Cobras, Kraits, Seasnakes, Death Adders, and Relatives (Elapidae)

Updated About encyclopedia.com content Print Article Share Article
views updated

Cobras, kraits, seasnakes, death adders, and relatives

(Elapidae)

Class Reptilia

Order Squamata

Suborder Serpentes

Family Elapidae


Thumbnail description
Small to large venomous snakes

Size
7–200 in (18–500 cm)

Number of genera, species
60 genera; more than 300 species

Habitat
Highly variable depending on species; desert, savanna, rainforest, fully arboreal to fully marine

Conservation status
Vulnerable: 7 species; Lower Risk/Near Threatened: 2 species

Distribution
Southern United States to Central and South America, Africa, Asia, Australia, and the Pacific and Indian Oceans

Evolution and systematics

The two major families of venomous snakes are Elapidae, or the elapid snakes, and Viperidae, the vipers and pitvipers. The snakes in these families are similar in that they have fangs in the front of the mouth. The two groups arose independently from nonvenomous snake ancestors, however, so there are important differences between them. The overall appearance of elapids is much more like that of the primarily non-venomous colubrids than it is of the generally plump, short-tailed vipers. The main differences between elapids and vipers are in the structure of the venom delivery apparatus and the nature of the venom. Elapids have proteroglyphic dentition, which means "fixed front fangs." Vipers have solenoglyphic dentition, which means "movable front fangs." In elapids, the fangs are fixed in one position and are relatively short to avoid puncturing the snake's bottom lip. Vipers have long fangs that are hinged and fold back into the mouth. The venom of elapids is quite different from that of vipers. Elapids have neurotoxic venom (nerve poison), which acts mainly on the central nervous system. The venom affects heart function and breathing but causes little or no damage at the bite site. Vipers have primarily hemotoxic and myotoxic venom, which produces severe damage at the bite site, including complete necrosis of the surrounding tissue.

The venomous elapid snakes include 60 genera and more than 300 species. Because elapids represent approximately 10% of living snake species and more than 50% of species of venomous snakes, they are of considerable medical importance. The elapids are fantastically diverse in size, shape, color, ecology, and behavior, but they can be classified as follows according to size and distribution: cobras and mambas; coral snakes; terrestrial kraits; Australo-Papuan elapids, which include brown snakes, taipans, and death adders; sea kraits; and seasnakes.

Little is known about the origin of elapid snakes except that they are related to some African forms that seem to have "protoelapid" fangs. For example, the African and Middle East members of the genus Atractaspis are venomous and have front fangs, but they also have a number of characteristics that differentiate them from elapids and unite them with primarily nonvenomous species. The southern African genus Homoroselaps is confusing in that it has elapid fangs and venom but seems to have characteristics of Atractaspis.

Despite the confusion, elapids seem to form a monophyletic group, as does each of the major elapid lineages. Together elapids are primarily defined by the presence of a venom delivery system comprising two small permanently erect front fangs. Diverse data sets have been used to elucidate relationships among and within elapid lineages, including various aspects of morphology, protein albumins, karyotypes, allozymes, venom protein sequences, and DNA sequences. There is still some disagreement about the relationships between the major groups of elapids.

The number and content of elapid families and subfamilies have varied widely. Depending on perceived levels of differentiation, various authors have recognized either a single family, Elapidae, with two to six subfamilies or two families: the Elapidae, terrestrial elapids, and the Hydrophiidae, seasnakes. Evidence from studies of morphology and DNA sequences shows that seasnakes are most closely related to Australo-Papuan elapids and thus are part of elapid radiation.

The fully marine seasnakes evolved from terrestrial live-bearing Australian ancestors, and the partially marine sea kraits seem to be most closely related to terrestrial elapids in Asia and Melanesia. Most authorities recognize a single family, Elapidae, that has two subfamilies: the Elapinae, including coral snakes, cobras, mambas, and terrestrial kraits, and the Hydrophiinae, including all the Australo-Papuan elapids, sea kraits, and seasnakes.

Definite elapid snake fossils are rare but have been found in Miocene deposits in Europe, North America, Africa, and Australia. Because there are so few, these fossils have contributed little to the understanding of elapid evolution.

