Climbing mantella

Males compete with one another for territory. Fighting bouts over territory take the form of wrestling, chasing, and leaping. These conflicts last anywhere from 10 seconds to over 1.5 hours. The resident male, usually the aggressor, typically wins the fight. When not in their own territory, male frogs will infrequently invade the territory of other males, hoping to mate with more females. On rare occasions, the intruder can convince females to mate in a well possessed by another male. If the territory resident discovers the intruder, the intruder can either initiate a fighting bout or submissively yield to amplexus. Resident males will not attempt to mate with an unresponsive frog, and the resident will leave the submitted invader after a couple of minutes.[7]

Although it is the only semi-arboreal member of the Mantella genus, the forest environment plays an important role in the climbing mantella’s reproductive behavior.[8] Males are highly territorial, claiming a given area of approximately 2 square metres (22 sq ft). Each territory contains at least one water-filled well (phytotelmata; often found in tree holes or broken bamboo stalks), and male frogs defend these possible oviposition sites from their rivals. Male climbing mantella choose wells based on the presence of crane flies, which prey on frog eggs, and other frog species. A greater amount of crane flies and other frog species correlates to a less desirable well.[7]

Female frogs will approach male frogs who advertise their territory with a two-tone call.[2] Female frogs are either mute or have weak calls.[9] Upon hearing the mating calls, female frogs will approach the well occupied by males. The male frog adopts a softer single-note courtship call, and the female frog proceeds to judge the well. The mating calls only attract female frogs to the male’s territory, and have no bearing on mate selection. Instead, mate selection from the perspective of the female is entirely based on the quality of the male’s well. Female frogs frequently abandon a male frog after inspecting the location. Thus, well sites are a limiting resource.[9] The most desirable well sites often have eggs from multiple different mating pairs.[7] The climbing mantella is the only member of the Mantella genus to use phytotelmata for breeding purposes.[10]

Climbing mantella usually only lay one large large egg (3–3.5 millimetres (0.12–0.14 in)), characteristics common among frogs with a high degree of parental care. Female frogs lay their eggs at the side of wells or above the water line, exhibiting a form of terrestrial oviposition–another indicator of high parental investment.[7] The climbing mantella is the only member of the genus Mantella where parent frogs care for oophagous tadpoles.[10]

Female climbing mantella engage in trophic egg laying, and care for their young by feeding them their unfertilized eggs (a behavior known as oophagy). When engaging in maternal care, female frogs ignore male mating calls and climb wells alone, depositing their unfertilized eggs at or below the water line in the well. The tadpole that resides in the well will then consume the trophic eggs. It is believed that maternal care is not obligatory, depending more on circumstance and environment than natural behavior.[7]

Male territorial defense is also considered a form of paternal care. The presence of a male climbing mantella in a well dissuades other species of frogs (esp. Plethodontohyla notostica and Anodonthyla boulengeri) from laying their eggs there. It is also possible that male frogs discourage land crabs, which have been observed from eating climbing mantella eggs, from entering wells.

Males also engage in parental care considered to be reproductive parasitism. If a male possesses a desirable well containing one of his offspring, he will always benefit: a male’s reproductive success increases with each reproductive event, because it either produces another one of his offspring or results in the creation of a new egg that will feed his existing offspring. Thus, males will often take females to wells that already contain their developing eggs or tadpoles.[7]

Both male and female frogs contribute to the tadpole’s sole diet of conspecific eggs. Female frogs will lay unfertilized eggs into wells that contain their offspring. Male frogs exhibit a form of reproductive parasitism by luring female frogs to wells that often contain offspring only belonging to the male. Any fertilized egg resulting from the courtship subsequently serves as food for tadpoles that are only related to the male. Female frogs develop mechanisms to defend themselves against parasitism and avoid laying their eggs in wells containing other tadpoles. In response, tadpoles evolve ways to evade detection by females.[7]