BIAWAK - International Varanid Interest Group

Biawak, 5(1/2), pp. 17-23© 2011 by International Varanid Interest GroupMating and Intraspecific Behavior ofVaranus salvator macromaculatus in an Urban PopulationMICHAEL COTAThailand Natural History MuseumNational Science Museum TechnopolisKhlong 5, Khlong LuangPathum Thani 12120, THE-mail: Herpetologe@gmail.comAbstract - Very little literature exists on mating events or intraspecific behavior of wild Varanussalvator. Populations in urban environments allow observation of behaviors rarely seen in the wildbecause of improved visibility and habituation to human presence. This study documents combat,pre-courtship, courtship, and mating behaviors, including polyandry and polygyny, and addressesseasonal variation in intraspecific interactions, among V. salvator macromaculatus in an urban parkin Bangkok, Thailand.IntroductionIn May 2008, courtship and mating was observed ina wild population of water monitors, Varanus salvatormacromaculatus at the Dusit (Bangkok) Zoo in the DusitDistrict of Bangkok, Thailand. The timing of observationswas chosen based on prior observations of hatchlings,back-estimated on the basis of reproductive chronology(Andrews and Gaulke, 1990; Gaulke and Horn, 2004)and what Kratzer (1973) reported about incubation time.The site may support the highest population density of V.salvator in Thailand (pers. obs.); one census counted 36adults (> 1.25 m in total length [TL]) within 0.25 km 2 ,corresponding to a density of 144 adults per km 2 (Cotaunpl. data). Counts of juveniles were not made due totheir cryptic behavior.The Dusit Zoo is 0.25 km 2 in area, with waterwaysforming two islands (Fig.1). One island is located in themiddle of a large pond located at 13° 46’ 15” N 100° 30’58” E, 11 m elev. Many of the largest individuals residehere and most of the observations during this studywere made on this island. The other island supportsa number of bird aviaries and has only a small stripof land accessible to the monitors (Fig. 1). The wateroriginates from a canal system pervading Bangkok,which merges with the Chao Phraya River within 2 kmof the zoo. Flood gates prevent tidal along with riverlevel fluctuations and maintain relatively stable waterlevels. Monitors can access other parts of the city usingFig. 1. Dusit (Bangkok) Zoo, a resource rich urbanenvironment which contains a Varanus salvatormacromaculatus population of high density. Image:Google Earth.