Physical characteristics

Elapids are generally slender, highly agile snakes with a colubrid-like head that is not very distinct from the neck and bears large, colubrid-like scales or scutes. Elapids lack the loreal scute that separates the nasal scute from the preorbital scutes (most nonvenomous colubrid snakes have this scute). Because the fangs are short, the mouth does not have to open wide when the snake strikes. The length of these snakes varies from 7 in (18 cm) (the rare Fijian, Ogmodon vitianus) to more than 200 in (5 m) (king cobra, Ophiophagus hannah). The body often has stripes that may be very colorful. Many cobras flatten when excited, and cobras are famous for the ability to spread their neck ribs to form a hood.

The coral snakes of the Americas can be unicolored (no bands), but most species are famous for having a bright series of alternating color bands. The snakes may be bicolored, tricolored, or even quadricolored. The bands serve as a warning to potential predators. Also famous is the diverse radiation of nonvenomous snake mimics of the coral snakes. Many species of nonvenomous snakes that live in the same regions as coral snakes have evolved coloration almost identical to that of coral snakes. It has been estimated that 18% of all snakes found in the Americas are coral snake mimics. There are twice the number of mimics as there are coral snake species.

Seasnakes have evolved many adaptations, from the partially marine existence of the sea kraits (Laticauda) to the fully marine existence of the seasnakes. The nostrils of all seasnakes have valves that form a tight seal around the mouth when the snake dives. Fully marine seasnakes move sinusoidally as do land snakes, but they propel themselves through the water with a paddle-shaped tail rather than by grabbing the substrate with wide belly scales as land snakes do. The belly scales of fully marine seasnakes are almost the same size as their other body scales.

Distribution

Elapids are found in the southern United States to Central and South America, Africa except for Madagascar, southern Asia, Australia, and the intervening Pacific and Indian Oceans. They are most diverse in equatorial regions. Although widely distributed, each of the major elapid groups tends to occupy a particular region. For example, the elapid fauna of the Americas includes only the diverse coral snake lineage, which has approximately 60 species. Several coral snake species exist in the United States from North Carolina to Florida and west to Arizona. Coral snake diversity increases greatly in Mexico and Central and South America. The cobra group occupies almost all of Africa, the Middle East, and all of southern Asia. Cobras reach to Java in the Indonesian archipelago. Mambas are found in southern and central Africa, and terrestrial kraits are found from India through Southeast Asia. The Australo-Papuan elapids are the most diverse in terms of species number. They are found throughout Australia and New Guinea. A few species of elapids are found on the Solomon Islands. The unusual Ogmodon vitianus is the sole species in Polynesia, where it lives deep underground on Fiji. Sea kraits are found in coastal areas of southern Asia through Southeast Asia, Melanesia, and Polynesia. Seasnakes are abundant on coral reefs in the warm waters around northern Australia, New Guinea, Indonesia, the Philippines, and all of Southeast Asia. A few species exist as far west as the Persian Gulf and as far east as French Polynesia. Only one species, the yellow-bellied seasnake (Pelamis platurus), extends beyond this region, and it is the only open-water or pelagic species. This snake is found in warm waters from the east coast of Africa to the west coast of North and Central America in the Pacific and Indian Oceans. It is almost certainly the most widely distributed snake species. No seasnakes are known to exist in the Atlantic Ocean.

Habitat

Elapid snakes have diverse habitats. Most are ground dwellers, found everywhere from rainforest to savanna to grassy plains to harsh desert. Some species have a preferred

habitat; others are generalists. Some elapids seek shelter under rocks or in rodent burrows; others burrow into loose soil. Most cobras are terrestrial, but some are mostly arboreal or aquatic. African mambas spend most of their time in trees, where they are exceptionally graceful and fast. Almost all of the fully marine seasnakes and the partially marine sea kraits inhabit coral reefs, where they forage for prey, mostly fish and eels. Sea kraits come onto beaches and the surrounding rocks when they need to rest or lay their eggs.

Behavior

Many elapid snakes are active at dusk and at night. Others are active daytime foragers. Because elapids, like all snakes, are ectoderms and therefore must thermoregulate, the time at which they are active depends on the temperature. In cooler regions, such as southern Africa and southern Australia, elapid activity follows the seasons. Peak activity occurs during the warmer months, and hibernation during the colder months, although many species emerge on sunny winter days to bask. During the heat of summer, diurnal snakes are most active in the morning, late afternoon, and early evening, when it is cooler. In the spring and autumn, these species are active throughout the day because they do not become overheated.

Because snakes can be difficult to find, surprisingly little research has been conducted on the behavior of elapid snakes and snakes in general. The introduction of radio transmitters small enough to be surgically implanted into snakes has allowed researchers to follow snakes and document their daily activity through the seasons. The findings have shown that many elapids once thought sedentary are actually highly mobile, such as Australian death adders (genus Acanthophis) and the Australian broad-headed snake (Hoplocephalus bungaroides).

