What we (don't) know about costs in animal contests.

Animal contests are central to understanding the evolution of aggressive behaviors and the strategic decisions that shape survival and reproductive success across species. A key aspect of contests is the role of individual costs in determining the outcome. However, despite its obvious meaning, a clear definition of contest costs is lacking. We argue that contest costs have both short- and long-term effects that affect how aggressive behaviors evolve and show that empirical studies rarely connect these two types of cost. To address this gap, we propose methodological approaches that integrate both cost perspectives. As a result, new research integrating short- and long-term contest costs can substantially advance our understanding of strategic decision-making evolution in animal contests.