Gray treefrog, Hyla versicolor 



advertise the male's presence; hciwever, when another 

 male gets too close, the single notes become a trill, a 

 signal that the caller's territory is being invaded. After 

 the breeding period, males still call, but in small chor- 

 uses, or singly. Unlike the western chorus frog, the 

 female spring peeper deposits one egg at a time on sub- 

 merged vegetation after it has been fertilized; thus, the 

 eggs are not found in gelatinous masses, but are scat- 

 tered along stems and leaves. 



The gray treefrog, Hyla versicolor, and Cope's 

 treefrog, Hyla chrysocelis, are considered together 

 because, even to the trained naturalist, they look alike 

 and both are about 1 . 5 to 2.0 inches in length. Because 

 of this similarity, they are still sometimes collectively 

 called gray treefrogs. The gray treefrog has a slower, 

 guttural trill, but to distinguish it from Cope's in the 

 field, the two must be calling near each other so their 

 calls may be compared under the same conditions — 

 temperature affects the speed of frog calls; the warmer 

 the frog the more rapid the call. 



These normally gray frogs can change to green or 

 to a pasty-white, have bumpy skin, webbed toes, fin- 

 gers ending in expanded disks, a distinctive white spot 

 under the eye, and yellow and brown mottling on the 

 groin and hidden surfaces of the thigh. Males have a 

 single vocal sac and a rough pad of tissue on the inner 

 thumb. The thumb pad is used for gripping the female 

 during amplexus, or mating. During dry weather these 

 frogs live in tree hollows, under tree bark, in rotten 

 stumps and even abandoned bird houses. The two gray 

 treefrog species spread their reproductive activity from 

 April to August, latitude having some influence on the 

 timing. 



Two other species of true treefrogs are found in the 

 southern part of Illinois. The bird-voice treefrog, Hyla 

 24 



avivoca, is a miniature version of the gray treefrogs, be- 

 ing 1 . 2 to 1.75 inches in length, and it inhabits wooded 

 swamps. This treefrog's call has been described as the 

 most beautiful of all in North America. Males produce 

 a clear, bird-like whistle at a pulse rate of about two 

 to five per second. The green treefrog, Hyla cinerea, 

 is leaf-green with a creamy side stripe, is 1.25 to 2.0 



Male frogs with vocal sacs inflated. Top: leopard frog: bottom: green 

 frog. 



inches long and inhabits swamps and marshes. Green 

 treefrogs have a "quank"- or "quonk"-like voice, but 

 when a large chorus is close to synchrony the sound 

 produced is similar to cow bells. Both the bird-voice 



