To Fight or Not to Fight, That is the Question

There’s no way around it, conflict is a part of life: animals must often compete with one another to ensure their own survival. But how does an animal know whether that food source, potential mate or shelter are worth the energy, getting injured, or possibly even dying? 

Theoretically, no conflict should occur when the costs outweigh the benefits. To determine whether the resources are worth the trouble, animals use information from the environment and about other organisms to make a decision. However, this is easier said than done. 

Two types of information are available to guide the decision: public and private. Public information is information collected about the opponent, particularly about their ability to protect their resources. Private information corresponds with an individual’s own abilities, including factors such as energy levels and fighting experience. A decision made using both public and private information is termed mutual assessment, and answers the question “Can [other animal] beat me?” A decision founded on solely private information is a self assessment and answers the question “Can I beat [other animal]?”.

Early theories of assessment strategy believed that strategies were species-specific and lifelong. However, recent research has shown that an animal’s preferred strategy can be affected by social hierarchies, and ecological factors such as the quality and availability of food, shelter, and mates.

A chart based on Mester-Gibbons & Heap (2014), who proposed that assessment strategy shifts depending on social and ecological conditions. “Careful” denotes a condition where large/strong individuals use a mutual assessment strategy and small/weak individuals use a self-assessment strategy. “Daring” represents the opposite strategies.

Researchers Stieneker, Jackson, and Moore investigated whether an animals’ preferred assessment strategies are as flexible as previously thought. They hypothesized that large or ‘strong’ animals will act differently than small or ‘weak’ animals depending on the resources available in the environment. More specifically, large animals in rich environments with mostly large individuals will adopt a mutual assessment strategy while small animals will adopt a self-assessment strategy, and the opposite will occur in poor environments with mostly small individuals.

To test their hypothesis, the researchers designed a two-step study. First, male tilapia were placed in a ‘priming’ environment for 24 hours, which was meant to simulate the combination of social and environmental pressures that would affect their decision making. They decided to focus on conditions which would cause the “careful” and “daring” portions of the chart above, as these would provide clear results according to the model.

A diagram representing the two priming conditions. Left is poor/small (PS), where there is only one shelter available (rectangle) and small fish outnumber large fish. Right is rich/large (RL), where there are many shelters available and large fish outnumber small fish. (Figure 1, Stienecker et al. 2019).

After priming, fish were removed from the environment and fights were staged in a neutral environment. Fish were paired based on similar body size between pairs of fish from a combination of conditions. Rich/large-skewed (RL) group fish were paired with fish from the same group, the same was true for poor/small-skewed (PS) group fish, and for comparison RS and PW individuals were paired. The fish were allowed 10 minutes to display aggressive behavior one time, and then separated. Typically, one fish would assert dominance rather quickly, displayed by a fins-out posture, and the loser would retreat. 

The results of this experiment confirmed that the environment does affect decision making about engaging in conflict. When primed in rich/large-skewed conditions, large fish preferred mutual assessment and small fish preferred self assessment, while the opposite was true for fish primed in poor/small-skewed conditions. However, no particular strategy was preferred in fish that encountered a fish primed in the opposite condition. 

Though animals change their strategy depending on the environment, more research is needed to determine which factors are particularly important. Whatever these are, animals must successfully choose fight or flight in order to live to see another day.

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