You are currently browsing the tag archive for the ‘venom’ tag.
Black necked spitting cobra (Naja nigricollis) image from angolafieldgroup.com
Who doesn’t love cobras? These beautiful and dangerous snakes have fascinated humankind since prehistory. Ferrebeekeeper has already written about a lovely red spitting cobra from East Africa: today we cast our eyes to sub-Saharan Africa to learn about the black-necked spitting cobra (Naja nigricollis) another spitting cobra which lives across the great continent.
The black-necked spitting cobra lives across a huge swath of Africa—from Northern Namibia to southern Mauritania in the west and from the Somali coast down to Tanzania in the east. The adaptable snakes can be found everywhere throughout this vast range except for the jungle fastnesses of the Congo rainforest. Except in dense rainforests, the snakes do well in all sorts of ecoregions and they are famous for thriving in scrublands, forests, grasslands, and deserts (as well as in new habitats like farms and cities). Although the snakes largely prey on small rodents, they are gifted hunters and can also live on virtually any small creatures (including arthropods, birds, reptiles, amphibians) and even on eggs. Its own predators include a variety of fierce raptors and certain other snakes. I find it alarming that Africa contains snakes capable of catching and eating a 2.3 meter (seven foot long) cobra which sprays venom!
The black-necked spitting cobra (Naja nigricollis)
The black-necked spitting cobra comes in an assortment of colors from yellowish copper to olive to reddish to gray. Many have distinct bands of red, white or gray on their necks (although some individuals are missing these bandings entirely). The most dramatic specimens are glossy black with red or white necks—like death metal priests! Female snake usually lay clutches of 10-15 eggs, but they can lay up to 22 eggs at a time. The snakes can be diurnal or nocturnal to suit circumstances (and their mood). Unlike the genteel red spitting cobra, black-necked spitting cobras love to spit venom and will do so at the slightest provocation (or for no reason at all—like Kid Rock).
photo by MrG http://www.photog.co.za)
In comparison with some of their relatives, the black-necked spitting cobras are not especially poisonous. Only five to ten percent of untreated human bites prove fatal. Their venom primarily consists of cytotoxins—compounds which damage cells instead of attacking organs or neuro-connections. Although fatalities from bites is low, bites can be accompanied with substantial tissue necrosis.
Why is he smiling about that? What a jerk!
In conclusion, the black-necked spitting cobra is a very interesting and visually striking snake (not to mention a born survivor) but I feel it would make an extremely poor housepet.
Atheris hispida
We’ll begin our week of serpents with a strange and magnificent-looking viper from the jungles and rainforests of Central Africa. Atheris hispida is also known as the rough-scaled bush viper or the spiny bush viper because of its most unusual physical characteristic—the pointed curving scales which give it a distinctive bristling “punk-rock” appearance. Atheris hispida is a member of the viper family and is thus related to rattlesnakes, adders, as well as numerous tropical vipers in Asia. The species is a strong climber and is often found basking on trees, flowers, or vines. They are among the smallest vipers: the male measures only 73 cm in length (and is longer than the female). Mostly nocturnal, they hunt the trees and rainforest brush for tree-frogs and lizards.
Atheris hispida
As far as I can tell, there are no effective anti-venoms for the furtive snakes (which range from the Congo west into Kenya and down into Uganda) so despite their hairy appearance and big anime eyes you may not want to pet them!
Timber Rattlesnake (Crotalus horridus)
The magnificent timber rattlesnake (Crotalus horridus) is a venomous pit viper which lives throughout the populated northeastern portion of the United States of America from Texas to New England. Ferrebeekeeper has considerable affection for the dangerous reptile (at an appropriate distance, of course!) and has already referenced the timber rattler as a metaphor for national liberty and, strangely, as a point of comparison for a large sports venue. But timber rattlesnakes are so much more. They were one of the first new world animals to utterly fascinate and horrify European colonizers. In the colonial period a serious rattlesnake bite was a death sentence (although we now have anti-venom) but the original natural scientists did not appreciate how complicated and remarkable the snakes were in other aspects.
