Cape cobra: Difference between revisions
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==Reproduction== |
==Reproduction== |
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This species is [[Oviparity|oviparous]]. Mating season is during the months of September and October, when these snakes may be more aggressive than usual. Females will lay between 8 and 20 eggs (roughly 60 X 25 mm in size) in midsummer (December-January), in a hole or an abandoned termite mound or some other warm, wet location.<ref name=Spawls/> The hatchlings measure between {{convert|34|and|40|cm|in}} in length<ref name=Marais/> and are completely independent from birth. |
This species is [[Oviparity|oviparous]]. Mating season is during the months of September and October, when these snakes may be more aggressive than usual. Females will lay between 8 and 20 eggs (roughly 60 X 25 mm in size) in midsummer (December-January), in a hole or an abandoned termite mound or some other warm, wet location.<ref name=Spawls/> The hatchlings measure between {{convert|34|and|40|cm|in}} in length<ref name=Marais/> and are completely independent from birth. In one captive study, mating occurred in the month of September and oviposition in November. Gestation period was approximately 42 days and the incubation period was 65-70 days at about 28-33°C (82.4-91.4°F). Clutch size was 11-14 (n=2) and hatchling ratio was one male to five females.<ref name=mh>{{cite web|last=Morgan, Haagner|first=Dave, Gerald|title=Husbandry and Propagation of the Cape cobra (''Naja nivea'') at the Manyeleti Reptile Centre|url=http://i.imgur.com/KtXVi.jpg|publisher=The Journal of Herpetological Association of Africa|accessdate=27 February 2012}}</ref> |
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==Venom== |
==Venom== |
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Revision as of 03:02, 27 February 2012
| Cape cobra | |
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| File:Cape-cobra-1.jpg | |
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| Species: | N. nivea
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| Binomial name | |
| Naja nivea | |
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| Distribution of the Cape cobra | |
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The Cape cobra (Naja nivea), also called the yellow cobra is a moderately sized, highly venomous cobra inhabiting a wide variety of biomes across southern Africa. This species has no known subspecies.
Etymology and names
Naja nivea was first described by Swedish zoologist Carl Linnaeus in 1758.[1] The generic name naja is a Latinisation of the Sanskrit word nāgá (नाग) meaning "cobra". Nivea is derived from Latin and either nix or nivis meaning "snow" or niveus meaning "snowy".[3]
The Cape cobra is also known as the "geelslang" (yellow snake) and "bruinkapel" (brown cobra). Afrikaans speaking South Africans refer to the Cape cobra as "koperkapel", mainly because of a rich yellow color variation.
Description
The Cape cobra is a medium sized species of cobra. Specimens typically average around 1.2 to 1.4 metres (3.9 to 4.6 ft) long, but it may grow up to 1.6 metres (5.2 ft) in length. The longest specimen on record was from Aus, Namibia and measured 1.87 metres (6.1 ft) long.[4] Males are slightly larger than females. Another very large specimen was a male found in De Hoop Nature Reserve with a total length of 1.85 metres (6.1 ft).[5][6] Their colouration varies greatly. This species shows a wide range of colour variation; from yellow and golden brown to dark brown and even black. In addition, individuals show a varying degree of black or pale stippling and blotches, and although it has been stated that colour and marking are geographically related, it is also possible to observe virtually all colour varieties at one location. For example, it is well known that the Kalahari Desert specimens in Botswana and Namibia are usually more consistently yellow than the more southerly populations.[7] However, at DeHoop, and other specific locations in the Western Cape, all colour variations have been recorded.[5]
Scalation
Dorsal scales on the midbody 21, ventral scales 195-227, Subcaudal scale is paired, subcaudal scales 50-68, anal plate is single, upper labials 7, upper labials to the eye 3+4, preoculairs 1, postoculairs 3 but can also be 4, lower labials 9 (8 – 10), and temporal 1+2 variable.[6]
Distribution
This species is endemic to southern Africa and is found in the southern half of Namibia, southwestern Botswana, and western Lesotho. In South Africa, where it mainly occurs, they can be found throughout the Cape Province, Free State Province, and southwestern Transvaal. They are also found in the Kalahari desert, particularly in the southern regions of the Kalahari.[5][7]
Habitat
Although the Cape cobra has the smallest geographical range of any other African cobra, it occurs in a variety of different habitats. This species' preferred habitat is fynbos, bushveld, karoo scrubland, arid savanna, and the Namib desert where it can be found in rodent burrows, abandoned termite mounds and, in arid regions, rock crevices. Where it occurs in temperate regions and arid karroid regions, it is often found along rivers and streams entering well drained open areas. In Lesotho, they can even be found in altitudes as high as 2,500 metres (8,200 ft) above sea level. They occur in forest and high grassland areas of Free State province. It can also be found in rocky hills of the Cape and in desert and semi-desert areas of its geographical range. Cape cobras are also known to venture into villages, partially developed suburbs, and squatter communities where they may enter houses to escape the heat of the day. This brings them into direct contact with humans.[7][4]
Behavior and diet
