“Siamese fighting fish” Betta splendens is an inhabitant
of shallow, murky waterways, such as lakes, slow-moving streams,
and rice paddies. Domesticated variants of both males and females are brightly-colored,
however, males have much larger dorsal, anal, caudal, and pelvic
fins. Male Betta fish engage in elaborate behavioral displays,
both with receptive females and with other males. Bettas have
been bred in captivity for hundreds of generations, and this
breeding program has accentuated the fin structure, coloration,
and display behavior of the male.
Male Bettas cannot be safely housed together. When two
mature males approach each other, each will typically darken,
extend its fins, flare its opercula (gill covers), extend the
brachiostegal membrane from behind the opercula, and swim
rapidly towards the other fish. Each tends to maintain an
orientation where its head is directed toward the side of its
opponent. The result is often a rapid, twirling “carousel”
action with the two fish spinning around each other. The
intensity of the behavior escalates until one fish, the “loser”,
backs down, lowers its fins, lightens its coloration, and swims
away. If neither fish backs down, the display will escalate
until one or both fish begin biting chunks out of the other’s
fins. Eventually one fish, generally the more damaged one, will
In this lab you will be studying the male-male display
behavior. When presented with a suitable display
target, male Betta fish reliably exhibit some or all of
the following readily identifiable behaviors and physiological
Orientation of the body towards the target
Extension of the fins, especially the dorsal, anal, and
Increased brilliance of body coloration
Darkening of the head area
Flaring of the gill covers (opercula)
Extension of the dark brachiostegal membrane from behind
Rapid beating of the fins
Gulping air from the surface of the water
Biting motions directed toward the target
The target may be another male fish in the same aquarium
or container. However, male Bettas are not terribly selective
about their targets. Indeed, the necessary and sufficient
trigger for display behavior corresponds to the classical
ethological construct of a “sign stimulus”, which we will be
discussing in class. Any object of
approximately the same size, orientation, and coloration as
another male will generally elicit at least some display
behavior. Experimentally, this means that a male will respond
to another male visible in an adjacent tank, a mirror image of
itself, or an appropriately crafted model.
1A: BEHAVIORAL OBSERVATIONS
MALE BETTA DISPLAY BEHAVIOR
As with any behavioral study you should begin by simply
observing your subject animals and familiarizing yourself with
the behaviors of interest.
Prior to your investigation, maintain several males in
individual containers, visually isolated from each other.
One-quart mason jars have been provided for this purpose. Make
sure that the visual barriers used for isolation are light
colored, so that individual fish are not inadvertently exposed
to mirrored images of themselves.
Transfer a single male to a 2˝ gallon aquarium, making
sure that the water is dechlorinated and matched in temperature
(see care notes below).
Position a mirror against the side of the aquarium.
Identify any display elements you observe.
Remove the mirror for at least five minutes. Try placing
one of the simple models in the aquarium and see if you can
elicit display behavior. Note: be patient, don’t try to elicit
the behavior by chasing the fish around and/or bludgeoning it
with the model.
Again, allow your fish a five minute “rest”. Now, place
a glass partition in the aquarium, isolating your subject fish
in one end. Transfer a second fish into the empty compartment.
Again observe any display elements that occur. Can you identify
a “winner” and “loser”, or do both fish continue to display?
Think about what aspects of the display or target response are
"unnatural" in both the mirror and the separated fish
Finally, remove the glass partition. Does the display
escalate? Be prepared with a net to separate the fish if the
display escalates to biting.
Return your fish to their isolated containers.
II. DO SOME READING
Several articles have been provided for you to look through.
Two of these deal with behavioral sampling methods. What
sampling methods would be most appropriate for the display
behavior which you have observed? What are the alternative ways
of quantifying behavioral “acts”? What are the alternative ways
of quantifying behavioral “states”? The remainder of the
articles deal with specific studies of Betta display and
reproductive behavior. These articles may give you some ideas
for simple experiments which you might conduct.
LAB 1B: EXPERIMENTAL ANALYSIS
I . CARE OF BETTA FISH
Container preparation. Use only glass or durable
plastic containers. Clean each container before use. To clean
Empty, wipe out, and if necessary scour out the
container. If you need to use soap or detergent, be sure to
completely rinse out the container at least three times with tap
Pour is a small amount of free-running (non-iodinized)
salt, add a bit of water, and scour out the container with a
clean, detergent-free scrubbie. This will serve to kill most
bacteria that are potentially harmful to fish. Again, rinse out
the container at least three time with tap water.