A cobra emerging from a woven basket and "dancing" to a snake charmer's flute is a familiar image. Egyptian, Asian, and Indian cobras are used for these demonstrations. Contrary to popular belief, the snakes are not being charmed or hypnotized. The snake is collected and placed in a woven basket, where it is secure. The charmer may reach into the basket and grab the snake at mid body but is careful to keep the snake off balance. When the charmer lifts the lid of the basket, the snake rises in a vertical defensive posture with hood spread. Because he knows cobras strike from a vertical posture downward, the charmer stays out of reach and sways from side to side as he plays. Snakes lack external ears and pick up only low-frequency airborne sounds, therefore the music has no influence on the cobra. The charmer's flute is only a prop; the cobra follows the charmer's movements. Some charmers use snakes immobilized by cooling, and some use unaltered cobras. There is evidence, however, that some charmers provoke cobras to strike a stick or a piece of rough cloth, which is forcefully pulled from the snake's mouth, taking the fangs with it.

Feeding ecology and diet

Elapids are diverse in both diet and method of obtaining food. These snakes use envenomation rather than constriction to subdue prey. The chief prey are small vertebrates (rats, mice, birds, snakes, lizards, frogs, and fishes) and sometimes eggs. Some snakes specialize. The southern African Rinkhal's cobra (Hemachatus haemachatus) has a special fondness for toads.

In Australia, only death adders (genus Acanthophis), brown snakes (genus Pseudonaja), black snakes (genus Pseudechis), and taipans (genus Oxyuranus) eat small mammals as a large part of the diet, but they also eat other prey. Many of Australia's diverse terrestrial elapid fauna specialize on small reptiles, mostly scincid lizards, which the snakes find by searching under cover or by active foraging. Other elapids specialize on frogs, which they find at water's edge or under cover.

Both the partially marine sea kraits (Laticauda) and the diverse fully marine seasnakes obtain all their food from the aquatic habitat. Sea kraits specialize on eels they find among the reefs. Seasnakes have diverse diets. Most eat relatively sedentary fish that are easy to catch, but they tend to specialize on one or a few fish shapes, ranging from short gobies to long eels to squid. Three species of seasnake eat only the egg masses of fishes.

King cobras eat other snakes, including venomous species. Australian bandy-bandy snakes (genus Vermicella) eat nothing but blindsnakes. Many coral snakes specialize on other snakes. Some species of Australian sand-swimming snakes of the genus Simoselaps eat nothing but the eggs of other reptiles. They ingest the small eggs whole and then, it is thought, regurgitate the empty shells.

Most elapids are active foragers. The Australian death adder (genus Acanthophis), however, stays in position and undulates the tip of its tail (which in contrast to the rest of the tail is yellowish white, resembling a larval insect) to lure prey. Australian whipsnakes (genus Demansia) have large eyes and are very active and visual daytime hunters. African mambas (genus Dendroaspis) also have large eyes to help them locate small mammals.

Reproductive biology

Elapids tend to reproduce once a year in spring, often after bouts of male combat over females. All coral snakes, mambas, terrestrial kraits, sea kraits, almost all cobras, and approximately half of the Australo-Papuan elapids are egg layers. Most snakes lay eggs, but viviparity (live-bearing) has evolved multiple times independently. Live-bearing is more common in species that live in cool climates because it is thought that mothers are able to control the developmental temperature of their offspring by behavioral thermoregulation. This ability is an important advantage in a short summer. The only cobra to evolve live-bearing is the southern African Rinkhal's cobra, which is reported to have litters of as many as 60 offspring. In Australia there is a diverse radiation of live-bearing elapids. Approximately half of the 20 genera and more than 90 species in Australia are live-bearers. There is dispute about how many times live-bearing has evolved in the Australian elapid radiation. It is known that live-bearing has evolved at least twice independently, once in the main live-bearing radiation and once in the red-bellied black snake (Pseudechis porphyriacus). The other members of this genus are egg layers. The fully marine seasnakes also are live-bearers.

Most elapids do not take care of their eggs or young. In egg-laying species, females find suitable spots to lay eggs— under a rock, in or under a log, or in a crevice—and vacate the site. The eggs incubate for approximately three months, and the young hatch and are immediately on their own. In live-bearing species, the mother goes through a three-month pregnancy and gives birth in a secluded spot. Like the hatch-lings, the liveborn young are immediately on their own. An exception is king cobras, which form a pair bond and build a nest from leaves and soil. King cobra pairs protect their nests and their eggs and can be very aggressive during breeding season.

