Antifertility effects of EP-1 (quinestrol and levonorgestrel) on Pacific rats (Rattus exulans)

Pest rodents pose a serious threat to island biodiversity.Fertility control could be an alternative approach to control the impact of rodents on these islands.In this study,we examined the antifertility effects of EP-1 baits containing quinestrol(E)and levonorgestrel(P)using a dose of 50 ppm E and P at three different ratios(E:P ratio=1:2,1:1,and 2:1)on Pacific rats(Rattus exulans)in the Xisha Islands,Hainan,China.Compared to the control group,all animals in EP-1 treatment groups showed significantly decreased food intake and body weight.In treated males,there were obvious abnormalities in testis structure and a significant decrease of relative seminal vesicle weight,but no significant effect on relative uterine and ovarian weights(g kg-1 body weight),or ovarian structure in females.Adding 8%sucrose to the original 50-ppm baits(E:P ratio=1:1)significantly increased bait palatability for males and females.This dose induced uterine edema and abnormalities of ovarian structure in females but had no significant negative effect on the relative testis,epididymis,and seminal vesicle weights(g kg-1 body weight)or sperm density in males.In summary,50-ppm EP-1(1:1)baits have the potential to disrupt the fertility of females,and 8%sucrose addition to the EP-1 baits(E:P ratio=1:1)could improve bait palatability.This dose disrupted the testis structure in males.Future studies are needed to improve bait acceptance and assess the antifertility effects of EP-1(1:1)on Pacific rats in captive breeding trials and underfield conditions.

Geographical variation of the acoustic signals in the spot-legged treefrog (Polypedates megacephalus) of Hainan Island

Geographical divergence in acoustic signals is often affected by multiple selective pressures.Environmental factors are expected to shape signals by adjusting for greater propagation efficiency.Nevertheless,such habitat-driven hypotheses have not been well-examined with multi-signal and multi-habitat types included simultaneously.In this study,we evaluated call similarity of the spot-legged treefrog(Polypedates megacephalus),characterized by multiple call types,from 11 geographic populations across Hainan Island.We also examined multiple factors(i.e.body mass,temperature,altitude,and vegetation)among different acoustical geographic clusters,and tested whether the variation in acoustic length and frequency among different habitats was in accordance with the predic-tion derived from the acoustic adaptation hypothesis.We showed that P.megacephalus from Hainan Island included 3 acoustic geographic clusters:the northeasternflatlands,the southwest mountains,and the hills around the moun-tains.We also showed that environmental factors(i.e.altitude and vegetation)varied across these 3 acoustically distinct areas.Moreover,the duration of the different call types supported the hypothesis that they should have opti-mal transmission in their own habitats.Thus,our results reveal the roles of ecological selection in the geographical divergence of anuran acoustic signals.