The Monitor Lizards of Southern Africa

Nile Monitor (Varanus niloticus)

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Family: Varanidae.

Length: 120-220cm.

Description: The lizard is black and yellow with an elongated head and a flat tail to aid in swimming. Juveniles are usually more vividly coloured than adults.

Distribution: The species is present in the eastern part of Southern Africa but it is also present along the Orange river all the way to the Atlantic ocean. The species reaches is southern-most  limit at Seekoei river, Eastern Cape and is thus not present in the Western Cape.

Habitat: Closely associated with water sources such as dams, pans and rivers where it can be found from 0-1600m above sea level.

Reproduction: Oviparous, a female can lay up to 60 eggs. females lay their eggs in live termite mounds and juveniles emerge from the termite mound 4-6 months later.

Diet:  Freshwater Crabs and  mussels, frogs, fish, birds and their eggs. Nile monitors are also known to eat the eggs of terrapins, sea turtles and crocodiles. Juveniles tend to stick to reed beds in shallow water where they hunt frogs and insects

Predators: Crocodiles and southern African pythons are among the main predators of the nile monitor.

Conservation concern: Common and widespread, no concern

Threat to humans: Non-venomous, but an adult may bite or thrash their powerful tail if they feel threatened.

Interesting facts: Africa’s largest lizard.

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Rock Monitor (Varanus albigularis)

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Family: Varanidae.

Length: 100-150cm.

Description: The rock monitor is smaller than the nile monitor. It has strong, stocky limbs and an large swollen snout. The tail is longer than the body and the body is dark brown/grey with dark blotches spread across the back. the juveniles are more vividly coloured than adults with a less pronounced snout.

Distribution: It is found throughout the savannah and semi-arid regions of the southern and eastern parts of Southern Africa. It is absent from western Western Cape and the southern Northern Cape.

Habitat: Closely associated with rocky outcrops where it tunnels underneath rock overhangs to create burrows. Also known to use abandoned animal burrows and climb trees.

Reproduction: Lays 8-50 eggs in soft soil.

Diet:  Mainly invertebrates but will hunt and eat animals small enough to swallow. Also eats carrion and baby tortoises.

Predators: The martial eagle is the main predator of adults.

Conservation concern: Common and widespread, no concern.

Threat to humans: Non-venomous, but an adult may bite or thrash their powerful tail if they feel threatened.

Interesting facts: If threatened, the rock monitor may eject its cloacal contents or sham death.

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Resources:

Bates, M.F., Branch, W.R., Bauer, A.M., Burger, M., Marais, J., Alexander, G.J. & de Villiers, M.S. (eds). 2014. (CD set). Atlas and Red List of the Reptiles of South Africa, Lesotho and Swaziland. Suricata 1. South African National Biodiversity Institute, Pretoria.

Branch, B. 1994. Snakes and other Reptiles of Southern Africa. Cape Town. STRUIK.

Branch, B. 2016. Snakes and other Reptiles of Southern Africa. Cape Town. STRUIK Nature.

Water Snakes of Grahamstown

This list contains all the water snakes that can be found in and around water in the Grahamstown area. As the names suggest, this means that these snakes are usually found in close proximity to water because of their diets that mostly consist of frogs, tadpoles and fish. Although not as closely related to water as the other snakes on this list, the red-lipped herald has been listed at the end because it is closely associated with damp, moist areas.

Common brown water snake (Lycodonomorphus rufulus)

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Family: Lamprophiidae.

Length: 60-85cm.

Description: The snake has a plain olive body with smooth scales and a pale, pearl underbelly. The eyes also have elliptical pupils.

Distribution: Endemic to Southern Africa. The species is present in every province except the Northern cape where it is only found along the outskirts of the province.

Habitat: Closely associated with water sources such as dams, streams and rivers where it is often found beneath rocks and debris on the banks of the water sources.

Reproduction: Oviparous, 6-23 eggs in summer.

Diet:  Mainly frogs, tadpoles and small fish  but can take small rodents. Nocturnal hunter.

Conservation concern: Least concern, common.

Threat to humans: None.

Interesting facts: The most common water snake in Southern Africa.

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 Dusky-bellied water snake (Lycodonomorphus laevissimus)img_3245

Family: Lamprophiidae.

Length: 70-120cm.

