Objectives:

• become familiar with studying the behavior of an insect
• gain experience in quantitative behavioral techniques
• explore behavior patterns of communication

Discussion and Pre-Lab Preparation: The House Cricket, Acheta domesticus, is an orthopteran in the family Gryllidae. Most male crickets sing, however, individuals differ widely in loudness, frequency. and patterning.

List of common behavior patterns in crickets

Any meaningful study of animal behavior depends on the availability of a comprehensive ethogram. You cannot ask proper questions about behavior until you are thoroughly familiar with the behavior patterns of the species you are studying. In behavior, as in any science, we begin with observations. This is perhaps the most difficult phase of the study, for it takes considerable practice and concentration in order to be able to see what an animal is doing. Anyone can watch an animal, but it is an acquired skill to be able to distinguish its behavior patterns. Once trained, however, an observer can apply this skill to the study of any species, with little modification. Do you see any cricket cleaning its antennae or its legs? If so, how does the cricket do this? Are any crickets eating or drinking water? Are individuals aggressive towards others? Do they defend a particular area within the arena? Are they chasing, fighting or biting others? if so, which ones are doing it? Are patterns consistent over the observation period? Feel free to add other behaviors to this list or modify definitions of existing ones as you see them. List descriptions clearly.

• AP = Approach one cricket of either sex approaches another
• AT = Attack one cricket of either sex bites or rushes at another
• CM = Chasing by Male usually directed toward female
• CF = Chasing by Female may be directed at male or another female
• ....

Exercise 1:

Question: Which behavior patterns are present during social encounters in Acheta domesticus?

Preparation: Social encounters are staged in observation tanks for groups of three students each. The tank contains gravel or sand and a small dish with food. You will also need a watch to record the timing of events.

Procedures: Place 2 males into the tank. Add 1 females from a separate holding tank where they had been kept isolated since hatching into adults. Set up an observation schedule of periods not less than 15 minutes in duration and observe the animals without disturbing them. Begin by watching everything the crickets do, including their responses to food and to other individuals. Soon you will begin to recognize patterns of movement, as you will see the same actions repeatedly. Once you have discovered a set of repeating behavior patterns of your animals you will have units of behavior with which to work further.

At this point in the study you should begin to record in a notebook everything you notice during your observation periods. Try to describe behavior patterns accurately, and give a descriptive name to each kind. An example is: Antennae cleaning - ...

From your records (= protocols) you can extract an inventory of behavior patterns with a description of each one. Such ethograms are important as studies of the "morphology" of species-typical behavior, as material for comparative study of closely or distantly related species (or higher taxa), and as a beginning point for asking further questions about behavior.

Each time you move or interfer with the cricket. it will react to you. Although they will soon habituate to your presence, you should avoid sudden movements. Keep your notebook well away from the tank when recording data, and preferably hold it so your hand movements during writing are not seen by the cricket. If crickets are seriously disturbed by your presence, turn off the room lights so that the tank alone is illuminated, and wear dark clothing.

Answer questions: How do such observations relate to the scientific method? Basic behavioral observations are associated with which point of the cycle of scientific inference - preliminary observations, formulate question and hypotheses, design, conduct, and analyze experiments, or communicate results?

Exercise 2:

Question: How can we obtain quantitative behavioral data from crickets?

Preparation: You will have noticed by this stage that some behavior patterns vary in degree of completeness or exaggeration, so that it is difficult at times to be sure that a crickets made a given movement, while other patterns seem to be complete and the same each time that they are given. Try to determine which patterns vary in this manner, and which do not. Are there in fact distinct intensities of these behaviors, or are they exhibited as a continuum?

The duration of a behavior pattern can serve as a measure of intensity as well. Use the stopwatch provided to time the duration of a few different patterns and determine how much variance there is. You will need an adequate sample for each pattern before you can determine the amount of variance. An example may be the length of time an antenna is being preened. You may consider recording behavior using techniques similar to those introduced in the lab on crayfish locomotion and fighting.

Another measure of intensity is the frequency with which a behavior pattern occurs, that is the number of occurrences per unit time. A change in protocol will enable you to record these measurement. First adopt a letter code for each pattern that you wish to study. Observe only one individual at a time and record the letter code of each behavior pattern in order of occurrence. Using a clock or timer, draw a line through the protocol at one minute intervals

Preparation: see exercise 1

Procedures: Quantify the behavior of a single male cricket in one of the above ways.

Answer questions: What are the particular advantages of each appraoch? What are the draw backs? What are the trade-offs?

last modified: 02/09/07