Agonistic and reproductive behaviors in the Malayan pit viper (Calloselasma rhodostoma)

Agonistic and reproductive behaviors in the Malayan pit viper (Calloselasma rhodostoma) were investigated and found to occur mainly during the scotophase. Techniques developed to conduct observations on the snakes during the active part of their daily cycle permitted the development of an ethogram and documentation of male combat, courtship, mating and brooding behavior.

Male combat was observed and videorecorded on 10 occasions. An ethogram was constructed for use in analyzing combat. Associations between the various behavioral categories were analyzed through the use of a unique high efficiency computer routine which generates and maximizes resolution of data in a sociomatric matrix. Functions of male combat in the Malayan pit viper are discussed with an emphasis on reasons as to why males of this species apparently do not obtain sizes greater than that of females. From this discussion, it is felt that a large clutch size and annual breeding cycle is having a stronger positive effect on size in females than combat is having in males.

Courtship and mating were observed and are described. Subsequent laying and brooding of the eggs by the female Malayan pit viper was videotaped. Possible functions that brooding might be playing were examined; these included regulation of heat, regulation of moisture the clutch received, and protection. No effect on clutch temperature due to brooding was found; however, the brooding female was found to adjust the amount of clutch exposure to accommodate different levels of relative humidity. During the period of brooding, the female would respond to conspecific or experimental perturbations by means of "body-jerking;" a behavior interpreted as defensive.

The video techniques developed for observations in the dark may have great use in dealing with similar problems in other species. Still, I found the Malayan pit viper to be an excellent representative species for investigations of the activities of nocturnal, crotaline snakes in a laboratory setting.