June 17, 2021



Behavioural Ecology and Wall Lizards

by David Capon – The science of ecology is in effect the science of Nature. It used to be defined as the scientific study of the distribution and abundance of organisms and the interactions that determine the distribution and abundance; basically scientific natural history. Unfortunately the word ecology has been corrupted and we now hear about ecological enterprises for instance, when what is meant is the enterprise has considered environmental issues.

While I was studying ecology I became interested in a lesser-known discipline, that of ethology. Ethology was the study of behaviour; what causes the behaviour, how the behaviour develops as the animal matures, useful consequences of the behavior and how the behaviour has evolved. I suppose that behaviour is affected by the animal’s environment, habitat and other species in the same area. It has evolved into Behavioural Ecology and together with Evolutionary Ecology they have become a very important disciplines of ecology. Nature is under threat from so many sources (most, if not all, have been created directly or indirectly by humans).

Thus interactions and understanding behavioural traits has become very important in determining how to conserve and protect species and much Behavioural Ecology research has taken place in recent times. Some of the findings have been astonishing and some revealing and a lot can be seen in human behaviour.

As an example of a behavioural link between animals and humans let us consider reactions to a section of society that was considered threatening.  Back in the early days skinheads were considered by many to be a danger and threat. Your personal consideration of the threat would probably depend upon your circumstances at the time.

If you were walking down, say Regent Street in London on a busy Friday afternoon, and there was a group of about 5 or 6 skinheads on the opposite side of the Street you would not feel any fear.

Transfer the location to a quiet village. As you turn a corner if you came face to face with the same group you may have become terrified. Your perception of the same ‘threatening’ group of people is different when you are alone. (I apologise to all who were skinheads reading this and were gentle people).

There have been studies on the reactions of birds to perceived threats. One of these studies concentrated on blackbirds and their timing of fleeing a situation. The research was carried out on blackbirds in parks and it was found that if the park was full of visitors the blackbird waited much longer before fleeing. If the park was empty the blackbird would move away very early. The blackbirds’ perception of threat was determined by the amount of activity in the local area. Both humans and blackbirds perceive danger in a similar way.

In many species the males are much more colourful than the females. This is found in many bird species and especially ducks where the male is much more decorated than the drab female. The male of the Cleopatra (butterfly), which is found on Crete, is much brighter and this colour difference is found in many other types of animal (e.g. fish). These colours are used to attract females and intimidate other males (perhaps there is a similarity with humans where some men use highly decorated clothes or tattoos). But these enhanced colours can also come at a price. If you are a female blue tit your preferred mate would have very intense blue of on the top of his head and the colour would include a lot of ultra-violet. For the male the more vivid the top of the head the more obvious he is to predators. A very difficult balance for the male blue tit!

About 3 years ago I purchased two large books. The first is Bat Ecology, which is a very interesting book and there are large sections, for example, on the roosting requirements of different species (this is important for their conservation), the interaction with humans and transmission of disease. Of great interest was the section dealing with the way that insect eating bats locate and catch their prey and the associated vocalizations.

The second book is ‘Lizard Ecology’ by Reilly, McBrayer and Miles. Lizards are much easier to watch and identify and this book covers a whole range of topics on their ecology. Two of the most interesting sections concerned hunting methods and movement. There are two different methods of hunting and different species are adapted to one or the other (this is also true for most reptiles and many animal species). The foraging methods are known often as active foraging and ambush foraging: for the first method the animal hunts for prey, whereas the latter sits and waits for prey to pass close by. Concealment is essential for the ambushers.

I am sure you will have seen images of a camouflaged chameleon sitting on a branch of a tree and thrusting its long tongue at high speed towards an unsuspecting prey victim. This is possibly one of the best examples of ambush. The active hunter requires a body that will take it long distances at certain times and requires the associated stamina. The body shape and structure is different for the two types of hunter and generally so is the type of food. Active foragers can be more specific with their prey whereas the ambushers need to accept a wide range of prey – almost anything that passes close.

Wall lizards are so called because they live in and around walls and can be seen climbing quite steep walls (they do not have the adaptations that geckos have allowing them to walk on ceilings).

The body, tail and head of wall lizards are adapted to provide additional help in climbing almost vertical walls. For example, the heads tend to be slim and flat – a large protruding head would provide a large gravitational pull.

Ignoring geckos and the Ocellated skink there are two species of lizard present here on Crete. One is the large and bright green lizard the Balkan green. The other is Erhard’s wall lizard. The lizards at the east of the island are slightly different to those on the west, but I am not sure they are considered separate subspecies.

Returning to Behavioural Ecology, there was a recent paper in the Journal ‘Behavioral Ecology’ that detailed investigations into the colouring of Erhard’s wall lizards in the Aegean area1. As with blue tits, the females like more showy males but more colour (even if slightly cryptic) make the males more obvious to avian predators (buzzards, kestrels and crows for instance). Thus male lizards are somewhat adapted for this problem. Usually female lizards are on the same level as the males and so the brightest colouring of the male is on the flanks, whereas the colouring on the back is subdued and more adapted to their environment. On the islands, there seems to be some evolutionary movement similar to Darwin’s finches. The wall lizards do not swim so the isolated populations on the islands are slowly evolving and adapting to their particular environment.

If you return to this earth and you have a choice I would suggest you do not opt to be a lizard here on Crete. Feral cats will chase anything and lizards are on the diet of so many animals (weasels, beech martens, snakes and many bird species, for example) and cars also account for many deaths. So for our lizards there are dangers everywhere.

Behavioural ecology is a fascinating subject. I wish I had time to read all the papers that are produced. Also many investigations include human behaviour. As you will understand from the blackbird example we have similar traits to many species. I suppose because we are indeed animals that is not surprising.

1. “Wall lizards display conspicuous signals to conspecifics and reduce detection by avian predators” by Kate L.A Marshall and Martin Steven

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