I was very wrong, and I don't know where this "Urt-Rrr" frog sound at night is coming from now! - These little guys are suppose to make a high pitch whistle sound, and I have not heard that kind of sound yet? - Could be a season, and I have not had these guys long enough yet..? - I would have a hard time believing they are making this very loud deep "Urt-Rrr sound, when a whistle sound would be more believable because of their tiny size!