Fungie, the bottlenose dolphin who lived alone around Dingle, Ireland for nearly 40 years

The Perils of the Ocean

Whaling was one of the biggest threats to larger whales in the 19th and earlier 20th centuries. Of the toothed whales, sperm whales were hit hardest. They were hunted for spermaceti, an oily substance used for oil lamps and lubrication. Although most nations signed up to end commercial whaling of large whales in the 1980s, the moratorium didn’t cover smaller species such as pilot whales and dolphins. Currently, two extremely controversial annual toothed whale hunts continue. The Faroe Islands take approximately 800 long-finned pilot whales a year, along with a few hundred dolphins and porpoises. The hunt involves driving the animals onto shore for slaughter. The Faroese insist it is a culturally important practice, but they have come under huge pressure from environmental organisations such as Sea Shepherd to stop. Japan likewise carries out a similar hunt of various dolphin species, with some animals killed for meat and some sent to aquariums.

Striped dolphin toothed whales
Striped dolphins like this one are one of a number of species targeted in Japanese hunting drives

Perhaps the biggest threats today, though, are pollution, ship strikes and fishing equipment entanglement and bycatch. Some chemicals and heavy metals break down extremely slowly. This means they can accumulate in whale and dolphin blubber over time, as well as pass via a mother’s milk to any offspring. As these chemicals become concentrated further up the food chain, apex predators such as orcas are especially vulnerable. They affect the animals’ health and reduce fertility levels. Some pods have had no new calves for years as a result. Noise pollution is a different kind of threat. Research links mass strandings to sonar used in naval exercises, as well as the seismic activities associated with oil and gas exploration. Increased shipping noise may also impact their ability to communicate with each other. Meanwhile, there are only 10 of the world’s smallest whale, the vaquita, left alive due to years of fishing net entanglement.

Dusty Doolin Harbour
This bottlenose dolphin appears to have some fishing markers attached to it
Common dolphin
Chemicals and pollutants concentrate in whale and dolphin blubber, reducing life expectancy

From Flipper to Free Willy

Since the 1870s, humans have also been capturing various toothed whale species for aquariums. Once people realised dolphins could be trained and how acrobatic they are, the captive industry boomed. By the 1960s, thousands of animals were being hunted solely to keep in tanks for human entertainment. Although hunters most commonly catch bottlenose dolphins, they also target belugas and orcas, along with a few other species. American theme park business SeaWorld, in particular, makes orcas a key attraction. Campaigns to end the practice have become more vocal in recent years, however. One concern is for the animals’ physical wellbeing. Animals frequently display poor skin condition as a result of bad water quality and sun exposure. Dental health is often also an issue, as well as a tendency to droopy, floppy dorsal fins rarely seen in the wild.

Common dolphin toothed whales
Common dolphins, like this one, are kept in captivity much less than bottlenose dolphins

Thankfully, in some countries, opposition to captive cetaceans is growing alongside our understanding of cetaceans’ complex intelligence and social lives. One element of this is the fact wide-ranging oceanic animals are kept in small, concrete tanks. Another is the social question. While some animals are put into tanks with animals from different locations, and therefore very likely different cultural and behavioural backgrounds, others are living more or less in solitary confinement. The psychological effects lead to self-destructive behaviour, fights between animals and extreme listlessness. They can have tragic consequences for humans, too, as illustrated by the tragic case of killer whale, Tilikum, the main subject of the 2013 documentary, Blackfish. Despite our knowledge about what captivity does to them, though, there are still a huge number of captive whales and dolphins around the world. China alone has over 1,000 animals, mostly bottlenose dolphins and beluga whales, in its numerous parks. At present, at least 60 orcas are in captivity.

These three members of the Northern Isles community of orcas are wild and free, as they should be

A Whale of a Tale

Toothed and baleen whales went their separate ways around 34 million years ago. But while over the last few decades we have learned much about toothed whales’ subsequent evolution, we are still only scratching the surface when it comes to understanding their complex lives. At the same time, they are facing more threats than ever. Pollution, hunting, entanglement and bycatch all threaten this diverse group of cetaceans. And we are as yet unsure what effect climate change will have on them. Let us hope that we are able to learn enough about them to help them weather the intensifying storms they face.

Sperm whale bone
The remains of a sperm whale washed up near Portmahomack, Scotland in 2013

Further Reading

One thing we can all do to help whales and dolphins is make informed choices. While the UK no longer has captive dolphins, there are a depressingly large number of captive cetaceans abroad. And many tour and cruise operators here sell tickets to dolphinariums or swimming with dolphin experiences overseas. You can vote with your wallet and not give money to any attractions involving captive whales or dolphins. The Dolphin Project, with their Empty the Tanks campaign, has more information.

If you are going out on a dolphin or whale watching boat trip anywhere, research the companies offering trips and ensure they are responsible operators. Responsible Travel has tips on how to choose a trip.

If you eat fish, research the fishing methods used; pole and line caught tuna, for example, is generally considered less dangerous to non-target marine species, although all fishing has an impact.

Dolphins are perhaps the most familiar of the toothed whales. Susan Casey’s wonderful book explores their complex lives as well as the tangled relationship we have with them. Often adored and even held up as some sort of spiritual animal, we nevertheless subject them to a range of threats from captivity to pollution and bycatch.

Erich Hoyt is an authority on orcas and has been studying them for decades. This updated edition of his classic book on the species is a must-read for anyone interested in this charismatic species.

Like the film Blackfish, this book is absolutely not for the fainthearted. It is an extremely distressing account of the horrors orcas face in captivity, primarily at SeaWorld parks. Former trainer testimonies are at the heart of the book, revealing a horrific life for these social, intelligent animals.

This beautifully illustrated guide to whales and dolphins, both baleen and toothed, includes every known species and subspecies. Perfect for getting to grips with this fascinating group of mammals.

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