Amphibians: Vary artificial rainfall to simulate seasonal changes in the wild
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
Background information and definitions
In some amphibian habitats, rainfall is highly seasonal with the onset of rain following a dry period signaling the start of the breeding season. It may be possible to trigger breeding by simulating these cues within an enclosure.
Supporting evidence from individual studies
A replicated, before-and-after study in 2008–2011 in Cologne, Germany found that egg deposition of harlequin toads Atelopus flavescens was stimulated by intensive rainfall following a dry period, whereas none had occurred previously. However, no offspring survived past 142 days. The first three breeding trials with no wet or dry seasons resulted in no egg production. Once a wet and dry season was simulated, two clutches of eggs were produced with 400–500 eggs (5–10% unfertilized). On day 43 after egg deposition, only two larvae survived. One tadpole survived to day 112, the other died as a toadlet at day 142. Males were housed in three groups of 12–15 in tanks (100 x 60 x 60 cm) with artificial streams. Four females were transferred to the tanks for breeding. Tanks were misted several times each day. A dry season with reduced water and misting was then simulated for three months followed by a wet season with increased rainfall using an artificial rain system.Study and other actions tested
Referenced paperGawor A., Rauhaus A., Karbe D., VanDerStraeten K., Lötters S. & Ziegler T. (2012) Is there a chance for conservation breeding? Ex situ management, reproduction, and early life stages of the harlequin toad Atelopus flavescens Duméril & Bibron, 1841 (Amphibia: Anura: Bufonidae). Amphibian & Reptile Conservation, 5, 29-44.
A before-and-after study in 2010-2012 in Vienna, Austria found that captive Staurois parvus and Staurois guttatus started breeding when wet and dry seasons were simulated, and frogs were moved to a larger enclosure with more calling, perching and laying sites, although no statistical tests were carried out. Neither species had bred successfully in captivity before 2011. Once the animals were moved to two breeding enclosures with simulated wet and dry seasons and with more calling perching and laying sites in August 2011, S. parvis tadpoles were observed from October 2011 and S. guttatus tadpoles from March 2012. By 2012, a total of 285 S. parvis froglets, 600 tadpoles and 180 juveniles had been raised and 76 S. guttatus tadpoles had been raised. In August 2011, five pairs of each species were moved from a medium-sized (50 × 60 × 70 cm) terraria with tree branches, plants and stones and no simulated wet and dry seasons, to two larger (150 × 120 × 100 cm) enclosures with controllable waterfalls, plants, small burrows, ledges for calling sites and perching sites. The waterfall for S. guttatus also had several tree branches. Each enclosure had a simulated 14 day dry period, followed by a 14 day simulated rainy season (4 hours daily rainfall) with the temperature in both enclosures at 22-27°C.Study and other actions tested