Wildlife
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TRANSCRIPT:
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Donovan: Where Two Deserts Meet is an official podcast of Joshua Tree National Park. Joshua Tree National Park acknowledges the Serrano, Cahuilla, Mojave, and Chemehuevi people as the original stewards of the land in which the park now sits. We are grateful to have the opportunity to work with the indigenous people in this place and we pay our respects to the people past, present, and emerging who have been here since time in Memorial.
Donovan: Hi, I'm Donovan.
Ian: And I'm Ian.
Donovan: And we're both park rangers here at Joshua Tree National Park. Where Two Deserts meet is a podcast where we investigate topics that often require a bit more detail, and sometimes, the help of an expert in the field to gain perspective.
Ian: Donovan, have you heard any good animal facts recently?
Donovan: My favorite go-to animal fact is that the rattlesnakes that we have in the park smell with their tongues.
Ian: Elaborate.
Donovan: Joshua Tree National Park is home to six different species of rattlesnakes which are part of the pit viper family. Pit vipers have special pit organs that they use to catch prey. Those cute little tongues that pop in and out of the rattlesnake’s mouth help transfer the smells and temperatures of its surrounding. The pit organs are located in the front of the face and they allow the rattlesnakes to sense out the smell and heat of its prey.
Ian: I'll admit that is a pretty good fact, but I've got a few of my own tucked up my sleeve. Did you know the desert tortoise moves at an average speed of 0.2 miles per hour.
Donovan: Okay, but how long would it take them to get to the other side?
Ian: Very clever.
Donovan: I'm sure that both of us can go on and on, but you know who would have even better facts about some of the wildlife here at Joshua Tree National Park Wildlife ecologists? Michael Vamstad. He always has some great insight about some of the amazing animals in this park such as bats, bighorn, and big old tortoises.
Michael: My name is Michael Vamstad and I'm the wildlife ecologist here at Joshua Tree.
Ian: Tree National Park is home to hundreds of different species of wildlife, including roughly 250 different species of birds and about 150 types of mammals and reptiles. As you can imagine, the roles and responsibilities of the lead wildlife ecologists here are very diverse. it's Michael's job to monitor and work with many of these species within the park, but some often require special attention.
Michael: The most common species that I work with, or the ones I spend the most time on, are the endangered species or the species that are of special management concern: desert tortoise, and big horn sheep. Nesting raptors are another thing that every year we spend a lot of time.
Donovan: In 1973, the Endangered Species Act was signed into law creating protections for all plants and wildlife listed as threatened or endangered. This law requires all federal agencies to consult with the US Fish and Wildlife Service to ensure that the actions they authorize, fund, or carry out are not likely to jeopardize the continued existence. Any listed species or result in the destruction or adverse modification of designated critical habitat of such species. That was a mouthful, but essentially, it's saying that there are millions of species on planet Earth and tools like the Endangered Species Act help us better protect species who are at high risk of extinction. There is quite a lengthy process to get a species listed as endangered, but of course, the first step is figuring out what species needs our help.
Michael: An endangered species is simply just a species that has seen its numbers shrink or its habitat shrink. Its numbers are to a point where we're concerned about it being able to self-sustain into the future. A classic example would be the condors or the bald eagle, where DDT thinned their eggs to a point where we weren't seeing very many bald eagles. When they classify the species as endangered, it's really based on their abundances and distributions, when there’s been a big change in reduction. You have fewer of them around and fewer places. The desert tortoise is like the main one that the US Fish and Wildlife has listed for us. It’s the one that is inhabited in the park, the one we spend the most time on. There are a few other species like the yellow-billed cuckoo and the California gnatcatcher and a couple rails that come through the park during migration. There’s not a lot the park can do to manage endangered species, per se, because they're just passing through. We really focus on our resident species that are having a hard time. We have a couple plants that are also endangered, but the desert tortoise clearly gets the most attention from the park to conserve them. We really have some of the best protected habitat for the desert tortoise in the Mojave Desert. We really try to protect the best we can, and then keep our millions of visitors away from affecting them negatively in any way. The populations of desert tortoise have really changed in Joshua Tree since like eighties and nineties. During that time we did some very light surveys to get an idea of abundance or how many of them were on the landscape. And it turns out there’s anywhere between thirty or forty, or sometimes even close to fifty tortoises counted per square kilometer. Nowadays when we do those surveys, we're only finding three to four tortoises per square kilometer. So going from thirty down to three is a huge change. And as a scientist, we call that an order of magnitude reduction. That means usually like a tenfold reduction. And there's really little that you can argue about that kind of change. A lot of scientists, we look at different survey methods. Each survey method is a little different, so your numbers can be a little different, but when it is an order of magnitude change, thirty down to three, it's kind of undeniable. At that point, historically, we had pretty good populations in the park and we probably had close to 30,000 tortoises in Joshua Tree. And nowadays I estimate about 3000 tortoises. We've been a putting these little radio transmitters on the back of tortoises. What that allows us to do is to go out once every couple weeks to see where they're at and to see how they're moving on the landscape. Do they move miles at a time or do they just move a hundred feet at a time? Do they keep a same home range over the years, or do they really change and move around? And so, what we're trying to figure out, how can we get an idea of the movement patterns for those tortoises that live by roads? Is there a way to work with our million visitors and all that traffic on our roads to keep the tortoises from getting smashed on the roads? For example, during rainstorms, we've found that they tend to go towards wherever the water is. This can be the road. We have signage at each one of our entrances that tells people, “There’s a rainstorm right now. Please watch out for tortoises on the road. Those rocks on the road may not be a rock, but a tortoise drinking water. Additionally, we have tortoise crossing signs in the park that make people aware that tortoises are there and to drive slowly to avoid hitting them. That really is the biggest issue that we have.
Ian: The desert tortoise was added to the federal endangered species lists in 1990 after a significant reduction in their numbers was observed over the past few decades in Joshua Tree National Park. Estimates from past research indicate there were approximately thirty tortoises per square kilometer. However, there is now an average of roughly three tortoises per square kilometer. That's a massive 90% reduction of the population within. Tortoises that were once abundant roaming the desert and a relatively common site are now something you need to be lucky or diligent to find.
Michael: Yeah, the big reduction that we saw from the late eighties and nineties to now. We believe had two big issues that happened at the same time, and they worked together synergistically and negatively. An upper respiratory tract disease was introduced to the desert tortoise sometime in the late nineties, but we think it didn't get into the park until the early 2000s. What happened is that they basically get a really bad cold during a time when they need to conserve. Imagine having a really runny nose from a chest or a head cold, but you couldn't drink water to hydrate yourself. These tortoises were dying from the disease. This was coupled with drought. We’re also seeing these recurring severe droughts happening in the Mojave and we really believe that's from climate change. The effect of climate change is more severe droughts. And then you have this disease issue going through the population at the same time. Those two things working together reduce the tortoise population in the park. We believe the disease came from a pet tortoise or a tortoise in captivity that got introduced into the park. It's not a native bacterium that got into the tortoise. We've seen it in other reptiles and predominantly within the pet trade of tortoises across the globe. The mycoplasma agassizii, which is the name of the bug that got into the tortoise here in the Mojave, was really derived from other mycoplasma and bacterium from around the world.
Ian: Michael brings up a great reminder here that the wild desert tortoises that we have inside the park shouldn't have play dates with any pet tortoises you may have at home. It's nothi
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