Mountain Yellow-Legged Frog: Restoring Ecosystem Balance

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Speaker 1: Hi, I'm Abney money and I'm Rick Schwartz. Welcome to Amazing Wildlife, where we explore unique stories of wildlife from around the world and uncover fascinating animal facts. This podcast is a production of my heart radio and San Diego Zoo Wildlife Alliance, in international nonprofit conservation organization behind the San Diego Zoo and Safari Park. This next animal is an endangered amphibian. Scientists estimate there are fewer than two hundred remaining in nature. Rick, the mountain yellow legged frog is endemic to California. So where in the state is it found? Ebony? These frogs are so fascinating and it starts with where they live. I think it's fair to say that most people, including myself when I was younger, think that frogs, well, that they like warm ponds or lakes and, you know, rivers in warm areas, maybe even tropical environments. But our friends the mountain yellow a good frog. Well, it's in their name. They kind of break the mold on what we kind of believe how and where frogs live. Found in the Sierra Nevada mountain ranges in California, including transverse ranges such as the San Gabriel Mountains and San Bernardino Mountains and more the mountain yellow legged frogs thrive in high elevations with cooler temperatures. They will inhabit high mountain lakes, ponds and streams. In the Alpine lakes used by mountain yellow legged frogs usually have open shorelines that are kind of grassy or muddy. Mountain yellow legged frogs also use stream habitats, especially in the northern parts of their range. So how would someone recognize mountain yellow lagged frog? That's a good question because, honestly, Ebony, they can be really hard to see. Even for the well trained scientists. They can have a hard time locating them, and that's partly because they are kind of small but also well camouflaged. On average, adults measure just over two inches to about two and a half inches in length from nose to rump, and they weigh about twin one to thirty three Graham. So keep in mind a normal sized paper clip ways just over one gram. So these frogs weigh about as much as taper clips. To kind of give you an example, it's not very big. And as far as their coloration, well, their underbelly is light in color, but they're back. Well, it's kind of this modeled mixture of black, greenish gray, Brown and yellow and, as the name suggests, there is a touch of yellow on their legs as well. So they may be hard to spot, but what about to hear? What sounds do they make? Do they have any recognizable sounds? Well, yes, evany the mountain yellow legged frogs. They do have a Croak, but it's sort of less of that ribbit ribbit that we, you know, are more accustomed to thinking frogs have. It's more of a raspy kind of Croak that well, when I've heard it, it it reminds me sort of like squeaky work boots. They also make clicking sounds as well, some of which can be communicated underwater. And male frogs will they have specific courtship calls to attract a mate, as well as calls to defend their territory and worn off other males. How common are these frogs in the Sierra Nevada region? Would people actually be hearing these sounds frequently? Unfortunately, Ebony, they are not as abundant as they once were. The mountain yellow legged frog was once considered the most numerous amphibian in the Sierra Nevada range, abundantly populating lakes, ponds and streams in the region. But at this time the data shows us that they have disappeared from over their historic range. So, yeah, not too many people are gonna be hearing them making their sounds. Wow, that's unfortunate. So when did the mountain yellow legged frogs numbers start to drop so dramatically? What? We look at the available studies, we can see that their numbers decline consistently in the early to mid nineteen hundreds and by the nineteen seventies it was noted that they were absent from most all of their native range and unfortunately, their numbers continued to drop in their early two thousands, and today it's estimated that there are less than two hundred individu rules left in the wild. So how did this happen? How did the mountain yellow legged frog go from being spotted throughout the Sierra Nevada to practically disappearing from its range? Yeah, their disappearance from their natural ranges has been a combination of a few things that, for lack of a better term, kind of created this perfect storm for their population loss. One of the early impacts that has been noted was the introduction of non native fish by humans to help create more opportunities for recreational fishing. Unfortunately, those fish prey upon the frogs, eggs and tadpoles, so these introduced predators basically are creating that impact. But again, that was just one thing of many that has contributed to their decline. Pesticides have also been found in the waterways and mining that has occurred throughout the Sierra Nevada ranges damaged habitats and polluted waterways as well. Long term droughts due to climate change have also impacted many species that rely on healthy waterways in the Sierra Nevada mountains. And if all that wasn't enough, well, is also disease. We have seen an alarming increase in the disease known as kittred fungus. This is a disease that impacts many amphibians around the world, including the mountain yellow legged frog, because it damages their skin, interfering with hydration, ion exchange and basically a majority of their functions that their skin offers them, essentially causing their body to shut down. It's amazing to hear how so many things are interconnected. So how has the disappearance of the mountain yellow legged frog impacted the ecosystem of that habitat? Well, I be like with many species, when we see their numbers drop, there is always a domino effect or something else that is impacted in the ecosystem. In the case with adult mountain yellow legged frogs eating insects on land and adult stages of aquatic insects, while the loss of the mountain yellow Lego frog population creates an increase in these insects, and with the Tadpoles or young mountain yellow lygod frogs before they're fully developed. They graze a lot on algae and keep the algae growth down in streams and lakes and ponds. Without them, that alergae starts to create algae blooms. Additionally, it is worth noting that when we see populations