Dinner for one

Text Pat McKrill Photographs Pat McKrill

The .01% of the South African population – those who can head off into the vast African bushveld to witness the cunning teamwork of a pride of lions tracking and killing their prey, or a pack of wild dogs whimpering and yapping instructions to each other as they run down a duiker – are fortunate to be able to partake in what us plebs might term a ‘bucket list’ experience – one that comes at a not inconsiderable cost. The other 99.99% of us have to sit at home and watch it on telly. Not the same is it?

But close to us in the garden, up in the Fever tree, down by the water feature, or under the dog’s kennel, we have the same scenario – in miniature – taking place, at no cost whatsoever. A wild predator is probably stalking its prey, killing and eating it. A rarely witnessed but regular occurrence, worth a thousand trips to any game park, is taking place right under our noses.

Over time, we’ve become more inured to the presence of snakes in our environment, tolerating them, having grudgingly accepted the fact that they’re doing a good job by killing rats and mice, and keeping the frogs down to manageable numbers. There’s nothing wrong with that somewhat simplistic reasoning, however across the species range, snakes are far more catholic in their tastes than we would assume, and different species have, considering their circumstances, some extremely interesting dietary preferences. To give you some idea of what I’m talking about, here’s a sampling of some of what goes on.

I’ve selected a few of my favourites – apologies if yours don’t feature – and we’ll take a brief overview of some of the lesser known stuff, such as their prey range, some of the ways in which they seek it out and capture it, and ultimately, the way in which they consume it. So as to get everybody on board from the beginning, I must remind you that snakes have no arms or legs to assist them, and they hunt singly, making the actual capture and feeding process that much more remarkable. Marginally in their favour however, is the fact that they have at least 4 movable jawbones in their skull, all of which can, to a lesser or greater extent, be independently controlled, enabling a prey animal to be manipulated during the swallowing process. The bones are interconnected with flexible ligaments, allowing the mouth to be greatly distended, enabling the snake to consume prey up to 4 to 5 times the size of the head. A high degree of body skin and rib-cage flexibility accommodates the prey on its way into the stomach, and the danger of cutting off the snake’s air supply is minimised by the elongated lung structure and the hardening of the oesophageal tube in the throat, thereby ensuring a free airflow.

As we’ve established in a previous article, not all of the 160 – odd species in South Africa have venom. Of those that do, those with the more potent venom – such as the mambas, cobras and true adders – use it principally to rapidly subdue and kill their prey, with the digestive accelerants in the enzymes that make up the venom, doing the rest. These guys are the lucky ones in that they don’t really need to physically subdue their prey. To use a well-known analogy, they go into a knife fight with a gun. But those who deserve the accolades, are the less fortunate, if we can call them that, who need to subdue their prey physically – long before any venom they might have, can take effect.

The non-venomous green ones (Philothamnus spp.) the Spotted Bush snakes and their cousins, the Natal Greens and the Green water snakes, as with all hunters, need to seek out their prey using taste, smell and sight. Their preferred diet, principally lizards and frogs, needs to be ambushed, alternatively, stalked and captured, using various devious ploys. Camouflage is vital – green is a handy colour to have in the bushes and reeds – as is sleight of hand (body) whereby the head remains unmoving, possibly even in view of the prey, whilst the body cunningly draws up, out of sight, forming a lethal spring that thrusts the business end forward at the speed of light at the right moment. The tooth-filled and gaping mouth is almost fired at the unsuspecting prey like a bullet out of a gun, engulfing it in a vice-like grip that hopefully secures it. The prey animal will not come along compliantly, nor will it hang around for a second strike if the first one misses, and once captured, it will certainly put up a massive fight for survival. The hungry snake that grabs the lizard’s tail-first will learn the hard way.

Now the fun starts. Whilst doing its best to hang on as the prey struggles to release itself, the snake chews onto the victim, and during this chewing process it works (not always successfully) at turning the victim around so that it can be swallowed head-first. Remember, that this is done with little or no other assistance – mouth only. If you’re ever privileged enough to witness a bush snake stalk, catch and swallow a gecko, you’ll see just how clever the process is. These snakes are not constrictors, and they’re fully aware that until the prey is on its way down the tube, it can still breathe and put up a damned good fight.

The non-venomous constrictors such as the common Brown House snake (Lamprophis capensis) and our national treasure in terms of reptiles, the Rock Python (Python natalensis) are typical foragers who seek out their prey within their home range, but the python is in addition to being a forager, out of necessity because of its size, also an ambush feeder. Apart from ambushing known animal paths, the python can also be found near water, within which it will lie and wait for its prey, anything from birds to small or medium sized mammals which it seizes as they come to drink. Because of their relative bulk, unless the local food source is threatened, constrictors do not travel extensively and remain reasonably territorial. The house snakes will be attracted to, and make themselves at home, where food – mainly rodents and skinks – is readily available. If left to do their work, they’ll make life extremely difficult for any rodent trying to raise a family in the neighbourhood – either the husband, wife or the kids will keep on disappearing!

