Summary 1.The delayed density-dependent predation of specialists such as weasels ( Mustela nivalis L.) may result in cycles in the abundance of their prey. We estimated the demographic impact of weasel predation on field-vole ( Microtus agrestis L.) survival using capture-recapture data from a large-scale, replicated predator-manipulation experiment conducted in six unfenced populations in Kielder Forest, northern England. The density of weasels was experimentally reduced through continuous live-trapping in the three removal populations. Field-vole survival was compared between paired removal and control populations during the increase, peak and decline phases of a vole population cycle. Apparent survival and recapture probabilities were estimated using open population Cormack-Jolly Seber models. 2. Field-vole survival varied extensively both spatially between populations and temporally, being highest in the late autumn and over winter and lowest each year in spring and early summer. Patterns of variation in male and female survival were similar between populations over time, but there was independent spatial and temporal variation between adults and juveniles. Variation in weasel abundance explained 18% of this independent spatial and temporal variation between adult and juvenile field-vole survival. 3. The average increase in annual vole survival resulting from weasel removal over the 2-year period was 27% and 25% for adult male and female field voles, respectively. Decreased weasel abundance increased adult field-vole survival. Adult-vole survival in the absence of weasels was predicted to be approximately 8% higher than in the presence of one weasel per 4-5 ha. Surprisingly, weasel removal resulted in lowered juvenile fieldvole survival, possibly reflecting increased emigration or mortality due to infanticide. A simple two age-class demographic model indicated that the decrease in juvenile survival in response to reduced weasel predation pressure did not fully compensate for the increase in adult survival. 4. As weasel numbers fluctuated seasonally, with highest weasel densities occurring in late summer and autumn and little spring to spring variation, the impact of weasel removal on field-vole survival was greatest during the breeding season. However, vole population-growth rates were unrelated to adult survival at that time and correspondingly no divergence was observed between the trajectories of control and removal vole populations even when weasel numbers were greatest in control sites. In contrast, vole population-growth rates were closely correlated with survival during the non-breeding season. Nevertheless all control and removal populations experienced a cyclic decline in winter 1999-2000 in spite of the increased adult survival in experimental treatments. 5. We conclude that the impact of weasel predation on field-vole survival was neither sufficient nor necessary to initiate and drive the cyclic decline of field-vole populations in Kielder Forest.

Assessments of the impact of offshore energy developments are constrained because it is not known whether fine-scale behavioural responses to noise lead to broader-scale displacement of protected small cetaceans. We used passive acoustic monitoring and digital aerial surveys to study changes in the occurrence of harbour porpoises across a 2000 km2 study area during a commercial two-dimensional seismic survey in the North Sea. Acoustic and visual data provided evidence of group responses to airgun noise from the 470 cu inch array over ranges of 5–10 km, at received peak-to-peak sound pressure levels of 165–172 dB re 1 µPa and sound exposure levels (SELs) of 145–151 dB re 1 µPa2 s−1. However, animals were typically detected again at affected sites within a few hours, and the level of response declined through the 10 day survey. Overall, acoustic detections decreased significantly during the survey period in the impact area compared with a control area, but this effect was small in relation to natural variation. These results demonstrate that prolonged seismic survey noise did not lead to broader-scale displacement into suboptimal or higher-risk habitats, and suggest that impact assessments should focus on sublethal effects resulting from changes in foraging performance of animals within affected sites.

