Q & A with Dr. Vance Vredenburg: Chytrid in Asia

Chytrid study

Dr. Vance Vredenburg swabs frogs to test for chytrid. (Photo courtesy of Vance Vredenburg, San Francisco University)

A new study published on Aug. 16 in the journal PLoS ONE found that Batrachochytrium dendrobatidis (Bd), the fungus that causes chytridiomycosis, is indeed present in Asia, but at significantly lower levels than anywhere else in the world. In fact, researchers found that just more than two percent of the individuals they tested were positive and that the fungus was present only in the Philippines, Kyrgyzstan, Laos, Indonesia, Malaysia and South Korea. Now scientists want to know why.

An international research team conducted this study between 2001 and 2009, examining more than 3,000 amphibians, most of which were frogs, from 15 Asian countries. It was the first large-scale investigation of the disease conducted in Asia.

We spoke with Dr. Vance Vredenburg of San Francisco University, one of the researchers from the study and a leading expert in this disease. Here’s what he had to say:

1)  This was the first comprehensive survey of chytrid in Asia. Why do you think this hasn’t been done before?

I think expense is probably a huge hindrance on research. Our study was conducted in 15 countries and our data was collected by a large number of field personnel. The cost of analyzing the samples is not cheap–costs range from $5 to $30 per sample, depending on where and how they are analyzed. We ran nearly 3,500 samples.

2)    What do your findings mean in the battle against chytrid, and what is your next step?

Our findings provide an important milestone because they are the first broad survey for Bd across a vast continent that harbors a large amount of amphibian diversity. Our hope is that researchers will now be able to return to many of these sites and see if the dynamics of the pathogen host system change and if so, in what direction. Our next step will be to follow up on as many sites as possible.

3)    Were you surprised by the findings? Why or why not?

Yes. I was surprised by how low the prevalence was across what appears to be such perfect habitat for this pathogen.

Hylarana similis

This frog, Hylarana similis, is native to the Phillipines and is a species now infected by chytrid. (Photo courtesy of Rafe M. Brown, University of Kansas)

4)   Why do you think that frogs in Asia aren’t being wiped out at the same rate as frogs in the neotropics?

There are only a few possibilities. We describe them in detail in the discussion [in the paper], but in short, either Bd is only just emerging in Asia and thus we haven’t seen mass die-offs due to chytridiomycosis yet, or it is endemic and there are either abiotic or biotic influences holding the pathogen at bay. We still don’t have the answer to this.

5)   If this outbreak in Asia is relatively recent, where did it originate on the continent?

We discovered one–and only one–place out of 300 sites where an outbreak may be occurring, at a site in the Philippines.

6)   The Philippines are a series of Islands. If you believe there is or is going to be an outbreak there, how did it get there and how can it spread to other places in the world?

We propose that human trade is involved, specifically that farms raising American bullfrogs could be the source of Bd that could then spread to wild frogs [if some escape]. We don’t know where it originated or how it spread for sure.

7)   Are there Asian amphibians other than frogs that appear to be affected by chytrid?

Asia has a rich fauna of both salamander and caecilians, but to date we do not know if they are affected by Bd. Our study did not sample caecilians and includes only a small number of salamanders.

8)   A few amphibian species, such as bullfrogs, are said to be carriers of Bd, but rarely seem to die from it. What exactly allows a species to be a “carrier,” or is there still not enough information known about that?

We don’t yet know how bullfrogs (Rana catesbeiana) are able to survive Bd infections without showing symptoms of chytridiomycosis.

9)   Do you believe that these Asian frogs that seem to be less affected may be carriers as well?

 We need more information to assess this. My guess is that there are probably some species that can sustain infections just like American bullfrogs and could act as carriers.

10)  What other threats do frogs in Asia face and what is being done to address those threats?

 The two major threats in Asia are habitat destruction and hunting and gathering amphibians to eat.

Sara Bloom Leeds, Smithsonian’s National Zoo

Dressing the part.

Masked tree frog (Smilisca phaeota)--John Dubicki (Flickr)
Masked tree frog (Smilisca phaeota)

Cute Frog of the Week: Sept. 26, 2011

The masked tree frog (Smilisca phaeota) is fond of costume changes. This three-inch frog is generally active at night during the wet season when males woo females with their calls, and it sleeps during the day atop large leaves of ferns. In preparation for its moonlit adventures, the frog changes the color of its back from tan to green.