Fill the container with dechlorinated water.
Appropriately dechlorinated water can be easily made by adding a
good squirt of StressCoat to a bucket of tap water, then
stirring it briefly to mix. StressCoat will bubble or foam up a
bit as it is strirred. This is normal, so don't panic. Don’t
worry about using too much StressCoat.
Water. Fish are very sensitive to chlorine and
Always dechlorinate tap water with StressCoat or another
commercial dechlorinating agent.
Do not move fish back and forth between different
temperature containers. The easiest way to avoid this is to
keep all of your containers at room temperature. The easiest
way to do this is to plan ahead and let all of your filled
containers sit for at least 12 hours to equilibrate to room
Once a week, replace 1/3 of the water in each fish’s
container with fresh, dechlorinated tap water. If your fish is
in cloudy water, you may change out up to 2/3 of the water.
Transferring fish. Fish may be transferred either by net
or by carefully dumping one container into another.
Feeding. The old admonition not to overfeed your fish is
accurate – the surest way to kill fish is to foul their water
with uneaten food. Feed your fish no more often than once a
day, and add only as much food as the fish will immediately
eat. Fish can safely go without food for at least a week. If
uneaten food accumulates in the container for more than 24
hours, try to siphon out the food and/or change out the water.
Bubble nests. If you notice a clump or mat of
bubbles at the top of your fish container, don't panic. This is
NOT a sign of detergent in the water. Healthy male Betta fish
regularly produce these bubble nests in preparation for
receiving and guarding fertilized eggs from a female. A bubble
nest is a sign that your male is healthy and sexually prepared,
if perhaps a bit frustrated.
II. YOUR EXPERIMENT
Your task in this two-week laboratory is to ask a simple
question, develop a simple hypothesis, design a simple
experimental test of your hypothesis, conduct the experiment,
gather quantitative data, and apply this data to evaluating your
hypothesis. The following guidelines should help you in this
Keep your question and design simple.
Determine exactly what you need in the way of fish,
continers, supplies, etc. Discuss this with the instructor AS
EARLY AS POSSIBLE, os that the supplies will be ready when you
nee them. Allow TWO FULL WORKING DAYS for the instructor to get
you additional fish.
Think about experimental controls. Bettas aren’t picky
about “natural” conditions, so you should not be either.
Try to design a study and conduct observations which
result in numbers. In other words, try to quantify the behavior
which you observe. Frequencies of discrete behavioral acts and
durations on persistent behavior states are standard kinds on
numbers to record. During the next two weeks we will be
discussing in detail behavioral sampling and quantification
Standard experimental methods involve physically
separated males, mirror displays, and the use of target models.
Possible general topics (from which you should derive and test a
very specific experimental question) include habituation,
sensitization, effects of isolation, supernormal stimuli, choice
between multiple targets, and “dominance” hierarchies.
6) Female Bettas may also be obtained, although they
are not as readily available as are males. Let the
instructor know well in advance if you need to order females.
Try to design several potential experiments. As you
think through your designs, consult with the instructor to
determine which designs are the most feasible and what materials
you will need to conduct you final experiment.
Useful experimental questions usually stem from direct
observations and take the forms of "why does this happen?",
"what stimulus features are important for this observed
behavior?", or "does this behavior correspond to this particular
theoretical model?". Providing a testable answer and applying a
carefully conducted test to such a question will generally
produce a good study, no matter what the outcome.
Try to avoid experimental questions which could be stated
in the form of "I wonder what the fish would do if I did this?"
or "wouldn't it be nice if I could show that the fish does this
when I do thus and so?". Such questions tend not to
produce meaningful results, no matter what the outcome.
you chose to write up this experiment, the deadline is Friday of
week 5 of the course. You may be able to conduct your
experiment entirely during lab period next week. However, it is
more likely that you will have to make some or all of your
observations on your own time.
III . WRITE-UP FOR THIS LAB
The write-up for this lab should follow the format of a complete
experimental report, with abstract, introduction, materials and
methods, results, and discussion sections. References are
not absolutely required, but would be a nice touch.