In situ conservation of the Splendid Leaf Frog (Cruziohyla calcarifer).
In 2003 we initiated an in situ conservation project for the splendid leaf frog within the C.R.A.R.C. Guayacán Rainforest Reserve. Plastic tubs were placed at strategic points in attempt to simulate breeding sites for this species. Cruziohyla calcarifer normally utilizes water-filled cavities in fallen or standing trees for reproduction. Their highly specialized reproductive mode targets a very limited reproductive resource in natural conditions. Our goal was to create artificial reproductive habitat in hopes to increase the size and vigor of existing populations of C. calcarifer within the reserve.
An area of mature secondary forest within the reserve was chosen as the site to initiate this project due to a high concentration of natural tree holes and mature forest coverage. A similar methodology that was used with the in situ conservation project for Agalychnis lemur of releasing tadpoles into the plastic tubs was followed. We released 25-50 C. calcarifer tadpoles originating from metapopulations of the reserve into three different tubs.
Eighteen months after we released the tadpoles we found the first eggs mass of C. calcarifer hanging on an aerial root above one of the plastic tubs. During the two months prior to seeing this first egg mass we had observed males calling from the vegetation surrounding the plastic tubs, but no reproduction was noted.
Following our initial success, in 2007 we put four 55 gallon plastic barrels into another more remote section of old-growth forest on the lower edge of the reserve. The tops of these four barrels were removed, and a 15 x 10 cm hole was placed approximately 1/3 down the from the top to serve as an overflow to release excess rainwater. The reason we decided to make this modification was to allow for ovipositing to take place on the plastic barrel surface above the waterline. Once the barrels had been filled with rainwater we collected approximately 150 tadpoles from the previously established artificial breeding sites in the reserve and released them into these new tubs.
To our surprise just four months after creating this new breeding site we found an egg mass of C. calcarifer, obvious from an immigrating group of individuals that colonized this new breeding resource. A couple years after we established this second artificial breeding site, the critically endangered Agalychnis lemur also arrived and started reproducing here as well. We never released any A. lemur tadpoles at this particular group of tubs on a remote section of the reserve, so like the initial breeding group of C. calcarifer that we found breeding at these tubs four months after their creation, the A. lemur also immigrated to this sight and colonized it as a reproductive resource.
A third artificial breeding tub was placed at a new site in the reserve in November of 2013, and within four months C. calcarifer adults had already colonized this tub and initiated breeding. Six months after placing this tub with the reserve A. lemur had also colonized it and started breeding there as well. Egg masses of C. calcarifer and A. lemur are now regularly found at this new artificial breeding site.
Since the initiation of this project in 2003 we have found it to be a large success in augmenting the population size and breeding success of another rare leaf frog, Cruziohyla calcarifer. It is now common to visit these sites and observe dozens of tadpoles, egg masses hanging above the water, and to see and hear males calling from the vegetation surrounding the sites.
Costa Rican Amphibian Research Center 