Meeting Abstract
Social behavior is a near-ubiquitous characteristic of vertebrates, and interaction dynamics are often driven by repeatable differences in behavior. Although variation in vertebrate social behavior has a well-known endocrine basis, most of the work on hormone-behavior relationships has focused on archetypal behaviors (e.g., aggression) in relatively simple social systems. As a result, we know little about how hormones modulate complex behaviors, like cooperation, that rely on repeated interactions within a dynamic social landscape. Here, we examined how testosterone (T) modulates social behavior in a lekking species, the wire-tailed manakin (Pipra filicauda), where territorial and non-territorial “floater” males form cooperative display coalitions. Our approach combined repeated hormone sampling, hormone manipulations and a novel automated telemetry system to measure social behavior. First, we asked if T could explain repeatable variation in male-male cooperation (i.e., the number of display partners and the frequency of interactions). Our results reveal that among-individual differences in circulating T predict behavior, but that these relationships are status-specific. Higher T correlates with increased cooperation among floater males but is inversely related to cooperative tendencies among territorial males. Additionally, T manipulations confirm that experimentally-elevated T can inhibit cooperation by territorial individuals with the strongest effects seen in males with lower endogenous T levels. We propose that these status-specific effects are due to differences in the neural activity of androgens and our results highlight how status specific differences in circulating T can influence cooperative behavior.
