You've probably heard of the desert tortoise
This 12-inch 10-pound reptile is a mojave's most iconic animal.
But you've probably never seen one.
The real deal is a rare sighting,
as they spend almost 95% of their lives underground.
And they're also disappearing.
Joshua Tree has lost 90% of its tortoises in the last 40 years.
But while some fear that we may be witnessing the end of the Mojave desert tortoise,
Joshua Tree is part of a national effort to save them.
Welcome to Desert Tortoise 101.
Today, we'll meet a tortoise:
We'll learn what they are,
where they live,
and how they survive in joshua tree national park
We'll also try to understand the threats they face,
and see what we can do to help them on their slow and steady march
into an uncertain future.
It is estimated that desert tortoises,
as we know them today,
have been around for 15 to 20 million years.
But what are they?
Well, they're tortoises.
a family of reptiles that, unlike their turtle relatives,
spend their whole lives on land.
They are herbivores,
meaning that they eat only plants.
and their serrated jaws make short work of their food.
But the most notable feature is their shell,
which is made up of bone
from their ribs and their spine,
but it's covered with a layer of keratin.
keratin is actually the same material as your fingernails!
Their shells grow with them throughout their lives,
ranging from the size of a silver dollar at birth
to a dinner plate at adult age.
When threatened,
they can pull their head and limbs
completely inside their shell for protection.
and they need this good defense
because they are, well,
slow.
when it comes to where they live,
there are actually three different species of desert tortoise
native to the deserts of North America.
There's the Sinaloan tortoise that's found in Mexico,
and the Sonoran tortoise that's found mainly in Arizona.
But we're focusing on a species found in Joshua Tree,
and the only one protected by the endangered species act,
and that is the Mojave desert tortoise.
Unsurprisingly, they live throughout the Mojave Desert,
and here in Joshua Tree,
they can be found virtually anywhere.
Valleys,
bajadas,
washes,
and up to 4 000 feet in elevation.
But tortoises are reptiles,
they're cold-blooded
which means they can't regulate their body temperature.
And if you've been to Joshua tree, you know that
we have some of the most extreme temperatures throughout the year.
Lows can be below freezing,
highs over 110 degrees
and ground temperatures, where these tortoises live,
can reach 140 degrees Fahrenheit.
Which begs the question:
How do they survive here?
We mentioned earlier that they spend up to 95% of their lives underground.
Those extreme temperatures help us to explain why.
Tortoises use their front legs to dig multiple burrows:
shallow underground hideouts to avoid the summer heat,
and tunnels up to 10 feet long for winter's cold.
In their winter burrows, they enter brumation, which is basically hibernation for reptiles,
between the months of October and February.
They'll use the same tactic when it's hot out in the summer,
by entering a state of torpor called aestivation.
In the spring and fall they emerge to eat and mate,
but unless it's nice outside they're going to stay underground
But even if you can survive extreme temperatures
by living mostly underground,
that still leaves the tortoise with one big problem:
water.
On average tortoises in Joshua Tree will only see 2.5 - 3 inches of rain each year.
Which really isn't much.
So it makes sense that they've learned to make the most
of what little they get.
Tortoises seem to have a mental map
of places in their habitat where water collects,
And head straight towards those areas during rainstorms.
Sometimes they'll even dig their own catchment basins in the dirt,
like a shallow depression,
to catch water.
But as it turns out, most of the water they get is extracted from their food.
Which can be green grasses, wildflowers
and even those fruits that grow in cactus.
So whether it's from a puddle or a prickly pear fruit,
they store that water in their bladder for a very long time.
Their bladders can hold 40 % of their body weight in water and waste
which helps them survive during prolonged dry conditions
But despite these adaptations, desert tortoises are struggling.
Before 1990, in Joshua Tree,
there were an estimated 30 tortoises per square kilometer.
Now there are only three tortoises per square kilometer .
We know this because we count them,
monitoring their populations almost like a tortoise census.
but we also want to follow their movements, and see where they spend their time.
And that's where technology like radio telemetry comes in handy.
We've outfitted some tortoises with non-invasive radio transmitters,
which emit a signal we can pick up using an antenna.
