Output from Console.print Stops, Alternatives to Serial Monitor

I am running a controller on a Mega with the Yun Shield using IDE 1.6.12. The controller outputs a line of debug text every 20 seconds using Console.print that I view with the Serial Monitor on a Mac. After a few hours the output stops. The contoller is still running fine and still updates ThingSpeak but no output. If I close and reopen the Serial Monitor the data continues.

I suspect that this may be a IDE issue. Is there an alternative to the Serial Monitor? The doesn't seem to be a device in /dev associated with the Yun port.