Social interactions during the aquatic breeding phase of the family Hynobiidae (Amphibia: Caudata)

Abstract

Social animals with a monophasic life cycle exhibit a more complex social system for reproduction than that of other social animals in which the life cycle is biphasic. The family Hynobiidae (Amphibia: Caudata) is phylogenetically basal to most other salamander families, practices external fertilization, and has a biphasic life cycle alternating between aquatic breeding and terrestrial nonbreeding phases. There are many controversial and specific social interactions during the aquatic breeding phase in several of the inspected species of this family when comparing their sexual or social behaviors with those of other animal species. Some papers describing these social interactions have misled us by erroneously referring to phenomena of territoriality, chase, amplexus/midwifing, mating ball formation, scramble competition, and parental care. Especially, I am skeptical of the male’s premating displays (e.g., chase, clasp, snout contact, chin rubbing, tail undulation, smelling, digging) regarded as “courtship” in some papers, except for Ranodon sibiricus that may produce a single large spermatophore, because most of these displays result in the female’s escape from the male. Also, I am skeptical of the behavior of a male, staying near deposited egg sacs, regarded as “parental care” because such a male can be predicted to change easily with other males and not to guard eggs or embryos against predators. Thus, I provide a focal review and correct observations on hynobiid sexual and social behavior by incorporating some unignorable descriptions that do not fit with previous descriptions on aquatic social interactions of this family.