Mycobacterium microti (vole tuberculosis) infections in small wild mammals were first described more than 60 years ago in several populations in Great Britain. Few studies of vole tuberculosis have been undertaken since then, and little is known about the relationship between M. microti isolates originating from different populations or at different times or of the prevalence of this infection in wild rodent populations, despite human cases of M. microti infections being increasingly reported. In this study, field voles (Microtus agrestis), bank voles (Clethrionomys glareolus), and wood mice (Apodemus sylvaticus) were found to be infected, with up to 8% having external tuberculous signs, in wild populations in Northumberland and Cheshire, England. Spoligotyping applied directly to the clinical material simultaneously detected and typed M. microti bacteria in skin lesions, lymph glands, and internal abcesses. IS6110 restriction fragment length polymorphism typing of cultured bacteria was used to compare these isolates with previously isolated strains from both animals and humans. This demonstrated that although the current rodent isolates were distinct from those isolated from voles in the 1930s in Great Britain, they had a high degree of similarity to these strains and were distinct from the M. microti isolates from humans, a pig, and a ferret from The Netherlands. Thus, M. microti infection seems to be widespread in wild rodent populations, but more studies are needed to understand how M. microti might be transmitted from animals to humans and to determine better the zoonotic risk posed.Tuberculosis (TB) in small wild mammals, namely, field voles (Microtus agrestis), bank voles (Clethrionomys glareolus), wood mice (Apodemus sylvaticus), and shrews (Sorex araneus), was first reported by Wells and Oxon in 1937 (25). The causative agent was named Mycobacterium tuberculosis subsp. muris (4) and later Mycobacterium microti (or vole tuberculosis), a member of the M. tuberculosis complex (24). The other members of this complex are M. tuberculosis, Mycobacterium bovis (including the attenuated BCG vaccine strains), Mycobacterium africanum, and the recently described subspecies Mycobacterium canetti (22,23). M. microti has a characteristic pleomorphic microscopic morphology, with sickle-shaped, spiral, or S-like forms being seen in fresh material. This typical curved appearance is, however, usually lost during in vitro culture (18). It is difficult to distinguish M. microti from other members of the M. tuberculosis complex on the basis of biochemical properties, but they are readily identified by PCR-based spoligotyping and/or IS6110 restriction fragment length polymorphism (RFLP) typing (23). The latter requires large numbers of cultivated bacteria but facilitates more detailed phylogenetic comparisons.Well's early studies showed a varying prevalence of M. microti of 9 to 31% in field voles, depending on the place and season of capture, and overall prevalences of 11% in bank voles, 2% in wood mice, and 1.5% in shrews (...

Summary1. Understanding which environmental factors drive foraging preferences is critical for the development of effective management measures, but resource use patterns may emerge from processes that occur at different spatial and temporal scales. Direct observations of foraging are also especially challenging in marine predators, but passive acoustic techniques provide opportunities to study the behaviour of echolocating species over a range of scales. 2. We used an extensive passive acoustic data set to investigate the distribution and temporal dynamics of foraging in bottlenose dolphins using the Moray Firth (Scotland, UK). Echolocation buzzes were identified with a mixture model of detected echolocation inter-click intervals and used as a proxy of foraging activity. A robust modelling approach accounting for autocorrelation in the data was then used to evaluate which environmental factors were associated with the observed dynamics at two different spatial and temporal scales. 3. At a broad scale, foraging varied seasonally and was also affected by seabed slope and shelf-sea fronts. At a finer scale, we identified variation in seasonal use and local interactions with tidal processes. Foraging was best predicted at a daily scale, accounting for site specificity in the shape of the estimated relationships. 4. This study demonstrates how passive acoustic data can be used to understand foraging ecology in echolocating species and provides a robust analytical procedure for describing spatiotemporal patterns. Associations between foraging and environmental characteristics varied according to spatial and temporal scale, highlighting the need for a multi-scale approach. Our results indicate that dolphins respond to coarser scale temporal dynamics, but have a detailed understanding of finer-scale spatial distribution of resources.

Animals exposed to anthropogenic disturbance make trade-offs between perceived risk and the cost of leaving disturbed areas. Impact assessments tend to focus on overt behavioural responses leading to displacement, but tradeoffs may also impact individual energy budgets through reduced foraging performance. Previous studies found no evidence for broad-scale displacement of harbour porpoises exposed to impulse noise from a 10 day two-dimensional seismic survey. Here, we used an array of passive acoustic loggers coupled with calibrated noise measurements to test whether the seismic survey influenced the activity patterns of porpoises remaining in the area. We showed that the probability of recording a buzz declined by 15% in the ensonified area and was positively related to distance from the source vessel. We also estimated received levels at the hydrophones and characterized the noise response curve. Our results demonstrate how environmental impact assessments can be developed to assess more subtle effects of noise disturbance on activity patterns and foraging efficiency.