Its stage is decorated with scenery from the humid lowland forests of Nicaragua, Costa Rica and northern Colombia where it can be found in shallow temporary pools of water. Like any true performer, it is not disturbed by drastically different scenery, and it can even be found in open country. Females lay their eggs in puddles of water which accumulate, covering the top of the water with a film of 2,000 eggs. Tadpoles develop quickly in the temporary pools and puddles, which are sometimes no more than a cattle footprint filled with water.

As a result of its adaptability, the population of masked tree frogs in the wild is considered stable by the IUCN.

Photo by John Dubicki via Flickr.

Banded horned tree frog (Hemiphractus fasciatus) ALL-NEW frog ringtones: Download the masked tree frog’s call!

Every week the Panama Amphibian Rescue and Conservation Project posts a new photo of a cute frog from anywhere in the world with an interesting, fun and unique story to tell. Be sure to check back every Monday for the latest addition.

Send us your own cute frogs by uploading your photos here: http://www.flickr.com/groups/cutefrogoftheweek/

Inflated confidence.

Cuban spotted toad (Peltophryne taladai)--Ariel Rodriguez
Cuban spotted toad (Peltophryne taladai)

Cute Frog of the Week: Sept. 19, 2011

This Cuban spotted toad (Peltophryne taladai) looks like it’s carrying a little extra weight around its tummy, but don’t fret, it does not need to go on a diet. A little extra volume can come in handy! When the Cuban spotted toad is threatened by a predator, it inflates itself to a most unappetizing size. The toad, which is normally between five and six inches long, becomes so enlarged no predator would be able to swallow it.

However, this toad attempts to avoid encounters with predators during the day by hiding under rocks and in holes it digs itself. It is most active at night when males call from shallow creeks, streams or from rocks. Their calls are quite raucous as they come together to form choruses.

Eggs are laid in very shallow areas of permanent streams and creeks, often in as little as five centimeters of water. Strings of eggs are attached to the roots of plants growing in at the edges of streams and creeks.

According to the IUCN, the Cuban spotted toad is a vulnerable species, with its population decreasing as the result of intensive agriculture, charcoaling and nickel mining.

Photo by Ariel Rodriguez via ARKive.

Every week the Panama Amphibian Rescue and Conservation Project posts a new photo of a cute frog from anywhere in the world with an interesting, fun and unique story to tell. Be sure to check back every Monday for the latest addition.

Send us your own cute frogs by uploading your photos here: http://www.flickr.com/groups/cutefrogoftheweek/

Be very, very quiet. I’m hunting…whatever I can catch.

Australian Lace-lid (Litoria dayi)
Australian Lace-lid (Litoria dayi)

Cute Frog of the Week: September 5, 2011

The Australian lace-lid, Litoria dayi, is a frog that goes out on a limb, in more ways than one. This frog is the only member of its genus that lives in Australia and researchers are still collecting information about their threats. The species is listed as endangered by the IUCN.

These frogs are indiscriminate of their prey, consuming both terrestrial and aquatic invertebrates, and their large eyes help them to be efficient nocturnal predators, catching a variety of cockroaches, flies, spiders and beetles. Confined to a small region of northeastern Australia, the Australian lace-lid grows to about 50 millimeters.  It is a rainforest specialist, associated with montane rainforests and fast-flowing creeks.  Males can be very territorial, possibly to help them attract mates, as no males have ever been found calling in a group or within 1 meter of another male’s territory.

This frog once inhabited an area that has since been populated more prominently by invasive feral pigs, which destroy the tropical shrubbery and growth this frog uses to hide. Although these pigs degrade the lace-lid’s habitats, it is unclear whether they are contributing to killing the frog. Researchers believe that continued exposure to cold, dry temperatures (possible at high elevations such as those the frog inhabits) decrease the frog’s activity and the chances of successful reproduction. They also believe that Australian lace-lids have been affected by the global spread of chytrid, even in their isolated mountain rainforests.

Photo by Jodi Rowley via ARKive.

Every week the Panama Amphibian Rescue and Conservation Project posts a new photo of a cute frog from anywhere in the world with an interesting, fun and unique story to tell. Be sure to check back every Monday for the latest addition.

Send us your own cute frogs by uploading your photos here: http://www.flickr.com/groups/cutefrogoftheweek/

The Amphibian Pet Trade: Good for Business, Bad for Biomes?

Tree frogs are among the popular amphibian species kept as pets. (Photo by Brian Gratwicke, Panama Amphibian Rescue and Conservation Project)

How many times have you walked into a pet store and been surprised by the variety of amphibians available for purchase? I tend to gawk, awestruck, at these amazing creatures, just as though I’m admiring them during a visit to the zoo: Pacman frogs, White’s tree frogs, Malayan leaf frogs, powder blue poison arrow frogs, the list goes on…and all of these are available to buy. Many of these species are exquisite, exciting, beautiful and definitely non-native to the U.S. of A. But as much as we may love frogs and want to keep them as pets, we have to consider whether taking in such a pet has conservation implications.

