How Animals Survive in Cold Conditions
Science of the Cold
One of the commonest questions
asked about animals in Antarctica is how do
they cope with the extreme cold conditions that
are found there?
Air temperatures averaging below freezing over
the year (usually well below freezing) with
a range in many places around -40°C
to +10°C and highs up to +22°C amongst
rocks and moss banks.
breed in the depths of the Antarctic
Weddell seals swim
in eater that is 2 degrees either side
of zero, the air temperature when they
leave the sea is often a lot colder
Much of Antarctica
is a cold largely featureless icy desert
where above freezing temperatures are hardly
reached if ever at all. The temperature of the
Antarctic Ocean that surrounds the continent
varies from -2°C to +2°C over the year.
Seawater freezes at -2°C so it can't get
any colder and still be water.
Antarctic birds and mammals
- penguins, whales and seals - are warm blooded
animals and they maintain similar internal
body temperatures to warm blooded animals in
any other climate zone - that is 35-42°C
(95-107°F) depending on the species. They
have to keep high body temperatures to remain
active. These animals are known as
+ therm-heat) as they generate their heat internally.
Antarctica's cold and wind mean that this heat
can very quickly be lost leading to
are ectotherms (ecto-outside)
, which means that they generate so little heat
internally they are dependent on the external
environment to warm them up to a level where
their body and enzymes function sufficiently
well enough for an active and functional life.
Typically they raise their temperature by basking
in the sun until they are warm enough to become
active. Reptiles and amphibians do this while
invertebrates are usually small enough to be
able to warm up quickly to the ambient temperature
from the air alone without basking in direct
A large ectothermic
Antarctic land animal would never get enough
energy regularly enough from the surroundings
to become sufficiently active once it had cooled.
All Antarctic land animals
of any size therefore need to be warm-blooded
to be active. Antarctica is such an extreme
environment that the size limit for an ectotherm
is about 12mm, the size of the largest
fully terrestrial (land) animal in Antarctica.
In other words any animal larger than this would
not be able to warm up enough to become active
before it started to get cold again.
is a land mass surrounded by a large very cold
ocean, so unlike the Arctic, purely land-dwelling
animals cannot readily migrate in order to leave
the continent in the long, harsh cold and dark
months of the austral winter. The largest purely
terrestrial animal found in Antarctica is a
flightless midge around 2-6 mm in length.
All other Antarctic animals are either smaller
than this or migrate spending some of the year
away from the deep south and the extreme cold.
They either swim or fly away - and back again.
Two examples of Antarctica's
largest land animal - the 1mm long wingless
midge Belgica antarctica has to stay
where it is year round (yes they are mating
Why do animals
go to Antarctica in the first place?
may seem very odd at first when you see pictures
of penguins and seals amongst ice strewn oceans
or snow and ice fields.
Why would any animal want to be there
at all? While it's all very picturesque and
makes for nice photos and videos, it's hardly
an inviting place to be, especially if you don't
have any shelter or support (as animals are).
The answer is a huge seasonal supply of food.
Due to upwelling's of deep ocean water bringing
high levels of nutrients to surface layers and
long day length of up to 24 hours for months
on end depending on the latitude, the southern
ocean is exceptionally productive.
This productivity starts as phytoplankton, microscopic
fast growing and reproducing plants that live
in the top layer of the ocean. These are eaten
by zooplankton especially Antarctic krill of
various Euphausia species, particularly
the species Euphausia superba (pictured).
There is literally millions of tonnes of potential
food in the Antarctic Ocean if you are able
to catch it and process it efficiently. Large
blue whales for instance can catch and eat 4
tonnes or more of krill a day for weeks on end
in the summer months.
Water has a thermal conductivity around
25 times greater than air when still, with movement
of the water and convection currents, this can
be 50 to 100 greater than air. This means that
you lose heat much quicker in water than air,
which you probably knew already.
The pink blush
on this chinstrap penguins flipper is
due to blood being diverted to cool
it down on in this just above freezing
point snow flurry
There is something called the "lower lethal
temperature" which is the temperature at
which an organism dies. This temperature in
water has never been measured for mammals such
as Antarctic seals and whales because it can't.
