ABSTRACT
The brown rat (Rattus norvegicus) is a relatively recent (<300 years) addition to the British fauna, but by association with negative impacts on public health, animal health and agriculture, it is regarded as one of the most important vertebrate pest species. Anticoagulant rodenticides were introduced for brown rat control in the 1950s and are widely used for rat control in the UK, but long-standing resistance has been linked to control failures in some regions. One thus far ignored aspect of resistance biology is the population structure of the brown rat. This paper investigates the role population structure has on the development of anticoagulant resistance. Using mitochondrial and microsatellite DNA, we examined 186 individuals (from 15 counties in England and one location in Wales near the Wales-England border) to investigate the population structure of rural brown rat populations. We also examined individual rats for variations of the VKORC1 gene previously associated with resistance to anticoagulant rodenticides. We show that the populations were structured to some degree, but that this was only apparent in the microsatellite data and not the mtDNA data. We discuss various reasons why this is the case. We show that the population as a whole appears not to be at equilibrium. The relative lack of diversity in the mtDNA sequences examined can be explained by founder effects and a subsequent spatial expansion of a species introduced to the UK relatively recently. We found there was a geographical distribution of resistance mutations, and relatively low rate of gene flow between populations, which has implications for the development and management of anticoagulant resistance.
ABSTRACT
BACKGROUND: Rose-ringed parakeets Psittacula krameri (Scop.) have recently become established in several European countries, with potential for significant negative economic and ecological impacts. However, in northern Europe the potential for reproductive output is largely unknown. In 2005 the authors established a captive outdoor colony in north-east England and examined breeding success over 2 years. RESULTS: In 2006 (19 pairs, 15 clutches) the average first clutch size was 3.6 (+/-0.3) eggs. Six clutches were infertile, and overall the colony produced 1.4 (+/-0.5) fertile eggs per pair. Eleven pairs produced a second clutch following removal of the first; seven were infertile, and overall productivity was 0.7 (+/-0.4) fertile eggs per pair. Unsuccessful pairs were rearranged or replaced. In 2007, overall productivity was 2.5 (+/-0.4) and 1.8 (+/-0.4) fertile eggs per pair for the first and second attempts respectively. For pairs that remained unchanged through 2006-2007, productivity was consistent between years and breeding attempts. CONCLUSION: Where food and nest sites were not limiting, clutch sizes in north-east England were similar to those in the native range, and consistent between first and second attempts. This has implications for the future expansion and management of the species.
Subject(s)
Psittacula/physiology , Reproduction , Animals , Breeding , England , Female , Male , Psittacula/geneticsABSTRACT
BACKGROUND: Tracking and census baiting are two techniques that are commonly advocated for monitoring the size of mouse populations. However, currently these techniques are only able to provide an index of population size, rather than an assessment of absolute numbers. In this study the authors tested the reliability of both tracking (footprints left on tiles of fixed size) and census baiting as indices of population size, and sought to calibrate levels of activity and bait consumption under both semi-natural and field conditions (inside farm buildings). RESULTS: Under semi-natural conditions, census baiting produced more satisfactory population estimates than those derived from tracking activity. An initial field trial established that the optimum bait point density for this technique was 1 point per 2 m. Subsequent field trials demonstrated that the bait census technique offers a way to estimate the approximate size of stable populations of mice (population size = (mean daily bait consumption - 36.3)/2.46). CONCLUSION: The results to date are sufficiently encouraging to support the use of this cost-effective approach to monitoring mouse numbers in the type of habitats investigated in this study.