As I write this, it is November and the rattlesnakes are all abed for the winter. Because they live in areas with harsh winters, timber rattlesnakes spend more than 7 months a year in hibernation. Large numbers will nest together in a community den—sometimes together with other snakes such as blacksnakes and copperheads. The den is usually a rocky chasm which extends deep beneath the frost line, and rattlesnakes may travel many miles to reach their hibernation den (a bi-annual journey which puts the snakes at great risk from predators and from cars).
Because of their large and diverse territory, timber rattlesnakes come in different sizes, colorations, and even have different venom types. The average timber rattlesnake grows to 100 cm (39 in) long and weighs between a half kilo and a kilogram (1 to 2 pounds). Much larger specimens are known (although there is considerable ridiculous dispute about the upper ranges of rattlesnake size). Female timer rattlesnakes are viviparous although, unlike mammals, rattelsankes protect their eggs within their bodies until they hatch. Rattlesnakes give birth to litters of 6-10 fully formed, fully poisonous little baby snakes, but they can only reproduce every few years since the experience is very hard on them.
Like catfishes, timber rattlesnakes have senses which we do not possess. Pit vipers are so named because they have nostril like spots (pits!) on the side of the head which they use to perceive infrared electromagnetic radiation. These pits are quite sensitive and act as third eyes. Snakes (and many other animals) also have special auxiliary olfactory sense organs called Jacobson’s organs which are extremely sensitive to various smells/tastes. Snakes characteristically pick up chemical traces with their tongues and waft these smells before their Jacobson’s organs in the characteristic tongue-flicking which is such a trademark.
Of course rattlesnakes are not just sensitive—they are also expressive. Among all other snakes they are distinctive in that they have a specialized structure at the end of their tail for making a warning noise. Rattlesnake rattles consists of hollow button-like segments which produce a distinctive buzzing when the snakes vibrate their tails. As a rattlesnake sheds her skin (every few months), she adds a new button to her tail. Rattles however are not perfect records of how many times snakes have shed their skin—sometimes buttons get knocked off, or just become brittle and fall away. The rattle has a high frequency and varies in loudness between 60-80 decibels from a distance of one meter (which falls somewhere between the noise level of an animated conversation and a garbage disposal). Ironically, the rattlesnakes themselves are deaf.
Timber Rattlesnakes can be masters of camouflage
The venom of timber rattlesnakes varies in toxicity depending on the subspecies, but the most toxic rattlesnakes are extremely venomous. Type A venom is a neurotoxin whereas type B venom is hemorrhagic and proteolytic (which is to say it causes bleeding and breaks down fundamental body proteins). Type C venom is largely harmless. In Arkansas and Louisiana, timeber rattlesnakes are particularly dangerous because cross-breeding has resulted in snakes which have type AB venom (yikes!). To a lesser extent rattlesnake venom also contains esoteric myotoxins which rapidly kill muscle tissues. This deadly cocktail of different venoms is of great interest to pharmacologists who continue to study the various toxic proteins to tease out potential medicines.
Fortunately timber rattlesnakes are good-natured and do not generally bite without much posturing, rattling, hissing, and feinting. They keep their retractable fangs folded up in a mouth sheath when not in use and they are capable of varying the amount of venom they inject based on how they are feeling. It is best not to antagonize rattlesnakes lest they abandon their amiable disposition.
Timber rattlesnakes are gifted ambush predators which particularly prey on small mammals such as squirrels, chipmunks, mice, and other rodents, but they also eat amphibians and birds. In turn rattlesnakes are preyed on by owls, hawks, bobcats, foxes, crows, skunks, and even turkeys! Rattlesnakes are an important part of the woodland ecosystem, but they face serious threats from habitat loss and traffic (cars being indifferent to the protective poison of snakes).
