Researchers already knew that the rodents sing to attract mates and repel rivals within their own species. But Pasch and colleagues found that these high-pitched tunes can serve as signals across species, too, helping males protect their turf.
Through experiments in the field and in the lab, the researchers noticed that the larger Chiriqui mice are less tolerant of heat. The creatures are typically spread throughout the cooler, higher-altitude parts of the cloud forests, and dominant Chiriqui males sing in response to potential intruders of both species, the researchers found.
Meanwhile, Alston's mice are more flexible when it comes to temperature; they will spread into cooler, higher habitats if no Chiriqui mice are around to push them out. But when an Alston's male hears the song of its larger cousin, it will stop its own singing and flee to avoid confrontation, the researchers found.
"The use of communication in mediating species limits is the major finding of our study and provides insight into how large-scale patterns are generated by individual interactions," Pasch explained in a statement.