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| The Australian Bockadam, Cerberus australis (Gray, 1842). Photographed in the Northern Territory, Australia. Inhabits northern coastal Australia and southern New Guinea. This species is very polymorphic, with red and gray color morphs being quite common. It inhabits estuaries, and coastlines, and will move up rivers to more inland locations. It feeds on fish, particularly the gobies known as mudskippers in the family family Periophthalmidae. Adults reach at least 737 mm. Habitats used include mud flats, mangrove forests, and streams that pass through these habitats. If the mud is soft it will dive into the mud and swim away, and then surface with only part of its head exposed. This species has been found in the stomach of the nervous shark, Carcharhinus caustus, which will enter the flooded mangrove forests to feed. |
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Asian Bockadam, Cerberus rynchops (Schneider, 1799). Photographed in southern Thailand. (Top photo taken near Trang, Andaman Sea, next two photos taken near Pak Phang Peninsula, Gulf of Thailand; next two photos snake and mangroves taken near Trang ). The Asian Bockadam is widespread in South Asia and Southeast Asia, but absent from tropical coastal China. It is in the Philippines and there is a population in Palau, Micronesia. It feeds on fish, primarily gobies, but will take other species and it will feed on carrion left behind by fishermen. Females reach a maximum known length of 1.075 m, males are somewhat smaller. A variety of coastal habitats are used by C. rynchops, and they include mangrove forests and associated mud flats, tidal creeks, estuaries, rivers, and some populations occasionally use coral reefs. While it most frequently occurs in salt water and brackish water, it will enter freshwater. It also appears tolerant of human activity, and it uses areas close to houses and fishing communities. Voris et al. (2002. Copeia pp. 906-915) used mtDNA to compare 16 species of homalopsids and found that Cerberus formed a clade with Erpeton and Homalopsis, and their sister was Enhydris bocourti. |
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| Bocourt's Mud Snake, Enhydris bocourti (Jan, 1865). Photographed in east central Thailand (top) and Lake Songhkla in southern Thailand (bottom). This snake reaches 1.2 m in adult length. Bocourt's Mud Snake is endemic to the area around the Gulf of Thailand. This highly aquatic snake uses swamps, shallow lakes, pools, and other stagnant water habitats. It reportedly is found with Acrochordus javanicus in swamps and pools; and it may move into deep water during the hottest part of the year. It is part of the Tonle Sap Snake Harvest in Cambodia and it is collected for its skin. There is some evidence to suggest that the species is imported into China and that it may be cultured there. A specimen from Tonlé Sap, Cambodia contained a 10.5 cm catfish, Mystus mysticetus (Siluriformes: Bagridae). A neonate obtained near Kabin Buri, Thailand contained a 145 mm freshwater eel (Monopterus albus, Synbranchidae). Several other specimens from the same locality contained unidentified fish remains. The second photo of this snake is from Thale Noi in southern Thailand, it was a gravid female that was 1.23 m long and gravid with 26 embryos. |
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Rainbow Mud Snake, Enhydris enhydris (Schneider, 1799). Photographed at Lake Songhkla, southern Thailand. This widespread species extends from Nepal and India eastward to Indochina and Indonesia. It is often a human commensal taking advantage of rice padi, aquiculture, and other man made bodies of water. It feeds on fish. Adult size is less than one meter. The head is exceptionally small and narrow on this snake, and the fore body is also slender compared to the body's posterior. Much of its time is spent in the mud-root tangle where it hunts for small fish. Females are larger than males, and release a pheromone that is used by the males to trail the female. Some localities have dense populations of this snake (Lake Songhkla, Thailand; Kabin Buri, Thailand; Tonlé Sap, Cambodia), these are lowland locations that have become freshwater habitats relatively recently. Lake Songhkla was an ocean bay 200 years ago and it undergoes salt water intrusions and is heavily fished. The other localities are disturbed habitats and are heavily impacted by the fishing industry and other human activities. Thus it appears that E. enhydris may be a disturbed habitat/early successional stage specialist. It is entirely possible that as aquatic ecosystems mature that these populations will undergo natural declines and stabilize at a much lower level. |
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| Longtailed Mud Snake, Enhydris longicauda (Bourret, 1934). Photographed at Siem Reap, Cambodia. The snake is endemic to the Great Lake (Tonle Sap), Cambodia. It feeds on fish. The Longtailed Mud Snake is closely related to Enhydris jagorii and E. innominata. This snake is harvested in large numbers in Tonle Sap for crocodile food, and for human food as are other homalopsid snakes living in the lake. |
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| Macleay's Mud Snake, Enhydris polylepis (Fisher, 1886). Photographed near Darwin, Australia. Feeds upon fish, but frogs and prawns have also been reported to be eaten. Inhabits freshwater in northern Australia and New Guinea.The largest snake I have measured was a female with a total length of 807 mm. This is a freshwater species that uses backwaters, billabongs, lagoons, swamps, marshes, creeks, rivers, stream impoundments, and other wetland habitats. Like many other homalopsids it rarely leaves the water to travel overland. Its diet includes crustaceans, fish, frogs, and their larvae. There is also a report of it scavenging chicken bones. Litter sizes in the literature range from 4 to 27. The relationship of this species to other Enhydris is unclear. It is the only species of Enhydris to have keeled scales and have the upper labials 4-6 under the eye. |
