Why do cetaceans strand?

5th Oct 2017

- Common dolphin strandin in Fareham Creek

When a common dolphin stranded in Fareham Creek, Hampshire, two members of the ORCA team were on hand as volunteers for the British Divers Marine Life Rescue.

We talked to one of them, our Education Coordinator Anna Bunney, to find out a little more about strandings and why they happen.

What does it mean when a cetacean is "stranded"?

Stranding describes any marine mammal (either alive or dead) that has become stuck on land and is unable to free itself. Most commonly it takes place on beaches when animals end up in shallower water and get into distress, but it can happen in rivers, estuaries and other waterways. In 2006, a northern bottlenose whale stranded several times in the Thames near to Battersea Bridge.

What causes strandings in cetaceans?

There are a number of theories as to why marine mammals strand, and it is likely that there are multiple causes. Typically animals who are distressed or disorientated are more likely to strand, and evidence has been found that noise pollution may confuse animals and result in strandings.

An increasing trend is also that animals who strand have high levels of plastics and associated toxins in their system. Sometimes this includes plastic bags and other litter in their stomachs, resulting in malnourishment, whilst other cases have seen other toxins, such as polychlorinated byphenals, in high volumes in the animals.

What risk does stranding pose to cetaceans?

Stranding is a potentially lethal threat to whales, dolphins and porpoises and so action needs to be taken very quickly. In the water, the mass of the animal is supported but on land this weight begins to put significant pressure on the animals internal organs and can cause significant damage very quickly.

Animals can also cause serious injury to themselves trying to refloat, and it is common to see physical injury as a result of stranding events.

What should you do if you come across a stranded animal?

If you come across a whale or dolphin that has been stranded, the first thing to ensure is that you keep well clear. Not only are these animals in distress and potentially vulnerable, but in the main they are also large and powerful animals and may inadvertently injure members of the public.

The first point of contact should be British Divers Marine Life Rescue (BDMLR). BDMLR have a team of trained volunteer Marine Mammal Medics who work across the UK to respond to animals in distress. You can find their contact details at www.bdmlr.org.uk.

Once BDMLR representatives are on site, they will take control and liaise with the relevant other agencies.

What can I do to prevent strandings?

Some human caused environmental factors have been associated with strandings, such as plastic and chemical pollution, so anything that minimises your environmental impact will help.

You can also support marine conservation charities, like ORCA and BDMLR, who are working to protect marine mammals across the UK.

Finally, you can even train as a volunteer to help have a more direct impact on marine conservation - ORCA have their network of Marine Mammal Surveyors, whilst BDMLR run their Marine Mammal Medics across the UK.