Description: This snake has an olive to brown-black body with a cream underbelly. The upper lip is usually spotted and the snake has small eyes with round pupils.

Distribution: Endemic to South Africa. It occurs in the Eastern cape where its range extends up through Kwazulu Natal and into Mpumulanaga and Swaziland.

Habitat: Closely associated with water sources such as dams, streams and rivers where it is often found beneath rocks either on the banks of water sources or in the water itself.

Reproduction: Oviparous, lays 17 eggs in summer.

Diet: Frogs, tadpoles and fish. Diurnal hunter.

Conservation concern: Least concern, common.

Threat to humans: None

Interesting facts: The largest water snake in the region. During the day, the snake takes refuge under submerged rocks in the water column where it ambushes fish and frogs.

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 Red-lipped herald (Crotaphopeltis hotamboeia)img_1902

FamilyColubridae.

Length: 60-75cm.

Description: The snakes has an olive body with white flecks. The snake is most easily recognized by its red lip which is absent from some individuals. It has large eyes and vertical pupils.

Distribution:  The species is present in every province except the Northern cape where it is only found along the outskirts of the province.

Habitat:Found in damp areas where it can be found under rocks and logs. It can also be found in termite mounds.

Reproduction: Oviparous, lays 6-19 eggs in early summer.

Diet: Mainly frogs and toads but can take lizards. Nocturnal hunter.

Conservation concern: Least concern, common.

Threat to humans: None, venom is incredibly mild.

Interesting facts: Along with the brown house snake, the red-lipped herald is the most commonly encountered snake in South Africa. The snake also flattens its head and flairs its red lips when threatened.

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Resources

Alexander, G. & Marais, J. 2007. A Guide to the Reptiles of Southern Africa. Cape Town. STRUIK Nature.

Branch, B. 2016. Snakes and other Reptiles of Southern Africa. Cape Town. STRUIK Nature.

Bates, M.F., Branch, W.R., Bauer, A.M., Burger, M., Marais, J., Alexander, G.J. & de Villiers, M.S. (eds). 2014. (CD set). Atlas and Red List of the Reptiles of South Africa, Lesotho and Swaziland. Suricata 1. South African National Biodiversity Institute, Pretoria.

Marais, J. 2014. Snakes and Snakebite in Southern Africa. Cape Town. STRUIK Nature.

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Green Snakes of the Eastern Cape

This list includes all the green snakes that can be found in the Eastern Cape. Barring the boomslang (Dispholidus typus), all the individuals listed come from the genus Philothamnus and they are all closely related. Although the many-spotted snake (Amplorhinus multimaculatus) can be found in the Eastern Cape, it has not been included on this list because not all individuals in this species are green, some are olive-brown. In the Eastern Cape, the boomslang  is not green. Females are olive and males are yellow and black. Irrespective of this, the boomslang has been included at the end of the list.

Green Water Snake (Philothamnus hoplogaster)

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Spotted-Bush Snake (Philothamnus semivariegatus)

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Western Natal Green Snake (Philothamnus natalensis occidentalis)

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Female Boomslang (Dispholidus typus) from the Eastern Cape

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The Skinks of Grahamstown

Listed below are the skinks that you are most likely to see or find in and around Grahamstown. 


Family: Scincidae

The Scincidae family is considered the most species-rich lizard family in the world. In South Africa, Lesotho and Swaziland combined, there are 59 recognized species and several subspecies. Skinks are characterized by shiny overlapping scales and a cylindrical, robust  body. Most skinks also feed on invertebrates and irrespective of whether they have limbs or not, these lizards can become hyper-abundant in certain localities, where they often form a large part of the diet of predators’.


Subfamily: Lygosominae

Genus: Trachylepsis

The members of this genus are referred to as ‘typical skinks’ and they are widespread and  present in all the major biomes of South Africa. There are currently 13 members of this genus in South Africa, most of which are viviparous (live bearing offspring). All the lizards in this group are diurnal (active by day) and most  spend their time on rocks where they can often be seen darting in and out crevices in search of food, safety and warmth.

