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Costa Rican frog call study

Whilst on the University of Manchester field course in Costa Rica I conducted a project on frog calls, surveying the main swamp area that receives heavy rainfall almost all year round. I focused on the acoustic activity of the Red-eyed Leaf Frog, Agalychnis callidryas. In this post I present the most important conclusions from this study, as well as some interesting notes on the acoustic behavior of other pond breeding frogs.

Wagner 2

Study Site at La Selva (c) W.Chaves

One accurate way to interpret behavior in pond breeders is to analyze their acoustic activity along a shared area. My main focus was tracking the calling activity of male A. callidryas throughout the night, but the study also allowed me to identify 5 other species that might influence the species’ presence in certain areas of the pond.

After 3 nights of sampling, I concluded that the calling activity of A. callidryas was strongly diminished by the calls of the Hourglass Tree Frog, Dendropsophus ebraccatus, which is a little bit smaller than A. callidryas (Males about 23-27mm). This species was also the most widely distributed species along the study area, in contrast to others, such as Scinax eleaochroa, which presented a particularly high calling activity during the first night (it reduced for the remaining 2 nights).


Hourglass Tree Frog, Dendropsophus ebraccatus (c) W.Chaves

The other three species (Tlalocohyla loquax, D. phlebodes, and A. saltator) presented a shy calling activity. However, the weather conditions could have influenced this as A. saltator is reported to be more active and even breed ‘en mass’ during heavy rainfalls. As for T. loquax and D. phlebodes, their low calling activity suggested no influence over the calls of the A. callidryas.

Since D. ebraccatus was the only species which proved to be affecting the calling activity of A. callidryas, I then decided to look more closely into this particular interspecific behaviour. While the A. callidryas males called in order to attract females to their higher perches, D. ebraccatus were usually found lower down, near shallow water where sedges or semiaquatic plants dominated. Although males of A. callidryas were also seen calling from low perches, there were few if any suitable leaves for this species to lay its egg masses on there. The calling of A. callidryas from low perches may also have been affected by neighbouring frogs at this level as these would cause a high level of acoustic interference.

 Almost at midnight, the calls of A. callidryas diminished along with the calling activity of all other hylid species found at the swamp. This group response could be interpreted as an anti-predatory strategy to decrease the risk of predation from bats. However, to hear the frog calls I was working with here is a sound recording I made that includes the species mentioned:  

Male Red-eyed Tree Frog, Agalychnis callidryas, at the study site. (c) W. Chaves

Conducting projects that investigate specific animal behaviours, such as the one which focuses on the calling activity of A. callidryas, are of growing importance. When considering future studies on the ecology, bio-acoustics, and the different aspects of reproduction in this species, an extension of this project’s methodology may be useful. I intend to develop it in future assessments of populations of this species along its Atlantic distribution.

I hope to share some more information on frogs of the Neotropics in further posts, but would like to encourage visitors to comment on my work  –  or if you have any suggestions or ideas for the project`s improvement or other future science projects please post a comment, I would love to hear from you. Many thanks, Wagner.

Frogs, foam, and fast exits!


Here are some photographs of the wonderful frog, Edalorhina perezi, from Ecuador. These frogs are usually brown to match their surroundings, but show their bright bold colours if disturbed by predators. They even enlarge themsleves and have two ‘eye spots’ when viewed from the rear, which makes them appear threatening to other animals. I found this pair breeding at the very back of a deep ‘cheese-press’  cave that I crawled inside. The ceiling was crawling with large whip-scorpions and at the back was  a colony of vampire bats. Just about managed to keep my cool as I photographed these frogs laying their eggs inside a foamy nest being whipped up by the male’s back legs. My back legs couldn’t get me out of fast enough afterwards when the whip-scorpions became active! 🙂

Re: Amphibian reproduction -Tadpoles blowing bubbles!

Talking of foam nesting frogs, here is short clip of the foam nest of the large South American frog Leptodactylus stenodema also found in Ecuador. I was out there with Dr Morley Read trying to record the calls of the frogs and get some nice footage. We managed to catch the intermittent mating call of the male, which as you can hear is loud and rauchous. When these frogs breed they lay their eggs in the large foamy nest they make, usually under a large leaf , in a dry area that is about to be flooded by imminent rain. However, sometimes the frogs get it wrong and it may be several weeks before the rains come and the tadpoles are able to swim away.  We found that in the mean time, the tadpoles appear to constantly blow bubbles in an effort to help maintain the nest. Apart from recording the call of the male frog, we were pleased to film this unusual tadpole behaviour for the first time.


Amphibian reproduction – Tree frogs use Bromeliads too!

untitled-3Most of us tend to think that its only Poison-dart frogs, like the one posted last week, that use bromeliads to help develop their tadpoles. However, there are also some treefrogs who do the same, even some species belonging to the genus Isthmohyla that are found in Central America live and breed exclusively in these type of plants.  Here is a photo of a most unusual treefrog belonging to the genus Phyllodytes that I found whilst exploring the highest peak in Trindad, El Tucuche,  with Professor Malcolm Kennedy from Glasgow University’s Department of Zoology, some years ago.  This is the beautiful Golden tree Frog Phyllodytes auratus. untitled-4I believe this little frog, which is  endemic to Trinidad, lives and breeds exclusively in only one type of giant bromeliad on this one mountain in the world – or did do.  Someone recently told me it has now gone, but I really hope this is not the case. During the trip we found gold-striped tadpoles (pictured right) only in the bromeliads that had a single adult frog present, suggesting the parent may care for their tadpoles in much the same way as poison-dart frogs do – by guarding and feeding them on unfertilized eggs. Here is bit more info on this interesting and extremely rare species:


Find out about more South and Central American Frogs Here

Question Re: Agalychnis or Cruziohyla?

