Desert
Desert
Desert
Desert
Some hot, some cold, some in-between.
As you will discover, each desert has
its own unique animals and plants.
form?
pictured here.
It is found throughout
the Sonoran Desert.
prefer this omnivore?
is the Sonoran?
is more dangerous?
cactus called and
what makes it
so extraordinary?
It's a javalina! Few people recognize it outside the region, as it doesn't get much press.
It may look like a domestic pig or a wild boar, but it is NEITHER. It is a distinct animal family.
Javalina have long, sharp canine teeth, or "tusks," that they use for defense and can be quite dangerous when threatened. They will fiercely defend their young. So don't mess with them.
Javelina live in large family groups of about 10 members. Each family defends their territory.
They communicate with each other through smells and sounds, as they have poor eyesight.
Though they PREFER agaves and prickly pears and eat cactus, berries and seeds, they are actually omnivores. In a pinch, they will eat eggs, snakes, fish, frogs, dead birds and rodents.
Not many predators other than a mountain
lion will attack an adult javelina.
Remember those tusks!
However, predators for younger or more
vulnerable javalinas include bobcats,
jaguars and coyotes.
With their poor vision, javalinas rely on their
sense of smell and keen hearing to detect
approaching predators.
The Sonoran Desert is a HOT desert. Summer temperatures exceed
40°C (104°F), frequently reaching 48°C (118°F). HOT! HOT! HOT!
Temperatures at night cool down by about 15-19°C (27-34°F).
So, HOT days and warm nights.
It is the most tropical desert in North America. At lower-elevations,
temperatures are warm year-round, and rainfall is irregular and
and infrequent, often less than 90 mm (approx. 3.5") annually.
The Arizona uplands are also warm year-round, but receive more
rainfall, averaging 100–300 mm (4–12") annually.
The saguaro is a tree-like cactus that only grows in the Sonoran Desert. It can be HUGE.
In fact, it is the largest cactus in the United States, growing 10 to 50 feet tall.
That is somewhere between a three and four story building!
They are only about 30 inches across.
They have massive root systems that can spread to 100 feet, which is double their height.
These cactuses can live up to 200 years. They only begin to develop their upturned arms
when they are around 75 to 100 years old. Some never grow arms at all and are called spears.
Saguaros are such a dominant feature of their habitats, that they have come to represent the entire Southwest in popular culture and media. They are an icon for the region. The saguaro
is also a keystone species, integral to the activities and life cycles of many other species.
Black widow spiders are significantly smaller than most tarantulas,
with female black widows measuring about 1.5 to 2 inches in length,
while tarantulas can reach up to 11 inches across their legs!
The bite from a tarantula supposedly feels like a bee sting, with pain in the area of the bite.
It looks like a bee sting, too, with redness and some swelling. Regardless, the tarantula's venom
is considered only mildly toxic and seldom triggers severe reactions in humans.
A black widow is another matter. These spiders have large fangs and glands that produce toxic venom.
When bitten, the venom attacks the nerve endings in your muscles, causing severe, bodywide muscle pain
and cramping. Only the female black widow bites. The males are too small and can’t break through human skin.
Black widow spider bites typically occur when humans come into direct contact with their webs.
They only bite when threatened. So DON'T threaten them. Seek medical attention if bitten.
no true wild camels live in the Sahara. They are either domesticated or feral. Camels
only arrived in the Sahara around 200 AD, as part of trade caravans from Arabia.
Camels are remarkably well-adapted to arid environments and can survive 10-21 days
without drinking water. Their humps store fat for use later for both energy and water.
Camels have incredible adaptions to AVOID losing water: thick, syrupy urine and
faeces so dry that they can be used to start fires.They even avoid losing water when
they breathe! Camels can withstand a loss of up to 30% of their bodyweight in water.
lions
hyenas
jackals
wolves
cheetahs
can prey on camels, especially young or weak ones, but predation is not a major
threat for healthy adult dromedaries, due to their size and the harsh desert conditions.
on Earth but it is only the third-largest desert overall.
The polar deserts of Antarctica and the Arctic are actually larger.
The Sahara is primarily composed of rocky plateaus and bare earth,
with sand dunes and sand seas covering only about 25% of its surface.
