Certain areas of the Tsubaki Grand Shrine of America complex are littered with frog statues, big and small. Apparently they were all gifts... in Japanese, frogs are called "kaeru", which is the same word as the verb "to return". Therefore frogs are associated with things returning, and as the main kami of this shrine are also associated with marriage and good relationships, the frogs are apt for prayers for the return of love or loved ones.
Additionally, it is thought that keeping a frog charm in your wallet will ensure the return of money.
As for this particular frog... I just found it with a leaf fallen on its head and thought it was cute.