Apart from their DNA profile, Cruziohyla frogs are differentiated from Agalychnis species by the unique peptides in thier skin and their morphology – colouration, extended skin to their legs and calcars, and eye colouration (they have two colours to the eye: grey and yellow). The two genera are also separated by a difference in breeding biology. Although both lay their eggs over water, Cruziohyla species lay their’s within or over the hollow water-filled trunks of fallen trees in primary forest. Here is short clip of finding the eggs of Cruziohyla craspedopus in Ecuador (before the two genera were separated).

Empty-handed, but heart-filled!

Finding the Rarest Frog in the World

Well, now I am back from that fabulous trip to Costa Rica I am hoping that people realised it was never really about finding an elusive Golden Toad.  But instead, I think I found something much more valuable to me personally. As I lay in my bunk on the last night before heading out of Monteverde Cloud Forest, after us triumphantly finding a trio of rare Isthmohyla rivularis specimens, including the gravid female, I wasn’t sleeping quite as soundly as you might think. I had dreamt of finding a pair of these frogs for so long, and here I was with the perfect opportunity to initiate a captive breeding programme for the species. But when I woke, in my heart, I knew I would rather leave them in the wild where they belonged than ever see them in captivity. I love animals, and have a passion for amphibians that has been with me from as early as I can remember. I have long believed that captive breeding was a way to save these wonderful creatures from extinction, but this year, that night, something inside me changed. I now believe that the only place for wild animals is in the wild. So I came back empty handed. Just to know that those beautiful, very special frogs will probably be calling tonight, in Monteverde, and that the female may have spawned in that crystal clear stream, fills me with more happiness than you might ever realise.

emply-handed, but the smile says it all!

emply-handed, but my smile says it all!



The other thing to come out of the amazing trip for me has been the realisation that there are many more committed individuals in Costa Rica who are passionate about the conservation of these and other rare frogs than I had thought. All the people I had the pleasure of sharing this trip with were particularly exceptional in that respect, Mark, Alex, all the guards that joined us, and colleagues at both the Monteverde Rainforest League and the Tropical Science Centre. The early part of the trip, which was spent filming frogs at The Costa Rican Amphibian Research Centre with my friend Brian Kubicki, was also very special. Brian was carefully raising some Anotheca spinosa, a rare tree hole dwelling species, from tadpoles to small froglets, in-situ. This ensures that most survive rather than perish, and that the young get the head start they need for a life in the wild. Brian’s attitude, knowledge, experience, and real hard work never fails to impress me – he is a true inspiration. I cannot speak highly enough of this guy and the commitment and effort he continues to put into real amphibian conservation.     See also BBC link: Whats next for Costa Rican Frogs: http://news.bbc.co.uk/1/hi/sci/tech/7612961.stm

Brian Kubicki

Brian Kubicki



World’s ‘rarest tree frog’ found!

Picture 289Andrew and the team have found what they were looking for – a female Isthmohyla rivularis alive and well in the Costa Rican cloud forest of Monteverde. They also found some more males of this species giving hope that they are surviving and breeding there. http://news.bbc.co.uk/1/hi/sci/tech/7609780.stm

This species was thought extinct for 20 years until Andrew found a single male when he was there last year. (See previous post for this story)


Rare frog found!

Picture 344

(c) Andrew Gray, 1997

Andrew and the team of researchers on the Costa Rican expedition have found the rare and critically endangered Red-eyed stream frog Duellmanohyla uranochroa. The BBC following the group have been able to film this species for the very first time! For more on this story see the link below.


The hunt is on!

Andrew is currently in Costa Rica on fieldwork and leading a team from Chester Zoo and the University of Manchester. They are searching for Isthmohyla rivularis (right), a frog that Andrew rediscovered last year after it had been thought extinct about 20 years.

Whilst there, he and Mark Dickinson from the Photon Science Institute at the University of Manchester will be taking a spectrometer into the field to investigate how different frog species reflect Inra-red light. Something, that up until now they have only had the opportunity to do with captive frogs in the laboratory (http://www.psi.manchester.ac.uk/aboutus/news/archive/2007/191107.html)

The team will also visit the last known breeding site of Lithobates vibicarius. The very remote area is where Andrew visited last year and returned with a few specimens to initiate a captive breeding program with Chester Zoo for the species. Tthey are returning to see how the population is fairing and help support a conservation program that Andrew proposed for protecting the species in the wild.

Following the group on this expedition are the BBC. Check out the following links to follow the groups adventures:

Experts poised for rare frog hunt: http://news.bbc.co.uk/1/hi/sci/tech/7591050.stm

Frog Hunt: In search for the world’s rarest frogs: http://news.bbc.co.uk/1/hi/sci/tech/7597865.stm

From poisonous hoppers to screaming frogs: http://news.bbc.co.uk/1/hi/sci/tech/7597701.stm

Check back soon for more updates to the expedition!!