Even the coldest water (-2°C) doesn't result
in death meaning that these animals can live
indefinitely in cold water without suffering
Their skin surface temperature is nearly identical
to the surrounding water, though at a depth
of around 50mm beneath the skin, the temperature
is the same as their core temperature. This
is due to the insulating properties of a layer
of blubber (fat) under the skin. Blubber insulates
in water, fur and feathers insulate in air.
In the air a seals' skin temperature will often
rise as it needs to lose heat due to the air
being less good at reducing temperature. The
skin is well supplied with blood vessels that
can shunt blood to the surface or deep within
by the constriction or relaxation of tiny muscles
that close or open up blood vessels.
Penguins, seals and whales have flippers and
flukes without blubber that are poorly insulated
though well supplied with blood vessels, these
too can be used to lose heat when needed. When
it is necessary to retain heat, arteries surrounded
by veins act as "counter current heat exchangers"
to ensure that blood from the body heats blood
returning from the flippers, so retaining heat
in the core and minimizing heat loss through
the flipper or fluke.
Birds have similar counter-current heat exchangers
in their legs so they don't lose heat when swimming
in frigid water. Like the seals and whales,
the muscles required to operate these are deeper
in the warm parts of the body and movements
made via cord-like tendons.
Rockhopper flipper showing how little muscle there is with tendons which attach to
muscles that are deeper in the penguins body
to prevent heat loss
Animals that generate heat
from within by metabolic activity (warm blooded).
your own heat from within that is sufficient
to maintain a steady body temperature
requires two elements, making warmth and
then hanging onto it.
1 - Enough energy taken
in as food to generate the heat.
2 - Anatomical, physiological and behavioural
adaptations to retain the heat generated.
These two are bound tightly together, unless
you can raise and maintain your temperature,
you cannot be active enough to gather food,
so there aren't any large cold blooded terrestrial
animals in polar regions, once cold they would
never get warm again.
How do endotherms (warm
blooded animals) stay warm in extreme cold?
- All -
Most of all you need
to be large to reduce the loss of
heat from your skin.
- All -
Extremities tend to
be small to prevent undue heat loss.
- All -
You need to be well
insulated, internally immediately
under the skin with stored fat (blubber)
and externally with fur (the best insulation
of all, though useless when wet) or feathers.
- All -
Eat lots of high energy
easy to digest food to generate warmth
from within. All large animals (from the
smallest birds upwards) in Antarctica are
carnivores. Meat is a more concentrated
energy rich source of food than is vegetable
matter that doesn't grow very well or very
widely in Antarctica except as tiny plankton
in the seas which requires extreme specialization
to gather. Food supply is the main problem,
small animals cannot eat enough to keep
warm in extreme cold, they lose heat faster
than they can replace it by releasing energy
- Some -
in large or small groups is a good way of
getting protection from the wind and retaining
warmth, e.g. penguins.
- Some - Whales
and dolphins - never
leave the sea, so little exposure
to extremes of air temperature, then migrating
north when the air temperature drops enough
to freeze the sea.
- Some - Seals
- entering the sea
at times of extremely cold air temperatures
and high winds, then migrating north
when the air temperature drops enough to
start making the sea freeze.
- Some -
exchangers in flippers and feet means
that these parts are kept at a lower temperature
than the rest of the body to reduce heat
loss, blood is cooled when it enters and
warmed up when it leaves the flipper or
foot. e.g. seals and whales flippers, penguins
flippers and feet.
More about how
penguins stay warm in the cold.
Animals that have to get
heat from the outside (ecto - outside) environment
as they cannot generate enough energy from internal
metabolic processes to maintain a stable body
can warm up by basking (as most reptiles) their
activity is determined by the external temperature,
when it gets cooler, they just slow down eventually
becoming torpid (dormant, inactive).
There are no reptiles or amphibians in Antarctica
and very, very few terrestrial invertebrates
compared to the rest of the world, it is the
only continent without ants for example.
The largest land animal in Antarctica is a wingless
fly about 13mm in length, this and other similar
invertebrates are inactive for much of the time,
when the sun comes out and warms them up, they
become active for a few hours as long as the
temperature remains high enough, cooling down
even below freezing point when it becomes colder.
As they are so small, they can warm up quickly,
if they were larger, they wouldn't have warmed
up to active temperature before the external
temperature started to drop again.
