First off, for reference, here is a USGS map showing the extent of the Mojave Desert

And here is the range of the Desert Tortoise

The USGS office in Henderson, NV


On the way to the first field site in Nevada.






The habitat here is characterized by Creosote bush(Larrea tridentata), White Bursage (Ambrosia dumosa), Mojave Yucca (Yucca schidigera), and Joshua Trees (Yucca brevifolia).

Landscape with Joshua Tree



They can get much bigger than this (up to 15 m) and may live for several hundred years. Joshua Trees are (for the most part) found only in the Mojave Desert and are an important component of the desert ecosystem as they provide shelter, food, and shade for many animals.




Young Joshua Tree from above


Mojave Yucca (Yucca schidigera)



Beavertail Cactus (Optunia basilaris)


Vanessa tracks a tortoise

Burrow entrance

Checking to see this is the right burrow

Making a burrow tag


On the way to another NV study site.

This is the site of a study examining the effects of invasive vegetation and dust suppressants on the physiology of desert tortoises. Each fenced in pen contains several young tortoises.



A sprinkler system provides water to the enclosures

While the Mojave has historically been free of fires, recently the spread of invasive grasses has facilitated fires. At this recently burned site we are studying the effects of fire on desert tortoises.

Burned Joshua Tree



Horse bones



The crew

AJ inserts temperature loggers into a tortoise burrow


Barrel Cactus (Ferocactus cylindraceus)




Hedgehog Cactus (Echinocereus engelmannii)


Silver/Golden Cholla (Cylindropuntia echinocarpa)



Cholla skeleton


Black-tailed Jackrabbit (Lepus californicus)


First herp sighting, a Side-blotched Lizard (Uta stansburiana)

Going for a hike



From up here you can clearly see the border between the burned (lighter) and unburned (darker) areas


Desert Trumpet (Eriogonum inflatum)

We took a trip to the Desert Tortoise Conservation Center (DTCC), which is home to over 1,000 “rescue” tortoises. See the DTCC’s blog here.


Las Vegas skyline in the distance

Adult tortoise pens


Pens housing juvenile tortoises being used for a USGS study

Emma checking out the pens


Baby tortoise out sunning

Another young tortoise in artificial burrow







Repairing the shade tarp over the pen


Now on to California…

Hiking to one of our many weather stations to download data




Checking out an old mine


Someone’s shack

Tort-ass (note cobwebs at burrow entrance – this tortoise has not left the burrow anytime recently)

A caliche burrow, for the more upscale tortoise

Tracking

Checking inside a burrow

Marianne and Jose recording data

Jose found a second tortoise in the burrow of the one he had tracked, so he pulled it out to see if we could put a transmitter on it.

They can be hard to reach

Got it! But notice it already has a transmitter – at the time we could not verify the identity of this tortoise, and because there was a possibility its transmitter had died, we attached a temporary one.




Annuli




Patrick tapes on the temporary transmitter



While most tortoises remain inactive during the winter here, there are exceptions. For example, here’s a young tortoise I found in the process of digging a new burrow. Note the portions of the carapace where parts of the keratinized scutes are missing and bone is exposed. Not sure of the cause of this, but it is apparently pretty common. Any thoughts?


Another mine


Oxidized copper


Tortoise plastron bones

Burrow with evidence of predation (tortoise could not be located)

Erodium cicutarium (introduced)


Patrick weighs a new tortoise

Measuring shell dimensions






You can tell this one is a male by its concave plastron

The shell is cleaned before attaching the transmitter

Attaching the transmitter

Labeling transmitter with the tortoise ID#


Extra reinforcement

Silicone gel is used between the scutes to allow for flexibility with growth

Finally, the tortoise ID# is glued onto the shell.


The finished product

Well that’s all for now, lots more to come once the tortoises start to warm up!
-Zach

Part 1
Part 2
Part 3
Part 4
Part 5
Part 6
Part 7