of amphibian species dropping, it's the first big warning sign that the ecosystem that they live in is out of balance and the population of other species will most likely start to drop two. It's kind of Mother Nature's way of telling us we better start making changes or risk the collapse of the entire ecosystem. So how has the San Diego Zoo Wildlife Alliance worked with conservation partners to address this problem. Oh, there's a lot of work being done, evity. It's really fascinating, in fact. In two thousand six San Diego Zoo Wildlife Alliance brought tadpoles in from two of the three remaining wild populations. The goal was to help manage their genetic diversity and to create a supplemental breeding population to help maintain population size. As time has moved forward, San Diego Zoo Wildlife Alliance and our partners have increased the population under our care and have reintroduced hundreds of Tadpoles back into higher elevation mountain streams and monitored their progress after reintroduction. Coming up, bookxplore how conservation science is being used to revive mountain yellow legged frog populations in the Sierra Nevada mountains. Right after this. Now it's time for the San Diego Zoom Minute, an opportunity for you to learn what's new at the zoo. The San Diego Zoos celebrated another milestone as wildlife care staff welcomed the birth of a rare male golden talking the second of this talking subspecies to be born in the western hemisphere and the first male. The zoo's wildlife care specialists performed a comprehensive first exam and confirmed he is doing well and adjusting to life with the herd. Did you know as an Amphibian, mountain yellow legged frogs never drink water with their mouths. Instead, they absorb water through their skin. We're continuing to learn about the mountain yellow legged frogs that live in the mountains of southern California. HABITAT LOSS, drought, predators and pollution are just some of the reasons for the mountain yellow legged frogs population decline. We're talking now with Leah James, Research Coordinator for San Diego Zoo Wildlife Alliances Mountain Yellow Legged Frog Program Hi Leiah, Hi Beny, thanks for having me. How has the near disappearance of the mountain yellow legged frog impacted it's southern California Mountain Habitat? That's a great question and I'm going to be kind of talking about amphibians as a whole, I suppose, here. But Amphibians not only have pretty large societal and cultural impacts around the world, they're also central to maintaining a healthy and resilient ecosystem. So, first and foremost, just because of their susceptibility to any sort of fluctuations and things like water quality or temperature, amphibians can be considered a first environmental indicator that something might be wrong in an ecosystem. Additionally to that, generally amphibians are important facets of the food chain and are common food items for many predators such as snakes, birds, lizards and fish. So with the decline of Amphibian populations there's also a decline in overall species diversity and health for Amphibian Predator populations. So, Leo, what makes Amphibians so vulnerable to? I guess environmental changes. Amphibians are incredibly vulnerable to any sort of fluctuations in environmental parameters because they breathe through their skin. So Amphibians need very clean, very oxygenated water in order to survive. In any time that changes, then they will struggle to survive in any habitat. Your Team Studies Mountain Yellow legged frogs reproductive physiology. What does that entail? So that's a great question and we do examine many aspects of the Mountaineo legged frogs reproductive biology and physiology. The program itself when it first started, it was primarily a salvage operation. Frogs were found in drying streams in the San Yoisinto mountains and brought into human care to try to save tadpoles from dying in these drying streams. And since then it became apparent that all of the southern California Mountaineo legged frogs were struggling with similar issues, and so the program itself fell into this execute breeding program in which we were trying to produce frogs that we could put back out onto the landscape and try to help see these declining populations. How does your team promote breeding among the mountain yellow leggot frogs? That is our current objective to try and breed our frogs so that we can produce the most and the most successful offspring for reintroduction and so to promote breeding. Maintaining our frogs in a naturalistic environment not only helps with the survivorship once they're reintroduced, but has also been found to help with maintaining and breeding our frogs. Exit you, breeding was not successful when we first brought our frogs in and even though we would pare them during their natural breeding season, which is April and May. In the spring, we just weren't seeing any sort of reproductive behaviors or output, and so we had to go back and examine what naturalistic character we maybe we're missing that was helping these frogs queue off of and helping them to reproduce. It became apparent that mimicking potentially the seasons that these frogs go through would be really important for breeding to occur. So the Mountain Yeo Legged Frog lives in these high elevation temporal sites and they experienced very cold winters, sometimes with snowfall. Sometimes their streams can even freeze in places, and during these times frogs will go through a period of hibernation in which they reduce their metabolism, they stopped feeding and they spend a lot of their time underwater in crevices or under boulders Um sometimes for months at a time. And we found that this seasonal phenomena is actually what was needed to promote breeding and breeding behaviors. And how we figured that out actually was by placing the frogs in a sort of hibernation. And it was actually kind of a funny story because the first hibernation we put our frogs through, they were in Tupperwares and placed into wine chillers, which are actually small refrigerators essentially that people will preserve their wine bottles in. So you know, we ordered a bunch of wine chillers and put our frogs in these chillers at forty degrees Fahrenheit for a period of three months and after those three months we started warming our frogs up, we paired them for breeding again and we found that they had reproductive behaviors, they were starting to breed