Animal Behavior

Introduction - Animal Behavior Why do animals do what they do? Why do birds sing? How do sea turtles navigate the ocean to lay their eggs on the same beach where they were hatched? How do honeybees know when the hive needs more food? Image from http://www.nps.gov Image from http://www.scottcamazine.com

Image from http://www.arcamax.com Introduction Animal behavior asks what, why, and how. Animal behavior is also referred to as ethology. Scientists who study animal behavior are called ethologists. Image from http://www.arcamax.com

Introduction Animal behavior is centered around the ability to move. Animals seek food, water, shelter. Animals play with each other. Animals seek mates. Image from http://www.e-magine.education.tas.gov.au

Introduction Behavior results as a reaction to a stimulus. A stimulus is a detectable change in the animal’s internal or external environment. Hunger. Sound. Pain. Visual cues. Hormonal changes. Image from http://www3.nau.edu/biology/

Introduction Ethologists do not attempt to describe WHY an animal does a behavior before describing WHAT the animal is doing. This removes as much bias as possible – good scientists don’t want to just “see what they want to see”. Need to make objective observations of animal behaviors, analyze the data statistically, then come to conclusions about WHY an animal behaves a certain way.

Introduction For example, you see two gophers interacting with each other, rolling and hopping around, running to and from each other. As a behavioral ecologist, you would first state the behavior you are observing. Once you made the observations about WHAT was happening, you could begin to determine WHY they are behaving that way.

Introduction The behavior you observed could have been many different things. Play. Mating rituals. Aggression, defending territory.

How to determine WHY – action patterns. Action patterns are complex behaviors that are always repeated the same way by a species of animal. We say that action patterns are stereotyped, since they occur the same way each time, and through to completion. After repeatedly observing action patterns, an ethologist can analyze the data statistically. Only then do we attempt to determine WHY a behavior is being done. Fixed Action Patterns (FAP) are INNATE

Niko Tinbergen Niko Tibergen was a pioneer in the field of animal behavior. He observed animals in their natural conditions, then manipulated, or varied the conditions to see how the animals responded. Image from http://nobelprize.org/

Niko Tinbergen Tinbergen observed how a wasp called the beewolf finds its nest among other beewolf nests. He observed that the beewolf would circle its nest in an ever-widening circle before flying away to hunt. This behavior was an action pattern – it was performed exactly the same way each time. Image from http://www.sciencenews.org

Niko Tinbergen After the beewolf flew off, Tinbergen would move certain landmarks around the nests. When the beewolf returned, it was disoriented. So, by manipulating the beewolf’s environment, Tinbergen came to the conclusion that the beewolf commits landmarks to memory to be able to find its nest when it comes back from hunting! Image from http://www.earthlife.org

Niko Tinbergen Tinbergen had to describe and investigate WHAT the organism was doing before attempting to explain WHY.

More on Action Patterns The egg-rolling behavior of the greylag goose is a good example of an action pattern. Niko Tibergen and another pioneer in ethology, Konrad Lorentz, originally observed this behavior. Image from http://www.grayimages.co.uk

More on Action Patterns The goose will roll an egg that is outside the nest back into the nest in the same manner every time. Interestingly, the goose will do this with any round object placed outside the nest! Every time this action pattern is initiated, it is carried through to completion.

Proximate vs. Ultimate Causes The question of “WHY” can have different answers. Proximate causes are related to internal changes in the animal. Hormones. Messages from the nervous system. “Proximate” means close. Ultimate causes are related to the survival and reproductive success of the animal. “Ultimate” means furthest, or utmost.

Proximate vs. Ultimate Causes An example incorporating both proximate and ultimate causes: Belding’s ground squirrels. When males reach about two months old, they leave the burrow where they were born. It is an increase in testosterone, or a hormonal change that triggers this behavior. So, the proximate cause of the nest-leaving behavior involves the increase in testosterone levels in the squirrel.

Proximate vs. Ultimate Causes There is more to the story than just hormones! When males leave the nest, they avoid inbreeding with sisters or cousins, etc. Their offspring are therefore healthier. The male offspring inherit the same genetic information that induces them to leave their nests at a young age. So, this behavior is passed on genetically, and it makes for a healthier population of squirrels. Avoiding inbreeding is therefore the ultimate cause of this “early nest-leaving” behavior.