Toothed whales

Toothed whales are much smaller than baleen whales, with the single exception of the sperm whale. Toothed whales have teeth (usually) as the name suggests and consequently have quite different feeding habits than the baleen whales. Instead of filtering bulk food from the ocean, such as swarms of small fishes or crustaceans, they chase individuals, mostly squid and fishes.

Dolphins are often treated separately from other whales but are in fact just a family within the toothed whales. The most abundant non-dolphin toothed whales around Iceland are the harbour porpoise in inshore waters and the bottlenose whale in offshore waters. Sperm whales are also quite common.

Some other species have occasionally been seen around Iceland. Belugas (Delphinapterus leucas) and narwhals (Monodon monoceros) are high Arctic species and rather rare guests from the north. Similar as with the bowhead whales, they are usually associated with cold years and drift ice from Greenland. As the drift ice, they most often occur along the north, northeast and east coast. Both of these species were seen in Icelandic waters in 2007, a live beluga off the east coast and a dead beached narwhal in Þistilfjörður in the northeast.

Three species of beaked whales are also known mainly from strandings, Sowerby´s, (Mesoplodon bidens), Blainville´s (Mesoplodon densirostris) and Cuvier´s beaked whales (Ziphius cavirostris). They are however deep sea whales from offshore waters and very little is known about them.

Sperm whale (Physeter macrocephalus)

The sperm whale is by far the largest of the toothed whales. It can reach about 18 m in length and 34 t in weight, roughly similar as the sei whale. It has a global distribution resembling that of the large baleen whales and can be found all around Iceland, but is thought to be most common above steep continental shelf slopes. Sperm whales are offshore and deep water species and have been known to dive down to 2000 m depth, and possibly more, in search of prey. The main food is squid but it is also known that they eat fishes such as redfishes and lumpsuckers around Iceland.

Sperm whales were caught in some numbers in Icelandic waters during the latter half of the 20th century, or around 100 animals annually between 1948 and 1985. Sperm whales are fairly common in the ocean around Iceland but because of the long diving habit of the species the stock size is difficult to estimate. Roughly estimated numbers in Icelandic and Faroese waters are about 11,000 animals.

In contrast to the large baleen whales, where the females are the slightly larger sex, sperm whales show large sexual dimorphism in the opposite direction. Consequently the males can be more than three times heavier than females. The males have harems during the breeding period and probably fight for them. This also means that many males do in fact never have the opportunity to breed as they never get the chance to gain control of a pod. All known sperm whales in Icelandic waters are males; the females rarely venture into colder waters.

Northern bottlenose whale (Hyperoodon ampullatus)

The bottlenose whale is an average sized whale but quite large for a toothed whale. The mean size for males is 9 m and 4.5 t, the females are smaller. Its distribution is restricted to the North Atlantic but a closely related species can be found in the southern hemisphere. It is a deep water whale similar to the sperm whale and is rarely seen close to land. It occurs all around Iceland, although most common over the continental shelf break east and west of the country. When close to shore they can be in trouble since bottlenose whale strandings are quite common. The primary food is squid but fishes have also been found in its stomach.

Northern bottlenose whales have not been actively hunted by Icelanders except on rare occasions when spotted very close to shore. However, during most of the 20^th century Norwegian boats did hunt them on a large scale all over the North Atlantic, including Icelandic waters. It is quite possible that this reduced stock size. Nevertheless, bottlenose whales are quite common now. The absolute numbers are difficult to estimate since its diving rate and time is largely unknown. A rough estimate, however, is that the total stock in the entire North Atlantic is 50,000 to 100,000 animals.

The harbour or common porpoise (Phocoena phocoena)

Porpoises and dolphins are often grouped together, as they are small and in some ways similar. They are, however, not at all related, apart from the fact that both are toothed whales. The harbour porpoise is among the smallest of cetacean species and the smallest one in Icelandic waters. The average size of males is 1.5 m and 52 kg and females 1.6 m and 77 kg. The maximum size is about 2 m long and 90 kg. It is quite distinct because of its small size, the oval shape and short nose as opposed to the dolphins. It is quite common in Icelandic waters and as it is also the most coastal of all the whale species, it is quite often to be seen from the seashore all around Iceland. The species is migratory as almost all other whales. It is rarely seen along the coast in winter but arrives there early in spring. The porpoise mainly feeds on small fishes such as capelin, sandeels or redfishes but is otherwise quite opportunistic.

The number of porpoises around Iceland has been estimated at around 27,000 individuals, based on whale surveys in 1987 by the Marine Research Institute. This is a conservative number as the survey was not conducted in close inshore waters, where the porpoise is probably most abundant. There is currently no direct harvest of the porpoise in Iceland, but it often gets entangled in gillnets for cod or lumpsucker and may subsequently be eaten. This has been occurring in Icelandic waters for decades and there are no signs that the porpoise stocks have declined as a result. The porpoise grows quite fast and becomes mature 2 or 3 years old, which makes the stock quite robust for harvest. Porpoises were exploited to some extent in Iceland in the past, especially in early spring when other food was scarce. They were originally caught with spears, but during the 20th century also with special nets.

References and further information

References: (Ólafsdóttir & Víkingsson, 2004a), (Ólafsdóttir & Víkingsson, 2004b), (Ólafsdóttir & Víkingsson, 2004c), (Ólafsdóttir & Víkingsson, 2004d), (Ólafsdóttir & Víkingsson, 2004e), (Ólafsdóttir & Víkingsson, 2004f), (Ólafsdóttir & Víkingsson, 2004g), (Ólafsdóttir & Víkingsson, 2004h), (Ólafsdóttir & Víkingsson, 2004i).

For full citation and further information on the main species in general see this page

Hreiðar Þór Valtýsson, University of Akureyri