The Cape cobra is a diurnal species and actively forages throughout the day. During very hot weather it may become crepuscular, but is rarely if ever observed during the hours of darkness.[5] A terrestrial snake, but will readily climb trees and bushes. When not active it likes to hide in holes, or sometimes under ground cover (brush piles, etc), often remaining in the same retreat for some time. It is a quick moving and alert species,[7] and although generally not as aggressive as some other African species of venomous snake,[5] when disturbed this snake will readily face its enemy, and spread a broad, impressive hood. Once on the defensive, it strikes readily.[7] If the threat remains motionless the snake will quickly look for an escape, but any sort of movement will get the snake into a defensive posture again.[4] The Cape cobra is more aggressive during the mating period.[7]
This species of cobra is a feeding generalist.[5] It feeds on a wide spectrum of prey, including other snakes, rodents, lizards, birds, and carrion. Recorded prey items for this species at DeHoop from October 2004 to March 2006 showed that 31% of the species' diet consisted of rodents, 20% was other snakes (including juvenile and small adult Puff adders), 11% lizards, 11% birds, 16% carrion, and 11% "conspecifics". In the same study period conducted at DeHoop, Cape cobras were seen scavenging and feeding on carrion on two occasions.[8] Both were road-killed snakes, the first, an adult P. rhombeatus, the second an adult Karoo whip snake, Psammophis notostictus. It is also well known for raiding Sociable Weaver (Philetairus socius) nests.[4] Cape cobras can be cannibalistic, sometimes eating the young of its own kind.[7]
Predators
Predators of the Cape cobra include the honey badger (Ratel),[9] other carnivorous mammals, various birds of prey (secretary birds and snake eagles), and other snakes may also prey on this species.[4] Meerkats and the mongoose, which have a high resistance to its venom, often prey on the Cape cobra and are its main enemies.[7]
Reproduction
This species is oviparous. Mating season is during the months of September and October, when these snakes may be more aggressive than usual. Females will lay between 8 and 20 eggs (roughly 60 X 25 mm in size) in midsummer (December-January), in a hole or an abandoned termite mound or some other warm, wet location.[7] The hatchlings measure between 34 and 40 centimetres (13 and 16 in) in length[4] and are completely independent from birth. In one captive study, mating occurred in the month of September and oviposition in November. Gestation period was approximately 42 days and the incubation period was 65-70 days at about 28-33°C (82.4-91.4°F). Clutch size was 11-14 (n=2) and hatchling ratio was one male to five females.[10]
Venom
The venom of this snake tends to be thick and syrupy in consistency and dries into shiny pale flakes, not unlike yellow sugar. It is highly toxic and may be more potent than that of any other African cobra.[7] The Cape cobras venom is made up of potent postsynaptic neurotoxins and might also contain cardiotoxins,[11] that affect the respiratory system, nervous system, and the heart. The mouse SC LD50 for this species' venom is 0.72 mg/kg.[12] The average venom yield per bite is 100 to 150 mg according to Minton. The mortality rate for untreated bites is not exactly known, but is thought to be high. A bite is not always fatal, even if untreated. This can be due to various factors including the amount of venom injected, psychological state of the bitten subject, the penetration of one or both fangs, and so on. Mechanical ventilation and symptom management is often enough to save a victim's life, but cases of serious Cape cobra envenomation will require antivenom. When death does occur, it normally takes anywhere from an hour (in severe cases) to ten hours (or more) and it's often as a result of respiratory failure because of the onset of paralysis.[11]
References
- ^ a b "Naja nivea". ITIS Standard Report Page. ITIS.gov. Retrieved 19 January 2012.
- ^ a b Uetz, Peter. "Naja nivea (LINNAEUS, 1758)". The Reptile Database. http://reptile-database.reptarium.cz. Retrieved 25 February 2012.
{{cite web}}: External link in|publisher= - ^ "Etymology of Nivis". Etymology. http://www.etymonline.com. Retrieved 19 January 2012.
{{cite web}}: External link in|publisher= - ^ a b c d e f Marais, Johan (2004). A Complete Guide to the Snakes of Southern Africa. Cape Town, South Africa: Struik Nature. pp. 100–101. ISBN 186872932X.
- ^ a b c d e f Phelps, T. "Observations of the Cape cobra, Naja nivea (Serpentes: Elapidae) in the DeHoop Nature Reserve, Western Cape Province, South Africa" (PDF). Herpetological Bulletin. Cape Reptile Institute. Retrieved 19 January 2012.
- ^ a b Mastenbroek, Richard. "Captive Care of the Cape Cobra Naja nivea" (PDF). www.devenomized.com. Retrieved 19 January 2012.
- ^ a b c d e f g h i j Spawls, Stephen; Branch, Bill (1995). Dangerous Snakes of Africa. London, UK: Blandford Press. pp. 81–82. ISBN 0713723947.
- ^ Phelps, T. "Elapidae (Naja nivea) Scavenging" (PDF). African Herp News (40) June 2006. Cape Reptile Institute. Retrieved 18 February 2012.
- ^ Begg, Colleen and Keith. "Honey Badgers". Honey badger research project by the Beggs. National Geographic Magazine. Retrieved 15 January 2012.
- ^ Morgan, Haagner, Dave, Gerald. "Husbandry and Propagation of the Cape cobra (Naja nivea) at the Manyeleti Reptile Centre". The Journal of Herpetological Association of Africa. Retrieved 27 February 2012.
{{cite web}}: CS1 maint: multiple names: authors list (link) - ^ a b "Naja nivea: General Details, Taxonomy and Biology, Venom, Clinical Effects, Treatment, First Aid, Antivenoms". Clinical Toxinology Resource. University of Adelaide. Retrieved 25 February 2012.
- ^ Fry, Dr. Bryan Grieg. "Sub-cutaneous LD-50s". Australian Venom Research Unit. University of Queensland. Retrieved 19 January 2012.