Parasitism, symbiosis and mutualism

Red billed oxpecker on a buffalo

Snakes in the wild will be prone to some form of parasitism. They get external – ticks, mites etc. – as well as internal parasites, and to some degree, they have an inbuilt resistance to many of these parasites, along with the ability to self-heal with their own antibodies, when illness comes along. Wild snakes are extremely healthy animals. Excluding parasitism, where only the parasite wins, can we say that snakes have a symbiotic and or mutualistic (S&M) relationship with other animals in the wild? Having lived my life in countries where snakes occur, I cannot think of any such relationship amongst them or any other (non-human) animal or plant. Could they perhaps have one with man?

Here’s my simple definition of the concepts.

Symbiosis

Symbiosis is a close relationship between two species in which at least one species benefits.

Mutualism

Mutualism is a symbiotic relationship in which both species benefit. 

I feel that despite what I might have believed previously, we actually do have an S&M relationship with what is probably the thing we fear most, the humble snake, as much as they do with us.

If I were to ask readers to give me a couple of examples of either or both of these classifications, relevant to humans, I could probably expect something along the lines of the following.

A farmer who grows crops, and houses and feeds those who tend those crops in lieu of rent, has a mutualistic relationship with his labour force, thereby both of them benefit.

Similarly, a handyman who rents the landlord’s cottage and carries out any necessary repairs and maintenance on the property in return for his rental, is enjoying the same mutualistic relationship. You scratch my back, etc.

On the other hand, a pub or Spaza shop owner, will always be the primary beneficiary, thereby having more of a symbiotic relationship with his clients.

We’re probably all too busy to see what’s going on nowadays, but right in front of our eyes – if we were to open them – we’d be able to see some amazing examples of S&M in the natural world around us. There are many species of insect that in return for their accommodation, protect the host trees in which they live, from passing browsers.

What about the mites living in the neck region of many of our larger beetles, acting like resident cleaning crews? For an example of this, carefully check out the neck region of the next lightbulb-smashing Rhino horn beetle you come across, and you’ll more than likely see them, busily clearing away and feeding on the detritus that collects in that area.

Perhaps the next time we visit a game reserve, we might be tempted to lower our eyes slightly, and raise our awareness at the same time, by looking for the numerous creatures that remove the ticks lurking in the less easily accessible regions of the bodies of their warm-blooded hosts; for example, oxpeckers taking ticks off the back of a buffalo, or perhaps a group of terrapins removing the ticks from the nether regions of a rhino lying in a waterhole.

Terrapins cleaning a rhino down at the waterhole bodywash.

Rinkhals in the hen house.

Now if I were to ask readers for any examples they’ve come across of any similar S&M inter-species relationships involving snakes and other animals or plants in the wild, I think I’d probably draw a blank. It’s unlikely I’d find snakes watching over birds’ nests in the tree canopy, as much as I’m hardly likely to witness a healthy Rinkhals, Hemachatus haemachatus, guarding mole burrows against unwanted predators. What about snakes acting like some of our birds’, issuing warning signals or sounds for the benefit of all when danger approaches? Puff adders Bitis arietans, sharing a kill with the local badger? That’s not going to happen.

Puff adder

Amongst the snakes themselves, we’ll come across the odd examples where different species might park off in different sections of the same ant bear or warthog burrow, termite mound, or under the same ledge of a granite outcrop on the side of a kopje now and again. They might even be sharing premises due to the proximity of a food source, or in the event of occasional extreme weather conditions. At the same time however, there’s always the danger that one of them, perhaps a Cape File snake, Mehelya capensis, with a taste for other snakes, might find its nearby fellow resident, perhaps a Spotted rock snake, Lamprophis guttatus, to be an enticing snack. Not exactly what we’d call a ‘relationship’.

File snake who loves other snakes.

Seldom seen rock-crevice dweller, the Spotted Rock snake.

If we were to add a human to the equation, and follow up in a reasonable space of time after a settling-in period, would we perhaps discover that there are situations that might exist, and of which we’ve thus far been oblivious? Perhaps there’s no need to set up the experiment because there’s every likelihood that this snake and man S&M relationship has been in existence for as far back as when man met his first snake. Upon reflection, it becomes a no-brainer.

I’ve covered this previously, from a different point of view, where I’ve talked of the ‘magnets’ we provide to entice Mother Nature’s creatures. If we want to attract wild animals, all we need to do is provide the necessary ingredients. Food is the primary attractant, followed closely by acceptable accommodation. From a snake’s point of view, despite not having to feed every day, what’s the point of having comfortable accommodation if you have to travel several kilometres in order to search for a meal next time you get hungry? Let’s take a look at these 2 magnets, starting with accommodation, and see if there’s any chance of a relationship being created, whether we want it or not.

Accommodation

The bushveld is full of hiding places. Holes in the ground or in trees, rocky crags with ample space between the rock plates, and all manner of similar situations where the animal could safely hide from its enemies. When we consider this, we might quite logically, be tempted to discount the need for man in the equation.

