Ensuring the Survival of One Remarkable Little Frog

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When I was a child dreaming of helping animals (as Steve Irwin, of course) all sorts of creatures were at the forefront of my mind. But there was one kind of animal that very rarely featured in little Angus’ mind: frogs. Now, after my time in Madagascar, I have a whole new appreciation for these incredible little fellas, who need all the help we can get. SO! In this post we have a doozy of an amphibian! Prepare yourself to meet the one, the only, the incredible lemur leaf frog!

The lemur leaf frog traditionally inhabits the rainforests of Costa Rica, Panama, and Colombia. It is unknown exactly how many of this frog are left in the wild, as research has shown that the Costa Rican population are genetically as different to the Panamanian population as to a completely different species of leaf frog! This leaves open the possibility of them being two separate species! Within Costa Rica, the frog is only known to be found in one or two locations, while the Panamanian population is currently known to be established in six protected reserves. Within these Latin American nations, the lemur leaf frog lives in mountainside and lowland rainforests.

 A gorgeous little lemur leaf frog taking on its active nocturnal colouration. Photo Credit: Costa Rican Amphibian Research Centre

A gorgeous little lemur leaf frog taking on its active nocturnal colouration. Photo Credit: Costa Rican Amphibian Research Centre

This species of leaf frog is slender and fairly frail looking, as their arms and legs lack distinct muscular structure. They have no webbing on their hands and feet, a feature which proved a bit troublesome when looking to confirm the genus of the species. Other frogs within the Agalychnis genus have webbing between their toes, explaining why the lemur leaf frog was classed within the Hylomantis genus for a long time. However, recent DNA profiling confirmed the taxonomic classification of the lemur leaf frog as, officially, Agalychnis lemur (Project Lemur Frog). 

 The daytime colouration of the lemur leaf frog. Even their irises are different colours! Photo Credit: Project Lemur Frog

The daytime colouration of the lemur leaf frog. Even their irises are different colours! Photo Credit: Project Lemur Frog

During the day they have a bright yellow-green colouration on the dorsal skin, but at night they take on a red-brown colouration. Yes, you read that right. This species of frog changes colour depending on the time of the day! From their vibrant daytime colours, as day turns to night, the lemur leaf frog shifts to its darker nocturnal ‘active’ colouration, ensuring that it does not stand out in its rainforest habitat. In addition, to make these frogs even more remarkable, another part of their body changes colour along with their dorsal skin! The lemur leaf frog is also capable of changing the colour of their eyes! During the day, their large bulging eyes are a silver or pale gold, while at night they shift to a purplish grey or brown colour (Project Lemur Frog). This is an amazing adaptation to maximise the effectiveness of their camouflage according to the time of the day, and how active this awesome amphibian is!

They have some other unique adaptations as well. Funnily enough, frogs tend to hate sitting in the sun for too long. It dries them out, and then they overheat. However, the lemur leaf frog has made a habit of basking in the sunlight, sitting on leaves in prime sunny locations without overheating! How cool is that?! This behaviour is not only unusual for amphibians, but it may also provide some key information in the battle to save amphibian species across the world (Morelle, 2008)! But how is this possible?

 An individual on the prowl! Photo Credit: Matt Wilson/Project Lemur Frog

An individual on the prowl! Photo Credit: Matt Wilson/Project Lemur Frog

Herpetologist Dr. Andrew Gray and a team of physicists from the Photon Science Institute at the University of Manchester used an unusual approach called Optical Coherence Tomography to reveal something very interesting about the lemur leaf frog. The frog’s skin contains a pigment called pterorhodin. Pterorhodin allows the lemur leaf frog to reflect light in the infrared spectrum instead of absorbing it (for reference most animals, including humans, have the pigment melanin in their skin, which absorbs light) (Morelle, 2008). This has been hypothesised to have a couple of effects. One is that it potentially helps the frog blend into the leaves they bask on, which also reflect light in that spectrum, to hide from predators (such as snakes) that can only see in the infrared wavelength. More importantly though, Dr. Gray believes that the pigment allows the frogs to thermo-regulate! They reflect the heat so that their bodies stay cool, even though the surface of the skin gets hot (Morelle, 2008). It is this, in particular, that provides scientists (such as Dr. Gray) with the potential to gain a greater understanding of the most immediate threat to amphibians: Batrachochytrium dendrobatidis (Bd).  

