Laboratory Exercises in Animal Behavior - Schooling Behavior in Fishes
Schooling Behavior in Fish
Some animals live solitary lives, coming together only to mate, but others are "social" and live in groups. Animal behaviorists have attempted to understand the reasons for (functions of) group living. There are several potential benefits of grouping, and most have to do with finding food or avoiding predators. One foraging benefit is that members of a group can find food by following other members of the same group. An "information center" may be especially important in flocks of birds or in schools of fish. When birds are not able to find food, they return to the "center" and wait to follow birds that have been successful. It is also beneficial to be a member of a group when members are trying to catch prey that would be too large or too elusive for one predator to handle (e.g., a lion hunting an adult buffalo or a wolf hunting an adult moose).
Foraging benefits are not always equal for all members of the group, however. When food is in short supply, the weakest, youngest, or lowest ranking group members may be forced to do without. In lions, for example, cubs eat last and only when the adults have enough food. Another cost to foraging in a group is that more attention is drawn to the group, so prey (or predators) may be more likely to notice the group than they would if individuals hunted alone.
Group foraging can also reduce foraging efficiency. In some cases, members of the group interfere with each other when they are hunting. An example is the redshank, a shorebird found on coastal mud flats of Britain. During the day redshank feed on shrimp that live in the mud with their tails sticking out. When the shrimp sense the "clomping" of the redshanks' feet they retreat into the mud so that the birds cannot detect them. Thus, the birds interfere with each other and hinder foraging. The situation is different at night when the birds feed on snails by touch. They use their beaks to sweep the mud. There is not any interference because the birds do not depend on sight to find their prey and the snails can not react quickly to the birds. The birds respond by feeding close together at night, but they spread out during the day.
Another consideration when discussing groups is predation. Large groups have an advantage over individuals because members of the group can take turns scanning an area for predators or foraging. Think, for example, of pigeons searching the ground for food. When a pigeon is foraging, it can either look up for predators or look down to forage, but it can't do both at the same time. A pigeon foraging alone must somehow try to accomplish both activities, and as a result will probably be less efficient at foraging and more at risk of predation. A pigeon foraging in a group, however, has the benefit of "many pairs of eyes" and so can afford to spend less time looking for predators and more time looking for food.
Of course, as is the case with foraging efficiency, there are also potential predation costs of grouping, such as increased risk of detection, because it's easier for a predator to spot a large group than a small one, and unequal benefit to group members. For example, the individuals on the side of the group closest to the predator may be at greater risk than individuals on the far side of the group. In addition, group members always run the risk that other members of their group will "cheat" and not look for predators when they should. These members gain more time to feed while other members look for predators.
Schooling Behavior
There are many areas of the behavior of groups that can be studied, but in this exercise we will focus on schooling behavior in fish. Schooling is the grouping of fish, often of similar size and age, who travel as a social unit with approximately equal spacing between members of the group. The closeness of the fish in a school can vary with the season and time of day, and depends on the social bonds between the members.
There are several advantages, such as protection from predators and enhanced foraging, of traveling in schools. A predator is less likely to attack a large group of fish because large numbers confuse the predator or because the school can resemble a large fish. The large numbers can be confusing because the members can scatter, making it harder for an attacking predator to catch individual fish. Schools make it easier for the fish to find food because there are more individuals looking, and because less successful individuals can follow more successful ones.
We want to examine the effects of schools on the foraging of fish. We also want to look at the role of school size on schooling behavior. Unlike our previous exercises, however, this time it is your turn to design the study.
Methods
Your group will spend the first day developing hypotheses and identifying ways you could test them. Some ideas to use as a jumping-off point when developing your study include looking at how foraging changes when the number of fish in the school changes or whether the number of fish in the school influences the behavior of fish in the school. Before proceeding to the implementation of your research design, you must consult your teacher, who will make suggestions and approve your study. Your study must be designed to be completed within the period specified by your teacher.
