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54 SECRETS OF ANIMAL LIFE 
frogs fall victim to the appetite of many enemies, 
such as birds of prey, stoats, and grass-snakes, 
so that only a fraction of the young migrants is 
left to make the return journey in late autumn. 
They are then about three-quarters of an inch long. 
As the grass-frog does not become mature for three 
years, it is likely that some of the youngsters 
winter in suitable quarters far afield. But Dr. 
Hempelmann, the author of a fine recent (1908) 
monograph on the frog, says of the species we have 
been discussing that the adults usually seek out 
the water again in autumn and spend about four 
months of winter buried in the mud thereof. What- 
ever be the exact truth about the winter-quarters, 
the frog’s year is eventful indeed. How many 
years are granted it we do not know. 