Conservation status

Nine species are listed on the IUCN Red List. Seven of these are categorized as Vulnerable: Austrelaps labialis, Denisonia maculata, Echiopsis atriceps, E. curta, Furina dunmalli, Hoplocephalus bungaroides, and Ogmodon vitianus. Two species are categorized as Lower Risk/Near Threatened: Elapognathus minor and Simoselaps calonotus.

Conservation of snakes is relatively rare in most parts of the world, partly because little is known about most species. The best-studied elapid snake is the Australian broad-headed snake. This snake is distributed only in the sandstone country that surrounds greater Sydney. It is now rare and considered Vulnerable. Over the course of more than 10 years, researchers from the University of Sydney have documented the movement, behavior, and habitat preference of these snakes. It has long been known that broad-headed snakes over-winter under rocks on the edges of cliffs. The snakes, however, seemed to disappear in summer, so radio tracking was used to follow their

movements. It was found that the snakes spend the summer far up in the forest canopy, where they hide in hollows, but that they use only large trees. The investigators also found that during the winter the snakes are very particular about the size of the rocks they use—too thin, and the snake becomes too hot; too thick, and the snake is not warm enough. Unfortunately for the snakes, the rocks are the same size that landscapers sell for gardens. Both large trees and appropriate-sized rocks must be preserved for the species to survive.

Much less is known about the conservation status of other elapid species. Hundreds of thousands of cobras are collected from the wild in Indonesia and other parts of Asia for the reptile skin trade. The cobra skins are turned into belts, wallets, and other pieces of apparel. There is little information about the effect of this practice on cobra populations. Similarly, degradation of the marine habitats of sea kraits and seasnakes is probably having an effect, but the effect has not been quantified. Loss of habitat is a primary concern for many elapid species because many of them are habitat specialists.

Significance to humans

Elapid snakes are one of the two major groups of venomous snakes. Many species are of special importance to humans because of the danger they represent. Many of the most venomous snakes are elapids. People are killed by elapid snakebites, but the danger of a snake has just as much to do with behavior as it does level of toxicity. For example, the Australian inland taipan, or fierce snake (Oxyuranus microlepidotus), has the most potent venom. Few people have been killed by this snake, however, because it inhabits inhospitable areas where people tend not to live. The taipan also is very shy and always retreats if it can. Similarly, seasnakes are highly venomous, but most are not inclined to bite, so the incidence of snake bites from seasnakes is extremely low. In contrast, some species of Asian cobra are less toxic but are common in densely populated regions, so people tend to encounter them more than they do more venomous snakes. Thus the incidence of fatal snake bites can be high. Australia has the greatest diversity of elapid snakes in terms of species number. Death from elapid bites is rare in Australia because of access to antivenin and widespread knowledge of the Sutherland pressure-immobilization first-aid technique (wrapping of the bitten area and splinting of the affected extremity). In parts of Africa, India, and southern Asia, death from elapid bite is a major medical problem.

Species accounts

List of Species

Black mamba
North American coral snake
Forest cobra
Black-necked spitting cobra
King cobra
Death adder
Olive seasnake
Turtle-headed seasnake
Sea krait
Tiger snake
Taipan
Yellow-bellied seasnake
Red-bellied black snake
Brown snake
Half-girdled snake
Bandy-bandy snake

Black mamba

Dendroaspis polylepis

subfamily

Elapinae

taxonomy

Dendroaspis polylepis Günther, 1864, Zambezi River, Mozambique.

other common names

French: Mamba noir; German: Schwarze Mamba.

physical characteristics

The black mamba has a length of 78–118 in (2–3 m). It is a dark olive, gray, or gunmetal color, with a large head and eyes.

distribution

Central and southern Africa.

habitat

The black mamba's habitat is highly arboreal but, unlike the green mamba, the species is equally at home on the ground, where it can move very quickly. It prefers low-lying savanna.

behavior

The black mamba is generally diurnal but crepuscular in some parts of its range. It often uses a semipermanent home base in holes or cracks in trees or termite mounds for many years. Although considered aggressive, black mambas usually flee if given the opportunity.

feeding ecology and diet

This elapid has a varied diet of small mammals but also feeds on birds and other snakes.

reproductive biology

The female lays six to 17 eggs.

conservation status

Not threatened.

significance to humans

The black mamba is highly venomous. As recently as the 1960s, bites from the black mamba were almost always fatal. Bites are still dangerous but are treatable if appropriate first aid is initiated and antivenin is administered quickly.


