Snakes of the Kloof and Highway area: what’s that under your jacket?Some unusual physical features of our Highway snakes
Text and photographs Pat McKrill
Those of you who have been following the articles in this Leopard’s Echo series will have noticed, nature added a few interesting bits and pieces to its creatures and plants, making them somewhat different or special. Often these additions might be hidden from sight, yet, unless proven otherwise, we must assume they would be intended for a specific function, not only to advertise the wares on offer. Although much of what snakes possess in the way of additional equipment is hidden, I’d caution you against picking one up in order to test the veracity of my observations.
Snakes have been on this earth for considerably longer than humans have, so none of these bits and pieces were intended for us. They were intended for those things that were around a long time ago, so a lot of what we see, might not make sense to us, but certainly for me, it’s been interesting to ponder the possibilities.
I certainly don’t have the answers to many of the questions I raise in my article, nevertheless, let’s have a look at a couple of the unusual tools of the snake trade. Maybe you can offer suggestions.
Although not generally visible – unless you’re on the business end – the finer details of a snake’s teeth can play an important part in the identification of a species when doubt exists. Here’s a bite-sized look at just some of the unusual dentition possessed by some of our Highway species.
The teeth of most snakes are simply sharp and pointed, they have to be if they’re going to catch their prey and hang onto it. As snakes don’t masticate their food as we do, their teeth are designed to serve a specific purpose – to secure their prey, and if they’re venomous, simultaneously insert their venom. The teeth are positioned strategically on the reasonably complicated upper and lower jaw structures, to assist with the initial capture process, and carry out the mechanical, controlled ‘feeding’ of the prey animal into the gullet for its thereafter muscularly assisted journey to the stomach. The specialist Egg-eaters Dasypeltis sp. have almost nothing in the way of conventional teeth, they don’t need them – eggs don’t run away when attacked – and they’ll not puncture the flesh in the unlikely event of a bite when roughly handled.
Southern brown egg eater
Where a snake is non-venomous, there will be a few necessary modifications to the tooth shape, but in the case of venomous snakes, there are various species-dependent modifications, ranging from shallow longitudinal grooves in the rear-fanged species, right through to the hinged, hollow tubes of the adders, all of which are designed to channel the flow of venom into the puncture wound made by the snake.
During the course of its life, a snake will change its teeth fairly often. Old teeth will get replaced, sometimes at the same time when the skin is shed.
The venomous snakes are able to address the potential problem of replacing venom fangs during this change period when it comes about, and the replacement fangs, in reserve in the event of a tooth change, become effective very quickly. I’ve seen up to 4 spare teeth in a tooth ‘socket’ in a boomslang, each of which would be capable of delivering venom not too long after the primary tooth had become ineffective. The same ability to rapidly replace effective teeth in the case of hollow-toothed fangs also applies in such snakes as the adders. Puff adders often have more than one potential venom-delivering fang in close proximity to the active fang.
Secondary fangs of a puff adder
Teeth have an important role to play in the life of any predator, and in terms of snakes, sometimes the shape of the teeth has a bearing on the common names of the snakes that wear them.
The inoffensive and non-venomous Common Wolf snake Lycophidion capense is named after the design of its teeth which are disproportionately longer and sharper than most snake teeth would be, and as the name suggests, perhaps like those of a Wolf. These enable it to grasp its smooth-scaled prey such as other snakes and lizards, without losing its grip.
Wolf snake with sharp recurved teeth
Our notoriously famous Stiletto snake Atractaspis bibronii previously called the Burrowing adder or Mole viper – is a rather excessively equipped little venomous dude that spends the bulk of its time underground or in the organic litter that collects above ground. Anybody who has ever been bitten by a Stiletto snake having picked it up in the mistaken belief that it’s a blind snake (this is a popular ‘club’ in Southern Africa), will never forget the bite.
Bibron’s stiletto snake. There’s some serious weaponry under that lip.
Photo: Nick Evans
The disproportionately long front fangs on each side of the top jaw, lie just beneath the upper ‘lip’, and their length and structure prevents the snake from actually opening its mouth and striking out to inject its venom in the conventional manner, particularly when hunting underground in a confined space. In order for it to insert venom, it would have to pass the prey animal, and then pull the head backwards on whichever side the prey lies, and simultaneously stab the animal in a backward and sideways motion, as would a fighter stab his enemy with a stiletto blade, hence the name.
As an interesting observation in his book Snakes of South Africa (1912), probably our best-known herpetologist, Dr F.W.Fitzsimons wrote when describing the snake, that “owing to their burrowing habits, their outward form has gradually been undergoing change, and doubtless in course of time, the fangs will disappear or become considerably smaller”. Not sure what time period he was referring to, but so far I notice, no dice.
Mention of the teeth of the Wolf snake brings to mind the undoubtedly purpose-built gnashers of our Natal Rock Python Python natalensis.
Bottom jaw of a python
Anything managing to escape from a full-mouthed bite by a Python, will certainly suffer from what the Americans call ‘collateral damage’ in the bitten area. Along with embedded broken teeth, there will also be plenty of holes and some serious skin damage, with a free dose of tetanus thrown in for good measure. Snakes don’t do mouthwash or twice-daily brushings. As constrictors have no venom to help with the immobilisation of their prey, they have to rely upon their strength and the catch-and-hold method of securing their prey, failing which, there goes lunch!