So as we search for one of these tortoises today,
let's talk about the threats they face.
one factor is habitat loss and degradation
due to development.
More and more people are moving to the Mojave,
putting up buildings where there once were burrows.
And while most of the development has happened outside park boundaries,
the impacts of development are far reaching.
Take ravens for example,
who thrive in human-built environments.
Their populations in the Mojave have exploded,
by some estimates, increasing 700 percent since 1967.
And ravens are smart enough to figure out that their beaks are stronger than juvenile tortoise shells.
It can take 10 years for tortoise shells to harden enough to protect them from ravens,
and another 10 years after that to reach maturity.
This means fewer tortoises can grow up and reproduce.
But even mature desert tortoises are threatened by development.
Roads are especially hazardous for desert tortoise.
This is because they're slow and steady,
it takes them a long time to cross the road.
But also, they're drawn to roads during rainfalls.
Water tends to collect on the pavement
and they'll make a b line straight for it.
The park tries to prevent these collisions
by setting practical speed limits,
installing warning signs at each and every entrance.
But that doesn't always work.
Finally, tortoises face pressure from climate change and drought.
despite their many adaptations that help them survive in the desert,
they do have their limits.
thanks to climate change, the Mojave desert is experiencing rising temperatures
and more severe droughts.
And studies project that tortoises will lose
most of their suitable habitat as this trend continues.
And to add insult to injury,
climate change also makes them more susceptible to disease.
Upper Respiratory Tract disease,
which was first found in the late 80s and early 90s,
can be lethal on its own.
But it's made deadlier by drought conditions.
All together, this paints a pretty bleak picture of the future.
So what are we doing about it?
As part of their ESA recovery plan, we continue to monitor tortoises like this one,
so we can better understand the threats they face,
and to make informed decisions about their management.
This tortoise is being outfitted with a brand new transmitter,
and will help us to understand how often they cross busy park roads,
if they're mating, and if they're laying eggs.
These are long-term projects.
Desert tortoises can live to be 80 years old,
and to study a long-lived species, you need a long-term data set.
Effective tortoise research can require upwards of 15 years worth of data.
We provide tortoise training to our partners our contractors,
and everyone working in the park.
Everyone at our work sites is tortoise aware.
We also have qualified biologists that are ready to respond whenever necessary.
They also have legal protections.
We talk with the public to make sure that everyone knows
that it's illegal to interfere with tortoises in any way.
The only exception is to help one get across the road,
and we have a whole video about that to do it safely.
But what can you do to protect tortoises during your time in the park?
Thankfully there are a lot of ways to help.
First of all, if you see one, give it space.
If you get too close to a tortoise they might void their bladders,
a defense mechanism that could waste hard-earned water,
and have life-threatening consequences.
That stress response is one of the factors behind the park's no pets on trail policy.
Even well-meaning pets are likely to put tortoises they come across at risk.
Next there's Leave No Trace principles.
It's always a good idea to leave our parks better than when you found them.
But when you clean up after yourself and others here in Joshua Tree,
you're reducing raven predation and protecting desert tortoises.
A big factor is to be mindful of your vehicle.
Tortoises are known to seek shade under cars,
so check under your tires before you drive away.
If you find one, give it space to move out on its own.
When you do drive, stick to the park roads.
Off-road travel, or even parking on the side of the road
can harm tortoises, collapse burrows, and damage habitat.
And the speed limit is what it is for a reason.
Any faster makes it hard to notice when a tortoise is crossing.
And finally, as desert tortoises grapple with these
hotter and drier conditions in Joshua Tree due to climate change
any meaningful efforts to curtail greenhouse gas emissions
will only improve their odds of surviving into the future.
There's a reason that desert tortoises are so beloved here in the park.
They've helped us understand and appreciate the desert.
A landscape that many find is hostile and uninviting,
but one that rewards those who move slowly, and look closely.
There are a lot of obstacles ahead for this lovable reptile,
but if it stands a chance,
it's because all of us are doing our part to help.
This has been Desert Tortoise 101,
thank you so much.