which to call from, but intruder males rarely displace residents from their nests. The intruders would move frequently without giving advertisement calls, but would produce territorial and encounter calls. While aggression from males is implicit in the English name of this species, male-male aggression and combat has only been observed in the Panamanian population of the species, not the Costa Rican one, likely due to the abundance of nest sites and low density of reproductively active males in the Costa Rican population. When observed, aggression in H. rosenbergi took three different forms: undirected, nonviolent, or violent. Undirected aggression includes territorial calls and encounter vocalizations that were not directed to a particular opponent. Nonviolent aggression occurs when males sense each other but no physical contact happens, as males charge and chase each other. Violent aggression occurs when males make physical contact with each other, either through wrestling or knocking opponents away, in or near a nest. Violent aggression also involved growling and hissing and the use of unsheathed prepollical spines, and can result in serious wounds or death. In addition, violent aggression is the most costly form of aggression due to the increased chance of being preyed upon as noise and exposure from the fight brings about attention from predators. It also is a large energetic cost for males who fight and typically forces them to leave the breeding area or it results in them being unable to call to find a mate. Predators Predators of H. rosenbergi include snakes (such as Leptodeira annulata), other frogs (such as Leptodactylus pentadactylus) and possibly mammals and crocodiles. Predation often occurs at night. References rosenbergi Amphibians of Colombia Amphibians of Costa Rica Amphibians of Ecuador Amphibians of Panama Amphibians described in 1898 Taxonomy articles created by Polbot