Male Emei music frogs (Babina dauchina) use vocal signals to advertise to females. These calls reflect genetic qualities such as physical condition, but females are also interested in resources like territories and nests. Males of this species construct burrows along pond edges and recently a group discovered that the calls from inside the nest differ from those made outside the nest. This evidence was presented in an article in Biology Letters (J. Cui, Y. Tang and P. Narrins 2012 click here for the link).
The authors found distinct differences in frog calls between inside and outside in terms of frequency range and note durations. They posit that the males are encoding information about their nest such as burrow mouth size and depth. Beyond this, females were given phonotaxis preference tests and indeed prefer the inside calls to outside calls. In short, the ladies prefer a man with his own flat. Watch the video below for an example of a call from inside a nest.
It would be interesting to see the specific female preference assesment when the call is broken down to the specific elements representing the architectural features of the nest. Does the female prefer a deeper nest and how strong is this preference?
Is it possible that males are simply altering their calls as a result of calling from inside the nest?