North American coral snake

Micrurus fulvius

subfamily

Elapinae

taxonomy

Coluber fulvius Linnaeus, 1766, Carolina.

other common names

English: Northern coral snake; Spanish: Serpiente-coralillo arlequin.

physical characteristics

This slender snake reaches a length of 18–28 in (45–70 cm), but one specimen was recorded at 51 in (130 cm). It has thick red and black bands and thin yellow bands in an alternating pattern with yellow between black and red.

distribution

Eastern and southeastern United States from North Carolina to the southern tip of Florida, west to eastern and southern Texas and south to central Mexico.

habitat

The North American coral snake habitat is highly variable, ranging from forest to desert.

behavior

Little is known.

feeding ecology and diet

This snake eats mainly small lizards, but it also consumes other snakes. It is an active forager that seems to be able to follow odor trails left by potential prey.

reproductive biology

The female snake lays as many as 13 eggs but generally fewer than nine.

conservation status

Not threatened.

significance to humans

This is a venomous species. Bites can be fatal, but fatal bites now are rare because of habitat encroachment and the introduction of antivenin.


Forest cobra

Naja melanoleuca

subfamily

Elapinae

taxonomy

Naja melanoleuca Hallowell, 1857, Gaboon.

other common names

None known.

physical characteristics

The forest cobra has a length of 79–118 in (2–3 m). With its large, thick body, it is Africa's largest cobra. Its color is variable by region but usually is dark with crossbars or blotches.

distribution

Western and central Africa and eastern coastal parts of southern Africa.

habitat

This species generally inhabits forest and woodland, but it can also be found in open savanna and grassland in some parts of its range.

behavior

The forest cobra is fast, very active, and an agile climber. It is active both day and night and can be aggressive if not able to retreat.

feeding ecology and diet

This is an active forager that feeds on a wide variety of prey, including mammals, birds, reptiles, and amphibians.

reproductive biology

The female lays 15–26 eggs.

conservation status

Not threatened.

significance to humans

This species is venomous, but little is known about the effects of a bite because the snake is successful at avoiding humans.


Black-necked spitting cobra

Naja nigricollis

subfamily

Elapinae

taxonomy

Naja nigricollis Reinhardt, 1843, Guinea. Genus probably includes several species.

other common names

French: Cobra à cou noir; German: Speikobra.

physical characteristics

This snake reaches a length of approximately 79 in (2 m). The species is highly variable in color, ranging from dull brown to contrasting black and white bands to jet black. Its fangs are like hypodermic needles in that each fang has an opening at the tip that points outward, thus allowing the cobra to "spit" venom a considerable distance.

distribution

Western, central, and southern Africa.

habitat

The black-necked spitting cobra generally prefers open savanna but can be found in all types of terrestrial habitat, including urban areas.

behavior

This cobra is terrestrial but is a good climber. It is generally active at night but sometimes during the day as well.

feeding ecology and diet

This cobra has a varied diet, including reptiles and amphibians (even toads), birds, and eggs.

reproductive biology

The female lays eight to 20 eggs.

conservation status

Not threatened.

significance to humans

The snake squirts venom from its fangs, aiming for the eyes of the target. A large snake can spit a jet of venom up to 118 in (3 m). The venom causes extreme pain and can cause temporary blindness if treatment is not initiated immediately. The bite can be fatal.


King cobra

Ophiophagus hannah

subfamily

Elapinae

taxonomy

Hamadryas hannah Cantor, 1836, Calcutta.

other common names

French: Cobra hannah; German: Königskobra.

physical characteristics

The king cobra has an average length of approximately 118 in (3 m), but has been reported to reach a length of more than 197 in (5 m). It is the longest venomous snake. Its color varies greatly in combinations of brown, yellow, olive green, and black. Some snakes are banded with a yellow venter.

distribution

India to southeastern China; Philippines and Indonesian archipelago.

habitat

The king cobra is found in dense, high jungle, often near water.

behavior

This is a shy species that avoids humans but can become aggressive when cornered. It attacks to guard its nest.

feeding ecology and diet

This species preys mainly on other snakes, which it finds through active foraging.

reproductive biology

The king cobra is one of the only snake species to construct a nest, which is made of dead vegetation and soil. Bamboo thickets

are the preferred nesting site. Both the male and female remain with the eggs and protect them until hatching.

conservation status

Not threatened.

significance to humans

This species is considered highly dangerous because of its large size and potent venom. It is revered in Indian and Southeast Asian societies because of these traits.


