Heterixalus punctatus seems to be the only possible species match for this frog, of the choices given in Glaw and Vences. Many details of the general appearance match Heterixalus, and the whitish back with approximately 25 black spots is the distinguishing characteristics of H. punctatus. However, this frog is much yellower than the few other photos of H. punctatus I've seen, so I'm not completely confident of the identification.

Here is a list of all the reptiles and frogs I saw on this trip to Madagascar.