and we had a much higher success rate for getting viable embryos from our frogs. There's an infectious disease, and I will not try to pronounce it, but there's an infectious disease caused by a fungus and it appears to be a major factor in dramatic amphibian declines in many parts of the world. How has this impacted the populations that your team is concerned with? Yes, unfortunately, kittred, which is what we call it, the kittred fungus, is a huge issue for our species in particular, and our species is very susceptible to getting kittreto micosis, which is that disease that the fungus causes. As of right now, we are trying to choose sites in which this fungus might be as prevalent. However, we are in the process of delving into some large scale research experiments looking at how to potentially create frogs that are more resistant to this fungus and this disease, and we've currently hired a post doc, Doctor Spencer sit ins, who will be helping us to try and figure out the best way that we can give our frogs everything they need to try to persist even in the face of this fungus. In working with the U S Geological Survey and other partners, I unders and your research team released more than two hundred and sixty endangered mountain yellow lake at frogs, adults, frog lets and and more than six hundred and eighty tadpoles in this mountainous region in southern California. What did you learn? We learned quite a bit from every reintroduction and in fact, for the last three or four years we've actually been able to reintroduce over two hundred and fifty frogs into the wild and tadpoles as well, so it's been pretty successful in terms of the amount of individuals that we're able to reintroduce every year and we do end up learning quite a bit about their movement patterns and where they like to stay. In the past few years we have increased the number of surveys that we perform, so after every reintroduction we have a series of field surveys that we do to try and track where our frogs might go and if they're surviving in the environment. And in a few of our sites we found that once we reintroduce, our frogs will actually move upstream quite a ways. Additionally, we found out that during this hibernation event that I mentioned previously, our frogs will hunker down in place and usually be found underneath boulders or in the water, somewhere underneath rocks or debris. So those are a few really large things we found in the previous years, but I think doing these surveys has really helped us kind of understand what's happening to our frogs after they're being reintroduced and what the potential stressors that we need to overcome might be in any sort of environment. So to help your team track these reintroduced frogs and to gather this data, I understand there were transmitters sent out with the frogs. What does it take to connect a frog to a transmitter? That's a great question and yes, we did do that. That was part of our hibernation studies so we could find out what our frogs are doing over winter and for us we used internal transmitters and so they were actually surgically implanted into our frogs. So our vet team here at San Diego Zoo Wildlife Alliance helped us to insert these small transmitters into our frogs and they did quite well with them and they were reintroduced and we monitored them almost every week throughout winter. Um, there are a variety of other transmitters that can be used for amphibians. I've seen little backpacks being used, I've seen little belts with antennas, but the particular ones we used were internally implanted. How can people better coexist with amphibians the environment and, in particular with Mountain Yellow nagged frogs? I think one of the biggest things is just to watch water usage. So our frogs obviously need to live in an aquatic environment. It is absolutely imperative for their survival and so if we can manage our water usage a little bit, I think that would go a long way to helping prolong some of these streams and the water you get in these mountain streams for our frogs. And I would also say that just being wary of maybe reintroducing any sort of non native species into the environment might have a huge impact. You know, don't release your gold fish into the streams or or anything else that might have an impact on tadpole survival or frog survival, and just be wary when you when you go out and walk along stream or like beds, that you're not stepping on any tadpoles or stepping on any frogs. I think those are kind of the major things that would go a long way and helping us to coexist with these amphibians. Leo, what would you say is the best part of your job working on this research project? That's such a fun question to answer. I actually love answering this question because the best part of my job and working with this species and in this conservation program is that I feel like the more I learned, the less I actually know about this species. They are constantly astounding me with what they can do and what they need. I learned something new about them every single day as soon as I think I understand their basic behavior. In biology something shifts and a new piece of the puzzle is added, and so my job is always interesting. I'm always learning and it's just really special to work with such an endangered species and be able to maintain probably one of the largest populations of southern California Mountain Yo legged frog in human care and learn about them every day. And we have also enjoyed learning so much more about the mountain yellow legged frog. We've been talking with Leah Jacobs, research coordinator for the San Diego Zoo Wildlife Alliances Mountain Yellow legged frog program thanks, Leah. Thank you. Thanks for listening. We hope you learned a lot about the mountain yellow legged frog. Be sure to subscribe and tune into next week's episode and which will bring you the story of a snake species with a unique warning system to help keep bigger animals away. I'm ebony money and I'm Rick Schwartz. Thanks for listening. If you would like to find out more about San Diego Zoo wild life alliance, please visit sdz W A dot org. Amazing Wildlife as a production of I heart radio. Our producer is Nikia swinton and our executive producer is marcy to peanut. Our audio engineer and editor is Sierra Spring. For more shows from my heart radio, check out the I heart radio APP apple podcast or wherever you listen to your favorite shows