Assessment of the energetic costs of parasitism is central to understanding the role of parasites in their hosts' foodwebs, but few studies have directly measured these costs. This study demonstrates that infection with the acanthocephalan parasite Acanthocephalus tehlequahensis causes a significant and direct energetic cost to its freshwater isopod intermediate host Ceacidotea communis at both individual and population levels. Bomb calorimetry was used to measure energy (kj·m^-2·y^-1) allocated to host growth, reproduction, and respiration in infected and uninfected isopods and to parasite tissue in infected isopods. Infected isopod individuals allocated ∼21% of their net production energy to parasite growth, and they were larger (length), consumed more leaf detritus, and lost significantly more energy to respiration than uninfected controls (P ≤ 0.05). They also allocated proportionally less energy to tissue growth, allocated zero energy to reproduction, and were less efficient at converting energy into isopod biomass when compared to uninfected controls (P ≤ 0.05). In the field, isopod populations were surveyed monthly for a year. The parasite had a mean infection prevalence in the stream of 30.19% ± 8.31 SE with a mean intensity of 1.12 ± 0.39 SE parasites/host in the population, and based on this infection rate, it is estimated that ∼6.7% of total production energy of the isopod population (infected and uninfected) is diverted towards the parasite.

Nomenclature: Say, 1818; Oetinger & Buckner, 1976.

In response to spatial heterogeneity of resources, many herbivores move between discrete areas to enhance access to the best foraging areas. Local forage removal by mobile herd-foraging herbivores in turn is likely to produce spatial variability in both plant nutritive quality and quantity. On the tundra of Bylot Island, Nunavut, owing to the recent demographic explosion of their population, most greater snow geese move out of their nesting area soon after hatch to rear their young at distant feeding sites. A previous study showed that goslings using these distant sites are generally heavier and larger than those that stay in the colony throughout the brood-rearing period. In this study, we examine the hypothesis that goslings' growth was reduced in the nesting area compared to distant brood-rearing areas because grazing pressure reduced standing crop. In light of the recent expansion in the distribution of geese during brood-rearing, we also investigated if the negative effect of chronic grazing on net above-ground primary production (NAPP) differed between the colony and distant brood-rearing sites. We monitored NAPP, grazing pressure, and intensity of use in the goose colony and in 2 distant brood-rearing areas over a 10-y period by sampling plant biomass inside and outside moveable goose exclosures erected annually and by counting goose feces along transects at the end of the summer. NAPP of graminoids in the nesting area was 40% lower than at the other brood-rearing areas, but the percentage of primary production consumed by geese (28%) did not differ among the 3 sites despite large annual variations. Cumulative feces density revealed that intensity of use of the 2 brood-rearing areas by geese was nearly 2 times higher than at the colony, but the timing of use differed as grazing on the brood-rearing areas occurred only after hatch, unlike the nesting area. We conclude that geese not only respond to spatial heterogeneity in resource availability but also create and sustain it through their foraging behaviour.

Nomenclature: Porsild & Cody, 1980; American Ornithologists' Union, 1998.

The brown creeper (Certhia americana) was recently identified as one of the forest bird species most sensitive to partial harvesting in North America. However, the processes underlying this sensitivity are poorly known. In this study, we quantified the immediate, post-treatment demographic response of this species to experimental selection harvesting in plots of northern hardwood forest in northwestern New Brunswick, Canada. We mapped individual detections and nest locations in 5 pairs (1 control and 1 treatment) of 25-ha plots in the first 2 y after single-tree selection harvesting. Linear mixed models with site and landscape context as random effects showed a significant negative effect of treatment on nest density and seasonal reproductive success. The density of large-diameter trees (≥ 30 cm dbh) was significantly lower in treated plots than in controls (mean: 77 versus 112 stems·ha-1), whereas the density of potential nesting substrates (snags with peeling bark) did not decrease significantly following treatment. Hence, the density of suitable foraging substrates may represent a limiting factor for both nest density and reproductive success, and partial harvesting may not be compatible with the persistence of breeding populations of brown creeper. Patches of untreated forest should be maintained in managed forest landscapes at all times for this and other taxa requiring old forest conditions.

Nomenclature: Marie-Victorin, 1995; American Ornithologists' Union, 2008.

