Deimatic behaviour and Aposematism in Animals

I have a love for the natural world and the flora and fauna within it. Part of this love and appreciation is shown through my photography where I aim to capture the incredible wonders and beauty of the world (usually around my local area).

One thing that has always fascinated me is the defensive measures that many animals have, it’s one thing to be a lion and at the top of the food chain, but it’s another to be an animal at the bottom of the food chain with very few defences.

One thing that is very commonly seen in the natural world is a set of behaviours called Deimatic behaviour (threat warning through bluffing) or Aposematism (warning predators that the animal may be not worth eating). In this post I wanted to talk a little bit about these different survival strategies and how they may be advantageous.

Deimatic behaviour

Deimatic behaviour is often seen in moths and other insects and can be considered as ‘bluffing’. This behaviour typically aims to dazzle or confuse the predator to allow the animal to try and escape.

There are many examples of this, for some insects such as a butterfly the warning behaviour can be markings on its wings which look like eyes that may startle the predator, but another example is the mantid which when startled may display their brightly coloured hind wings.

Orthodera ministralis, common name garden mantis or Australian green mantis, these have brightly coloured hind wings (not shown) which can startle predators.

In addition to color startling predators, it can also function as a warning to potential predators that that animal may be unpalatable or not worth eating commonly due to being toxic, this is known as Aposematism which we will discuss later.

Deimatic behaviour is not just limited to insects such as butterflies and mantids, it is also seen in other insects and in vertebrates.

Spiders (whilst often poisonous) also display this behaviour, when threatened, spiders may vibrate to make themselves look bigger, or they may rear back and show their fangs. It is worth noting that Deimatic behaviour is about bluffing, but a creature may display Deimatic behaviour to warn off some predators (i.e., spider-hunting wasps can overcome the poison of spiders, so when a spider displays threat behaviour to a spider-hunting wasp it’s a bluff and thus Deimatic behaviour, but to other animals it is Aposematism).

Deimatic behaviour is seen in vertebrates as well, this varies but it can include more warning markings, but can also involve the animal making itself look like a bigger threat than it is (through making itself look larger. The two common examples of this are the frill necked lizard that exposes its frills when threatened to make itself look larger, or even the red panda which stands on its hind legs to make itself look bigger (and thus more of a threat than it is), even a cat can display this startle behaviour by arching its back.

Clearly this bluffing behaviour is important in the survival of many of these animals, having often very little real defences means that they need to take any opportunity they have to escape predation, even something as simple as a quick startle of the predator may be the difference between survival and death.

Threat displays are not always about bluffing though, in some cases a threat display is not a Deimatic behaviour / bluff) but can be a display of Aposematism. Some grasshoppers for example have bright colouring on their hind wings, but also produce distasteful secretions. Often the distinction between Deimatic behaviour and Aposematism depends on context, a display may be Deimatic to one predator, or for another it may be a case of Aposematism.

Aposematism

Aposematism is often referred to as ‘warning colouring ’ although its expression is not limited to just color. Ultimately Aposematism is about advertising yourself to potential predators as being unpalatable or difficult to kill and eat. The features or adaptations that indicate this can include things like foul taste or smell, venom, toxicity, aggressiveness or even things like sharp spines.

This defence mechanism often relies on the memory of a predator, for example a bird may eat an insect that has a foul taste and remembers never to eat that insect again.

The Monarch butterfly is a great example of Aposematism, it’s bright warning colors seek to warn potential predators that is may be dangerous to eat in this case due to the presence of toxins known as cardiac glycosides.

The Monarch Butterfly from the Melbourne Zoo. This displays Aposematism through its bright orange and black colors warning of the presence of toxins (cardiac glycosides) that are stored in its body

Aposematism is more than color though, Cane toads produce toxins (bufodienolides) throughout their bodies which can often kill many animals.

Aposematism is most common in insects, occasionally occurs in fish and reptiles, and far less common in vertebrates. There are some potential examples of Aposematism in plants like where the plant may be unpalatable due to its taste or even things like spikes.

Clearly the ability to warn predators of your unpalatable nature is a huge advantage, as it means there is less need for speed and agility as most predators will avoid trying to eat you. Often (but not always) these animals are fairly tough so that they can withstand an attack enough to sting the predator, or for the predator to quickly learn that it is not worth continuing to attack you (i.e. , hedgehog quills vs predator)

What does Photography have to do with any of this?

The reason I mention Deimatic behaviour and Aposematism is that often when photographing animals you see these expressed, clearly the aim is not to startle an animal to see this behaviour, but if I am photographing an insect for example and a bird flies by then these behaviours can be seen.

Really these behaviours have nothing to do with photography though, I witness them through photography, and this article aims to explain them as much for me, and if someone else gets benefit out of it then great!

The natural world is truly fascinating!

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