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Alfaro et al. (2004) studied the phylogeny and phylogeography of the coastal marine colubrid (Homalopsinae) snake genus Cerberus, a group of rear-fanged water snakes found in Southeast Asia and Australia. Historically, three Cerberus species have been recognized: C. australis (from Australia), C. microlepis (known only from Lake Buhi in the Philippines), and the widely distributed C. rynchops (found from India to Wallacea). However, Allfaro et al. (2004) found that C. australis is highly divergent and probably needs to be excluded from the genus Cerberus to make it monophyletic. Murphy et al. (2012) recognized five Cerberus species: Cerberus rhynchops (southern Asia), C. schneiderii (Southeast Asia and Philippines), C. microlepis (Philippines), C. australis (Australopapuan region), and a newly described species from Micronesia, C. dunsoni.
The dangerously venomous Cerberus rynchops is associated with tidal mudflats and coastal mangrove forests in Southeast Asia. It is an edge species typically associated with mangrove forest and mudflats along the shores of brackish estuarine and marine coastal situations; however, it is euryhaline and may be found in freshwater as well. Although usually associated with coastal and estuarine mangrove forests and tidal mudflats, it has been reported in hypersaline environments (790 mm Cl) as well as freshwater streams and ponds (see references in Karns et al. 2000). The saltwater tolerance of C. rynchops has been investigated, revealing a rudimentary premaxillary salt gland and salt excretion, the only homalopsine snake known to possess a salt gland (see references in Karns et al. 2000). Dehydrated estuarine C. rynchops discriminate between salt and freshwater, but hydrated snakes do not show a preference for either fresh or saltwater when given an option. Cerberus rynchops is a generalist feeder, taking a variety of fish representing several families, as well as some crustaceans, and possibly frogs and tadpoles. Predators known to feed on C. rynchops include crabs, Tiger Sharks (Caracharhinus caustus), and several raptors, including White-bellied Sea Eagle (Haliaeutus leucogaster), Brahminy Kite (Haliaster indus), and Pariah Kite (Milvus migrans) (Voris and Murphy 2002 and references therein)