The importance of landscape heterogeneity for the abundance and distribution of wildlife is well recognized. General relationships have been developed to link landscape pattern to demographic processes, although these relations are best demonstrated for species with specialized habitat requirements and often in landscapes that can be generalized to a simple habitat-matrix structure. Habitat generalists may interact in more complex ways with a mosaic of landscape features. A novel method for quantifying the habitat relationships of generalist species using thematic vegetation maps was proposed by Brotons et al. (2005) and based on a theoretical model by Andrén, Delin, and Seiler (1997). We tested the efficacy of this approach on moose (Alces alces) distribution in the heterogeneous landscapes of the Foothills Natural Region, Alberta, Canada, using 8 broad vegetation types. Fecal pellet group data, an index of moose occurrence, was compared across pre-selected sites. Sites were selected to represent the variable amounts and combinations of the different vegetation types available in the study area. Moose habitat preference was determined using a Chi-square test and Bonferroni confidence intervals. Moose preferred shrublands and deciduous forests. Shrubland was considered primary moose habitat as it had the highest observed proportion of pellet groups of the preferred habitats. Each vegetation type was assessed regarding its role in habitat amount, habitat compensation, supplementation, complementation, and fragmentation models using general linear modelling. Habitat amount and fragmentation were related to moose pellet occurrence. However, there was no indication of supplementation, compensation, or complementation. This mosaic approach effectively revealed habitat relationships and the potential impacts of habitat change for a generalist species at the landscape scale.

Nomenclature: Kays & Wilson, 2002.

Phyllostomid bats form some of the most speciose mammalian assemblages known, with more than 70 species estimated to co-occur on one site. These species encompass a dietary spectrum that ranges across several trophic levels, and many show morphological specializations for their dietary behaviour (e.g., long tongues in nectar-feeding bats). However, previously reported diets have varied among studies including assignments of species to feeding ensembles. In this study we present data that demonstrate that phyllostomid bats are opportunistic omnivores despite their specializations. We analyzed the diet of 67 phyllostomid bat species from the Neotropics based on both fecal analyses and nitrogen isotope ratios in wing tissue and found that most species complemented their primary diet with nutrients from many different food sources. From these new dietary data, we were unable to distinguish meaningful feeding ensembles of species based on diet. Thus, we argue that interspecific competition is not restricted to species within an ensemble but seems instead to occur across the entire assemblage. Our results suggest that phyllostomid species have specialized successively on distinct diets during their radiation without sacrificing their capability to exploit a variety of food types. The combination of morphological and behavioural specialization on the one hand and opportunistic omnivory on the other might promote the high diversity of phyllostomid bat assemblages.

Nomenclature: Timm & LaVal, 1998; Albuja, 1999; Tirira, 1999; Baker, 2002; Muchhala, Mena & Albuja, 2005; Sánchez-Hernandez, Romero-A. & Schnell, 2005.

To maximize potential fitness, reproductive females should invest available resources in either larger propagules (egg and/or hatchling size) or more propagules (clutch size). Females may also enhance offspring performance by selecting nest sites with optimal conditions for the developing eggs. This study examined maternal investment in a population of spotted turtles (Clemmys guttata) in Ontario, Canada over 2 y using radio telemetry, x-ray photography, and indirect assessments of hatchling fitness. Analyses were conducted at 2 scales (clutch and female), utilizing 2 measures of available resources (body size and body condition). Larger females produced wider eggs, and similarity in the slopes of egg width and maternal pelvic aperture on body size may indicate a physical constraint on egg size. However, body size did not explain variation in egg morphometrics (length, width, or mass) when considering the reproductive output of each female over the entire study. Instead, females in better body condition produced more eggs. With respect to nest site selection, no selection for thermal properties was observed, and females exhibited stronger fidelity to nest substrates than to nest locations. Hatchling righting response was not related to hatchling body size or condition, but hatchlings from a clutch performed similarly, indicating maternal genetic effects or an effect of nest conditions. Thus, females in good condition maximize the number of eggs produced over multiple years, and hatchling morphometrics may not directly influence hatchling success.

Nomenclature: Ernst & Lovich, 2009.

We examined tree diameter, age structure, and successional trends in 100 montane forest plots to identify the effects of variation in the return interval, severity, and extent of fires on forest structure and dynamics in the southern Cascade Range, California. We classified 100 forest plots into 8 groups based on stand structural characteristics. Median point fire return intervals were shortest in lower montane mixed conifer and Jeffrey pine—white fir stands (13–25 y) and upper montane red fir—white fir stands (14.5–19.5 y), intermediate in lodgepole pine stands (50–76.5 y), and longest in high-elevation red fir—mountain hemlock stands (100 y). Fire severity was mainly moderate to high in all forest structural groups except red fir—mountain hemlock. In the late 19th century, large, mostly high-severity fires burned through all forests. Fire extent varied among structural groups, burning from 13% to 85% of plots in a group on average. Stands differed in composition, but size and age structures were similar across structural groups, with few trees > 100 y old and peaks of establishment between 1895 and 1955 for all groups except red fir—mountain hemlock. Distinct pulses of tree recruitment followed the most recent (1883, 1885, 1889, 1918) large and mainly high-severity fires. Suppression of fire since 1905 has increased understory density of shade-tolerant, fire-intolerant species and caused forest compositional shifts, particularly in lower-elevation Jeffrey pine—white fir and mixed conifer stands, and lodgepole pine stands on well-drained sites. Structural or compositional change is less pronounced in upper montane red fir—white fir and red fir—mountain hemlock forests. The combination of gently sloping terrain with few fire breaks, extensive, moderate- to high-severity fires in all forest types and gradient positions and fire suppression has promoted homogenization of forest structure that may lead to large and severe fires in the future.

