Various sizes of frogs and fish were offered in captivity to examine the effects of prey size and type on predatory behavior of newborns of Rhabdophis tigrinus, which has well-developed Duvernoy's glands. Frogs were more easily captured and handled than fish. There were no clear differences in swallowing efficiency between frogs and fish. Relative prey size did not affect direction of ingestion or condition of prey at ingestion in either prey type. Fish, some of which were dead, tended to be swallowed head first, whereas all frogs were swallowed alive without a preference for direction of ingestion. In frogs, direction of ingestion seemed to largely depend on initial bite position. In either prey type, direction of ingestion did not affect swallowing duration. Death of the fish seemed to be related to longer handling duration. Except for the absence of head first ingestion of frogs, neonate R. tigrinus seemed to be more efficient in frog handling than fish handling.

View full abstract

This paper reports the muscular twisting and convolution of the uterus in Crotalus durissus terrificus as a strategy to store sperm over winter (long-term sperm storage). Aspects of the female reproductive cycle are reported such as mating season (austral autumn), size of follicles (0.5 to 3.0cm), time of ovulation (austral spring), and gestation period (4 to 5 months). Morphological and physyological changes were observed in the uterus of adult females soon after mating. This condition lasted for only one season (austral winter) and after ovulation the uterus relaxed and spermatozoa ascended the oviducts. The anatomy of the genital tract is described and the terminology is discussed in comparison with other temperate relatives (C. viridis viridis). The importance of such physiological process is hypothesized as a way to avoid waste of vitellogenic follicles, which are not ready to be fertilized at the time of mating. Due to the asynchrony of the reproductive events in this species, long-term sperm storage is an obligatory component.

View full abstract

Male-male aggressive behaviors, the appearance of males at the breeding pond, the duration of grasping twigs by males, and the conditions of spawning were observed at a small pond in Shimoshozenji Joetsu city, Niigata Prefecture during the peak of the breeding season in 1992. The total number of males observed was 13, and the average was 8.2. One male attacked others when multiple males grasped the same twig. Because the attacked males immediately swam away, the ineteraction did not last for long. Although there were several twigs in the breeding site, males did not grasp them separately. During the observation period 22 egg sacs were laid, and 20 of them were laid on 5 twigs which were close to each other. It is suggested that males do not grasp twigs separately because females lay eggs on only a few twigs. Each male grasped a twig for a few seconds to 3 hours with an average of 14 minutes. Males that stayed for a long time at the breeding pond grasped a twig for a comparatively long time. However, a few males grasped a twig for only a short time even if they stayed there for a long time. There was dominance in individual relationships among males. The behavior of males (grasping a twig and excluding other males from it) is regarded as territorial behavior. Males that did not have a territory stayed near there as opportunists. Head width and body mass of males with territories were not larger than those of opportunist males.

View full abstract