Baleen whales are large whales that have plates of ‘baleen’ in their mouths which are used for feeding instead of teeth. They are mammals and so breathe air, have warm blood and give birth to live young that are fed milk produced by their mothers. They have no fur but have a thick layer of blubber under their skin to keep them warm. Baleen whales, like other whales, have ancestors that were once land mammals. These ancestors returned to the water millions of years ago. They have adapted to the water so well that they now have to spend their entire lives at sea. They have two blow holes in the tops of their heads for breathing. The largest of all the baleen whales is the blue whale which is the largest animal the world. Many of the baleen whales have been hunted by the whaling industry and their numbers reduced to very low levels. They are found all over the world and often undertake great migrations from feeding grounds in polar waters to breeding grounds in tropical waters. Some of them sing ‘songs’ which act as mating calls and some have very loud, very low frequency calls that can travel across entire oceans.
Sylvia Annie Adam
Group size range:
6.5m - 30m
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|Other names these organisms are known as:
Baleen whales include blue, fin, sei, minke, humpback, right, gray and bowhead whales.
|What do they look like?
The baleen whales are all large whales that have baleen plates in their mouths instead of teeth. Most of them are over 10m long. They swim relatively slowly but can sometimes leap out of the water in a spectacular ‘breach’. When they breathe out, they send a great stream of water vapour, known as a ‘blow’, several metres into the air. They all have a large and powerful horizontal tail and ‘pectoral’ or side fins or varying length. They may have a small dorsal fin. They all have large heads compared to the size of their bodies and have large wide mouths with the bottom jaw often much larger than the top jaw. Some have many long parallel grooves along their throats and bellies which allow their throats to expand when they feed. They can usually be found in small groups or ‘pods’. Their skin is often covered in white scars from being injured by fish, sharks and other whales. The young appear to be very similar to the adults although usually of a lighter colour. They vary in colour from grey to black, their bellies usually lighter than their backs.
|Where do they live?
Baleen whales are found in all oceans and all temperature zones of the world. They are found in both deep and shallow water. Many of them live, at least for part of the year, in the polar oceans where there is a rich abundance of food. Others live in tropical and temperate waters. Some undertake great annual migrations from polar to tropical waters. Little is known at all about the distribution and movements of some, while others, like the humpback, live in reasonably well defined populations with a well defined pattern of movement and migration. They are usually either solitary or found in small groups.
|How and what do they eat?
Baleen whales eat a diet of small fish and zooplankton. Their diet changes depending on where they are. In the Southern Ocean near Antarctica, they live on krill, a small shrimp-like zooplankton. In the waters of the Arctic, however, the same species of whale will eat small fish instead. These whales are filter feeders. They take a great mouth full of water and then close their mouths and squirt the water back out through the baleen which acts like a sieve, letting out the water but trapping any fish or plankton in the baleen. Often the whales feed cooperatively. ‘Bubble-netting’ is a good example of this where several whales swim in ever smaller circles around a school of fish or krill blowing bubbles as they go, herding their prey into a tight mass, then swimming up through the concentrated school of prey with their mouths open. Some migrating whales, like the humpback, may not feed for several months while they are migrating and in the tropics, feeding again only on their return to colder waters during the summer.
|What eats them?
Baleen whales have very few predators and are considered to be very close to the top of the food chain. There are very few other examples of animals so high on a food chain existing entirely on animals that are so low (eg. krill). Killer whales and large shark have been seen attacking baleen whales, particularly calves, but it is very rare to see an adult attacked by any natural predator. The biggest predator of whales has been man with the commercial whaling industry taking millions of whales over the last few centuries.
|How do they grow and reproduce?
Baleen whales are mammals and, like most other mammals, give birth to live young which then suckle on milk produced by the female (‘cow’). Only one young is produced at a time. Due to the size of the whales, many of the young are very large at birth, a newborn blue whale being 7m long and weighing several tons. Gestation is 10 to 12 months. Unlike most mammals, the calves are born tail-first or ‘breech’ presentation. The calf has then to get to the surface to take its first breath and is often helped up by the mother or ‘nurses’ that may be accompanying the mother. The calf is fully formed and very active almost immediately after the birth. The whales’ milk is very nourishing and the calves grow at an enormous rate. A blue whale calf will grow 9m and increase its weight 10 fold in 7 months. Most calves are weaned off the cow within a year or so of birth. Little is known about the life span of baleen whales, but it is thought that they probably live for at least 30 years, some people suggesting up to 100 years for some species.
|Who do they live with?
Most baleen whales tend to be either solitary or occur in small groups or ‘pods’. Occasionally larger pods will occur during the breeding season or during cooperative feeding. Several species may be seen close to each other without apparent antagonism especially when the whales are feeding on large schools of fish or ‘blooms’ of krill. Baleen whales have their own species of parasites including intestinal worms internally and ‘whale lice’ externally. One theory as to why whales may strand is that they may get a parasitic infection of the inner ear or brain that may cause them to become disorientated and so strand, either by accident, or to prevent drowning. Sometimes dolphins have been seen ‘bow riding’ in front of baleen whales.
|Their connection with people.
The greatest interaction between humans and baleen whales has been, until recently, commercial hunting. Hunting whales has occurred since prehistoric times, but its impact on the whales has increased along with our sea-faring ability. By the mid-nineteenth century whaling had spread to every ocean in the world and many whale populations had disappeared or were under severe threat. Today there is still some limited hunting of baleen whales occurring around the world but on a much smaller scale than in the past. These days the greatest direct interaction with humans is with tourism or ‘whale watching’ where people, fascinated by the whales, take trips out to see and photograph the whales in their natural environment. There is some debate as to whether this close attention is having a negative impact on the whales. The whales themselves are considered quite harmless but can display aggressively if they are unduly harassed or disturbed by people. Occasionally boats have been known to accidentally hit whales while at sea causing damage to the boat and probably to the whale. Scientists also study baleen whales in the wild because they are too big to keep in captivity.
Baleen Whales and Sound Some baleen whales can make powerful and complex noises. Sound travels much further underwater than light and so is used by whales for communication. The blue and fin whales are known to produce very powerful sounds that are so low that we cannot hear them. These sounds can travel for many thousands of kilometres underwater and so can potentially be used to communicate over entire oceans. Humpbacks produce a great variety of different sounds like moans, groans, trills, crying sounds and squeaks. They arrange these sounds into ‘songs’ which are sung by the males during the breeding season probably to attract females. These sound do not travel nearly as far as the blue and fin whales’ sounds but may be heard over distances of at least 50km. Most baleen whales also use sound as a short range communication to maintain links between members of a pod, especially between cows and calves. These sounds tend to be much simpler grunts and groans.
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