These animals have lives
of temperature dependent stop-go, the stop
part can last for weeks or even months, the
go part can be just a few hours. They
live in and amongst rocks, moss and other vegetation.
Were they any larger or if they came out into
the open, they would be easy prey for birds,
especially if the temperature dropped causing
them to slow down while the warm blooded
animals could remain active.
Ocean is cold but the temperature is very
stable varying between -2°C and +2°C over
the year. It can
go down to nearly -2°C (actually -1.9°C)
before it freezes because the dissolved salt
reduces the freezing point of sea-water.
The Antarctic Ocean has been at this temperature
for around 20 million years giving plenty of
time for plants and animals that live there
to become adapted to life in temperatures that
would cause most aquatic animals to simply
slow down to a state of near torpidity (or
That they can do this is down to having very
specialized cold temperature adapted enzyme
systems, many Antarctic marine species are as
active at 0°C as their temperate counterparts
are at 20°C. Cool the temperate species
down and they virtually stop - however warm the
Antarctic species up and they soon start to suffer,
finding life at even +5°C difficult and most
probably dying long before reaching 20°C.
Many species of Antarctic fish have anti-freeze
in their blood, not so much against the temperature
per-se as against touching ice which at low
temperatures could cause a nucleation point
making the ice spread through their cooled bodies.
These anti-freezes are large
glycoprotein molecules that surround any small
ice crystals that may form, so preventing their
spread throughout the animals tissues which
would mean death. They also provide a tiny
cushion for the end of sharp ice crystals so
they are less likely to puncture cell
Interestingly only fish that are likely to encounter
ice have these anti-freezes, deeper living fish
way below the level of floating ice don't have
anti-freeze, they have a freezing
point above that of the sea-water in which they
live. They spend their entire lives in a state
of being "supercooled" that is, at
a temperature that is below their freezing temperature.
They can do this as they never come into contact
with ice crystals - such fish do not have anti-freeze
and live in the depths of the Antarctic ocean
- ice is only found in the upper reaches.
If these fish are brought to
the surface where they can come into contact
with ice, the ice will cause a nucleation point
that spreads in their bodies causing instant
freezing and death.
ectotherm, poikiliotherm, homeotherm,
heliotherm, warm blooded, cold blooded
There are many words used to describe the ability
of animals to maintain their body temperature.
Some are infrequently used these days but all
are used at some time or other.
The basic distinction is between animals such
as birds and mammals that maintain a stable
core temperature of around 35-42°C irrespective
of the environmental temperature and those whose
temperature is variable, more closely reflecting
the environmental temperature.
The reason that the nomenclature is not straightforward
is that there are animals that refuse to sit
cleanly in one of the two apparent obvious categories.
Some organisms clearly didn't read the rules
and sometimes make bits of themselves warmer
than other bits irrespective of the ambient
temperature or manage to maintain a stable internal
temperature without necessarily generating that
Warm blooded - Animals
that maintain a stable warm core temperature
of around 35-42°C, the temperature itself
usually being closely monitored, the actual
temperature is species dependent and often very
precise, 37°C in humans for example,
slightly more or less can cause major
Endotherm - Animals
that generate heat from within by metabolic
activity, usually this means that they can maintain
a stable core temperature of around 35-42°C.
The term can also apply some of the time to
fish such as tuna that are able to maintain
their active swimming muscles at 20°C or
so above the temperature of the rest of their
body by means of a counter-current heat exchanger,
this keeps the swimming muscle warm so it works
better and prevents heat loss to the rest of
Homeotherm - homo-same,
therm-heat, an animal that maintains a stable
warm body temperature.
Cold blooded - Animals
that have a body temperature the same as the
environmental temperature and are unable to
warm it above this.
Ectotherm - Animals
that cannot generate enough energy from internal
metabolic processes to maintain a stable body
temperature, heat comes from outside of the
An animal whose internal temperature varies
quite considerably (little used any more).
Heliotherm - An
organism that warms itself up by basking in
the direct rays of the sun.
Heterotherm - hetero-other,
therm-heat, an animal that differs in its body
temperature at different times.
It is possible that more than one of these terms
may apply to a particular animal at different
times, which could be daily or annually.