Northern bottlenose whales

NORTHERN BOTTLENOSE WHALES

Documenting unusual coastal occurrences of North Atlantic beaked whales

Northern bottlenose whales are a mysterious species of beaked whale found only in the North Atlantic. They generally live far offshore and little is know about their ecology and life history. They are rarely found in shallow coastal waters and when they are, it could mean that something has gone wrong. Over the years, we have documented unusual occurrences of northern bottlenose whales in coastal Iceland and Scotland, sometimes involving fatal strandings, in an effort to understand why they were there and whether it could be prevented. In collaboration with the University of Iceland and University of Edinburgh.

Background

Diving to feed for hours at a time in offshore regions, beaked whales are incredibly difficult to study. The northern bottlenose whale (NBW) is no exception. One of the largest beaked whales, NBWs are found in cold temperate and sub-Arctic waters of the North Atlantic. Like all beaked whales, NBWs are deep divers, with the current record being 2339 m for 94 minutes! They dive to feed (mostly fish and squid, but also sea cucumbers and starfish!) or possibly to evade predators.

Unlike most beaked whale species, NBWs are very curious and will often approach boats. Partly because of this, NBWs were commercially hunted, with more than 60,000 whales caught in the 19^th and 20^th centuries. Whilst populations have recovered in some areas, numbers are likely well below pre-exploitation levels. NBWs also face modern threats from humans. For example, they are very sensitive to underwater noise, particularly naval sonar. As far as we know, they respond to sonar by diving deep and away from the source. After such long, deep dives, dangerous gas bubbles can form within their tissues, commonly known as the bends (as in humans), when whales quickly ascend to the surface. If severe, this may lead to death or stranding; this phenomenon has led to several mass mortality (stranding) events for beaked whales in recent decades.

Aims

In response to unusual coastal occurrences and strandings of NBWs, we aim to:

1. Document the occurrence and stranding in as much detail as possible
2. Understand why these occurrences and fatalities have taken place

Project details

We have studied NBWs in two locations: North Iceland and southwest Scotland. Our experience with NBWs started in 2018 with unprecedented occurrence and strandings in Skjálfandi Bay and wider North Iceland. Large numbers of animals were seen over a prolonged period, whales became increasingly emaciated and six animals died. We published this information in Marine Mammal Science in collaboration with the University of Iceland and University of Edinburgh. This study used whale-watching vessels as opportunistic research platforms and was an amazing citizen science effort.

We have studied NBWs in two locations: North Iceland and southwest Scotland. Our experience with NBWs started in 2018 with unprecedented occurrence and strandings in Skjálfandi Bay and wider North Iceland. Large numbers of animals were seen over a prolonged period, whales became increasingly emaciated and six animals died. We published this information in Marine Mammal Science in collaboration with the University of Iceland and University of Edinburgh. This study used whale-watching vessels as opportunistic research platforms and was an amazing citizen science effort.

In 2020, similar occurrences took place in Scotland, particularly the lochs of the southwest. We spent two weekends looking for and tracking the movements of bottlenose whales, at least three of which sadly died soon after. In particular, we used a theodolite to collect movement data from a group of three NBWs in Gareloch – home to one of the largest naval bases in the UK, Faslane – with the University of Edinburgh.

We have continued to observe NBWs outside of these times, including a group of mother–calf pairs in the Westfjords and a dead stranded male NBW in the Westfjords. Whilst we haven’t discovered what caused these particular occurrences and deaths, it could be natural or human-caused. By adding to a limited knowledge base about this species, we hope that our observations will contribute to addressing these questions in the future. We do not have specific plans for future NBW monitoring but we are always ready to document future occurrences to add to the body of information for these beaked whales.