Blog by Hanna Michel, Special Tours Guide
Earlier this month, we encountered a couple of killer whales or orcas on one of our whale watching tours here in Faxaflói, the bay off the coast of Reykjavik. Even though they do not belong to the species that we typically see in the bay, we would like to take this sighting as an opportunity to tell you more about them.
The two individuals that we came across a very well known: They belong to a pod (group) of orcas that travel between Iceland and Scotland (Northern Scotland, Shetland, and Orkney)! These seasonal movements were first reported in 2015 when seven orcas had been sighted in both places. However, in the meantime, the number of these intrepid orcas has increased to at least 20 that we know of. Still, it is a small number compared to the over 300 orcas that have been identified in Icelandic waters so far. This is known from comparing photos of orcas from both Iceland and Scotland. The dorsal fin and the gray saddle patch behind it look different in each orca – it allows the identification of individuals just like with human fingerprints. This is an important research method called photo-identification which is used on a variety of whale and dolphin species all over the world.
In other places like the East coast of North America, killer whales have been photo-identified for longer than here in Iceland. By having recorded individuals for more than 50 years now, we have learned so many things about their social life as well: They live in tight family groups that are typically led by the oldest female, i. e. the mother or grandmother of the family group. Her children and grandchildren will often stay with her for their entire lives – this is very special in the animal kingdom, only a few other cetacean species appear to live in similar family structures! The young ones learn their family´s hunting strategies, customs, and dialect over the first few years of their lives. Their lifespan is comparable to humans: Especially female orcas regularly live beyond their 60s and can live to be older than 100 years!
Orcas, in general, hunt a large variety of prey species, from fish, seals, birds, large whales, and other marine critters like octopi. However, each group has its preferences and Icelandic orcas are specialized herring hunters. While hunting herring, they emit a low-frequency call that makes the swim bladder of the herring vibrate. Studies suggest that herring react to these calls by forming a tight swarm which makes it easier for the orcas to hunt them. Typically, orcas use their fluke (tail fin) to debilitate the herring and then feed on the stunned fish. Therefore, the closer the herring swims together, the more effective are their tail slaps. The Icelandic Orca Project is doing great work studying our local populations and solving some of the mysteries revolving around orcas. We still have a lot to learn about them.
The IUNC (International Union for the Conservation of Nature), which maintains and updates the so-called “Red List” of endangered and threatened wildlife, classifies orcas as “data deficient”. That means that we do not have enough data on the species to evaluate their status and risk of extinction. However, some distinct populations of orcas, e.g. Southern Residents of the Pacific Northwest, are classified as endangered. Unfortunately, the outlook for many populations is rather grim. As an apex predator at the very top of the food chain, what can cause a problem for killer whales? The culprit is the pollution of our oceans with chemicals like PCBs. These substances were once widely used in paints, hydraulic fluids, coatings of electrical cables, and more. They are persistent and build up in the food chain through a process called bioaccumulation. The further up the food chain a species is, the higher will be the concentration of the chemicals they accumulate throughout their lifetime. In this way, their status as apex predators becomes a disaster for orcas. PCBs affect the animals’ immune and reproductive systems, leaving them prone to disease and infertility. A recent study predicts the collapse of many orca populations over the next 100 years. With each of them, we are in danger of losing a unique part of our marine ecosystems forever.
PCBs have been banned near-globally for more than 30 years. However, once these chemicals have leaked into the environment, they are extremely difficult to remove. The least we can do now is becoming better stewards of our oceans and make sure no other chemicals like PCBs keep polluting them.