Australian_Geographic_-_February_2016_

January. February 35

A

USTRALIA

has a long
history of
whale strandings.
They often occur
(or are noticed
more) in summer
months and are most common in
Tasmania, but they occur with some
regularity all around our southern
coastline. On a global scale, Australia and
New Zealand are hotspots for mass
strandings. Within Tasmania, Circular
Head and Macquarie Harbour/Ocean
Beach are areas where they frequently
occur, and this may be related to coastal
topography. Strandings can also occur
singly, and in these cases the animal is
often sick or dying.
Recent mass strandings include:
29 pilot whales that died at New
Zealand’s Stewart Island in November
last year, 18 that were stranded (and 12
that died) at Bunbury in Western
Australia in March, and seven sperm
whales that died on South Australia’s
Yorke Peninsula in December 2014.
Other strandings have been even more
dramatic – 38 dolphins and 44 pilot
whales were beached at New Year
Island, north-west of Tasmania, in 2012;
while another incident in 2009 saw 177
animals stranded on nearby King Island.

But why do mass strandings occur?

There are many reasons and little clarity

as to the major culprit, but there are

some patterns. The kind of whales that

beach en masse are more likely to be

open-ocean species that don’t spend a

lot of time in the shallows (though this

is not an absolute rule), and are those

that live in close-knit social groups.

Whales that strand are often toothed

species – such as sperm whales, com-

mon dolphins, and pilot whales – not

filter-feeding baleen whales. More

than 3500 long-finned pilot whales

have been stranded in Tasmania since

records were first kept.

Sometimes strandings are down to

navigational errors. Research from the

University of Tasmania and the

University of WA shows that the flow

of cold, food-rich ocean currents close

to shore, and places that have wide,

gently sloping coastlines, can lead to

confusion, which results in disaster.

Strandings at Tasmania’s 33km Ocean

Beach are thought to be down to such

topography. Ear infections, which limit

the use of echolocation, have also been

implicated – and if one pod member

becomes stranded, its distress calls can

lead other members of the group to

follow, with often fatal consequences.

In some cases, sickness from toxic

Australia is a global hotspot for mass whale strandings.

The causes of these events are many, varied and often mysterious.

Why do whales

strand themselves?

NATURE

algal blooms, viruses and other agents

have been implicated. In that situation,

the animals may simply have been too

sick to swim anymore.

There’s also evidence that shipping

noises and military sonar frighten or

distress whales, causing internal haem-

orrhaging or decompression sickness as

they flee towards the surface. There’s

little doubt sonar is responsible on some

occasions, but since mass strandings

were written about by Ancient Greek

philosopher Aristotle in 350 BC, it’s

clearly not the only explanation.

Perhaps the oddest theory is that

whales intentionally beach themselves

in mass suicides – mooted in situations

where casualties appear otherwise

healthy – but there is little evidence to

confirm this seemingly far-fetched idea.

Processes for helping stranded

whales have been improved in recent

years, meaning smaller whales can be

refloated if rescuers act swiftly, and act

carefully to minimise chances of them

stranding again. Larger sperm whales,

which can reach 18m in length, are

much more difficult to refloat and

often have internal injuries caused by

the pressure of gravity on internal

organs, meaning they can’t be

saved. If you spot stranded

whales it is important to call

local authorities to summon

help quickly. In Tasmania

you can dial the Whale

Hotline on 0427-WHALES

or 0427 942 537.

Wild Australia

with John Pickrell

JOHN PICKRELL

is the editor of AUSTRALIAN

GEOGRAPHIC. Follow him on

Twitter: @john_pickrell.

Pilot whales

strand more than

any other species.