The central Sahara is hyperarid, with sparse vegetation. It receives less
than 1 inch (25 mm) of rain annually, and some areas may go years without
any rainfall at all. The northern and southern reaches of the desert, and the
highlands, have areas of sparse grassland and desert shrub, with trees and taller
shrubs in wadis, which are shallow depressed areas where moisture can collect.
carnivores
consume this
herbivore?
large
herbivore
shown below?
the climate
like in the
Sahara?
is the
Sahara
located?
summers and cool winters, but with little to no rainfall throughout the year.
Daytime summer temperatures are extreme, with average highs often exceeding
40°C (104°F) and potentially reaching record highs of 50°C (122°F) or more.
Worse yet, is the heat of the ground itself, which can easily reach 80 °C (176 °F) or more!
On average, nighttime temperatures tend to be only 13–20 °C (23–36 °F) cooler
than in the daytime. So nights are warmer than legend might have you believe!
During winter, daytime temperatures in the hyperarid regions are generally mild,
hovering around 18-25°C (64-77°F). It is cooler in the northern and highland regions.
Sahara's most
poisonous
animals?
Its venom has a potent neurotoxin that can cause
excruciating pain, and in severe cases, can be lethal.
Deathstalkers are adapted to the desert environment.
They hide under rocks and in burrows,
emerging at night to hunt insects, not people!
They play a crucial role in the desert ecosystem
by helping to control insect populations.
carnivore that
raises its young
in Antarctica
carnivore have
any predators
on land?
Antarctica
considered
a desert?
the penguins
get their food?
windiest continent on Earth. It is a desert because its yearly precipitation can be less
than 51 mm (2 inches) in the interior. That is HALF the rainfall average for the Sahara!
Ironically, Antarctica has more than 90% of the Earth's fresh water locked up in its
permanent ice sheets. With so little precipitation, where did all this water come from? Around 34 million years ago, a shift in climate caused the continent to enter
a "34 million year winter" -- lots of time to accumulate snow when it never melts!
one-third of chick deaths in some colonies.They also scavenge dead penguins.
A far greater threat to penguins is climate change. Emperor penguins breed on sea-ice platforms, with chicks hatching in the winter (Southerm Hemisphere) from late July to mid-August. The chicks are reared until they develop waterproof feathers, typically in December ahead of the summer melt. But if the ice melts too early, the chicks do not have this waterproofing. Their feathers become water logged and the chicks either drown or freeze.
and sometimes krill in the cold but productive currents around Antarctica. Penguins are
great divers, frequently exceeding depths of 1700 feet (500 m) in their search for food.
Male emperor penguins go without food for as long as four months, from the time they arrive
at the breeding colony until the egg has hatched and the mother returns. Males lose almost
half of their body weight fulfilling these parenting duties. They rely entirely on the reserve
of body fat that they built up during their summer feeding to survive the long winter.
of the Australian outback?
What makes it unique?
most common predator?
in the Australian deserts?
has become a dominant
herbivore in the outback?
of Australia and why is it
sometimes called
"porcupine" grass?
settlers in the 1840s. Camels were very useful for transport into the dry interior of the continent.
As railroads and modern transport methods replaced camels, their handlers, who had often formed
deep bonds with their camels, frequently released them into the wild. There are now over one million
feral camels in Australia and that population may be doubling in size every eight to nine years!
Average daily summer temperatures are typically 37-39°C (98-102°F).
Occasionally, it may climb into the low 50's (120's). Scortching!
Nighttime temperatures typically drop to around 20°C (68°F), warm but not punishing.
Average daily winter temperatures range between a very pleasant 16-24° C (61-77°F).
Nighttime temperatures in winter rarely drop below -2 or 3°C (28-26°F).
Spinifex or "porcupine" grass is not a green carpet you would want to tip-toe through with bare feet!
This grass has spiky quill-like extensions that resemble the quills of a porcupine. OUCH!
These long, stiff, needle-like structures have barbs that can pierce the skin
when stepped on directly, hence the term, "porcupine" grass.
Spinifex is native to Australia and is extremely drought tolerant.