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| Boie’s Mud Snake, Enhydris plumbea (Boie, 1827). Photographed in central Thailand. A widespread species, known from Myanmar and China to the Sunda Shelf Islands of Indonesia. The largest individual of 91 specimens I have measured was a 713 mm female with a 63 mm tail from Kabin Buri, Thailand. Often found in agroecosystems where if feeds on fish and frogs. This is an aquatic snake, but it is the most terrestrial of the homalopsids studied to date based upon field observations. In Sabah, Voris and Karns, (1996. Herpetological Natural History, 4:111-126) found this snake associated with wet sites (wallows, marshes, ditches, stream, pond banks) where it was most frequently found in the tangle of roots and mud 10 - 20 cm below surface debris during the day and night. The krait, Bungarus multicinctus, and the common cobra, Naja naja prey upon Enhydris plumbea. Voris and Karns (1996) suggested that the mud-root tangle is a relatively predator-free microhabitat. They found it very difficult to extract the snakes from this refuge and it seems likely that the snakes are relatively safe from wading birds and large predatory fish. However, plumbea is probably not safe from snake predators, in this environment. |
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Mekong Mud Snake, Enhydris subtaeniata (Bourret, 1934). Photographed in central Thailand, in the Khorat Basin. This species has long been confused with Enhydris enhydris and Enhydris jagorii. It appears to be restricted to the Mekong Drainage. Its diet is poorly known but it does feeds on fish and frogs. Adults reach at least 800 mm in total length. It is found in Thailand, Laos, Cambodia, and Vietnam. The largest female I measured had a total length of 870 mm, males are smaller. This aquatic snake uses streams impoundments, padi, ditches, klongs, ponds, and probably many other aquatic microhabitats. There are several localities in Thailand where E. enhydris and E. subtaeniata co-exists in similar numbers and both species have been collected in the same gill net. The population around Tonlé Sap, Cambodia also coexists with E. enhydris. |
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The Crab Eating Snake, Fordonia leucobalia (Schlegel, 1837). Photographed near Darwin, Australia. It inhabits coastal areas from Myanmar to the Philippines and Australia and New Guinea. It feeds upon crabs, mud lobsters and perhaps other marine invertebrates. There is little or no evidence that it eats fish. Populations from the Australia-New Guinea area tend to be very polymorphic in terms of color and pattern, while those from Southeast Asia tend to be uniform black or gray. Fordonia uses the intertidal burrow system. Karns et al. (2002. Raffles Bulletin of Zoology 50:487-498) monitored the movements of three male snakes over a period of five weeks using radiotelemetry in Singapore’s Pasir Ris Park, a mangrove forest. Snakes monitored for 7 - 10 days were relatively sedentary (46.6% of the days they were inactive) and when they did move it was only for short distances (1.8 - 14.0 m, = 4.4 m). Two of the snakes were always located in mud lobster mounds (100% of the telemetric locations), but did not show a preference for lobster mounds of a particular size. A third snake used the mud-root tangle of the mangrove 59% of the time, and an area under a boardwalk the other 41% of the time. It was usually associated with two mud lobster mounds. While these individual snakes frequented the mud lobster mounds and the landward edge of the mangrove, they were observed foraging on tidal mud flats. Body temperatures (26.3 - 29.0°C, = 28°C) for these three snakes were consistently above the temperature of the microhabitat they were using and significantly different. Of the three monitored snakes only one moved once during the day, and all other activity was nocturnal, and the snakes were active throughout the night. |
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| Gerard's Mud Snake, Gerarda prevostiana (Eydoux and Gervais). Photographed in Singapore. This snake is poorly known but apparently widespread. It ranges from the west coast of India to the Philippines. But it is restricted to coastal environments with mangrove forests. Gerard's Mud Snake uses the intertidal burrow system making it difficult to find. It feeds only on newly molted (soft-shelled) crabs which it may tear apart using loops of its body. This snake is the sister species to Fordonia leucobalia. |
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| Dwarf Estuarine Snake, Myron richardsonii (Gray, 1849). Photographed near Darwin, Australia. A small homalopsid, with adults reaching about 430 mm. This snake feeds on fish and perhaps some estuarine invertebrates. It inhabits coastal areas of northern Australia, New Guinea, and the Aru Islands. |
| Homalopsid snakes are a group of ten genera and 37 species. They range from Pakistan to the Philippines and southward to northern Australia. One species, Cerberus rynchops, has extended its distribution into Micronesia. A few species are widespread, but many are restricted to single drainage basins, coastlines or islands and as a group they are poorly known. Homalopsids use a range of aquatic habitats. One species (Enhydris plumbea) uses wet pastures and rice padi while others such as Bitia hydroides rarely come out of the ocean or estuaries. Most of them have small eyes, nostrils with valves, and a host of other adaptations that allow them to stay submerged. Small fish are the most common prey but some will eat frogs, and others have specialized for eating crustaceans. They have been previously considered part of the Colubridae, but recent molecular studies show they are not part of that lineage, but are more basal to the advanced snakes (Vidal et al. 2007, C. R. Biologies 330:182-187). All species that are known give birth to live young, and females and embryos form a placenta for food and gas exchange. For an overview of these snakes see Murphy, 2007. Homalopsid Snakes, Evolution in the Mud. Krieger Publishing. |
For An Extensive (100 page) Bibliography for these snakes Click Here: PDF |