Animal Behavior

People have probably always been fascinated by the behavior of animals. Indeed an understanding of the behavior of prey animals must have been essential to our early ancestors; their paintings on the walls of caves suggest that they could have been fairly familiar with behavioral concepts such as herd size and

migration. The earliest stock-farmers would have needed to understand the behavior of the charges in their care just as their modern counterparts do today.

Some members of society (and even some biology students) may wrongly think of the study of animal behavior in an academic context as being a soft science or even an easy option.

However, I hope to show you in this introduction to the subject that it is an important and rigorous science and that it has a clear application to some of the problems that we face in the modern world.

Cephalopod inking behavior :

Many species of octopus and squid are known to exhibit a particularly effective behavior that enables them to escape from predators. In the region of their intestines the animals have a special sac-like organ. In the wall of this sac there is a gland which secretes a brown or black liquid rich in the pigment melanin, this

is ink. When threatened the animal has the ability to compress the ink sac and squirt a jet of the liquid from its anus. It is thought that the cloud of ink hanging in the water forms a dummy squid termed a pseudomorph, which attracts and holds the attention of the predator allowing the animal to dart away to safety. The

deception is made all the more effective because long thin species produce long thin pseudomorphs and more round species produce rounder clouds of ink Squid and octopus are molluscs, taxonomic relatives of the

garden slug and snail. Can you imagine a slug squirting out ink to  leave a pseudomorph hanging in the air to decoy a bird predator while the slug made its escape? Of course you can’t, for the simple reason that this behavioral strategy can only work when the animal is surrounded by a medium that will support the ink cloud for a sufficient period to allow the escape. In water this works, but in the less dense medium of air it would not.

Some species of octopus and squid are inhabitants of the ocean depths. Here light penetration from the surface is minimal or zero and the seawater is a constant inky black. Obviously the inkdummy strategy would be no more effective here than it would be in air. The pseudomorph would hang in the water column, but it

is unlikely that an ink-black shape would be seen against the inky-black backdrop. In this situation species such as the deepwater squid Heteroteuthis secrete a luminescent ink, creating a brief flash of light which is thought to confuse a potential predator just long enough for an escape to be affected.

From this example I hope that I have made a few key points about behavior. Firstly, that behaviors are adaptations which serve specific functions, and we will consider this point further later in this chapter. Secondly, that a single behavior may not serve, or serve the same function, in all situations (a point to be

borne in mind throughout this book). Finally, behaviors are adapted to be effective in the environment of the animal performing them.