44 Mark S. Davis and George W. Folkerts 



stage 21 (cornea transparent), and average 10.7 mm (R = 9.8 to 11.0, SD 

 = .34, N = 10) in length. Meeks and Nagel (1973) found that hatchling 

 size in eastern Tennessee averaged 8.0 mm, but did not indicate devel- 

 opmental stage at hatching. Herreid and Kinney (1967) found that 

 hatching occurred at stage 20 in Alaskan populations. 



An easily observed size difference between hatchling R. sylvatica 

 and R. sphenocephala allowed us to monitor larval development of 

 these two species at one pond during 1979. Leopard frog tadpoles hatch 

 at slightly earlier stages, usually stage 19 (heartbeat) or stage 20, but are 

 considerably smaller than R. sylvatica tadpoles, averaging 6.6 mm (R = 

 6.2 to 6.8 mm, SD = .17, N = 10) in length. The results obtained from 

 the samples are summarized in Figure 3. 



Wood frog tadpoles grew more rapidly than leopard frog tadpoles 

 until about 15 April, at which time the tadpoles of both species were 

 approximately the same length (R. sylvatica: x- 40.9 mm, N = 10; R. 

 sphenocephala: x = 40.7 mm, N = 10); however, wood frog tadpoles at 

 this time were 5 to 1 1 developmental stages beyond leopard frog tad- 

 poles. Leopard frog tadpoles then continued to increase in length, where- 

 as wood frog tadpoles began to decrease as a result of initial tail resorp- 

 tion with the onset of metamorphic climax. Wood frog tadpoles were 

 last collected in the pond on 29 April, at which time most were in stage 

 42 (both forelimbs erupted) and averaged 40.5 mm in length. Leopard 

 frog tadpoles averaged 53.6 mm in length at this time, with most indi- 

 viduals in stage 35 (toes 1 and 2 joined, others separate). Leopard frog 

 tadpoles collected between 29 April and 5 May revealed that tadpoles of 

 this species continue to grow. Mean length of R. sphenocephala tad- 

 poles collected on 5 May (not shown on graph) was 56.0 mm, at which 

 time larvae were in stage 38 (metatarsal tubercle formation). 



It has been shown that wood frog and leopard frog tadpoles may 

 behave as ecological equals (DeBenedictus 1974). The larger size and 

 more advanced stage of development at hatching may give R. sylvatica 

 tadpoles some initial competitive advantage over those of R. spheno- 

 cephala. The more rapid development of R. sylvatica probably repre- 

 sents an adaptation to breeding in temporary pools and might result in 

 some resource partitioning on those infrequent occasions when these 

 two species use the same breeding ponds. Alford and Crump (1982) 

 found size class segregations in R. sphenocephala tadpoles, both in 

 laboratory experiments and field situations, and felt that the negative 

 correlation between large (and/ or older) and small (and/ or younger) 

 tadpoles indicated habitat partitioning. 



Since newly transformed R. sylvatica froglets were not collected in 

 the field, the exact amount of time from oviposition until transforma- 

 tion is not known. No wood frog tadpoles were collected on 5 May, 



