Reproductive Traits And Aggressive Behavior Of Tadpoles In The Tiger Frog,Hoplobatrachus Rugulosus

The tiger frog (Hoplobatrachus nigulosus) is one of animals under Class II State Protection in China. I examined reproductive output, patterns of mating behavior, and larval kin discrimination ability and the effect of density on the ability of kin discrimination of the frog. I also studied the effects of temperature and group size on aggressive behavior in larval tiger frogs.1. Reproductive output and mating patterns in the tiger frogI collected data for the tiger frog on two successive years to study reproductive output and patterns of mating behavior. We examined the large-male mating advantage model by comparing SVL between reproductively successful and unsuccessful males, and examined the size-assortative mating model by comparing SVL between successfully paired males and females. One-way ANOVA revealed that here was no significant differences in SVL between reproductively successful and unsuccessful males, and Pearson’s correlation revealed a strong positive association of SVL between successfully paired males and females. These findings suggest that the tiger frog follows a size-related mating pattern of mate choice. Clutch size, egg volume and clutch volume were positively correlated with female SVL,indicating that female tiger frogs increased reproductive output through increasing SVL. Holding female SVL constant with partial correlation analysis, the correlation between clutch size and egg volume was not significant, suggesting the absence of the trade-off between the size and number of offspring in the frog. Results of repeated measures ANOVA and Tukey’s post hoc test showed that:(1) clutch size differed among clutches successively deposited in the breeding season; and (2) clutch size was greater in the first clutch than in the suqsequent two clutches, but did not differ between the suqsequent two clutches. These findings indicate that females invest more energy in the first clutch than in the subsequent clutches. 2. The effects of density and kinship on attack frequency and activity level of tiger frog tadpolesI designed a4x2factorial experiment, four density levels of10,20,40,80tadpoles/L and two kinship levels of sibling groups and mixed groups, to examin the effects of density and kinship on attack frequency and activity level of tiger frog tadpoles(Hoplobatrachus chinensis). Resuils of two-way ANOVA showed that:(1) there are no significant differences in attack frequency and activity level between sibling and mixed groups;(2) attack frequency was affected by density, with attack frequency increasing as density increased;(3) activity level of tadpoles was not affected by density, and (4) the interaction between the density and kinship did not affect attack frequency and activity level of tadpoles. At different levels of density, there are no significant difference in attack frequency and activity level of sibling groups and mixed groups, and these results indicated the absence of kin discrimination in tadpoles and the lack of the influence of density on kin discrimination in tiger frog tadpoles.3. The effect of temperature and group size on the behavior in the tadpoles of the tiger frog, comparing with the black-spined toad (Bufo melanostictus)I examined the effects of temperature and group size on attack frequency and activity level of tiger frog tadpoles, and activity level of black-spined toad tadpoles. I designed a2x3x3factorial experiment to conduct the experiment:two temperature treatments (25℃and30℃); three group sizes (10,20,40tadpoles/L); and three species combinations, tiger frog tadpoles only, black-spined toad tadpoles only, and mixed tiger frog tadpoles and black-spined toad tadpoles, half tiger frog tadpoles and half black-spined toad tadpoles in each group size. Resuils of three-way ANOVA indicated that:(1) the species combination affected attack frequency of tiger frog tadpoles, with the mixed combination having higher attack frequencies than the single-species group;(2) attack targets affected attack frequency of tiger frog tadpoles, with tiger frog tadpoles attacking conspecific tadpoles more frequently than black-spined toad tadpoles, and the interaction between temperature and attack targets, and the interaction of temperature, group size and attack targets significantly affected attack frequency of tiger frog tadpoles;(3) group size and the species combination affected activity level of tiger frog tadpoles, with activity level decreasing as density increased, and activity levels were higher in the mixed species combination than in the single-species combination; and (4) temperature, group size and species combination affected activity level of black-spined toad tadpoles, activity level of black-spined toad tadpoles was lower at30℃than at25℃, activity level decreased as density increased, meanwhile, and activity level was lower in the mixed combination than the single-species group; and (5) other factors examined did not affect behavior in tiger frog tadpoles or black-spined toad tadpoles.