Cape Skink (Trachylepis capensis)

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Red-Sided Skink (Trachylepis homalocephala) 

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Variable Skink (Trachylepis varia) 

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Subfamily: Acontinae

Genus: Acontias

This genus is highly diverse with 20 species currently residing in South Africa. Twelve of these are endemic to South Africa and thus exist nowhere else in world. The legless skinks are fossorial skinks (live underground) that tend to  favour soft sediments. Whilst you are unlikely to spot them basking in the daylight, they can often be found under loose rocks, rubble, fallen logs or at the base of grass tufts. Once spotted however, they often escape quickly into the ground with the help of their large rostral scale on their snouts which enables them to plough through the sediment with ease. This group is also characterized by a lack of limbs, an adaptation which aids them in their fossorial lifestyles.

Eastern Cape Legless Skink (Acontias orientalis)

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References:

Alexander, G. & Marais, J. 2007. A Guide to the Reptiles of Southern Africa. Cape Town. STRUIK Nature.

Bates, M.F., Branch, W.R., Bauer, A.M., Burger, M., Marais, J., Alexander, G.J. & de Villiers, M.S. (eds). 2014. (CD set). Atlas and Red List of the Reptiles of South Africa, Lesotho and Swaziland. Suricata 1. South African National Biodiversity Institute, Pretoria.

 

Puff Adders: In Search of Mates

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So now that winter is coming to an end, snakes and other reptiles are starting to become far more abundant. One species that has become particularly abundant in the last few weeks, is the puff adder (Bitis arietans). To give context, in the last week, I have come across three puff adders. Two of them were average-sized adult males and the the third was a very large, very pregnant, female puff adder, which was on the verge of popping.

The reason for the increase in puff adder sightings is the direct result of the time of year we find ourselves in. We are smack-bang in the middle of breeding season, and males are prowling for receptive females. Although large, puff adders are usually very hard to find, and this is a product of their amazing cryptic camouflage coupled with their ability to remain motionless even when you are on the verge of stepping on them. Puff adders spend much of their time concealed beneath tufts of grass, but when it comes to breeding season (Late winter/early spring), males leave the safety of their hiding spaces in search of mates, which they find with the help of pheromone trails left by the females.

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So whilst some people may believe these snakes have finally decided to take over Africa, the truth is; the puff adders are on the hunt, not for food and not for you, but rather for love. To put it bluntly, they are looking for a ‘betty’ and they will fight with any male puff adder that gets in their way. Because the female drops a scent trail, she has the ability to draw a large number of males, and in some cases, seven males have answered the call of just one female.

Interesting facts about puff adder mating:

Females give birth to live young 

Males engage in combat for females

Puff adders can hybridize with Gaboon adders (Bitis gabonica)

One Kenyan puff adder has given birth to 156 juveniles, the largest recorded litter of any snake species

Whilst many males may follow the same scent trail, only one male is allowed to mate, and to determine this, male puff adders engage in neck-to-neck wrestling matches in which they wrap their bodies around their competitors and attempt to force their competitors’ to the ground. The male which wins the bout approaches the female, wraps his tail around hers, inserts his hemipenes into her cloaca and proceeds to mate. Mating can last several hours, but once done, both snakes part ways.

After 7-9 months, the female gives birth to 20-40 live young (viviparous), which measure anywhere between 15 and 20cm. Broods of up to 80 juveniles have been recorded, but the record still resides with a puff adder from Kenya, which gave birth to 156 juveniles in a Czech zoo.

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So whilst puff adders may be dangerous and scary to those who are not fond of snakes, I hope this article illustrates just how fascinating these snake can be, because after all, If you can produce 156 children in one sitting, and live to tell the tail, you surely are a marvel to behold.

References:

Alexander, G. & Marais, J. 2007. A  Guide to the Reptiles of Southern Africa. Cape Town, STRUIK Nature.

Marais, J. 2004. A Complete Guide to the Snakes of Southern Africa. Cape Town, STRUIK.

Marais, J. 2014. Snakes & Snakebite in Southern Africa. Cape Town, STRUIK Nature.

More about puff adders:

Additional Information

Additional Pictures

 

 

Ten of the more common snake species found around Grahamstown


The List is in no particular order, all info ascertained from books published by Johan Marais. References are listed at the end.


