how big can this get?
It reaches maturity at three to seven years old but there is great variability between populations.
Common toad
The common toad reaches maturity at three to seven years old but there is great variability between populations. 
what is the name of a small toad The common toad.
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Common toad [SEP] Development and growth
The common toad reaches maturity at three to seven years old but there is great variability between populations. Juveniles are often parasitised by the lung nematode "Rhabdias bufonis". This slows growth rates and reduces stamina and fitness. Larger juveniles at metamorphosis always outgrow smaller ones that have been reared in more crowded ponds. Even when they have heavy worm burdens, large juveniles grow faster than smaller individuals with light worm burdens. After several months of heavy worm infection, some juveniles in a study were only half as heavy as control juveniles. Their parasite-induced anorexia caused a decrease in food intake and some died.