Constrictors strike out and seize their prey by mouth, and then they envelop it in a series of body coils that get thrown around it and tightened to squeeze the air from the animal and restrict its ability to breathe freely, thereby killing it by asphyxiation. Only in the movies do they break a whole bunch of bones. Once the animal is dead – the snake can sense the lack of heartbeat – a number of coils will be relaxed, and the snake will then inspect its victim and start the swallowing process, using some of the coils to help with the food manipulation, something akin to a kid with an ice-cream cone.

To avoid the danger of being ripped apart by its victim should it fight its way down the alimentary canal, a snake that consumes larger prey, will do its best to ensure that the prey animal is dead beforehand.

Female boomslang, photo by Pat McKrill
Female boomslang, photo by Pat McKrill
Female boomslang, photo by Pat McKrill

The egg-eaters can be divided into two groups; those who include eggs in their varied diet, and those who are specialised egg-eaters. The former, comprised mainly of cobras and boomslang, swallow the eggs whole and digest them within the system, but the specialists (Dasypeltis), are designed to engulf the egg and extract the contents, before regurgitating the empty shell. Our most common Highway egg-eater is the Southern Brown (D.inornata), a small-bird breeder’s nemesis. They raid nests and aviaries, and leave behind empty compressed egg cases and the occasional confused bird. They can engulf fairly large eggs relative to their head size, and the modified bones in the spine behind the head, are used to saw through the shell which is then compressed and drained of its contents. The snake, which is non-venomous, can put up a pretty impressive display of aggression if so inclined, striking out repeatedly with mouth agape, but it’s all for show, as it has no teeth to speak of, and would rather just be left alone. Its keeled scales and brown colouration can occasionally lead to misidentification and they’re sometimes confused with the female boomslang. They have relatively small eyes with distinct elliptical pupils, quite unlike the boomslang’s large eye and round pupil.

Female boomslang, photo by Pat McKrill

The non-venomous Common Slug eaters (Duberria lutrix) are the gardener’s friends that unfortunately get the Order of the Spade every time they’re seen doing what they do best, eating slugs and snails in the veggie patch. They grow to about 400mm in length, and have a wide reddish-brown band down their back, with lighter brown sides. Their common defensive tactic is to roll up like the twisted dry tobacco plugs that grandpa used to buy at the corner store, hence their Afrikaans nickname, Tabakrolletjie. As their prey is not renowned for its overland speed, slug eaters can pick and choose as they like, without the need to stalk or chase. The prey animal is swallowed live and is unlikely to inflict damage to the snake. Snails are more difficult to consume as the snail has to be extricated from the shell, and there are records of these snakes dying with their heads stuck in the snail’s shell, possibly as a result of asphyxiation. Poetic justice?

I once received photographs showing one slug eater having swallowed another, but although we’ll never know in this case, this could have been as a result of the two snakes trying to eat the same slug, with the one merely consuming the other during the process – not unusual where two snakes become attached to opposing ends of the same prey. In this case, the swallowed snake was removed, and went off as if nothing untoward had happened.

We also have snakes who spend most of their lives beneath the shrubbery, hunting in the subterranean highways. The fairly common Cape Centipede Eater (Aparallactis capensis) pops up every now and again to have its head beaten in by the not-so environmentally friendly gardener. Although mildly venomous, they have teeth that are unlikely to pierce human skin, they’re not harmful to man or his pets, and spend their time sleeping or hunting centipedes.

Although we’re aware that some hatchlings start out their lives by feeding on insects and changing over to the bigger stuff as they grow up, Centipede eaters on the other hand, are one of the few species that actually specialise in feeding on insects or their near relatives, in their case, seeking out centipedes and biting them continuously, until their venom takes effect.

Female boomslang, photo by Pat McKrill
Female boomslang, photo by Pat McKrill

One of the snakes that we mentioned in the last edition of the Leopard’s Echo, Bibron’s Stiletto snake, (Atractaspis bibronii) operates predominantly within underground tunnels, overtaking its victims – other reptiles or rodents for example – and biting them – or should I say, stabbing them, via a sideways and backward stab (hence the ‘Stiletto’ moniker) – without having to open its mouth. Apart from these grossly overgrown fangs, it has no other teeth, relying almost entirely upon the potency of its venom to secure the meal.

The well-known frog eaters, the Night adders (Causus rhombeatus), the Heralds (Crotaphopeltis hotamboeia) and the Brown water snakes (Lycodonomorphus rufulus), whether venomous or not, have to hang on and swallow – dead prey or not – and hope that you don’t come along and ‘rescue‘ the frog they’ve just spent considerable time stalking and capturing.

Female boomslang, photo by Pat McKrill
Female boomslang, photo by Pat McKrill
Female boomslang, photo by Pat McKrill

Why not let nature take its course? Get your camera, and profit from the experience.

Author photo: Pat McKrill

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.