Australia, and the largest living marsupial. Marsupials carry their developing young in a pouch.
A joey is barely the size of a jellybean when first born. This tiny embryo manages to crawl into
its mother's pouch, where it continues to develop for eight months before it begins to venture out.
Kangaroos are herbivores. To escape their predators, they have developed great leaping skills.
Adult red kangaroos can jump as high as six feet (1.8 m) and leap a distance of 29 feet (8.8 m).
Dingoes can and do attack adult kangaroos. The dogs hunt in packs, chasing a targeted kangaroo
to exhaustion. Dingoes do not bark like a dog. They howl, yelp, whine, growl, snort and even purr.
Dingoes have a strict social hierarchy and tend to mate for life.
The tasmanian tiger used to hunt kangaroos, but humans hunted the tiger to extinction.
So humans eliminated one predator and introduced another! Humans, themselves, also hunt roos.
large herbivore
still found in the Gobi?
common predator
of this wild ass?
are now gone,
or nearly so,
from the Gobi?
is the Gobi?
Describe its weather.
expanding?
fast runner. It has never been successfully domesticated.
One of its unique adaptations to the Gobi Desert, is its penchant for digging wells to
access underground water in apparently dry river beds. Other animals in the Gobi, both
wild and domestic, including humans, rely on these wells for survival.
This cantankerous nomad migrates vast distances in search of food and water in the Gobi.
Unfortunately, the Mongolian wild ass population is declining due to poaching and competition from grazing livestock. The species is classified as endangered.
The snow leopard has fewer than 1000 individuals left in Mongolia, so it is not likely that they represent much of a predation issue for the Mongolian ass, at this time.
Confrontation with and poaching by humans represents a far greater threat.
The Gobi is a cold desert, as it is both far north and on a plateau that is 910–1,520 m (2,990–4,990 ft) above sea level. It qualifies as a desert, as it gets about 194 mm (7.6 in) of rainfall annually.
Average winter minimums are a frigid −21 °C (−6 °F),
while summertime maximums are a warm 27 °C (81 °F).
Most precipitation falls during the summer. The day and night temperatures vary greatly, as much as 35 °C (63 °F) in 24-hours!
A small, threatened population
of 7000 exists in the northern Gobi Desert. It may survive.
Wild Bactrian camel
There are only about 950 wild Bactrian alive today. A small proportion of these live in a protected area in Mongolia.
Caspian Tiger
This tiger species once inhabited the Gobi Desert, and surrounding areas. It was officially declared extinct in 2003.
The Gobi is the fastest growing desert on Earth.
It is also a significant source of dust. The ongoing desertification, particularly in the southern regions, has increased the frequency and intensity of these dust storm events. The image to the left is of Beijing in Feb, 2021 during one of these storms. The NASA image above it, shows the world wide flow of dust coming from the Gobi and from the Sahara in 2001. Lots of DUST!
at our planet.
Look at the HOT deserts
on the map on the next slide
Do you see a pattern?
In which latitudes do most of them form?
The most arid regions are between 15° and 35°
north and south latitudes. (NASA)
Do hot desert form on the eastern
or western edges of each large land mass?
Most hot deserts are found on the WESTERN
sides of continents in the subtropics.
What causes these patterns?
Hadley cells and prevailing winds.
Go to the next slide to discover more.
you need to know that the Sun
does NOT heat the Earth uniformly.
The equator gets the most intense heating.
Watch this video.
As the air rises, it cools. Cold air cannot hold as much moisture as hot air, so it rain and rains, creating conditions around the equator for rainforests to thrive.
The air that rises at the equator, eventually sinks back down at the 30th parallel. This downward flow of very dry air creates hyperarid HOT deserts. These great cells of circulating air are called Hadley cells. Watch this video.
the great cells of circulating air
that help determine the location of
climate zones and biomes across out planet.
Where Deserts Form on Earth
the Hadley cells appear to be expanding and widening.
Imagine the impact on precipitation and agriculture were the hyperarid regions
of hot deserts to widen and expand toward the 40th parallel.
Hot Dry Deserts in the Subtropics.
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2.jpg "Beijing Sandstorm March 2021 (2)2")
