Welcome to our first monthly whale feature. We will start this series with the sperm whale, which is the 15th whale you will encounter with our audio guide.
The sperm whale is typically dark grey with white lips, and they have very large heads (25-35% of their total length). Sperm whales are the largest of the toothed whales, meaning they have teeth instead of baleen plates. There is a noticeable difference in size between males and females, with females averaging 11 meters in length and weighing 13.5 tonnes. Males are quite a bit larger, averaging 16 meters in length and weighing 44 tonnes.
Sperm whales use strong echolocation clicks to search for food and communicate with each other. It‘s believed that their clicks are strong enough to knock a human diver unconscious if the diver is close enough!
They regularly dive to depths of 500-1000 meters and remain underwater for 40 minutes at a time. Some individuals have been known to to dive more than 2000 meters for up to 2 hours, and they are believed to be able to dive to depths of over 3000 meters.
The main food source for sperm whales are medium and large squid and fish. Many sperm whales bear scars along their body from battles with giant squid. Sperm whales around Iceland tend to hunt for bony fish more than squid.
Close family ties exist within groups, especially with the females. Males will form temporary groups with other males of a similar age, and older and larger males that have reached full maturity commonly separate from the groups to lead solitary lives. Only male sperm whales have been observed in Icelandic waters, as the females and calves tend to stay in temperate and equatorial waters.
The life expectancy of sperm whales is 60-70 years. It‘s quite difficult to make accurate stock assessments as they spend very little time at the surface and have a wide global distribution. Some estimates place the population at 360,000 individuals and others place them at 1.5-2 million, with an estimated population between 1 and 3 million before whaling began.
Today the only natural enemy of the sperm whale is the killer whale, which preys on calves and injured individuals. Sperm whales were hunted from around 1500 well into the 20th century, which decimated their numbers. Today the largest threats that sperm whales face is sound pollution and becoming entangled in the fishing nets.
Sperm whales can be seen off the west coast of Iceland, and occasionally in the north. They are most commonly seen in late spring and summer (April-September).