Death adder

Acanthophis antarcticus

subfamily

Hydrophiinae

taxonomy

Boa antarctica Shaw, 1794, Australia.

other common names

German: Todesotter.

physical characteristics

This species has an average length of 20–39 in (0.5–1 m). Unlike other elapids, it is thick bodied and thus resembles vipers. It is variable in color, ranging from light brown to nearly black, usually with a banding pattern.

distribution

Eastern and southern Australia.

habitat

The death adder inhabits grasslands to desert.

behavior

Unlike most elapids, death adders wait for prey. They bury themselves in substrate and attract prey with a worm-like tail. The species is nocturnal and secretive.

feeding ecology and diet

The death adder feeds mostly on small reptiles, but it also preys on frogs and small mammals.

reproductive biology

This species is live-bearing, with females giving birth to up to 20 young.

conservation status

Not threatened.

significance to humans

The death adder is considered one of the most dangerous snakes because it is so highly venomous. The death rate due to bites has declined because of the availability of antivenin and widespread knowledge of the Sutherland pressure-immobilization first-aid technique. This snake is sometimes found in urban areas.


Olive seasnake

Aipysurus laevis

subfamily

Hydrophiinae

taxonomy

Aipysurus laevis Lacepèdé, 1804, Arafura Sea.

other common names

None known.

physical characteristics

This species has an average length of 47–79 in (1.2–2 m). One of the largest of the fully marine seasnakes, it is thick bodied and highly variable in color and pattern, ranging from light brown to dark with speckles.

distribution

Warm tropical waters of northern Australia and New Guinea.

habitat

This species inhabits coral reefs.

behavior

This seasnake is unusually curious. Many scuba divers and snorkelers have experienced close encounters with olive seasnakes.

feeding ecology and diet

Olive seasnakes eat a wide variety of fish.

reproductive biology

This live-bearing snake gives birth to two to six young.

conservation status

Not threatened.

significance to humans

Because of curiosity, abundance, and large size, the olive seasnake is considered dangerous to humans.


Turtle-headed seasnake

Emydocephalus annulatus

subfamily

Hydrophiinae

taxonomy

Emydocephalus annulatus Krefft, 1869, Loyalty Islands.

other common names

None known.

physical characteristics

This species has an average length of approximately 30 in (75 cm). It is highly variable in color and pattern, ranging from a strong pattern with light and dark bands to almost uniform black or gray.

distribution

Warm tropical waters of Australia.

habitat

This species is found in shallow coral reefs.

behavior

The turtle-headed seasnake lives in very high densities on some reefs.

feeding ecology and diet

This seasnake specializes on egg masses of fishes, particularly the eggs of small gobies and blennies.

reproductive biology

This species is live-bearing, but little else is known about its reproduction.

conservation status

Not threatened.

significance to humans

This species is venomous but of little threat to humans.


Sea krait

Laticauda colubrina

subfamily

Hydrophiinae

taxonomy

Hydrus colubrinus Schneider, 1799, type locality unknown.

other common names

None known.

physical characteristics

The sea krait has an average length of approximately 39 in (1 m) but can reach 55 in (1.4 m). It has a striking banded pattern with alternating blue or bluish gray and black bands. Adaptations for marine life include valved nostrils and a paddle-shaped tail. Well-developed ventrals facilitate terrestrial locomotion after emergence from water.

distribution

Coastal regions from India through Southeast Asia to New Guinea and many Pacific islands.

habitat

This snake forages on coral reefs and comes onto beaches and nearby rocky areas to rest and lay eggs. It occasionally enters mangrove areas.

behavior

The sea krait is mainly nocturnal but sometimes forages during the day.

feeding ecology and diet

This snake feeds almost exclusively on eels in coral reefs.

reproductive biology

The female lays up to 18 eggs on land.

conservation status

Not threatened

significance to humans

The sea krait is highly venomous but has a gentle nature and rarely bites humans.