Brown House Snake (Boaedon capensis)

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Family: Colubridae

Average length: 60-90cm

Habitat: Common around houses where it is often found under building rubble, rocks and corrugated metal

Diet: Rodents and other small vertebrates

Danger to man: None


Common Slug Eater (Duberria lutrix)

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Family: Colubridae

Average length: 30-35cm

Habitat: Often found underneath rocks, logs, tufts of grass and other vegetation

Diet: Slugs and snails

Danger to man: None


Puff Adder (Bitis arietans)

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Family: Viperidae

Average length: 90-100cm

Habitat: The snake spends much of its time under bushy cover where it uses its’ camouflage to blend into its surroundings

Diet: Rats, mice and other small vertebrates

Danger to man: Very dangerous cytotoxic venom that and can kill if left untreated


Western Natal Green Snake (Philothamnus natalensis occidentalis)

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Family: Colubridae

Average length: 60-90cm

Habitat: This snake is a fantastic climber that spends much of its time in trees and shrubs near water

Diet: Lizards, geckos and frogs

Danger to man: None


Spotted Skaapsteker (Psammophylax rhombeatus rhombeatus)

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Family: Colubridae

Average length: 45-85cm

Habitat: Found in a range of habitats, mainly  under rocks and fallen debris.

Diet: Rodents and other small vertebrates

Danger to man: Mildly venomous but posses no threat to man


Bibron’s Beaked Blind Snake (Typhlops bibronii)

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Family: Typhlopidae

Average length: 30-38cm

Habitat: burrowing snake that spends much of its time underground, but can be found above ground after heavy rains

Diet: Ants and termite larva

Danger to man: None


Rhombic Night Adder (Causus rhombeatus)

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Family: Viperidae

Average length: 30-60cm

Habitat: Common in damp areas where it can be found in old termite mounds, under rocks and under logs

Diet: Toads and other frogs

Danger to man: Mild cytotoxic venom that is dangerous but not life-threatening, hospitalization may be required though


Cross-Marked Whip Snake (Psammophis crucifer)

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Family: Colubridae

Average length: 60cm

Habitat: Found mainly inside old termie mounds and under rocks and other fallen debris

Diet: Lizards, geckos and frogs

Danger to man: Mildly venomous, but the venom is of no concern to man


Red-Lipped Herald (Crotaphopeltis hotamboeia)

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Family: Colubridae

Average length: 30-70cm

Habitat: More commonly found in damp areas under rocks, building debris and compost heaps

Diet: Frogs, toads and sometimes lizards

Danger to man: Mildly venomous, but the venom is of no concern to man


Rhombic Egg Eater (Dasypeltis scabra)

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Family: Colubridae

Average length: 40-75cm

Habitat: Can be found in most habitats, but it is particularly common in old termite mounds

Diet: Bird eggs

Danger to man: None


References:

Marais, J. 2004. A Complete Guide to the Snakes of Southern Africa. Cape Town, STRUIK.

Marais, J. 2014. Snakes & Snakebite in Southern Africa. Cape Town, STRUIK Nature.


Why can snakes and lizards produce live young when birds cannot?

In the animal kingdom, the ability to reproduce is one of the most critical abilities in an animal’s arsenal because it ensures the survival of the species. There are however three different types of reproduction namely viviparous, ovoviviparous and oviparous reproduction. Viviparity is the ability to produce live young, oviparity is the ability to produce eggs that hatch outside of the uterus and ovoviviparous reproduction is the retention of the egg within the uterus until hatching.

Viviparity is the most recently evolved method of reproduction and has evolved over 160 times in animals. Viviparity is thus present in bony fish, amphibians and most mammals with at least 20% of the snake and lizard species displaying viviparity. What is so interesting about viviparity is that is not present in any birds yet it is present in both lizards and snakes which represent an older order of animals. Birds date back to the Jurassic and there are approximately 9000 species of them which exhibit incredible morphological and ecological diversity, yet not one of them has the ability to produce live young.

The only other class among the vertebrates that cannot produce live young is the class Agnatha which represent the lampreys and hagfish. They lack the prerequisites for viviparous reproduction which include internal fertilization and a chamber rich in blood vessels for incubating the developing egg. Birds however have both of these physical attributes.

Why don’t birds produce live young?

Many hypothesis exist to explain the lack of viviparity in birds but the two most studied include the flight hypothesis and the cledoic egg hypothesis. It is hypothesised that flight is a reason viviparity is absent from the bird kingdom because internal development of an embryo would incur additional weight on the bird and negatively affect the ability of the bird to fly. The hypothesis is however not fool-proof because flightless birds (ratites) such as ostriches still produce eggs even though they lack the ability to fly. Bats are another example because although they are mammals and subsequently produce live young via viviparity, they are highly accomplished fliers.

