Volume 6, Spring 2008 - Saddleback College

Fall 2007 Biology 3A Abstracts
Effect of Differing Color on the Timed Length of Aggressive Response of Betta splenens
Lancelot Beier and Harrison Pham
Department of Biological Sciences
Saddleback College
Mission Viejo, CA 92692
Siamese Fighting Fish are famous for their aggressive behavior towards other male
fighting fish. It is known that fin size has a major effect on the evoked response of the
opposing fish but few studies have been preformed to test whether or not color has an effect
on the aggressive response of bettas. This study introduced betta fish to images of other
male bettas in aggressive display that varied in colors. The aggressive response was
measured by calculating the mean timed display length per aggressive show for each
different color stimuli. The mean timed length of aggressive display for green, red, yellow
and blue stimuli were 7.24 seconds (± 0.833 s.e.), 6.59 seconds (± 0.957 s.e.), 6.95 seconds
(± 0.678 s.e.) and 7.69 seconds (± 1.306 s.e.) respectively. When compared, statistical
analyses showed that there was no significant difference between the average lengths of
aggressive displays when presented with differing colors of stimuli.
Introduction
Male Betta splendens, or Siamese Fighting
Fish are well known for their aggressive behavior,
especially towards other male betta fish. They typically
exhibit an unlearned, or instinctual, aggressive display
prior to attacking an opposing fish; this aggressive
response consists of alternating displays (Thompson
1963). The first method involves the displaying fish to
be facing the opponent head-on with its opercular
covers flared to increase its apparent size. The second
method involves the displaying fish to be profile to the
opponent fish while fanning out its dorsal, caudal and
pelvic fins also to increase its apparent size (Bando
2004). Betta fish respond to an opponent with an
aggressive response that consists of numerous shows.
They typically flare their fins and opercula for a short
period of time per show. This will continue until the
fish attack one another usually ending when one
retreats or dies (Bronstein 1981a).
Domesticated Betta fish, which can be easily
found at almost all pet and aquarium supply stores,
have been selectively bred to have larger fins and
greater varieties of color. In addition to fin size and
color, domesticated Betta fish are much more
aggressive than their wildtype counterparts (Simpson
1968). Fin size has already been shown to be a major
contributor to the aggressive response seen in male to
male Betta interaction (Allan and Nicoletto 1997), but
this study looks to test whether or not color of fish
plays an important role as well. It is hypothesized that
the new variety of colors will evoke different degrees
of aggressive response, which will be monitored as the
length of display per show.
Materials and Methods
Five male Betta fish were purchased from
Petco pet stores (Capo Beach, Ca). The fish were kept
in a quiet, sun-lit room at a residential home in Dana
Point in individual containers that were visually
separated from each other. In this way, they were in
complete isolation for five days before testing was to
begin, as to get them acclimated to being alone, and
more importantly, not seeing other male Betta fish
(they were kept in visual contact before being
purchased and their aggressive response had been
diminished due to over exposure to other males). After
isolation and the return of their aggressive response the
first of the trials was preformed in which the aggressive
display was monitored in response to visual stimuli.
This study looked to test whether or not color of visual
stimuli affected the average time of aggressive display
per show.
Betta fish were in isolation when not in trial,
kept in dechlorinated water that was changed twice a
week, and fed once every three days. When trials began
the fish were introduced into a larger container (8”x5”)
with flat surfaces so that they could see outside the
container clearly with no distortion for even slight
distortion of a curved container could weaken the
aggressive response of Bettas (Bronstein 1983). Three
of the four sides were covered with white paper so as to
keep any other outside stimuli from distracting the fish.
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Saddleback Journal of Biology
Spring 2008