Rinkhals

The rinkhals (/ˈrɪŋk(h)æls/; Hemachatus haemachatus), also known as the ringhals /ˈrɪŋhæls/^[4] or ring-necked spitting cobra,^[5] is a species of venomous snake in the family Elapidae. The species is found in parts of southern Africa.^[1][3] It is not a true cobra in that it does not belong to the genus Naja, but instead belongs to the monotypic genus Hemachatus. While rinkhals bear a great resemblance to true cobras, they also possess some remarkable differences from these, resulting in their placement outside the genus Naja.^[6] In 2023, the Zimbabwe population was described as a new species, H. nyangensis.^[7]

Rinkhals
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Elapidae
Genus:	Hemachatus Fleming, 1822
Species:	H. haemachatus
Binomial name
Hemachatus haemachatus (Bonnaterre, 1790)
Extant (resident)   Possibly extinct   Presence Uncertain & Origin Uncertain
Synonyms
Coluber haemachates Bonnaterre, 1790 Vipera haemachates — Latreille, 1802 Sepedon haemachates — Merrem, 1820 Naja haemachates — Schlegel, 1837 Aspidelaps haemachates — Jan, 1863 Sepedon hæmachates — Boulenger, 1896 Hemachatus haemachatus — Stejneger, 1936[2]: 389 [3]

Description

Rinkhals in uKhahlamba-Drakensberg Park.

Colouration of the rinkhals varies throughout its distribution area, but a characteristic of the species is that the belly is dark with one or two light-coloured crossbands on the throat. Its usual total length (tail included) is 90–110 cm (35–43 in).^[6] Some individuals may have a mostly black body, while others are striped. The dorsal scales are distinct from those of Naja cobras in that they are keeled. Also unlike members of the genus Naja, the rinkhals lacks solid teeth on the maxilla.^[8]

Scale pattern

Scalation:^[9]

• dorsal scales are keeled^[10]
• 17–19 rows of dorsal scales at midbody
• 116–150 ventral scales
• anal plate is entire
• 30–47 subcaudal scales, paired
• 7 upper labial scales
• upper labials 3 and 4 entering the eye
• 1 preocular (rarely up to 3)
• 3 postoculars
• 8–9 lower labials

Geographic range

A South African rinkhals with hood spread

This species, Hemachatus haemachatus, is found in the Western and Eastern Cape provinces of South Africa, northeast through the Free State, Lesotho, KwaZulu-Natal, South Africa, Western Eswatini, Mpumalanga and parts of Gauteng, South Africa. An isolated population is centered on Inyanga on the Zimbabwe-Mozambique border.^[6] There are no recent records from this population; so scientists assume this population may be extinct.^[1]

Habitat

The rinkhals generally prefers grassland habitats ranging from the coast to altitudes of up to 2,000 m (6,600 ft). The rinkhals is extremely common on the Highveld and in the grasslands of KwaZulu-Natal.^[10] Since the rinkhals has a natural propensity to eat frogs and toads, it can also commonly be found near wetlands in its range.^[11]

Behaviour and diet

The rinkhals is diurnal, and hunts during the daytime hours. The rinkhals has a varied diet, and will prey upon any vertebrate that is small enough for it to eat.^[12] The rinkhals will most commonly eat toads in the wild, but it has also been recorded to consume rodents and other small vertebrates such as lizards.^[8]

When distressed the rinkhals will spread its hood, showing its distinctive striped neck. As a defense mechanism, the rinkhals will spit venom.^[8] It will normally spit from a reared position, lunging and hissing while doing so. The rinkhals has ample control over its venom glands, and can accurately spit venom at ranges up to 3 m (9.8 ft).^[8] The rinkhals is also known to fake death, a behavior seen in other snakes such as those of the genus Heterodon. A rinkhals engaging in thanatosis will roll over onto its back, open its mouth, and stick out its toungue.^[8]

If all other methods of defense fail, the rinkhals will bite to ward off predators. Since it relies on other forms of defense, bites are usually very rare. Bites most often occur when people try to handle the snake.^[11]

Reproduction

Unlike members of the genus Naja, the rinkhals is ovoviviparous. Instead of laying eggs, the rinkhals gives birth to live young. Litter size is usually around twenty to thirty live young, but some females can give birth to over sixty live young.^[10] The rinkhals usually gives birth in the late summer, which in the southern hemisphere corresponds to the months ranging from December to March.^[10]

Venom

Detail of head

Illustration of species in South Africa.

The venom of the rinkhals is neurotoxic and partially cytotoxic, and is less viscous than that of other African elapids.^[6] When confronting a human, it generally aims its venom at the face. If the venom gets injected, it causes a great amount of pain and even necrosis due to the cytotoxic effect. Local symptoms of swelling and bruising are reported in about 25% (a quarter) of cases.^[6] General symptoms of drowsiness, nausea, vomiting, violent abdominal pain, cramps and vertigo often occur, as does a mild pyrexial reaction.^[6][13] Polyvalent antivenom is effective for the treatment of rinkhals envenomation, and a fatality from a rinkhals bite has not been recorded in over 40 years.^[8][11]

If the venom enters the eyes, it causes great pain and inflammation.^[13] Corneal damage can occur if left untreated, although timely first aid and eye-washing will usually lead to recovery after a few days.^[8]

A polyvalent antivenom exists in South Africa and is manufactured by the South African Vaccine Producers.^[8]A polyvalent antivenom is currently being developed by the Universidad de Costa Rica's Instituto Clodomiro Picado.