Chytridiomycosis, the disease caused by Bd has had such an impact that it is regarded as “the worst infectious disease ever recorded among vertebrates in terms of the number of species impacted, and its propensity to drive them to extinction (Gascon et al, 2007).” We could, and will eventually, devote a whole post to this epidemic but for now, the most important part is understanding just how much of an impact this disease has been having. The Zoological Science of London describes it has “one of the most important biodiversity crises facing us today” (ZSL). Making sure that we can get on top of this fungal disease before it wipes out any more of our frogs is vital! Luckily, the chytrid fungus can only survive at certain temperatures, so raising the temperature of a frog’s skin temporarily can clear them of the fungus when in captivity… sound familiar? It is possible that this is what species like the lemur leaf frog, that can sunbathe without overheating, utilise as a form of natural defence against the fungus! They think that this is probably why the frog hasn’t been entirely wiped out.  (For more information regarding the Chytrid fungus, check out Amphibian Ark)

Frogs are recognised as “biological indicators”, like a canary down a mine so to speak (BBC, 2014). They are highly susceptible to changes in the environment, so mass extinction of frogs is a disaster in terms of the loss of biodiversity, but also in our ability to monitor the effects of climate change. One such example of this is actually the lemur leaf frog. If the frogs sunbathing is, in fact, a natural defence, as Dr. Gray suggests, then fewer opportunities for thermoregulation would greatly impact their ability to fight off the infection. Over the last 10 years, areas of Costa Rica, like the Monteverde rainforest, have seen a significant increase in cloud cover… which in turn leaves less foliage for the frogs to sunbathe on, decreasing their ability to clear themselves of the fungus. I’m going to let you come to your own conclusions there.   

 The cute little face (and massive eyes!) of our favourite little fella! Photo Credit: Norden's Ark

The cute little face (and massive eyes!) of our favourite little fella! Photo Credit: Norden's Ark

Lemur leaf frogs are nocturnal, spending their days sleeping on the underside of leaves (helping to explain why their diurnal colouration is so vivid perhaps. We’ll leave that for you to decide). When night comes around, they leave their resting places to hunt and reproduce. They are slow-moving, stealthy hunters, moving hand over hand, and rarely jumping. They choose their movements precisely as they sneak through low vegetation, searching out their favourite invertebrates to snack on (World Association of Zoos and Aquariums)! At least, until they feel threatened… As soon as that happens, they’re gone, leaping away almost as quick as you can blink!

 On the move. Photo Credit: Justin Touchon/Smithsonian Tropical Research Institute

On the move. Photo Credit: Justin Touchon/Smithsonian Tropical Research Institute

The lemur leaf frog lays up to 30 eggs on the undersides of leaves, where rain eventually washes the larvae into the water. Between 90 to 150 days later, the tadpoles develop into adult frogs. Interestingly, this rate of transformation is altered depending on the temperature of the water, with tadpoles developing much faster in warm than cold water. This presents obstacles for the lemur leaf frog, as perhaps surprisingly permanent pools of water are difficult to come by. Without these pools our little frog is unable to reproduce, only further confounding the threats posed by the fungus and climate change. Sadly, the lemur leaf frog’s dependence on water pools for tadpole development has come to present a serious obstacle to its continued survival.

The lemur leaf frog is critically endangered. Once found in abundance throughout the montane rainforests of Costa Rica, Panama, and Colombia, they have been reduced to only a few isolated regions. The population of the lemur leaf frog fell by about 80% over a ten-year period (IUCN Red List). This decline saw a drastic reduction in the population in Costa Rica in particular. Sadly, part of the reasoning behind the IUCN listing the species as critically endangered is because of the “likelihood that extensive declines will take place within central and eastern Panama in the near future” (IUCN Red List).

However, there is plenty of hope to save this species and bring it back from the brink. Those working for the lemur leaf frog have conducted perhaps one of the best examples of a successful in-situ (in location) conservation efforts. These amazing efforts are undertaken by the Costa Rican Amphibian Research Centre (CRARC), based out of the Guayacán Rainforest Reserve, and focus on providing the frogs with protected breeding sites that allow them the greatest opportunity to survive and flourish.  

 In this image, an Agalychnis lemur tadpole is visible nearing metamorphosis in one of the breeding tubs in the C.R.A.R.C. reserve. Photo Credit: Costa Rican Amphibian Research Centre

In this image, an Agalychnis lemur tadpole is visible nearing metamorphosis in one of the breeding tubs in the C.R.A.R.C. reserve. Photo Credit: Costa Rican Amphibian Research Centre

In 2003 the team at the CRARC set up a number of semi-natural and artificial breeding sites, which represented the first in situ conservation project for the species. A number of small ponds were created, between one and two metres in diameter, along with large plastic tubs at strategic points. Within some of these tubs 25-50 tadpoles were introduced, with the hope that they would act as breeding founders at each specific site. Only a year later, adult individuals were being observed on a regular basis in the vegetation surrounding the created sites (CRARC). Excitingly, they were observed to be breeding! Soon, they began to expand the project. In 2005 they placed more tubs in a different area of the reserve that was made up of mature secondary forest, once again taking a number of tadpoles from the previous sites to set up breeding populations at the newly created locations.

The ongoing work of the CRARC has been a remarkable success! Strong populations of this gorgeous critically endangered frog are now found within the Reserve. They report that “it is common to see numerous A. lemur individuals among the vegetation at different breeding sites within the reserve” (CRARC). Perhaps most excitingly though, the frogs are now being found in neighbouring forest outside of the CRARC reserve sites. During surveys in previous years, lemur leaf frogs were unable to be found. These remarkable efforts provide great hope for the survival of the Agalychnis lemur moving forward, particularly in conjunction with some of the ex situ efforts.  