Tiger snake

Notechis scutatus

subfamily

Hydrophiinae

taxonomy

Naja scutata Peters, 1861, Java (in error). The taxonomy is confused and in dispute. Two species are recognized, but considerable DNA evidence suggests that tiger snakes are a single highly variable species.

other common names

English: Tropical rat snake; French: Serpents tigrés; German: Tigerottern.

physical characteristics

Average length is approximately 47 in (1.2 m) for most mainland individuals. Some island populations have giants that can reach nearly 79 in (2 m) and dwarfs that are shorter than 28 in (70 cm). The tiger snake is highly variable in color and pattern, ranging from light gray to brown to black with or without a banded pattern.

distribution

Southern and southeastern Australia.

habitat

This snake's habitat is highly variable, but it is often found around moist areas near creeks and other bodies of water.

behavior

The tiger snake is generally active during the day but becomes nocturnal on warm nights. Males sometimes engage in combat over females.

feeding ecology and diet

This snake has a varied diet. It preys on both reptiles and mammals, but frogs make up a large part of the diet of many populations. The island giants, such as the Chappell Island tiger snake, eat large prey, including mutton bird chicks and stick-nest rats.

reproductive biology

This species is live-bearing. Females give birth to up to 30 young.

conservation status

Not threatened.

significance to humans

The tiger snake is highly venomous. It is dangerous because it is often found in or near urban areas. The bite can be fatal, but the death rate has decreased owing to the availability of antivenin and widespread knowledge of the Sutherland pressure-immobilization technique.


Taipan

Oxyuranus scutellatus

subfamily

Hydrophiinae

taxonomy

Oxyuranus scutellatus Peters, 1867, Rockhampton.

other common names

None known.

physical characteristics

This species often reaches a length more than 79 in (2 m). Its coloration is generally light to dark brown with no obvious pattern.

distribution

Eastern Queensland, northeastern Western Australia, and Northern Territory.

habitat

The taipan inhabits forest to open savanna.

behavior

This snake is mainly active during the day.

feeding ecology and diet

The taipan specializes on small mammals.

reproductive biology

The female lays up to 20 eggs.

conservation status

Not threatened.

significance to humans

The taipan is considered the second most venomous snake. Only its close relative, the inland taipan, or fierce snake, is more venomous. Few fatal bites occur, however, because taipans inhabit inhospitable areas where people tend not to live. The taipan also is very shy and always retreats if it can.


Yellow-bellied seasnake

Pelamis platurus

subfamily

Hydrophiinae

taxonomy

Anguis platurus Linnaeus, 1766, no type locality.

other common names

German: Plättchen-Seeschlange; Spanish: Serpiente-marina pelágica.

physical characteristics

This species has an average length of approximately 28 in (70 cm). Yellow and black stripes run the length of the body.

distribution

Equatorial waters of the Pacific and Indian Oceans from the east coast of Africa to the west coast of the Americas.

habitat

This species is fully pelagic, inhabiting open waters.

behavior

This seasnake may use migratory routes. It reaches high density in warm tropical waters. To molt, the snake coils itself into a ball, rubbing the skin of one area of its body against the skin of another area.

feeding ecology and diet

This species preys on surface-active fish in slicks, areas of calm water where two ocean currents meet.

reproductive biology

This snake is live-bearing, with females giving birth to two to six young.

conservation status

Not threatened.

significance to humans

This species is venomous but of little threat to humans.


Red-bellied black snake

Pseudechis porphyriacus

subfamily

Hydrophiinae

taxonomy

Coluber porphyriacus Shaw, 1794, Australia.

other common names

None known.

physical characteristics

This snake's average length is approximately 59 in (1.5 m). It is shiny black with a bright red venter.

distribution

Southeastern Australia; isolated populations in coastal Queensland.

habitat

This snake inhabits creeks, ponds, and swamps.

behavior

This species is active during the day. It is gentle and calm and slow to react. Males engage in combat over females.

feeding ecology and diet

The red-bellied black snake's diet consists primarily of frogs, but it also preys on reptiles and small mammals.

reproductive biology

The species is live-bearing; the female gives birth to eight to 40 young.

conservation status

Not threatened.

significance to humans

This snake is highly venomous. Fatal bites have occurred, but this snake has a calm disposition and tries to avoid human contact. However, it is often found in urban areas.


