On the Intraspecies Agonistic Behavior of Betta Splendens

Abstract

In investigating the agonistic behavior of the Siamese fighting fish, properly known as Betta splendens, we observed male to male B. splendens agonistic behavior, male to female behavior, and we observed the male’s agonistic behavior towards his own reflection. Our hypothesis entailed that the male B.Splendens would exhibit prolonged aggressive behavior towards other males, including flaring of gills and broadside displays. Male to female behavior would be more docile and submissive in nature. We also predicted that self-recognition would be non-existent in that our subject B. splendens would exhibit aggressive behavior towards his reflection. As hypothesized, our subject B. splendens displayed aggressive behavior when confronted with a male of the same species, not ending its gill flaring towards the male in any of our three trials. Broadside displays also occurred for approximately thirty seconds in each of our ninety second trials accompanied by rapid swimming. Male to female behavior proved more docile, with broadside displays occurring but no flaring of the gills or the rapid swimming characteristic of the aggressive behavior towards the male. The subject also exhibited the same aggressive behavior towards his own reflection as towards the live male of the species. Future work will possibly entail the observation B. splendens agonistic directed towards a dead B. splendens and/or a dead B. splendens.

Introduction

The Siamese fighting fish is native to the tropical waters of Southeast Asia Malay, Thailand, Kampuchea, and Southern Vietnam. They dwell in rice paddies, shallow ponds, and slow moving streams, and are renowned for the ability to surface and gulp the air from above water in these relatively, fetid oxygen-poor environments. Most experienced aquarium hobbyists know that only one male B. splendens may be kept in an aquarium at a time as they exhibit extremely aggressive behavior toward males of their own species (thought they exhibit more submissive behavior towards attacks from other species and tend to get their fins pecked apart in a community aquarium.) They will fight to complete exhaustion, nipping at each others’ fins until one is too tired to continue. By this time, both combatants’ fins will often resemble torn rags. It is on this information that my partner and I posit the hypothesis that males will react aggressively towards other males, submissive and/or docile towards females, and with aggression again when confronted with their own reflection.

Methods

The control for the experiment was our subject B. splendens under what would be considered normal circumstances (i.e. minimal external stimuli, swimming free in a bowl.) After a period of observation, we introduced the mirror in three ninety-second intervals with rest periods in between, starting, as we did with all timings in this experiment, at the first display of agonistic behavior. After a period of rest, we then introduced the subject to a female in three ninety-second trials. Finally, we exposed the subject to another, separate bowl containing a male observing in three ninety-second trials.

Results

When exposed to the mirror or another male, the subject would flare its gills continuously, either facing the stimulus or displaying its broad side to it. The broadside display persisted for about sixty seconds in the first trial and then about thirty seconds for the last two trials. When the male was exposed to a female, it would move its fins in a rippling manner and only engage in the broadside display. We observed very similar results in each trial with the male keeping up a broadside display for sixty seconds with the last trial being a little more than fifty seconds. Gill flaring never occurred when encountering the female. Below is a graph of our data:

Male-Male Interaction Recording Broadside Display and Gill Flaring

Broadside Display (seconds) Gill Flaring (seconds)

Trial 1 (90 seconds) 62 90