Interesting charges indeed! I keep a male/female pair of Tiger salamanders, and I hope to get them to breed someday. The juvenile form of A. tigrinus closely resembles the regular color morph of the axlotl. The term "water dog" is also erroneously used to refer to these juvenile individuals.
I wish to find out the trigger mechanisms that make them retain their neotenic features without being cannibalistic... i.e., true "Tiger Axlotls", as the juvies are also known.
As far as I know, low air pressure and temperature are the only triggers for the retention of neotenic traits in 'terrestrial' salamanders.
Interestingly enough, the late lake Texcoco, and several connected lake systems, where the true Axlotl is from and is threatened today, are several thousand feet above sea-level. Supposedly, the retention of the gills is an adaptation to lower oxygen availability. Keep them happy!