Water Wise Animals
Teacher notes to accompany the Water Wise Student Work Sheet to be completed
at Alice Springs Desert Park
BEFORE YOUR VISIT
To prepare your students for a visit to the Desert Park to complete this task, you may
like to do some preliminary work on the requirements of animals, in particular their
need for water. You may then go on to discuss how animals that live in the desert
need to be very Water Wise to ensure their survival.
You may also like to learn about the behavioural and physical adaptations of animals
before you visit the Park, and simply use your visit to look at the examples, or you
could teach all the information below in a single visit to the Park. The method you
chose will be dependent on how deep you want to go, how long your visit is, and of
course, the learning needs of your students.
If you require assistance with planning, or would like a guide to accompany you
please contact the Park on (08) 8951 8788.
FACTS
Australian deserts are characterised by huge extremes in temperature & highly
unpredictable rainfall. During the middle of summer, daytime air temperatures climb
into the high 40's and the temperature of the ground may be 70 degrees or more. In
winter, night temperatures can drop well below zero, the climb into the 20’s the next
day.
Access to an adequate supply of water is essential for all life because water is a major
part of the cells of living things. The major survival problem faced by desert animals is
that of water conservation (maintaining their "water budget"). Animals that live in the
desert have special features that help them survive the dry heat. These special
features are called adaptations.
There are two main ways that animals can adapt to improve their water conservation:
•
Physiological adaptations - an animal’s PHYSICAL structures that help it
survive the dry heat (eg desert frogs having the ability to store water in their
bladders & in the tissues between their muscles & skin).
and
•
Behavioural adaptations - an ACTION that an animal can take to help it
survive the dry heat (eg to avoid the heat desert frogs burrow underground
where it is cooler & they can remain dormant until the next rain).
PHYSICAL ADAPTATIONS
Reptiles are very well suited to the desert environment due to their physical
adaptations. This is why Central Australia is often referred to as the Land of the
Lizard – we have more reptiles (particularly in Sand Country) than in any other
habitat in the world.
NOTE: Reptiles do also have behavioural adaptations (e.g. basking in the sun) but
for now we are going to concentrate on their physical ones.
1. Reptile skin is highly keratinised (keratin is the protein that our hands and
nails are made of). This means that reptile skin is very resistant to water loss
(we sweat though our skin but not through our nails!)
2. Reptiles have special mechanisms for reducing water loss from their eyes.
Some, like the Central Netted Dragon, have shades over their eyes, and
snakes have a clear piece of skin over their eyes.
3. Reptiles don’t pee! Unlike mammals, that need to flush waste out of their
kidney with water and produce liquid urine, reptiles excrete non water soluble
waste that can be almost solid. This means that reptiles don’t waste precious
water when they go to the toilet.
4. Reptiles have a high salt tolerance. If we don’t drink enough, we can end up
with a dangerous build up of salt in our cells. We drink water to dilute it and
flush it out. We store salt INSIDE our cells. Reptiles have the ability to store
salt in the spaces IN BETWEEN their cells, so the salt levels in their cells
don’t get too high. Many reptiles have salt secreting glands, which enable
them to get rid of this salt when it builds up. For example skinks and goannas
have nasal salt glands and are able to ‘sneeze’ the salt out.
5. Reptiles’ bodies are designed to get 90% of their body heat from the sun and
only 10% from food (mammals like us get all our energy from food). This
means reptiles need less food (an advantage in the desert where food is often
scarce). If we compare a mammal and reptile eg a 1kg Quoll and a 1kg
Goanna, the Quoll would need approximately 65kg of food per year and the
Goanna would only need 5kg.
1. Thorny devil (Moloch horridus)
• The striking colours of the Moloch are not only used for camouflage but also aid
in the regulation of body temperature. They achieve this by moving melanin to the
skin surface to draw more heat (thus becoming darker) or allowing it to recede
when they have attained their preferred body temp (thus becoming more pale).
This ability does not appear until a Moloch is 13-14 weeks of age.
• Life in a place often devoid of rain has led the Moloch to develop another
remarkable adaptation. Narrow grooves separating the scales of the skin form a
continuous network to the mouth. This means that a light rain or any moisture
drawn from the soil moves to the mouth by way of capillary action (can use the
crack in cement analogy).
• The Moloch’s overall life strategies can be regarded as conservative. Their
exclusive diet of small ants is not particularly nutritious and therefore does not
permit a high-energy output or rapid reproduction. They are relatively slow to
mature and live for up to 15 years.
2. Military dragon (Ctenophorus isolepis)
• The life strategies of the military dragon stand in stark contrast with those of the
Moloch in the previous display - that is, they live fast and die young.
