Figure 1- Betta splendens male anatomy2

Aggressive and Submissive Behavior of Male Betta splendens in Response to Visual Stimuli Introduction-

Male Betta splendens (Siamese fighting fish) are known for their aggressive behavior toward other males, usually by flaring out its fins (Figure 3) and charging. Aggressive behavior also includes faster swimming and increased movement of operculum and pectoral fins relative to neutral behavior. Such actions are most-likely made to deter another male from mating with a female in the area1. Bettas may also display submissive behavior in the midst of a more dominant opponent, such as backing away or fleeing, typically with no flared display. When another male is not present or is unseen, Bettas exhibit neutral behavior, in which all fins are relaxed and the Betta tends to remain within the same area, although any movement made is slow and not toward any location of urgency. The purpose of this experiment was to determine what aspects of a visual stimulus are significant in eliciting an active response behavior in male Betta splendens.

Methods and Materials- Twelve male Betta fish (half of which were red and half of which were blue) were placed in individual containers and isolated from external visual stimuli to establish a baseline of neutral behavior. Three simple models of identical size and shape of male Betta bodies were constructed using yellow, red, and blue clay. Models were presented immediately outside of each Betta’s container, where both frontal charges and side displays were simulated. Any behavior observed within thirty seconds of the model’s introduction was recorded as aggressive, submissive, or non-responsive based on the criteria stated in Introduction. Models were later modified to include paper fins. Fins were of appropriate size and shape to mimic aggressive behavior and matched the clay body in color. The same process was repeated using these models. Going through a cycle, both trials (body only and body with fins) were done with two repetitions. Each subject was also exposed to a mirror to assess the efficacy of red and blue models.

Hypothesis- Subjects will react in the same manner regardless of a model’s color, but will more frequently display an active response behavior when fins are present in the model. Overall, male Bettas will exhibit similar behavior in response to visual stimuli regardless of their own color as well.

TRENERRY, Michael Carleton Summer Science Institute 2012, Carleton College, One North Street, Northfield, MN 55057  

Figure 2- Male Betta splendens displaying neutral behavior.

Figure 3- Male Betta splendens displaying aggressive behavior. (Dorsal, pelvic, ventral, and caudal fins are flared in a side display.

Results- Two repetitions were performed for each treatment, although both trials yielded the same response behavior in each subject.  

R1 R2 R3 R4 R5 R6 B1 B2 B3 B4 B5 B6 Yellow NF NR NR NR AGG NR NR NR NR NR NR AGG AGG

Yellow F NR SUB AGG AGG NR NR AGG SUB AGG AGG NR AGG Red NF NR NR NR NR NR NR NR NR NR NR NR NR Red F NR AGG AGG AGG AGG SUB NR NR AGG AGG NR NR Blue NF NR AGG NR NR NR NR NR NR AGG AGG NR NR Blue F SUB AGG SUB AGG AGG AGG SUB NR AGG AGG AGG AGG Mirror NR AGG AGG AGG AGG AGG SUB NR AGG AGG AGG AGG Figure 4- All observed behavior is classified as either aggressive (AGG), submissive (SUB), or non-responsive (NR) based upon the aforementioned behavioral criteria. Active response (aggressive and submissive) behaviors are indicated by indigo cells in the table above. Models are classified based on color and the presence (F) or absence (NF) of fins.

Statistical Analysis of Data-

AGG NR SUB Y 9 13 2 R 6 17 1 B 11 10 3

AGG NR SUB Y 8.667 13.333 2 R 8.667 13.333 2 B 8.667 13.333 2

Observed Expected

Figure 5- Observed versus expected response behavior in regard to model color. The significance of varying model color was analyzed using a Chi-Square test of significance; α=0.05.

RED BLUE AGG 17 18 SUB 4 3 NR 21 21

RED BLUE AGG 17.5 17.5 SUB 3.5 3.5 NR 21 21

Observed Expected

Figure 6- Observed versus expected response behavior in regard to Betta splendens color. The significance of red versus blue color was analyzed using a Chi-Square test of significance; α=0.05.

p ̂ 1= 0.7222, p ̂ 2= 0.1667. n1= 36, n2= 36.

Conclusions- Through various tests of statistical significance, it was proven that the color of a visual stimulus, as well as the color of a subject itself, were not significant factors in generating an active response behavior in male Betta splendens. However, it was determined that the presence of fins in a visual stimulus was a significant factor in generating an active response behavior. In all tests conducted using models with fins, aggressive behavior was more commonly observed than submissive behavior. These behaviors support all facets of the original experimental hypothesis. Two further tests of statistical significance assessed the efficacy of red and blue models, based on male Bettas’ responses to models of their respective color versus responses to a mirror (Red p=0.5738, Blue p=1). Findings show that both models were effective, and validate experimental findings. It should be noted that due to relatively low sample size, statistical significance is primarily relevant in a limited laboratory environment. To guarentee universal statistical significance, a larger sample size is needed.

Hypothesis: Differences in observed behavior in response to varying model colors are not statistically significant. p=0.3655 df=4 Since the reported p-value is greater than the projected alpha-value, the effect of color is not statistically significant, and the hypothesis is proven true.

Hypothesis: Differences in observed behavior of red versus blue Bettas are not statistically significant. p=0.9179, df=2 Since the reported p-value is greater than the projected alpha-value, the effect of Betta fish color is not statistically significant, and the hypothesis is proven true. Hypothesis: The presence of fins has a statistically significant effect on Betta behavior, such that models with fins will be more likely to elicit an active response behavior than models without fins. p=1.1052 x 10-6 Since the reported p-value does not exceed the projected alpha-value, the effect of fins in Betta models is statistically significant, and the hypothesis is proven true.

Figure 7- Observed active response rates of male Betta splendens when exposed to models with (Group 1) and without (Group 2) fins. The significance of the presence of fins in models was analyzed using a two-sample P-test of proportionality; α=0.05.

Sources and Acknowledgements- 1.  Eberhard, C. Conflict behavior in Siamese Fighting Fish 2.  (Picture )

http://www.bio.miami.edu/dana/160/160S12_20.html 3.  Photographs taken by author I would like to thank Prof. Amy Moore, Brie Farley, and Cassandra Iroz for their resources and encouragement that made this independent experiment possible.