TEEE-TOAD 661 



Pacific Tree-toad. Hyla regilla Baird and Girard 



Field characters. — Size small; total length 2 inches or less; ends of toes with small 

 rounded discs. Coloration extremely variable, ranging from pale light gray through 

 vivid green and brown to nearly black; a dark streak is always evident on side of head 

 extending from tip of nose at level of eye to behind ear membrane; under surface 

 white, unspotted, blackish on throat in males; back may or may not be marked with 

 dark streaks or spots. Voice: Song note a loud, raucous Tcreclc-elc, repeated at frequent 

 intervals; call note a single low prolonged, guttural kr-r-r-eclc. 



Occurrence. — Distributed throughout the Yosemite section without regard to life zone. 

 Eecorded from Snelling eastward across Sierra Nevada to Walker Lake and up to 10,600 

 feet altitude on Conness Mountain. Lives chiefly in damp situations and on the ground, 

 seldom being found in trees or even in bushes. Essentially solitary except when 

 spawning. 



The Pacific Tree-toad is one of the very few species of animals in the 

 Yosemite section which ranges uninterruptedly from the San Joaquin 

 plains to the highest passes of the Sierra Nevada. Of other land verte- 

 brates only the Gambel White-footed Mouse, the Red-shafted Flicker, and 

 the Western Chipping Sparrow can be said to do the same. The range of 

 the Pacific Tree-toad is most remarkable when we remember that it is a 

 'cold-blooded' animal which has a body temperature always close to that 

 of its environment, while each of the other species mentioned has a heat- 

 regulating mechanism which maintains its body at practically constant 

 temperature irrespective of that of the surroundings. 



At Snelling the air temperature at different seasons of the year varies 

 from slightly below freezing to above 110° F., while on Tuolumne Meadows 

 it undoubtedly goes below F°. in winter and may reach above 85° F. in 

 summer ; yet tree-toads are found in both of these places. The animals 

 keep to moist situations near the surface of the earth, where the tem- 

 perature fluctuations are somewhat less than those given, and in freezing 

 weather must of necessity seek shelters below the frost line. Even so, the 

 Tree-toads must be subject to considerable variation in the temperature 

 of their surroundings. The hardihood of these diminutive creatures is 

 indicated by the fact that in Yosemite Valley on February 28, 1916, when 

 there was two feet or more of snow on the Valley floor, tree-toads were 

 chorusing in open marshy ponds below the Royal Arches; and on Mount 

 Hoffmann on June 29, 1915, their voices were heard coming from beneath 

 deep snow banks on the north side of the mountain. On July 8, 1915, 

 several were croaking in a small lake covered almost completely with ice 

 on Conness Mountain at 10,600 feet altitude. By way of contrast it may 

 be mentioned that on May 27, 1915, at Snelling, when the air was to us 

 uncomfortably hot, tree-toads were heard in voice near the river margin. 



Among all the toads and frogs of the Yosemite region the Pacific Tree- 

 toad may be known at a glance by the expanded discs on the ends of all its 



