A survey of the antimicrobial susceptibility of Escherichia coli isolated from Sable Island horses.

The feral horses of Sable Island are a geographically isolated population located ∼160 km off the east coast of Nova Scotia, Canada. Because these horses have no contact with domestic animals, have minimal contact with people, and have never received antimicrobials, they offer a unique opportunity to study the dissemination of antimicrobial resistance in unmanaged populations. As part of an ongoing multidisciplinary and individual-based monitoring program, we collected feces from 508 geolocalized horses (92% of the total population) between July and September 2014. We selectively cultured Escherichia coli on MacConkey and CHROMagar ESBL media. Antimicrobial susceptibilities were determined, and organisms resistant to ß-lactam antimicrobials were screened for ß-lactamase genes by PCR. Escherichia coli was recovered from 146 (28.7%) individuals, and the majority of isolates (97%) were susceptible to all drugs tested. Resistance to tetracycline was most common, including organisms isolated from 4 (2.7%) of the colonized horses. A single isolate resistant to ampicillin, ceftriaxone, and ceftiofur was identified, which possessed the CTX-M-1 gene. Our findings demonstrate that although antimicrobial resistance is not common in this remote population, clinically relevant resistance genes are present.

Sex-based differences in density-dependent sociality: an experiment with a gregarious ungulate.

For animals living in natural or semi-natural settings, empirical data on how sociality changes in response to increasing population density are few, especially with respect to true conspecific density and not group size. However, insight into this line of research may be far-reaching--from understanding density dependence in sexual selection to improving models of disease transmission. Using elk (Cervus elaphus Linnaeus) held in enclosures, we conducted sex-stratified experiments to test how the frequency of dyadic pairings (interaction rate) and their quality (duration) responded to manipulations in exposure to density. Using proximity-logging radio collars we recorded when and for how long individuals shared a space within 1.4 m of each other. As predicted, males increased their interaction rate as density increased. Female interaction rates, however, increased initially as density increased but soon declined to become indistinguishable from rates at low density. Females interacted for longer periods at medium densities, whereas male interaction length clearly decreased as density increased. We highlight a sexually dichotomous, density-dependent response in sociality that has yet to be reported. In addition to furthering our understanding of sociobiology (e.g., implications of time constraints presented by density on dyadic interactions), our results have implications for managing communicable disease in gregarious species of livestock and wildlife.

Lifetime reproductive success and composition of the home range in a large herbivore.

The relationship between individual performance and nonrandom use of habitat is fundamental to ecology; however, empirical tests of this relationship remain limited, especially for higher orders of selection like that of the home range. We quantified the association between lifetime reproductive success (LRS) and variables describing lifetime home ranges during the period of maternal care (spring to autumn) for 77 female roe deer (Capreolus capreolus) at Trois-Fontaines, Champagne-Ardenne, France (1976-2000). We maintained population growth rate (adjusted to account for removals of non-focal animals) near rmax, which enabled us to define the fitness-habitat relationship in the absence of density effects. Using a negative binomial model, we showed that a roe deer's incorporation into its home range of habitat components important to food, cover, and edge (meadows, thickets, and increased density of road allowances) was significantly related to LRS. Further, LRS decreased with increasing age of naturally reclaimed meadows at the time of a deer's birth, which may have reflected a cohort effect related to, but not entirely explained by, a decline in quality of meadows through time. Predictive capacity of the selected model, estimated as the median correlation (rs) between predicted and observed LRS among deer of cross-validation samples, was 0.55. The strength of this relationship suggests that processes like selection of the site of a home range during dispersal may play a more important role in determining fitness of individuals than previously thought. Individual fitness of highly sedentary income breeders with high reproductive output such as roe deer should be more dependent on home range quality during the period of maternal care compared to capital breeders with low reproductive output. Identification of the most important habitat attributes to survival and reproduction at low density (low levels of intraspecific competition) may prove useful for defining habitat value ("intrinsic habitat value").

Pethidine reverses morphine-induced delirium.

A young patient had unexpected and prolonged postoperative delirium apparently associated with morphine-induced biliary colic. Naloxone had no therapeutic effect, but a small dose of pethidine produced a dramatic return to lucidity. Unrecognized biliary spasm should be considered as a cause of agitation in the recovery room in postoperative patients who have received morphine.