Preoviposition paternal care in a fully aquatic giant salamander: nest cleaning by a den master

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Parental care in salamanders is thought to be simple and typically limited to female egg attendance. No elaborate preoviposition parental care had been described from salamanders. Recent studies revealed complex care behaviours by male Japanese giant salamanders (Andrias japonicus), a fully aquatic, secretive species with external fertilization. These studies emphasize behavioural convergence in paternal care between some of the fish species and the giant salamanders. The fish examples further imply the possibility that males of A. japonicus provide preoviposition parental care in the form of nest cleaning and building. We tested this possibility and also predicted that cleaning effort by a male salamander, if exists, would increase as it approaches the spawning event. Prior to the breeding season, large males (i.e. den masters) of A. japonicus occupy and guard suitable burrows well-hidden along the stream bank. In the falls of 2012, 2013 and 2015, we videotaped and examined a single den master’s pre- and postoviposition behaviours at Asa Zoological Park in Hiroshima, Japan. The den master repeatedly exhibited vigorous movements of front and hind limbs in a paddling motion at the bottom of the nest every day for the three separate years. The cleaning effort by the den master lineally increased as the spawning event approached, after which the den master completely ceased cleaning. With the cleaning behaviour, the den master made the den filled with debris including leaves and twigs buried in the sand. The floating debris was subsequently removed by the water current flowing through the nest. Water mould infection is a major cause of offspring mortality of aquatic amphibians including A. japonicus. By reducing the amount of organic matter that provides food sources for water mould, the nest cleaning likely reduces the risk of water mould infection among the offspring, serving as an important preoviposition parental care.


Journal of Zoology





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Animal Behavior

Second Department