Amphibians: Manipulate sex ratio within the enclosure
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
Background information and definitions
By manipulating sex ratios, increased competition between males for a mate could stimulate more breeding calls or mating. However, males from more aggressive species may need to be separated during this time to minimise injury to tank mates, eggs or larvae.
Supporting evidence from individual studies
A replicated, before-and-after study in 1994–1996 of roseate frogs Geocrinia rosea at Melbourne Zoo, Australia found that fertile eggs were only laid after sex ratios were manipulated, females carrying eggs were introduced to males, recorded mating calls were played, and frogs had been moved to an indoor enclosure which allowed temporary flooding and had a mix of organic substrates. The only fertile spawning occurred in spring 1996, which contained 25 eggs, but they were destroyed by fungus. From 1994-1995 , two male and three sub-adult frogs were housed in two outdoor tanks (120 x 60 x 60 cm) with a sub-surface water depth 50-100 mm. Males called when they were in outdoor enclosures, but fertile eggs were not produced until animals were moved to indoor tanks. From 1996, 6–7 frogs were housed in each of the five indoor enclosures.Study and other actions tested