Why do whales beach themselves? The theories behind marine mammal strandings
Issued: 20 Oct 8 mins read

Potential causes of marine mammal strandings

While the causes of marine mammal strandings aren’t fully understood, scientists and marine biologists have solid theories as to why these creatures beach themselves. Some of the factors below can interplay, which makes it tricky to pinpoint why a marine mammal winds up on the beach.

Natural causes

An animal that is sick or injured, senile, lost, having trouble finding food, or even just old can be prone to stranding. A weaker animal may get carried by the current until they reach the shore, while a disoriented creature can simply wander into the shallows and get stuck. Birthing and mating behaviours also bring whales closer to shore, which naturally increases their risk of beaching.

Navigational errors

Some stretches of coastal ocean switch alarmingly quickly between deep water to sand banks. The echolocation whales use to navigate is designed for the open ocean, so their sense of direction can get thrown off in the shallows. Sandbanks absorb the whales’ sonar too fast, effectively turning a whale’s internal GPS off – then before they know it, they’re land-bound.

This issue is limited to toothed whales (also known as Odontocetes). Inshore populations like bottlenose dolphin, snubfin dolphin, and humpback dolphin species are very comfortable navigating shallow coastal waters.

Predation

Like humans, animals will flee from a threat driven by pure panic – sometimes without any regard for what’s ahead. In their haste to escape a predator, whales and other marine mammals can get too close to the shore and become stranded.

Topography

The unique, shallow nature and tidal ranges of coastal areas make them a bit of a trap for larger marine life. Tides can move incredibly quickly – sometimes receding several kilometres in a matter of minutes – which leaves animals close to the shore high and dry.

Mass strandings can occur repeatedly in the same coastal areas – New Zealand’s Golden Bay is a prime example, with the area seeing multiple whales come ashore throughout the year. That being said, there are plenty of locations with large tides and shallow waters where strandings don’t happen – there are many variables at play.

Human causes of marine mammal strandings

Not all strandings are natural – many are linked, directly or indirectly, to human activity. Noise pollution from ships, sonar, and industrial operations can interfere with the whales’ finely tuned hearing, disrupting their ability to communicate, navigate, and hunt. In extreme cases, sudden bursts of intense underwater noise have been linked to mass strandings of deep-diving whales.

Pollution and runoff also play a role. Chemicals, plastics, and agricultural waste entering the ocean can accumulate in the food chain, leading to illness, poisoning, or disorientation in marine mammals. Harmful algal blooms, sometimes fuelled by nutrient-rich runoff, have been shown to produce toxins that affect the brains and behaviour of dugongs, dolphins, and whales – leaving them vulnerable to stranding.

On top of this, fishing gear entanglements and ship strikes can injure or weaken animals, making them more likely to wash ashore. Climate change adds yet another layer of stress, shifting prey availability and altering migration routes in ways that can push whales and dolphins into unfamiliar – and sometimes dangerous – coastal areas.

What to do if you find a stranded marine mammal

If you’ve spotted a stranded marine mammal, it can be tempting to get right in there and help. However, it’s vital that you keep your distance – it’s best for you and the animal. Here are the right steps to follow if you encounter beached marine life in Queensland:

• If you see a marine mammal stranding, report it by using the free QWildlife app for iOS and Android, or call 1300 130 372 (Press option 1). This will alert a nearby Queensland Government officer or trained strandings responder.

• Provide as much information as possible such as your location, a description of the problem, and what type of animal is stranded (along with as many identifying features as possible).

• Take photos if possible – this can be very helpful.

• Leave your name and phone number for any follow-ups.

Once you’ve made contact, the staff on the line will give you instructions on any next steps you can take. If you can’t get through to an officer or responder, leave a message with the above details. Be sure not to approach, touch, or interfere with the animal – just maintain a safe distance and keep quiet. Ensuring any curious dogs, small children, and bystanders are kept away is vital.

As tragic as it is to come across a deceased stranded marine mammal, these unfortunate events are part of the natural circle of life. The best thing you can do is follow the advice above to keep all parties involved safe.

Committed to threatened species protection

While marine mammal strandings are largely out of our control, plenty of initiatives are in place to protect vulnerable species in Queensland from other threats. The Queensland Government is dedicated to leading the charge on threatened species research, conservation, and recovery through investment and direct action.

By collaborating with First Nations people, landholders, researchers, businesses, government, non-government organisations, volunteers, and local communities, we’re doing the work to address threats to our natural world – including our precious marine life.