Some readers might recall my mention in a previous article, of the fact that most of the holes I identified to have been chosen by snakes as accommodation, seemed to have the beneficial aspect of year-round temperature maintenance – somewhere around 22 degrees Celsius – give or take a degree or two either way. Many of the larger animals that do not have snakes on their diet, will dig or create their own holes for accommodation. Ant bears, wild pigs and warthog, to name a few, dig those that will adequately suit themselves, and coincidentally, any snake looking for a ready-made home.

I’ve mentioned previously, that for a number of reasons, most snakes are itinerant rather than permanent residents, and they move around. Termite burrows and mounds provide prime multi-storey residential accommodation for those looking for somewhere to stay, as do the abandoned burrows of the smaller rodents, birds, and in many cases, frogs. I use the term ‘abandoned’ rather loosely, because as is quite possible in the wild, the originator of the home has probably been eaten by the snake who has moved in. Night adders, Causus rhombeatus, are a classic example of this, happily taking over the space provided by the guttural toad they’ve just eaten.

I’ve seen snakes living in all sorts of situations, some beyond comprehension, but it’s a fact, snakes can live virtually anywhere they choose to, provided the circumstances meet their requirements.

Night adder enjoying a morning head bask.

What, if anything, have humans done to contribute to the accommodation requirements listed above?

If we look inward from the wild and woolly over the fence, we’ll find that apart from the underground termite city we’re happily living atop, (contrary to what our termite eradication certificates state), there are also bird friendly mature trees and hedges that we’ve nurtured over the years in addition to some of the following: gutters with downpipes, waste water pipes, electric cable service pipes and meter boxes. There are also numerous suitable cavities within our building foundations and the ubiquitous ‘retaining walls’ that are in fact, high rise condominiums for all manner of creatures, including snakes. Any steel fence poles or tubular gates are perfect, as are letter boxes, clothes-line poles and pool filter houses. And despite what I’ve listed, we continue to add eminently suitable premises through our quaint way of dumping broken appliances, fridges, stoves, motor vehicles etc. in ‘out of the way’ areas (which remain untouched for years thereafter) within our properties, not to mention the cluttered garages, storehouses and compost pits/heaps. I could go on, but I’m sure you’ve got the picture.

The birds we attract to our gardens will in turn, attract predators.

So that’s the accommodation sorted, now what about the food?

I hope that what I’m saying won’t unduly concern some readers, but it’s the reality, and we must understand this. Snakes are predators, so within reason, just about anything that moves, eats and breathes is fair game. In talking about the S&M relationship that I think exists between man and snakes, when it comes to food, apart from the bigger wild animals that the larger snakes predate upon, there would be little in the way of differentiation between what snakes find in the wild, and what they find in our gardens.

To make things easier for the reader, I’ll give you just a taste of what we are providing for the snakes we fear so much, and give you some idea of what species might visit you in their pursuit of this food you unwittingly provide. To help matters, I would suggest you get yourself a good snake book, all reputable book shops should have them, which can help you hone some of your identification skills, which will help to answer some of your often unreasonable fears. You’ve no idea what you’re missing.

Before I go any further, I’d like to stress that what we have is a natural, evolutionary development that is essentially unstoppable – and unless we live in glass houses and never go outside, we will experience those changes.

Centipede eater

Photo: Nick Evans

In the garden, we’ve got vegetables and other delicacies that attract slugs and snails, which attract the Slug eaters, Duberria lutrix. Paved areas and compost heaps are the sort of territory that’s tailor made for centipedes, just the job for the local Centipede eater Aparallactus capensis, as well as for some of the ‘blind or thread snakes’ Leptotyphlops spp. 

The good ol’ water feature. A frog magnet of note.

The Herald helping to keep the toads honest.

Our love of water features leads us to supply magnificent breeding grounds for all manner of insect, which will in turn lead to the inevitable influx of amphibians, most of whom appear on the dietary ‘must have’ list of a number of snakes, Night adders, Causus rhombeatus, Herald snakes, Crotaphopeltis hotamboeia and the Mozambique cobra, Naja mossambica, being at the front of the queue.

Mozambique cobra, loves toads as well as other snakes.

The bird feeders we erect, seed trays or sugar water bottles, will, along with the birds, also attract other interested parties, such as the rats and mice that eat any fallen grain, and the snakes that eat the rats and mice, House snakes Lamprophis spp. for example. Egg eating snakes, e.g. Dasypeltis spp. will come to eat the eggs laid by the birds who often nest in the proximity of the food tables. These nesting birds as well as those visitors to the tables and water bottles, are a prime target for the bird eating snakes, amongst them, the Boomslang (Dispholidus typus), along with the Vine snake (Thelotornis capensis), in certain areas – if you’re lucky.

Every one of the 160 or so species that lives in our country has a job to do, each in its own way, as an environmental control agent. We cannot do without them. The list of what humans can take responsibility for is pretty extensive, but there’s no question that we have a strong symbiotic and mutualistic relationship with snakes, as do they with us.

Surely it’s time we accepted the concept, weighed up the undoubted benefits, and learned to live with it?

Southern brown egg eater, specialist of note.

Boomslang. More common than realised, worthy of respect.

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.

Pat can be contacted at: herpet@eastcoast.co.za.