 Photo Credit:  Justin C. Touchon/Smithsonian Tropical Research Institute     Courtesy: National Science Foundation

Photo Credit: Justin C. Touchon/Smithsonian Tropical Research Institute  Courtesy: National Science Foundation

Project Lemur Frog (essentially the coalition in charge of ex situ efforts) represents a coalition of individuals and institutions (including Bristol Zoo, CRARC, Chester Zoo, Manchester Museum, Nordens Ark), who are fighting to save the Lemur Leaf Frog from extinction. This coalition is hoping to use a combination of “specific research, education, and ex-situ conservation” (Project Lemur Frog) in their attempts to bring this species back from the brink of extinction. The project is headed up by someone we’ve come across earlier, the impressive Dr. Andrew Gray (project leader, and Curator of Herpetology at the Manchester Museum), Nordens Ark (Sweden), and the team at Bristol Zoo. In 2001 captive breeding populations were established at Manchester Museum, and more recently at Bristol Zoo and Nordens Ark, both of whom have found marked success in creating dedicated facilities for the species. The international studbook is currently held at Bristol Zoo, a testament to their great work as they have been working towards “establishing preliminary guidelines for the captive maintenance of adult Lemur leaf frogs and husbandry guidelines for raising the frogs” (Project Lemur Frog). Most recently, the creation of the amphipod at Bristol Zoo, a designated area for the conservation of Lemur Leaf Frogs and the Golden Mantella (Mantella aurantiaca) have been met with great success!

Finally, as if we needed another reason to try and save the lemur leaf frog, there is one more incredible thing about them. They are a part of the subfamily Phyllomedusinae, a subfamily that is known for producing skin-secreted peptides. Over 80 peptides secreted by frogs within this group have been found to have anti-microbial properties (Amiche et al. 2008), which is remarkable! The lemur leaf frog releases a noteworthy number of peptides that have some amazing properties. On top of the anti-microbial agents, some peptides have been shown to inhibit the growth of Bd(!!!) (Conlon et al. 2007), one has been seen to stimulate the production of insulin in rats (potentially an anti-diabetes agent) (Abdel-Wahab et al. 2008), and one that has the potential to be engineered into an anti-cancer agent (Conlon et al. 2007). That’s some pretty incredible potential benefits from these peptides, and considering that not many of the lemur leaf frog’s peptides have actually been studied, there is absolutely a chance that more benefits could be discovered. But for that to happen, we need the lemur leaf frog to survive. I didn’t need much more convincing, but the potential medical benefits that could be identified within these peptides should hopefully convince anyone else too!  

Normally when you hear the word lemur, you perhaps think of Madagascar. Perhaps you think of the island nation itself, or perhaps you think of King Julian and the Pixar animated film. But there are not many out there whose mind would drift to frogs (myself included)! It’s no wonder that this is the case. Being a frog, and a critically endangered one from the rainforests of Costa Rica at that, is perhaps not the easiest of selling points. Most people just think of slimy little things, or of loud noises that keep them up at night. At the end of the day though, more people need to be thinking about the lemur leaf frog. These amazing, critically endangered, little amphibians need all the help that they can get. Zoos, museums, conservationists, and biologists are doing everything they can to bring these guys back from the brink of extinction. As we’ve seen with the black-footed ferret, these efforts can make a difference. They take time, plenty of effort, and even a little money. So the next time you hear or think about ‘lemur’, let your mind wander. Remember this gorgeous frog, spread the word, if you have a bit of money to spare even donate if you can! Who knows? One day we might be able to tick it off that critically endangered list, and not because it’s extinct!   

 How could you not want to save this little cutie!? 

How could you not want to save this little cutie!? 

References

Abdel-Wahab, Y. H. A., Power, G. J., Flatt, P. R., Woodhams, D. C., Rollins-Smith, L. A., and Conlon, J. M. (2008). ''Hylomantis lemur (Phyllomedusinae) with potent in vitro and in vivo insulin-releasing activity.'' Peptides, 29, 2136-2143.

Amiche, M., Ladram, A., and Nicolas, P. (2008). ''A consistent nomenclature of antimicrobial peptides isolated from frogs of the subfamily Phyllomedusinae.'' Peptides, 29, 2074-2082.

Conlon, J. M., Woodhams, D. C., Raza, H., Coquet, L., Leprince, J., Jouenne, T., Vaudry, H., and Rollins-Smith, L. A. (2007). ''Peptides with differential cytolytic activity from skin secretions of the lemur leaf frog Hylomantis lemur (Hylidae: Phyllomedusinae).'' Toxicon, 50, 498-506.

Gascon C., J.P. Collins, R.D. Moore et al., editors: Amphibian Conservation Action Plan. IUCN/SSC Amphibian Specialist Group. Gland, Switzerland and Cambridge UK, 2007.