• Military dragons usually only live for one year in the wild (but some of our display
animals are 4-5 years old), and are dead before their offspring hatch. This
usually means that emerging young do not have to compete with the previous
generation for food, which is a good strategy if you live in a drought prone area
where food may be scarce.
• This species has long hind legs and long toes that enable it to run at high speeds
to catch larger ants (such as the fast “racehorse” ants) and other insects - and to
escape from predators.
3. Panther skink (Ctenotus pantherinus)
• Its streamlined body-shape enables it to swim through the spinifex as it hunts
juicy termites, spiders and other insects.
• The Panther skink prefers a lower body temperature to that of other lizards (and
is thus referred to as a "cool lizard"), coming out to hunt in the late afternoon and
early morning.
4. Mulga Snake (Pseudechis australis)
• If you look at its eyes you’ll see that like all snakes it has a clear spectacle over
its eyes which helps reduce water-loss.
• These snakes can change their behaviour during different seasons, and may be
diurnal in the cooler months but more crepuscular or nocturnal in the summer
months.
BEHAVIOURAL ADAPTATIONS
The native MAMMALS found in the desert regions of Australia are great examples
of animals that use behavioural strategies to survive in the hot dry desert. (Not
having as many physical adaptations as the reptiles, it is mainly their behavioural
adaptations that have helped them survive).
The main behavioural adaptation displayed by most of these mammals is to AVOID
the heat & dehydration:
1) By being NOCTURNAL - only active in the cool of the night.
2) By digging BURROWS or nesting in well insulated logs/nests (a burrow a metre
deep maintains a constant temperature of around 25 degrees C, even if it is 40
degrees or – 4 below zero, on the surface). This also creates a more humid
“microclimate”.
3) When possible eating food with a high water content such as invertebrates (which
are 60-80% water) meaning most small desert mammals rarely need to drink.
4) SMALL is BEST - small size is a formula for success for desert animals.
It means smaller amounts of food to support less body weight. Although rarely
seen, there are a surprising variety of small mouse-like creatures in the
Australian deserts.
1. Mala (Lagorchestes hirsuitus)
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•
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Prefer succulent, nutritious herbs and grasses but when times are tough they
can survive on harsh fibrous desert plants like spinifex, supplemented with
insects and seeds. Because of this Mala do not need to drink. (Mala have a
large caecum (part of their digestive system) for extra fermentation of the difficult
to digest fibrous plants like spinifex).
Mala escape the heat during the day either in shallow scrapes under bushes or
tussocks of grass or in a burrow dug up to the length of a human arm. The
burrow not only protects it from heat but also from fires.
Mala being a species of wallaby also hop like kangaroos, which is a very energy
efficient form of locomotion in the deserts.
2. Bilby (Macrotis lagotis)
•
Bilbies are very good at digging and dig burrows up to 2m deep and 3m long,
spiraling steeply down, often with side tunnels and separate entrances in
termite mounds, grass tussocks or below shrubs. In the middle of summer in
•
the heat of the day when the sand is 60-70 degrees two metres down in the
burrow it would be in the early twenties.
Having large ears helps cool down these animals by acting like air
conditioning units. The warm blood supply is very close to the skin surface (&
thus to the air), & heat can be released from the animal’s body.
3. Spinifex Hopping Mice (Notomys alexis)
•
•
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live on a relatively dry diet of grass, seeds and roots, so how does it survive
without drinking water? Well they have very effective kidneys that absorb
every drop of water from the waste, so little moisture passes out by excretion.
In other words these rodents have the world's most concentrated urine of any
mammal, however even with its “super kidneys” it still can’t compete with
reptile excretion:
If we compare the concentrated urine produced by the Spinifex Hopping
Mouse, to that of a goanna, the Hopping Mouse has a 7 millilitre water loss for
every gram of waste nitrogen, the goanna only has a 2.7 millilitre water loss!
4. Ghost Bats (Macroderma gigas)
•
•
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Shelter from the heat in cool caves and come out at night to hunt.
Being carnivores means that their diet has a high water content.
They use their wings not only for flight but also to wrap around themselves
when it is cold and to fan themselves when it is hot.
Concluding notes
You may like to summarise all the different Water Wise strategies that you have seen
today and then link them to humans. For example “unlike the animals of the desert,
we are not physically adapted to the dry conditions, we sweat to keep cool and so need
to drink water frequently in the heat”. You may also like to discuss a variety of Water
Wise behaviours that humans can demonstrate in their daily lives.
Links for further study
If you have not already connected with the Water Wise Project Officer, you may
like to talk to them about further Water Wise activities that your students can do.
[email protected]