Presentation of results.-The results of your schooling study will be presented in a "fish schooling symposium." Each group will give a short (2030 minutes) oral presentation complete with visual aids. Oral presentations are another important way in which scientists inform other scientists of their results. Scientific societies hold annual meetings at which members give oral (or poster) presentations and get feedback from their peers before they attempt to publish their work in scientific journals. Each presentation typically has the same major elements as a written report (introduction, methods and materials, results, and discussion), but because your audience cannot read your paper, you must present the information in a way (and in an amount) that they can remember. Pictures (visual aids) and a strong, clear organization will help a lot. So will a confident and polished delivery.
Materials Needed
- large aquaria or children's wading pools
- goldfish
- fish food
- other material depending on the study you design
Things to Think about
In our previous exercises you have been told what to do and how to do it. In this exercise you have been given some background information and a topic, but no specific instructions on what to do. Your job is to design and conduct your own research project. This is your chance to apply the principles of scientific investigation that we have been practicing. Remember, the "scientific method" consists of the following conceptual steps: (1) make observations and identify a problem, or ask a question; (2) propose hypotheses to explain the problem or answer the question; (3) make predictions (results of observations or experiments that haven't been done yet) on the basis of each hypothesis; (4) design and implement observations and experiments to test each prediction; (5) compare the results to those predicted and accept or reject each hypothesis, or propose new hypotheses that take into account your new results.
Think carefully about which hypotheses you want to test, and especially about the predictions each makes. Once you have come up with a list of predictions, then try to design observations or experiments that test only those predictions. Remember that a properly designed experiment must include a "control" in which all other factors (except the one you are testing) are the same as in the experimental group.
Make sure your presentation is well organized and practiced. Remember that your audience will consist of other fish school researchers, so you probably don't need to spend lots of time introducing your topic. You will, however, need to identify your hypotheses and their predictions, and to specify your methods in enough detail that your audience knows what you did (although not necessarily exactly how you did it). Be sure to concentrate on presenting your results clearly and concisely, and to discuss these results in light of the hypotheses and predictions that you introduced at the beginning of your presentation. And don't forget to leave time (about five minutes) for questions.
Tips for Teachers
This is your students' first opportunity to "solo," so you will play a key role. In general, you should think of yourself as a supervisor or manager; give them lots of room to operate, but keep close tabs on them and ask for frequent progress reports. Above all, stay close during the design phase of the study. Be sure they have identified at least one reasonable, working hypothesis, and make sure they have realistic, testable predictions to examine. Remind them that they only have a certain amount of time (determined by you) to complete their study, and only a limited amount and type of equipment to use.
One important consideration that we have ignored thus far is proper animal care and use. Animal research at colleges and universities must be approved by an "institutional animal care and use committee" (IACUC). The IACUC must determine that the research is worthwhile, and that the animal care and use are proper. Research that inflicts pain or that requires animals to be killed must be well justified, and approved, humane procedures must be followed. Contrary to popular belief, scientific organizations such as the Animal Behavior Society are very concerned with animal welfare. The society publishes its own guidelines for the proper care and use of animals in research, and it demands that any animal behaviorist who publishes an article in its journal conforms to these guidelines. Tell your students that they have two goals in this exercise. The first is to learn something about the function of schooling in fish; the second is to conduct their research in a way that causes minimal discomfort to their animal subjects.
In any group undertaking, it is important for all group members to contribute (note the analogy to the "cheaters" in the example above). The contributions, however, need not be identical to be fair. Encourage your groups to assign or negotiate specific roles; have them divide the work that is acceptable to all group members.
One of the most important aspects of this exercise is the students' design of their own experiments. You will need to prepare them and to work with them if they are to produce "proper" experimental designs. The key ingredient in designing an experiment is a proper "control." Although controls are discussed briefly above, some examples and simple exercises will help your students to understand what they are and how to design them. TV commercials offer some interesting insights into experimental design because, for the most part, they offer outstanding examples of how designs can be wrong. Two of our favorite examples are provided by an air freshener and a dish washing detergent. Both seem to portray "scientific" or "experimental" evidence that the product works well, but each is an example of an uncontrolled manipulation (that is, not a proper experiment). The air freshener commercial shows a smoky room and then says that this particular brand of freshener will clear the room of smoke. In the next scene, a hand appears holding a can of the aerosol spray, and then, magically, the smoke disappears when the room is sprayed. In the dish detergent commercial, a glass tank containing water and the detergent is shown. Then grease is poured into the tank and a plate is submerged half way into the water. Magically, the grease rises to the top and does not spread in the water.