And there goes another legend that says Pythons hang from trees and haul you off your bicycle with their tail as you ride by.
The long, hinged fangs of the Puff adders, Bitis arietans, are designed to penetrate deeply into the flesh of their prey, thereby ensuring envenomation. There is a downside however, in that this has led to a firmly held belief amongst some people that these snakes hang onto their prey, rather than merely strike and release. This belief has more than likely come from the fact that there have been cases where the long fangs have become unintentionally hooked into the fabric of the garment the unfortunate victim was wearing when it was bitten. The victim, whilst running away from the snake, might inadvertently have taken it with them for a bit of a run down the road thereafter.
Snake scales are essentially part of a coverall that covers the actual skin of the snake. Scales are an integral part of this overall, and are not individual slabs of protective plating, as in the case of fish scales. We have a few interesting scale types represented in our Highway snakes, for example.
Some snakes have what are termed ‘keeled’ scales covering the dorsal (upper body) surface including the head. A keel, is a raised ridge along the scale that divides the scale into two angled sides, almost like the spine on a leaf. Sometimes, as in the case of a few of the climbing snakes – our Spotted bush snake Philothamnus semivariegatus is a good example – although having smooth dorsal scales, some have belly or ventral scales, with a ridge or keel on either extremity of the wide scale, allowing the snake to use it as a sort of ‘cleat’ that can help it to gain adhesion when climbing difficult surfaces.
Spotted bush snake using its cleated scales
Spotted bush snake showing ventral scale cleats
File snake. Heavily keeled.
Our most common highway species with strongly keeled scales are the Boomslang Dispholidus typus, Puff adder, the Southern brown egg eater Dasypeltis inornata, and the less commonly encountered Cape file snake Mehelya capensis. The Night Adder Causus rhombeatus, has visible but less strongly keeled scales.
Southern brown egg eater with its keeled scales and night-vision pupils
Night adder, lesser keeled scales
The specialised egg eaters, particularly the Rhombic egg eater D.rhombeatus, are known to rub their scales together by writhing their bodies to create a ‘hissing’ sound that scientist assume to be a warning sound. However, apart from making them less shiny, the reason for having keeled scales has never been convincingly explained to me. Any volunteers?
As far as most of us are aware, a snake’s tongue is a primary sensing device, used in conjunction with their vomeronasal organ, an organ of smell, the organ of Jacobson. The tongue collects chemical information via its two tips, which can be moved about independently. This information is fed, via two small ‘pits’ in the roof of the mouth, into a specialised olfactory bulb in the brain for analysis.
Herald relaxed and tasting
Apart from being a means of detecting food and/or enemies, it is particularly useful during the mating season, when there’s plenty of pheromonal messaging going on, both by way of airborne particles from other snakes, as well as physically deposited scents.
I find it helpful to watch the head of the snake when it is motionless, in order to determine whether it could be awake or asleep. An alert snake like a Puff adder might not move a muscle when detecting movement, but will soon produce its tongue to determine the source of movement of which it’s become aware. A sleeping snake is unlikely to do so.
Scientists have noted that some prey animals respond to movements made by the tongue of a snake, particularly those tongues with attractive colours. Amongst our snakes with interestingly coloured tongues, we have the Vine snakes Thelotornis sp. with a black-tipped red tongue, and many others, some of them fossorial feeders, have bright red or pink tongues – goodness knows why. The Night adder has a dark tongue with blue stripes running the length of both sides.
Night adder tongue and scales
Unless it is designed to attract or lure other animals, I question why else would a seldom-seen organ – such as a snake’s tongue – be given an attractive or interesting colour? Plenty of room for research.
The head shape
From the point of view of our subject, once you’ve lost the ability to hook meals out of nooks and crannies with your pinkie – as happened when they lost their limbs – there comes a need to adapt. Among those adaptations came the redesigned head shapes. I might be taking some poetic licence here in my reasoning for different head shapes, but I think I’m on the right track.
If you wanted to embed 2, 15mm sharp needles into the rump of a large veld rat charging by, you’re not going to succeed with the dainty little head of a Spotted bush snake, you’ll need a power-driver of a head – ask any Puff adder.
Puff adder. Heavy keels, heavy head.
Similarly, any snake seeking out lizards in rocky crevices – our Spotted rock snake Lamprophis guttatus for example – would need a tapered head because it won’t get too far with a head shaped like that of its cousin, the Olive house snake Lamprophis inornatus who has a large blunt head.
Spotted rock snakes
Photo: Colleen Easton
Our Boomslang and Vine snakes have head shapes that enable them to enjoy binocular vision, and some snakes, like our Herald Crotaphopeltis hotamboeia can change the shape of their head to frighten off predators.
Herald with an angry head shape
So much to learn – so little time. Have fun.
About the author
Pat was born in the UK, educated and brought up in Rhodesia/Zimbabwe, and came to South Africa in 1983. He developed an early interest in the study of the behavioural aspects of insects and animals, rather than the deeper scientific side, and he’s worked with snakes for most of his life. Pat conducts educational walks and talks throughout SA and into neighbouring countries where snakes are grossly misunderstood and needlessly killed. He writes articles for a number of publications, and has written the book ‘Getting to Know the Neighbours’, which is all about understanding snake behaviour and is aimed at teaching others how to come to terms with them.
Learn more on his website, Snake Country.