New Unusual Parenting Behavior Discovered in a Treefrog Species

Researchers in Singapore have identified a new and unusual parenting behavior in one particular species of treefrog family.

In a new finding, researcher at the Department of Biological Sciences at the National University of Singapore (NUS) Faculty of Science, have discovered that Chrimantis hansenae (C.hansenae), a type of tree frog, practices a unique parental care that is known to boost survival chances of its offspring.

C.hansenae is a small treefrog  native to northeastern forests of Thailand and parts of Cambodia. The IUCN lists C. handenae as Data Deficient.  The form of parent care exhibited by the small treefrog is termed egg attendance. Led by assistant professor David Bickford and Sinlan Poo, a PhD student, from the NUS, it was seen that in egg attendance, the parent stays with the egg at a fixed place. It cares for the offspring by blanketing the egg mass with its body.  The mother frog heads to ponds occasionally to soak up water and returns to secrete the water over the egg mass in order to keep it moist.

"Our study is the first experimental investigation of parental care in Southeast Asia, a region with over 700 species of amphibians. This highlights the need for more of such natural history studies. Currently, much of the mechanisms, adaptations, and driving forces of egg attendance in C. hansenae require further exploration, through which a more coherent understanding of parental care can be formed," said Sinlan Poo.

 To proceed with the finding, the researchers compared the survival of the offspring between natural egg masses and egg masses where parent frogs were removed experimentally. Though these small treefrogs breed close to water bodies, the eggs still suffer from the high risk of drying out called egg desiccation. Due to this factor, the parent's behavior is crucial for the survival of the offspring.

The findings were made after analyzing 1,448 field observations of 126 egg masses over two years from July 2010-October 2012.

Though egg attendance is the common form of parental care among amphibians, C.hansenae has other characteristics that deviate from parental care of other species.

One such example is that other frogs have lesser and bigger eggs and breed in terrestrial habitats. It is males that care for direct developing eggs in which eggs hatch directly as frogs. Unlike the majority of these frogs, the small treefrog has several tiny eggs that breed above pond and it is not males but the females that care for non-direct developing eggs.

"This research is significant because Sinlan has shown how parental care works in Asian treefrogs, at least in the context of her study system in Thailand. Moreover, the impact for the larger scientific community is that we now know more about how and why parental care evolves, and the forces like evolution and natural selection that enable such behaviors to evolve - even in frogs," said  professor  Bickford.

The finding was published in Nature and Science.