Hi, with the 5 they were about 1.5cm to 2cm max when I got them (I don't know how old they were) However it really wasnt very long before the first one started to vocalise only a month or so and it wasn't necessarily the largest one who started to call first! Their first sounds were the quietest sort of cheep or squeet, more birdlike than frog like but don't be fooled they just want to lull you into false security it does not take long before they learn the full call which they then practice frequently! A couple of ours (for those who dont know I probably have 7 Im still not certain of one who I hardly dare hope to be a girl!) can even be heard above the noise of the hoover which they always try to compeat with lol On the other hand one of the others still does more of a tweety-trill if that makes any sense? I do so love my boys they never cease to astonish and amuse. I wanted to split the group into two tanks but they are bonding into such a wonderful group Im not at all certain that the stress of splitting them up wouldn't be worse than keeping them together! I would think once they are fully grown i will have to house them in smaller groups but at the moment I am just keeping a watchful eye on them as the slowest growers decide how big they will grow. 3 of them are still no bigger than 2.5cm and they make as much noise as the older boys who must be a good 3 or even 3.5cm and are about 9 months older. I am wondering whether mine called so young because they could hear the older ones calling!