enemy effects towards conspecific or heterospecific competitors

Abstract Many territorial animals exhibit reduced aggression towards neighbours. Known as “the dear enemy effect”, this phenomenon has been documented among conspecific animals across a wide range of animal taxa. In theory, dear enemy effects can also exist between individuals of different species, particularly when those species compete for shared resources. To date, heterospecific dear enemy effects have only been documented in ants. In this study, we test for both conspecific and heterospecific dear enemy effects in neotropical rufous-and-white wrens Thryophilus rufalbus. This species competes for resources with banded wrens Thryophilus pleurostictus, a closely related sympatric congener. We used acoustic playback to simulate Rufous-and-white Wren and Banded Wren neighbours and non-neighbours at the edges of rufous-and-white Wren territories. Rufous-and-white wrens responded more strongly to signals from their own species, demonstrating that resident males discriminate between conspecific and heterospecific rivals. They did not, however, exhibit conspecific dear enemy effects. Further, they did not exhibit heterospecific dear enemy effects. This could be due to neighbours and non-neighbours posing similar levels of threat in this system, to the possibility that playback from the edges of the subjects ’ large territories did not simulate a threatening signal, or to other factors. Our study provides the first test of a heterospecific dear enemy effect in vertebrates, and presents a valuable experimental approach for testing heterospecific dear enemy effects in other animals [Current Zoology 61 (1) : – , 2015]