Birds have cledoic eggs which are highly calcified and thick, they allow the movement of gases but are poor at allowing the movement of water and nitrogenous waste through the walls of their shell.  Bird’s eggs resemble crocodile and turtle eggs very closely and of the 250 species of turtle and 21 species of crocodile neither of them have evolved viviparity, making the cledoic egg a possible reason for the lack of viviparity in animals. Embryos have a high metabolic requirement and due to the specialised shell of the bird, don’t grow well in the low oxygen and high carbon dioxide environment of the uterus.

Another hypothesis is that the internal temperatures of birds are unsuitable for the production of live young. The resting temperature of birds is approximately 41 degrees whilst the optimal temperature for egg incubation lies between 34 and 38 degrees. In chickens, eggs have a higher chance of mortality if they are retained by the mother for too long due to an excess of heat and carbon dioxide.

Viviparity is a reproductive strategy and would only evolve in birds if the benefits of having it outweighed the costs. In simple terms maybe viviparity never evolved in birds because oviparity was already a successful form of reproduction.

Birds have adapted a suite of reproductive strategies that work hand in hand with oviparity. These include the production of multiple offspring, complex parental care and incubation. Developing embryos are protected from disease and environmental factors by the albumen, egg shell and the accompanying membranes. Parents provide protection and warmth via thermoregulation whilst egg camouflage and nests protect the eggs from predators. The introduction of viviparity could very well decrease the fitness of birds by reducing the amount of offspring they can produce, increasing the chance of death in the mother and reducing the amount of male investment in chick rearing.

The special adaptations associated with egg laying in birds probably evolved early in the history of the class and certainly before the period in which birds started diversifying into the many species we have today. Although it is unknown why birds reproduce in the way they do it is common knowledge in the scientific community that they are a highly successful class that reproduce highly effectively regardless of the fact that they still lay eggs.

How does viviparity occur in snakes and lizards?

If not a single bird is able to produce live young, how it that snakes and lizards are able to when all of their ancestors previously produced eggs.

Firstly, birds are very different from the oviparous vertebrate ancestors that eventually made the leap to viviparity. Secondly, not all reptiles are able to reproduce live young. Neither the dinosaurs of the Jurassic period nor the crocodiles or turtles of today can produce live young.

What links all these animals is the structure of the egg: the eggs are thick and heavily calcified, making it harder for certain gases to pass through their membranes. In the closed off environment of the uterus, gas movement becomes an even bigger problem. Squamate (snakes and lizards) shells are markedly thinner and less rigid making this less of a problem.

In the squamates it is believed that exposure to cold environments is one of the deciding factors in their movement towards producing live young. In a cold environment the egg of the mother would experience that cold because of its presence in the nest. These cold conditions could slow or even cause death in the developing embryo. If the egg is retained within the mother its chances of survival are markedly improved because it can acquire the optimal incubating temperature from within the mother because she can attain a high body temperature through her interaction with the environment.

Other factors that influence the evolution of viviparity in squamates include predation, flooding, dehydration, ultraviolet attack, microbial attacks and moisture extremes. If a mother is burdened with an embryo she is less able to move and feed which can be a limiting factor, but when it comes to reptiles such as snakes and lizards, they tend to huddle around their eggs once laid to protect them so retaining the embryo won’t make much difference to the female.

In terms of predation, if the egg is retained within the female it can’t be eaten unless the mother herself is eaten. Finally moisture extremes on the ground can cause disease so if the egg is retained, it is protected from extremes in the environment.

Conclusion

Much like birds, the reproductive capability of live birthing will only evolve in squamates if the benefits outweigh the costs. In order to become fully viviparous, evolution must favour the intermediary stages because evolution is gradual. What this means is that an animal isn’t instantly viviparous but rather becomes viviparous over time with changes such as the lengthening of the time the egg is retained within the female and the development of a placenta. In certain squamates it is clear that viviparity is beneficial because it exists in the animal and thus the lack of viviparity in birds is a sign that birds don’t gain any benefit from viviparity because no viviparous birds exist.