Brown snake

Pseudonaja textilis

subfamily

Hydrophiinae

taxonomy

Furina textilis Duméril Bibron, and Duméril, 1854, New South Wales.

other common names

English: DeKay's brown snake; French: Couleuvre brune, serpents jaunes; German: Braunschlangen; Spanish: Culebra-parda de Kay.

physical characteristics

This snake reaches an average length of approximately 59 in (1.5 m). It is variable in color and pattern. The young often are heavily banded in alternating black and brown, but the bands fade as the snakes mature. Adults usually are a uniform light brown color but can be almost black.

distribution

Much of the eastern half of Australia.

habitat

This species is found from desert to savanna to thick forest. It can be found in urban areas.

behavior

The brown snake is very fast moving and is active during the day.

feeding ecology and diet

This species' diet is variable, but it feeds mostly on small mammals and reptiles. It is an active hunter.

reproductive biology

The female lays 10–35 eggs.

conservation status

Not threatened.

significance to humans

The brown snake is considered highly dangerous because of its abundance and highly toxic venom. Fatal bites used to be common, but the death rate has decreased because of the availability of antivenin and widespread knowledge of the Sutherland pressure-immobilization technique.


Half-girdled snake

Simoselaps semifasciatus

subfamily

Hydrophiinae

taxonomy

Brachyurophis semifasciatus Günther, 1863, Western Australia.

other common names

English: Sand swimmer.

physical characteristics

This snake has an average length of 12 in (30 cm). It has an alternating pattern of varying light and dark blotches and bars but is highly variable in color and pattern. This snake is also known by the common name sand swimmer because of its use of an upturned snout for burrowing.

distribution

Western Australia and much of the Northern Territory, South Australia, and Queensland.

habitat

This snake is found in arid and semiarid habitats, including grasslands and coastal dunes.

behavior

The half-girdled snake is highly secretive, and its behavior is not well known.

feeding ecology and diet

This snake preys on the eggs of other reptiles.

reproductive biology

This species lays eggs, but little else is known.

conservation status

Not threatened.

significance to humans

This snake is venomous but poses almost no threat to humans because of its small size and distribution in generally uninhabited areas.


Bandy-bandy snake

Vermicella annulata

subfamily

Hydrophiinae

taxonomy

Calamaria annulata Gray, 1849, Australia.

other common names

None known.

physical characteristics

This snake has an average length of 24–39 in (0.6–1 m). It has an alternating pattern of black and white bands.

distribution

Queensland, New South Wales, and parts of Victoria and South Australia.

habitat

This snake can be found in almost any habitat.

behavior

The bandy-bandy snake is a secretive and shy burrower. Usually seen only after heavy rains, it is well known for a defensive display in which it alternates between thrashing and contorting itself into one or more large, vertically oriented coils, apparently to frighten predators.

feeding ecology and diet

This snake feeds exclusively on blindsnakes nearly equal in size to itself.

reproductive biology

The female lays two to 13 eggs.

conservation status

Not threatened.

significance to humans

This species is venomous but poses almost no threat to humans because of its small size and distribution in generally uninhabited areas.


Resources

Books

Branch, B. Field Guide to Snakes and Other Reptiles of Southern Africa. Cape Town: Struik Publishers, 1998.

Broadley, D. G. FitzSimons' Snakes of Southern Africa. Johannesburg: Delta Books, 1983.

Campbell, J. A., and W. W. Lamar. The Venomous Reptiles of Latin America. Ithaca: Cornell University Press, 1989.

Cogger, H. G. Reptiles and Amphibians of Australia. 6th edition. Sydney: Reed New Holland, 2000.

Greene, Harry W. Snakes: The Evolution of Mystery in Nature. Berkley: University of California Press, 1997.

Greer, A. The Biology and Evolution of Australian Snakes. Chipping Norton, New South Wales: Surrey Beatty and Sons, 1997.

Heatwole, H. Sea Snakes. Sydney: University of New South Wales Press, 1999.

Roze, J. A. Coral Snakes of the Americas: Biology, Identification, and Venoms. Malabar, FL: Krieger Publishing, 1998.

Shine, R. Australian Snakes: A Natural History. Ithaca: Cornell University Press, 1991.

Spawls, S., and B. Branch. The Dangerous Snakes of Africa. Halfway House, South Africa: Southern Book Publishers, 1995.

Periodicals

Keogh, J. S. "Molecular Phylogeny of Elapid Snakes and a Consideration of Their Biogeographic History." Biological Journal of the Linnean Society 63 (1998): 177–203.

Shine, R. "Allometric Patterns in the Ecology of Australian Snakes." Copeia 1994 (1994): 851–867.

——. "Sexual Size Dimorphism in Snakes Revisited." Copeia 1994 (1994): 326–346.

Slowinski, J., and J. S. Keogh. "Phylogenetic Relationships of Elapid Snakes Based on Cytochrome b mtDNA Sequences." Molecular Phylogenetics and Evolution 15 (2000): 157–164.

J. Scott Keogh, PhD