Population response of rodents to control with rodenticides

We summarize theoretical approaches and practice of rodent pest control in Russia and former USSR during last 50 years. We review literature as well as original data to understand mechanisms of rodent populations recovery after chemical control campaigns in urban areas, agricultural lands and natural foci of plague. Laboratory and field experiments indicate that inherent individual variation in behavioural, physiological and life-history traits provides survival of heterogeneous mix of individuals in residual population with increased resistance to poisonous baits and high reproductive potential that leads to fast recovery of a population. In a series of field experiments with various rodent and lagomorph species （Mus musculus, Rattus norvegicus, Meriones unguiculatus, M. meridianus, M. tamariscinus, Ochotona pallasii ） we have shown that patterns of recolonization of depopulated area and mechanisms of population recovery vary among species and depend on species-specific social organization. After control territorial and group-living species demonstrated an increase in mobility and affiliative and marking behaviour and a decrease in intraspecific aggression. The rate of recolonization of treated areas was high due to redistribution of survived individuals and immigration by neighbors. Population recovered to original level due to increased breeding performance and fecundity of both survived residents and immigrants. In contrast, socially-independent species exhibited minor changes in behaviour. Recolonization was mainly due to better survival and recruitment of youngs, so the rate of recolonization was low. Species-specificity of behavioural compensation mechanisms to control should be considered when developing ecologically based rodent management strategies

Advance in the research of sterilants against rodents

The advances in the application of sterilizing techniques against pest rodents in China are introduced in the paper. The development of chemosterilants, improvements of botanic sterilants, production of new steroid hormone sterilants, introduction of immunosterility and excellent properties of the sterilants are outlined. The 揝pace Occupation Theory?of sterile techniques is advanced after practice. The botanic sterilants with gossypol and trichosanthin as its main agents were screened and successfully applied in the large area control in the northern forest area of China. The safety of sterilants to non-target animals such as rats, rabbits, dogs, monkeys and chickens was summarized.

Rodent Damage and Control Methods in Hami Grassland of Xinjiang

Since 2002,Hami City,Xinjiang Province,has implemented"construction project of rodent-free demonstration area".Artificial eagle frames are installed on the grassland to control rodent damage,receiving remarkable control effect.The rodent density in the treatment area is below the threshold of hazard.Moreover,the implementation of the project increases the grassland biomass and improves the vegetation coverage,receiving good economic,ecological and social benefits.

Rodent management in Aotearoa New Zealand: approaches and challenges to landscape-scale control

Aotearoa—New Zealand has only four rodent species,all introduced.In order of arrival,they are Pacific rat Rattus exulans,brown rat R.norvegicus,house mouse Mus musculus,and black rat R.rattus.Rodent management in New Zealand aims mainly to conserve indigenous biodiversity rather than to protect crops or manage diseases,as is usual elsewhere.We describe four major“regimes”and one major vision for rodent control in New Zealand to meet ecological restoration objectives.Current challenges for island eradications are for large islands that are remote or populated by people.Aerial 1080 is the only large-scale(tens of thousands of hectares)option for black rat control,but its application requires adjustment to counter subsequent rapid black rat repopulation.Unfenced“ecosanctuaries”(mean 720 ha)use ground-based traps and poisons to target mainly black rats and face constant reinvasion.Ecosanctuaries with mammal-resistant fences(up to 3500 ha)limit reinvasion and target more pest species and have enabled the return of previously extirpated taxa to the main islands.Predator Free 2050 aims to eradicate the rat species(but not mice)plus some other introduced mammals from New Zealand by 2050.This vision is not attainable with current tools,but research and experimental management is exploring techniques and technologies.The large scale(to 100000 ha)at which black rats are now targeted for control to extremely low abundance seems to be unique to New Zealand.

Reproductive ecology of the black rat (Rattus rattus) in Madagascar: the influence of density-dependent and -independent effects

The black rat(Rattus rattus)poses a severe threat to food security and public health in Madagascar,where it is a major cause of pre-and post-harvest crop losses and an important reservoir for many zoonotic diseases,including plague.Elsewhere,ecologically based rodent management(EBRM)strategies have been developed using ecologi-cal information to inform decisions on where and when to target control.EBRM could deliver improved health and well-being outcomes in Madagascar if adapted to the local ecological context.Using data collected from removal studies,we explored spatio-temporal patterns in the breeding activity of the black rat(R.rattus)in domestic and agricultural habitats across Madagascar and investigated to what extent these trends are influenced by rainfall and rat density.We identified clear spatio-temporal variation in the seasonality of R.rattus reproduction.Reproduction was highly seasonal both inside and outside of houses,but seasonal trends varied between these two habitats.Sea-sonal trends were explained,in part,by variation in rainfall;however,the effect of rainfall on reproductive rates did itself vary by season and habitat type.A decline in breeding intensity with increasing rat density was recorded outside of houses.This has important implications for control,as populations may compensate for removal through increased reproduction.We recommend that sustained control initiated before the main breeding season,combined with improved hygiene and adequate rodent-proofing in homes and grain stores,could curtail population growth and reduce pre-and post-harvest losses provided that these measures overcome the compensatory response of rodent populations.

Recovery of fertility in quinestrol-treated or diethylstilbestroltreated mice:Implications for rodent management

Fertility control is an alternative strategy to traditional culling for the management of rodent pests.Previous studies have demonstrated that quinestrol is a potential contraceptive for male rodents,but the recovery of fertility in quinestrol-treated rodents has not been evaluated.This study used C57BL/6J mice to evaluate the recovery rate of male fertility after the administration of quinestrol.Diethylstilbestrol(DES),a non-steroid estrogenic compound,was used for comparison.Different groups of mice were treated with 1 mg/kg quinestrol,1 mg/kg DES,or castor oil separately for 7 days.These mice were then killed on days 8,22 and 50 respectively.Our results indicated that the weight of epididymides and seminal vesicles decreased significantly on days 8 and 22 in quinestrol/DES-treated mice,with extensive histological changes in the seminiferous tubules.Sperm concentrations in the cauda epididymal fluid were significantly reduced on days 8 and 22 in both quinestrol and DES treatment groups and on day 50 for the DES,but not the quinestrol group.Further analysis revealed that DES-treated mice exhibited a higher proportion of abnormal sperm accumulation in the epididymis,indicating that the normal sperm transportation to the cauda epididymis was blocked.Our results indicate that the anti-fertility effects on male mice given quinestrol were of shorter duration than for those receiving DES at the dose of 1 mg/kg body weight.