link to AFSC home page
Mobile users can use the Site Map to access the principal pages

link to AFSC home page link to NMFS home page link to NOAA home page

What do you know about cetacean strandings?

Every year, hundreds of whales, dolphins, and porpoises strand along ocean coastlines around the world.  This phenomenon is known as stranding. 

What are strandings?

Strandings are a natural phenomenon when whales get "stranded" or stuck on a beach.  Most stranded cetaceans are already dead or very ill; however some cetaceans are alive and seemingly healthy.

Which species of cetacea strand on beaches?

Of 78 species of cetacea, only 10 species regularly mass strand and another 10 species occasionally strand.  Interestingly enough, most mass strandings occur in toothed whales species (such as sperm whales,  beluga whales and pygmy sperm whales). 

What causes cetaceans to strand?

Scientists don't know.   Some think that whales strand intentionally to rest or seek safety of land or to rub their skin.  Others believe that disorientation,  confusion of sonar signals in shallow water, or effects of parasite infestation of the inner ear may cause strandings.  However, the most compelling scientific theory about strandings has  to do with whales using the earth's magnetic field to navigate their environment. 

What magnetic sense?  Do cetaceans have a magnetic sense?

Many animals can detect the earth's magnetic field.   For example birds use this sense to migrate from North to South during the long seasonal migrations and it is thought that some cetaceans may also use magnetic sensing.   Anatomical evidence shows that many whales have crystals of "magnetite" in their brains.  This magnetite could be used by whales to sense the magnetic field of the earth.  

What are single strandings?

Single strandings occur when one cetacean strands on a beach.  Single strandings are most often the result of illness or injury.  Sometimes this means that the cetacean died of natural causes and then tides and winds washed them ashore. Other times this means the cetacean is alive when it strands but usually it dies soon afterward. 

What are mass strandings?

Mass or multiple strandings are rare.   Mass strandings often result in the death of a whole group of whales.  Occasionally the animals can be saved by refloating the entire group and releasing them all together.  Cetaceans in a mass stranding that are released one by one tend to re-strand themselves--possibly because of the attachment that they feels towards the rest of their groups.

Do all cetacea die when stranded?

Unfortunately, most whales are already dead or do die when stranded.   However some stranded cetacea are saved by tides (they just swim away) and some others are saved by human efforts. 

If I find a whale, dolphin, or porpoise stranded on the beach, what should I do?

Strandings are one of the few ways that people get a first-hand look at marine mammals.  In most cases, the animal will be dead and maybe even decomposed.  All you can do is report this stranding to local authorities and/or a local, appropriate, scientific organization.  

If the animal is newly stranded it may still be alive but physiological stress will be weakening the animal by the minute.  Check to see if the animal is alive by watching for breathing through the blowhole at the top of its head.   Whales can hold their breaths for up to 15 minutes so you may not be able to tell however if the animal is breathing immediately.  Notify the local authorities so that they can call a stranding network or local veterinarian.  While waiting for help to arrive, you can keep the animal's skin moist with water or by draping it with a soaked cloth. Do not splash or cover the blowhole and do make sure that the blowhole is clear of water and sand. When help arrives it is possible that they may or may not be able to save the animal.   If there is no help available, allow the animal to die in peace by simply leaving it alone and allowing no other people near it.  Under no circumstances should you ever try to put the animal out of its misery.  Stranding is a sad but very natural part of life.

Go back.


This portion of the MML website is intended for a student audience and their educators.
Information within the education website should not be cited in scientific journals or publications.


            | Home | Site Map | Contact Us | FOIA | Privacy | Disclaimer | USA.gov | Accessibility | Print |           doc logo