# Male Strategic Association With Mating Partners Under Varying Social Contexts in a Livebearing Fish

## TL;DR

Male pygmy halfbeaks prefer to associate with opposite-sex pairs over rival males, suggesting mating opportunities influence their social choices.

## Contribution

This study reveals that male pygmy halfbeaks use mating-related information to guide their association strategies in social groups.

## Key findings

- Males prefer opposite sex pairs over rival males, indicating mating-driven association strategies.
- Association preferences correlate with observed courtship behavior under specific social scenarios.
- The number of fish presented does not influence male association preferences, ruling out shoaling behavior as a driver.

## Abstract

Group living species are constantly facing decisions about which conspecifics to associate with. These decisions are likely guided by the benefits and costs of associations. Associating in larger groups can minimize predation risk, while also providing individuals with beneficial social information from conspecifics. By contrast, associating with multiple individuals could also increase potentially costly conflicts over resources and/or mates. Here, we examine male association strategies in a shoaling fish, the pygmy halfbeak (
Dermogenys collettei
), by confronting males with four different social scenarios. We found that males preferentially associated with an opposite sex pair (i.e., a female and a male) over rival males, but showed no preference when choosing between a pair and females. By contrast, the number of presented fish (one or two) did not influence male association preferences, indicating that the observed male behavior was not driven by shoaling behavior. Finally, male association preference correlated with the duration of courtship behavior that the male observed, but only under specific social scenarios. Overall, our data show that males followed informed association strategies that are primarily driven by mating opportunities. Using a simplified social environment, we illuminate which basic rules might drive association behavior in complex social groups.

We found that in halfbeaks, a shoaling fish species, males preferentially associated with an opposite sex pair (i.e., a female and a male) over rival males, but showed no preference when choosing between a pair and females. Overall, our data show that males followed informed association strategies that are primarily driven by mating opportunities. Using a simplified social environment, we illuminate which basic rules might drive association behavior in complex social groups.