100 



Current Herpetol. 20(2) 2001 



anuran larvae) occurred in 32.4% of frog 

 stomachs, but comprised only 6.1% and 

 9.3% in number and volume, respectively. 



Comparisons among sex-age classes 



Adult females, significantly larger than 

 adult males in all measurements (SVL, 

 mouth width, and body mass: Mann- 

 Whitney U-test, p<0.01 for all, see Table 

 2), tended to take larger prey on average 

 than did adult males and juveniles. Even 

 so, significant difference was detected only 

 between adult females and juveniles 

 (Dunn's multiple comparison test, p<0.05). 

 Although diet composition varied among 

 sex-age classes (Table 1), only the 

 frequency of ants showed statistically sig- 

 nificant difference in the between-class 

 comparisons: it was significantly higher 

 in juveniles (87.5%) than in adult males 

 (35.7%) and adult females (33.3%) (x"- 

 contingency table test, df=2, X"=6.88, 

 p<0.05). Absence of significant differences 

 in the number and volume of prey items 

 among the three classes (Dunn's multiple 

 comparison test, p>0.05), may be attribut- 

 able to the within-class large variation, 

 and/or small sample size for each class. 



Table 2. Means (±SD) of character dimens 

 given in parentheses. 



Discussion 



This study revealed that R. limnocharis 

 from central Japan feeds predominantly 

 on arthropods like most other ranid 

 frogs hitherto studied (e.g., Jenssen and 

 Klimstra, 1966; Houston, 1973; Whitaker 

 et al., 1983; Hirai and Matsui, 1999). 

 According to the past studies on the popu- 

 lations of R. limnocharis outside of Japan, 

 arthropods comprised 89-100% in number 

 of total prey items in the diet (Liu and 

 Chen, 1933; Berry, 1965; Monhanthy- 

 Hejmadi and Acharya, 1982). The value 

 obtained by our study (94.8%) falls within 

 this range. 



Among diverse arthropod prey taxa, ants 

 were reported to comprise the largest 

 proportion in rice fields of China (27%; 

 Liu and Chen, 1933), and in the swamps 

 of Singapore (28%; Berry, 1965). These 

 reported proportions are quite similar to 

 the value in our result (26.9%). The pre- 

 vious studies, however, did not examine 

 diet variations between juvenile and adult 

 R. limnocharis. As shown in this study, 

 the numeric proportion of ants is much 

 larger in juveniles than in aduhs. This 



of frogs and prey. Sample size and range are 



Juveniles Adult males Adult females 



Frogs 



SVL (mm) 29.3+2.7 35.8+2.9 41.4+3.5 



(8:24.4-31.2) (15:32.2-40.2) (17:34.8-46.5) 



Mouth width (mm) 10.1±0.9 11.9+1.0 13.6±1.3 



(8:8.6-10.9) (15:10.9-14.0) (17:11.4-16.0) 



Body mass (g) 1.9+0.4 3.6±0.9 6.2±1.6 



(8:1.1-2.3) (15:2.4-5.6) (17:3.6-9.7) 



Prey 



Length (mm) 3.6+0.9 5.0±1.5 7.6+4.9 



(7: 2.5-4.9) (9: 3.3-8.3) (9: 3.4-19.4) 



Number/stomach 10.0±8.6 4.9±4.8 5.3±4.0 



(8: 2-30) (14: 1-20) (12: 1-13) 



Volume/stomach (mm^) 40.3+48.6 133.9+257.1 166.0±137.1 



(8: 0.7-149.0) (14: 3.4-985.6) (12: 5.4-384.7) 



