Why are so many North Atlantic right whales turning up dead and injured?

North Atlantic right whales are one of the most critically endangered species in the world. Scientists estimate that fewer than 340 remain—and fewer than 70 are reproductive females capable of bringing new calves into the world.  

With numbers that low, every death brings the species closer to extinction.  

Since 2017, the North Atlantic right whale population has been devastated by an unusual mortality event. But what does that mean, why is it important, and how can we stop it? 

What is a marine mammal unusual mortality event? 

The U.S. Marine Mammal Protection Act defines an unusual mortality event as "a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response."  

Because it is U.S. federal legislation, the act covers strandings on U.S. beaches or shores, or in waters under U.S. jurisdiction. Of course, unusual mortality events can—and do—happen in other countries too. But when they happen somewhere the U.S. has jurisdiction, the Marine Mammal Protection Act outlines immediate actions that government agencies must take to research the cause and to minimise further deaths. 

The U.S. has declared more than 70 marine mammal unusual mortality events since 1991. 

What happens when there is a suspected unusual mortality event? 

A working group of marine experts is alerted within 24 hours of a potential unusual mortality event. Katie Moore, IFAW’s deputy vice president—animal rescue, is currently a member of the working group. 

If the working group decides that the strandings meet the definition, they provide their recommendation to either NOAA Fisheries or the U.S. Fish and Wildlife Service, depending on which marine mammals are affected. In the case of North Atlantic right whales and other cetaceans, NOAA Fisheries is responsible and has a National Contingency Plan outlining which actions to take. 

The working group also recommends how money from the UME Fund should be used. For example, this fund can help wildlife organisations care for ill or injured animals or allow researchers to collect tissue samples and investigate causes of death. 

What’s causing the current North Atlantic right whale unusual mortality event? 

This mortality event is ongoing since 2017, when 17 North Atlantic right whales died. 

The leading causes are vessel strikes and entanglements in fishing gear. Vessel strikes cause agonising and deadly injuries, such as open wounds and blunt-force trauma. Fishing gear weighs whales down, stopping them from moving freely, feeding, or reproducing. The gear can also cut into their blubber, muscle, and even bones and they slowly die of infection, exhaustion, or starvation. 

But why are so many whales coming into deadly contact with ships and fishing gear? 

One reason is that North Atlantic right whales live in coastal waters, mostly along the continental shelf. They feed on plankton often found near the ocean’s surface. 

Another reason is that their migration patterns are changing. Climate change and a warmer ocean means their food sources are moving further north in summer, now extending to the Gulf of St. Lawrence in Canada, which is heavily used by fishing and shipping industries. 

Why is this unusual mortality event particularly worrying? 

The species was declared endangered in 1970, and since 2010 its numbers have fallen rapidly. In 2020, the IUCN moved the species to the critically endangered list, noting that the total population had declined by approximately 15% since 2011.  

In 2023, 114 deaths, injuries, and illnesses have been documented within the UME. Worryingly, research suggests only a third of right whale deaths are documented, so the actual figure is much higher. 

That’s compared to only 57 calves born since 2017. Instead of having calves every three years, females now have calves every six to ten years. This may be due to stress from entanglements, navigation of vessel traffic, increasing ocean noise, as well as their food sources being negatively impacted by climate change. 

Studies also indicate that females are dying at faster rates than males and that their average lifespan is shrinking from around 70 years to around 45 years. Again, this is likely due to human-caused factors placing too much stress on bodies that are already vulnerable from reproducing. Tragically, when females die, they can leave behind calves who depend on them for survival. 

That means the effects of this mortality event are long-term, complex and could push the species to extinction. 

How can we reduce the threats North Atlantic right whales face? 

IFAW’s biologists, veterinarians, and policy experts are tackling the crisis from many angles by collaborating with other scientists, local fishermen, consumers, and policy makers in the U.S. and Canada.

Science 

Our Song of the Whale research expedition is helping us understand these whales’ changing migration patterns, so we know how and where to reduce the life-threatening risks they face.  

Our Whale Alert app is a tool based on citizen science, where whale sightings submitted by the general public are used to help to establish speed zones and trigger alerts to mariners to be cautious of whales present in the area. This ultimately reduces the risk of vessel strikes to whales. 

Technology 

We are leading the way in whale conservation by developing methods to save injured and entangled whales at sea. This is the only project on the East Coast of the U.S. with the equipment and experienced personnel to deliver medications to fight infections caused by extensive injuries, or sedatives to calm right whales so they can be disentangled. 

We also work directly with the fishing industry and underwater technology companies to advance on-demand fishing gear—crucial for allowing fishermen to sustainably continue their livelihoods while protecting whales’ lives. 

Policy 

We’ve worked with members of the U.S. Congress to introduce, and ultimately pass, the North Atlantic Right Whale Coexistence Act and with the U.S. and Canadian governments to implement and enforce speed restrictions for vessels, as well as advocating for rerouting of high-volume shipping lanes to protect right whales during migration season.  

By performing necropsies on right whales, our team determines causes of death and assesses health. We use that critical information to evaluate the efficacy of existing conservation policies and inform future policies needed to ensure population recovery.  

If we don’t act now, these incredible creatures could reach a tipping point in the next five years. Because human actions are pushing these whales to extinction, we can—and must—make changes that will protect and conserve them.