What's wrong with these two commercials? Nothing, if your job is to sell the products, but everything is you job is to design a controlled experiment. In both cases, a scientist would say, "but what is the control?" The problem is that although the manufacturers would like us to believe that their products are responsible for the nearly miraculous results, other factors are just as likely (perhaps even more likely). Let's think about the air freshener first. Was it the brand of freshener (that is its active ingredients) that cleared the smoke, or something else? How could we design a controlled experiment to determine whether the active ingredients cleared the smoke? What we would need is two smoky rooms and two aerosol cans. One can would be the regular air freshener (the experimental treatment) and the other would be the same kind and size of can without any of the active ingredients (the control). The control consists of the can and the propellant-what do you think would happen if you spray a stream of air (or propellant) in a cloud of smoke? Do you suppose the smoke would be dispersed?
Now let's think about the dish detergent. What would be an appropriate control? How about water in the same glass tank, but with no detergent in it? What would happen if you poured cooking grease into water? Wouldn't the grease float to the top (that is not spread in the water)? As you (and your students) can see, without an appropriate control, we cannot be sure what factor was responsible for the effect we witnessed. The purpose of a control, then, is to isolate the experimental factor so that any difference in results between control and experimental treatments must be due to the experimental factor or manipulation alone.
A good example of a commercial that uses a proper control is for a brand of adhesive bandage. A finger with a cut is shown, and the claim is made that application of an adhesive bandage will promote healing. Then, half of the cut is covered by a bandage. After some fixed period, the bandage is removed and the two sides of the cut (covered and uncovered) are compared. Ask your students to explain which side is the control and which is the experimental. Ask them to state the two hypotheses being tested in this experiment (the bandage promotes healing, and the bandage inhibits healing), and the prediction made by each (the experimental side is more healed, and the control side is more healed). Of course, a scientific study would use many fingers, the control versus experimental sides would be randomly chosen, and explicit measurements or criteria would be used to judge the amount of healing.
Next, ask them to divide into their fish groups to design a study to answer the following question: what ingredient in a cup of coffee makes you need to urinate (that is, what is responsible for the diuretic effect of coffee)? The should be able to think of several potential factors (for example, the volume of water, the temperature of the drink, the caffeine) and then design experiments to isolate the effects of each (for example, to test the hypothesis that caffeine is the diuretic, compare cups of regular versus decaf prepared identically).
Once their studies are completed, you should discuss oral presentations with them. Most of us try to follow some version of the so-called "Army method": (1) tell 'em what you're gonna tell 'em, then (2) tell 'em, and then (3) tell 'em what you told 'em. Stress the importance and usefulness of good pictures, a smooth style, and correct usage. Tell them to practice so they don't constantly say "um", and "aah." Tell them to avoid useless phrases such as "you know," and "like," and "basically." And remind them forcefully to avoid incorrect usage. Remember that, despite current vernacular usage, "hopefully" does not mean "I hope," and "myself" does not mean "me." ["Hopefully, more studies will be performed" is INCORRECT; "I hope more studies will be performed is CORRECT. "Observations were done by Allison and myself" is INCORRECT; "Observations were done my Allison and me" is CORRECT.] Be sure to remind your students that the word "data" is plural ("datum" is singular), so that "this data is" is INCORRECT; "these data are" is CORRECT. Lastly, encourage your students to begin and end their presentations with a strong "take home" message. Most listeners will remember the first and last things said (psychologists refer to these as "primacy" and "recency" effects).
Finally, be sure to tell your students that they are responsible for offering constructive criticism for the presenters. It won't help anyone concerned to say, "Your presentation was bad." A good tactic to use is to mention a strength of the presentation first, then a weakness, along with a suggestion on how to improve the weaker aspect. For example, a constructive critic might say, "I thought your description of the experimental design was very good, but your design was very complicated. It would have been easier for us to understand it if you had included a diagram showing the different manipulations."
