1925] 
St over: A Synopsis of the Amphibia of California 
265 
Life-history. — The known facts concerning the life of this frog 
indicate that it differs considerably from the lowland races of boylii. 
Streams are inhabited bv sierrae where available, but many individ- 
uals live in glacial lakes. Their habits in these places are, however, 
more like those of boylii than of the strictly pond-inhabiting frogs 
( aurora ssp.) elsewhere in California, as sierrae sits on rocks adjoin- 
ing the lakes “ within one jump of the water.” A person’s 
. . . progress along the bank of a pool is announced by a series of splashes ten to 
twenty-five feet ahead, as the numerous frogs in quick succession take to the safety 
of the water. Once under the surface a few quick strokes of the hind legs with 
their broad foot-webs put the frog under some sheltering rock. The mottled pat- 
tern of the upper surface is quite protective in character when the animal comes 
to rest. When once on the bottom the frog is likely to remain there quietly unless 
further disturbed. When the frog is in motion, either jumping or swimming, the 
yellow color on the legs shows contrastingly against the dark upper surface of 
the body, but it is almost entirely masked when the frog is at rest (Grinnell and 
Storer, 1924, p. 664). 
It seems likely that these alpine frogs winter in the lakes which 
form their summer habitat, going down deep enough to escape 
freezing. 
The spawning season of this subspecies is delayed until midsum- 
mer. On June 22, 1915, adults collected at Peregoy and Mono 
meadows, in Yosemite National Park, had, for the most part, deposited 
their eggs; some of the females collected at, and near, Tuolumne 
Meadows the same year during the first half of July had already laid, 
while others contained eggs ready to lay. 
Eggs obtained in Cathedral Pass, Sunrise Trail, Yosemite National 
Park, on July 4, 1922, by Professor Stanley B. Freeborn, prove to be 
approximately like those of boy In in the lowlands. Exact measure- 
ments are not feasible, as the material was not fixed in a manner favor- 
able to preservation of the original size. 
In the foothill district, where there is a long spell of warm weather, the tad- 
poles (subspecies boylii) are able to grow to the size necessary for transforming 
into frogs in a single season. But with the high mountain animals (subspecies 
sierrae ) the case is different. The eggs are not laid until June or July, and there 
is then but a short season, scarcely three months in length, before cold weather 
sets in again. Consequently the tadpoles which hatch from the eggs in any one 
season go through the winter still in the tadpole condition and do not transform 
into frogs until the following summer. Thus the numbers of tadpoles, 2 inches 
or more in length, found in Young Lake on July 8 and 9, 1915, came from eggs 
which had been laid in 1914. On the dates mentioned, many of the tadpoles had 
the hind legs fully developed and in all probability would soon have completed 
their metamorphosis (Grinnell and Storer, loc. cit.). 