The term “exotic” calls to mind word associations like “foreign” and “interesting,” which are not necessarily bad words, but certainly indicate something beyond the garden variety of whatever it is that we are comparing, be they automobiles, eggplants or footwear. With regards to organisms, however, “exotic” can mean something a little more problematic. Exotic, or introduced, species are defined by the National Park Service as “those that occur in a given place as a result of direct or indirect, deliberate or accidental actions by humans.”

If introduced to an environment, a non-native species can become an invasive species, outcompeting native species. For instance, it is quite likely that the Burmese pythons now prevalent in the Florida Everglades were initially kept as pets and became invasives upon their intended or accidental release, adapting quickly to environments similar to their own Amazon estuaries and southeast Asian swamps, respectively. Adaptations like high reproductive rates, longevity and the ability to consume large prey, combined with their misplacement, can allow them to outcompete and often consume native species like American alligators, opossums and even great blue herons, according to an article published in the Wilson Journal of Ornithology.

A few particularly popular amphibian species that might not have quite the same effects as their serpentine kin–but are just as exotic—include the tomato frog and the well-known families of Dendrobatidae (poison dart frogs) and Hylidae (red-eyed tree frogs and spring peepers, to name two). These particular amphibians are regulated by the Convention on International Trade in Endangered Species of Wild Fauna and Flora, or CITES, which establishes controls, protocol and limits for managing species that are endangered in the wild but for which there is high consumer demand. These frogs are listed among either the first or second appendices of CITES, meaning that they are restricted from being captured in the wild or are threatened in the wild, and their trade or sale may be regulated or restricted at any time. However, captive-bred individuals of these species are acceptable for trade and sale. Pets that are illegal to own generally depend on state laws, and many states have clear laws discussing what animals are illegal to be kept as pets and which animals require a permit to keep. For instance, the state of New Jersey requires a permit to own African clawed frogs, red-eyed tree frogs and a variety of other common pet trade frogs.

The quality and conduct of the facilities that breed and supply these amphibians should be assessed by the consumer prior to purchasing, according to Ed Smith, a biologist at the Smithsonian’s National Zoo. The amphibian pet trade is thought to be contributing to declining amphibian populations in the wild by overharvesting wild rare species and may play a role in spreading diseases. While the over collection of restricted range amphibians has contributed greatly to population decreases, habitat destruction and a species’ natural confinements can also negatively affect its survival rates. If you are considering investing in an exotic species, please be sure of two things. First, that the amphibian you are purchasing is not an illegal species prohibited by CITES. Second, that the farm or source has raised or procured the frog sustainably and in accordance to the best husbandry practice. Simply because a species can be traded does not necessarily mean that it is okay to purchase one. Do some background research on the species that you plan to purchase, not only to determine what kind of care and conditions you will need to provide your amphibious friend, but also to determine if this is a species that you can own without adversely affecting wild populations.

The Salamander Room by Anne Mazer

“The Salamander Room” by Anne Mazer discusses a young boy’s enthusiasm about keeping a salamander as a pet and how keeping the salamander changes his life literally and figuratively.

Smith advises that anyone interested in caring for amphibians read a book called “The Salamander Room” by Anne Mazer. This picture book discusses a young boy’s enthusiasm about keeping a salamander as a pet and how keeping the salamander changes his life literally and figuratively.

“Like the boy in the story who models his room after the salamander’s habitat, we often find that fascination with one thing becomes a window to a world of further amazement,” Smith said. “Wanting to provide his salamander with everything it needed, the boy in the story considered each element of its habitat, one clump of moss and decomposing log at a time, until he had re-created the forest itself. There is something about the keeping of an aquarium or terrarium that leads conscientious caretakers to appreciate the details of an ecosystem—the essence of such an enterprise, or hobby, is caring.”

So before you run down to the pet store or queue up that pet distributor’s website, consider these parting thoughts from Ed Smith:

Two basic questions to ask when purchasing an amphibian (or any pet): “Can you care for it well? Are you harming amphibians at large with this purchase?”

Should you buy captive-bred or wild-caught amphibians for pets? “Consider captive-bred first (meaning animals that are already acclimatized, disease-free and not diminishing wild populations).”

Motivation for investing in an amphibian: “The business of caring for living things hones our focus to allow us to appreciate their complexities and hopefully enables us to better appreciate the diversity of plants and animals in the wild.”

Phil Jaseph, Smithsonian’s National Zoo