C. horridus eating a chipmunk by unhinging its jaw (Photo taken by Kevin Ostanek)
Not only are many rattlesnakes killed by traffic, they must also face persecution. Many are killed by angry villagers carrying torches and pitchforks. Gawping Texans take this to a particular extreme and organize great “rattlesnake round-ups” where huge numbers of rattlesnakes are wantonly tormented and killed for no particular reason (except perhaps to demonstrate a hatred of the world and its creatures). This is particularly sad since rattlesnakes, like whales, or elephants (or ourselves) are k-selected animals. They live long but reproduce slowly, which makes them especially vulnerable to population crashes.
If, by some appalling circumstance, you have read this far while a timber rattlesnake sits nearby buzzing its tail, you should run away from the snake! Do not attempt to molest it. If you feel threatened, call animal control. The timber rattlesnake is already vanishing from great expanses of its territory. It would be a shame if this beautiful and fearsome serpent were to slip away from the earth.
Timber Rattlesnake by Hazel Galloway
The Red Spitting Cobra (Naja pallida)
If I were forced to choose a favorite spitting cobra, I would enthusiastically choose the red spitting cobra (Naja pallida), a swift-moving hunter which inhabits the dry scrub-land of East Africa. A small cobra measuring less than 120 centimeters (4 feet), the cobra hunts for small mammals and reptiles. The lovely snake can be found in a range of ruddy hues including deep orange, pale red, pinkish and light brown– but the fanciest and loveliest specimens are a dramatic blood red. Although the name makes the red spitting cobra sound uncouth, the designation is actually a misnomer. Red spitting cobras do not wander around spitting like rustic bumpkins in a cowpoke bar, instead they carefully and deliberately spray a high velocity jet of toxins into a predator’s eyes (let’s see the bumpkin try that!). The red spitting cobra is not aggressive, but if provoked it will rear up, hiss loudly, and flare its cobra hood. If, after receiving this warning, the provocateur stupidly continues to antagonize the snake, the cobra is likely to spray venom directly into its antagonist’s face and eyes. A direct ocular hit can cause permanent blindness (and is certain to cause stupendous searing pain).
As with most cobras, the venom of the spitting cobra contains a mixture of neurotoxic and cytotoxic compounds. The red-spitting cobra rarely bites predators or people (reserving its poison for hunting and spraying). However if you somehow manage to find one of these rare snakes which live in the arid wastelands of East Africa and then provoke it into biting you, you should seek treatment immediately!
Poison is very common in the animal kingdom (and throughout the other kingdoms of life) both as a means of defense and as a weapon for hunting, however only a tiny handful of mammals are poisonous. A few shrews have mildly venomous bites. The European mole has a toxin in its saliva which can send earthworms into a coma (allowing it to store them in the larder for later). The Solenodon, a strange burrowing nocturnal insectivore is perhaps most toxic among the mammals–with one glaring exception. At the beginning of the month we wrote about the clever echidna–a monotreme with unusual brain physiology. The echidna’s closest relative, and the world’s only other remaining monotreme, the duck-billed platypus is the planet’s most poisonous mammal by far. Not only do platypuses have bills, lay eggs, and utilize electrical sensory apparatus to hunt, but the male has a moveable poisonous spur on his hind legs which is attached to a venom-producing crural gland. Only the male platypus is capable of producing a toxic peptide cocktail and injecting it through his spurs. Female platypuses (and all echidnas) have rudimentary spurs which drop off and lack functioning crural glands. Platypus venom causes pain and hyperalgesia—which means an increased sensitivity to pain–so you shouldn’t cuddle male platypuses no matter how adorable their funny little bills may look to you.
The crural glands...and the spur!
The Stanford neuroblog (from whom I borrowed the attached image of a platypuses’ poisonous organs and appendages), notes the similarity of platypus venoms with reptile venoms, “One evolutionary curiosity: the defensin-like peptides found within the platypus venom are also found within reptile venom. However, genetic analysis in 2008 revealed that the platypus peptides evolved independently from the reptile peptides, although both were derived from the same gene family.” Its curious to think of how our ties with reptile forbears are manifested in the curious and endearing (and poisonous!) platypus.
Eek! Get down...he's got a platypus!
ferrebeekeeper 