In this study, the ecological effects of culling programs are considered in the context of rodent pest management.Despite the escalation of rodent problems globally, over the past quarter of a century there have not b...In this study, the ecological effects of culling programs are considered in the context of rodent pest management.Despite the escalation of rodent problems globally, over the past quarter of a century there have not been many newdevelopments in culling programs directed at managing these populations. There is a strong reliance on broad scaleuse of chemical rodenticides or other lethal methods of control. The ecological consequences of culling programsbased on chemical rodenticides and bounty systems are considered. Although rodents cause tremendous economichardship to people on a continental scale, usually less than 10% of species cause substantial impacts. Indeed, manyspecies of rodent provide important “ecological services” and, given that culling programs rarely distinguishbetween rodent species, often the non-pest rodents are at grave risk. Rodent control is conducted with littleappreciation of what proportion of the population would need to be culled for a significant reduction in economicdamage. In Indonesian rice fields, once rodent densities are high then a reduction in yield loss from 30% to 15%would require more than 75% of the population to be culled;a reduction to less than 5% yield loss would requiremore than a 95% cull. The negative ecological consequences of culling can be better managed if the method isspecifically tailored to the species that need to be managed. A greater emphasis on ecologically-based rodentmanagement would assist markedly in reducing the unwanted and unintended effects of culling.展开更多
The ricefield rat,Rattus argentiventer,is a significant pest of rice in Southeast Asia.Fertility control methods have the potential to provide safe and effective alternatives to control methods that often include indisc...The ricefield rat,Rattus argentiventer,is a significant pest of rice in Southeast Asia.Fertility control methods have the potential to provide safe and effective alternatives to control methods that often include indiscriminate use of rodenticides or electric barriers.The aim of this laboratory study was to assess uptake of bait coated with different concentrations of the contraceptive hormones,quinestrol(E)and levonorgestrel(P),delivered alone and in combination(i.e.EP-1)and determine the short-term effects on reproductive parameters of adult male and female R.argentiventer.In Experiment 1,2 concentrations of E,P,and EP-1(10,20 ppm)were fed to groups of wild-caught rats for 7 days.In females,both E and EP-1 induced uterine edema.In males,EP-1 reduced epididymis and seminal vesicle weights and lowered sperm motility.However,these responses were inconsistent due to low bait acceptance,especially with increasing concentrations.In Experiment 2,EP-1(0,20,50,100 ppm)was administered by oral gavage daily for 7 days to male R.argentiventer.There were significant reductions in epididymal and seminal vesicle weights for all oral doses of EP-1,in sperm counts for the 50 ppm dose,and in sperm motility for the 20 and 50 ppm doses compared to the control group.To select the optimum dose of EP-1,we must address the poor acceptance of contraceptive-coated baits by ricefield rats.Further research is required to improve the palatability of EP-1 and to test its uptake underfield conditions.展开更多
文摘In this study, the ecological effects of culling programs are considered in the context of rodent pest management.Despite the escalation of rodent problems globally, over the past quarter of a century there have not been many newdevelopments in culling programs directed at managing these populations. There is a strong reliance on broad scaleuse of chemical rodenticides or other lethal methods of control. The ecological consequences of culling programsbased on chemical rodenticides and bounty systems are considered. Although rodents cause tremendous economichardship to people on a continental scale, usually less than 10% of species cause substantial impacts. Indeed, manyspecies of rodent provide important “ecological services” and, given that culling programs rarely distinguishbetween rodent species, often the non-pest rodents are at grave risk. Rodent control is conducted with littleappreciation of what proportion of the population would need to be culled for a significant reduction in economicdamage. In Indonesian rice fields, once rodent densities are high then a reduction in yield loss from 30% to 15%would require more than 75% of the population to be culled;a reduction to less than 5% yield loss would requiremore than a 95% cull. The negative ecological consequences of culling can be better managed if the method isspecifically tailored to the species that need to be managed. A greater emphasis on ecologically-based rodentmanagement would assist markedly in reducing the unwanted and unintended effects of culling.
基金All experiments followed the guidelines of the American Society of Mammalogists(Sikes et al.2016)The protocol and procedures employed were ethically reviewed and approved by the Institute of Zoology(IOZ-IACUC-2021-093)The study was supported by the International Partnership Program of Chinese Academy of Sciences,Grant No.152111KYSB20160089.
文摘The ricefield rat,Rattus argentiventer,is a significant pest of rice in Southeast Asia.Fertility control methods have the potential to provide safe and effective alternatives to control methods that often include indiscriminate use of rodenticides or electric barriers.The aim of this laboratory study was to assess uptake of bait coated with different concentrations of the contraceptive hormones,quinestrol(E)and levonorgestrel(P),delivered alone and in combination(i.e.EP-1)and determine the short-term effects on reproductive parameters of adult male and female R.argentiventer.In Experiment 1,2 concentrations of E,P,and EP-1(10,20 ppm)were fed to groups of wild-caught rats for 7 days.In females,both E and EP-1 induced uterine edema.In males,EP-1 reduced epididymis and seminal vesicle weights and lowered sperm motility.However,these responses were inconsistent due to low bait acceptance,especially with increasing concentrations.In Experiment 2,EP-1(0,20,50,100 ppm)was administered by oral gavage daily for 7 days to male R.argentiventer.There were significant reductions in epididymal and seminal vesicle weights for all oral doses of EP-1,in sperm counts for the 50 ppm dose,and in sperm motility for the 20 and 50 ppm doses compared to the control group.To select the optimum dose of EP-1,we must address the poor acceptance of contraceptive-coated baits by ricefield rats.Further research is required to improve the palatability of EP-1 and to test its uptake underfield conditions.
