Reproductive Behavior of the Salamander Hynobius nigrescens: Monopoly of Egg Sacs during Scramble Competition

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Why is it important?

The potential selective advantage of increased head width during the aquatic phase is unknown in hynobiid salamanders. If a male with well-developed secondary sexual characteristics, including increased head width, monopolizes egg sacs during the formation of a mating ball, male-male competition may be responsible for increased head width. Major findings (no correlation between male size and monopolization potential of egg sacs during scramble competition, a negative correlation between the monopolist male's snout–vent length and head width and the length of time the mating balls with scrambler males last) suggest that an ejaculation time of a monopolist male is controlled by his increased head width.