Nomenclature: Hickman, 1993.

We examined whether stable isotopes of carbon (δ¹³C) and nitrogen (δ¹⁵N) differed consistently between linear features (e.g., pipelines) and forest for plants, fungi, soil, small mammals, and arthropods in the southern Northwest Territories and northern Alberta, Canada. Overall, linear features were significantly enriched in ¹³C ( 0.3‰) and depleted in ¹⁵N (-1.0‰) compared to forest. However, the small magnitude of the linear feature effect means isotope values probably cannot be used to directly trace whether insects or small mammals preferentially use linear features for foraging. However, deer mice (Peromyscus maniculatus), red-backed voles (Myodes spp.), and meadow voles (Microtus pennsylvanicus) differed significantly in stable isotope ratios. Each of these species also varied in their use of linear feature habitat, making it plausible to track where predators of small mammals obtain their prey using stable isotope ratios from predator tissues.

Nomenclature: Kartesz, 1994; Wilson & Reeder, 2005.

Lichens are often important photosynthetic organisms in oligotrophic environments where high-quality fodder plants are rare. A strong herbivore defence and/or low nutritional quality allows the accumulation of a high lichen biomass in such areas. However, it is not known how N deposition influences lichen palatability. This study analyzes possible changes in gastropod grazing preference after 3 months simulated N deposition on 3 foliose (Lobaria scrobiculata, Platismatia glauca, and Xanthoria aureola) and 1 pendulous lichen species (Alectoria sarmentosa). Lichens were daily irrigated in the field with rainwater containing 1.625 mM NH₄NO₃ from June to September, equivalent to a deposition of 50 kg N·ha^-1·y^-1. Irrigations applied at night, morning, or noon simulated different C-gain regimes. Afterwards in the lab, we offered 2 common lichen-feeding gastropods the choice between N-fertilized thalli and control thalli irrigated with artificial rainwater. The gastropods clearly preferred the unfertilized thalli of the 3 foliose species. For the pendulous A. sarmentosa, the gastropods preferred N-enriched thalli (irrigated at night) to controls. In conclusion, N-enrichment changes the palatability of lichens in species-specific ways.

Nomenclature: Lid et al., 2005; Gilbert, James & Wolseley, 2009.

Identifying habitats in which a species is likely to be found is extremely important for understanding the life history and general ecology of the species. Studies of habitat selection by species at risk provide information for management and recovery programs on critical habitat and are essential for conservation programs to be effective. Many studies on species at risk are conducted in highly altered or degraded habitats because few areas have not experienced human impacts. We investigated habitat selection by Blanding's turtles (Emydoidea blandingii) in a large protected area, Algonquin Park. Specifically, we evaluated macrohabitat selection at 2 spatial scales (home range and individual location) and microhabitat selection at one scale. Macrohabitat selection was significant at the home range scale but not at the scale of individual location, and no shift in habitat selection was detected among different seasons. Habitat ranks were ambiguous because all wetland types were preferred over lotic and upland habitats. The microhabitat selection data showed no preference for habitat features or shifts among different seasons. These data combined with those from other studies suggest that large study sites in relatively pristine areas may include a large amount of suitable high-quality habitats such that habitat selection at a fine scale may not be detected or multiple habitat types may provide the resources necessary to support populations.

Nomenclature: Ernst & Lovich, 2009.

Predators can have an important influence on prey survival and fitness, and many prey species exhibit morphological or behavioural responses to perceived predation risk. Although basic characteristics of anti-predator responses have been well documented, physiological pathways underlying such responses are poorly understood. We sought evidence for a role of corticosterone, a major stress hormone in amphibians, in the behavioural and morphological anti-predator responses of leopard frog tadpoles (Rana pipiens) exposed to caged dragonfly nymphs (Aeshna spp.). By superimposing a metyrapone treatment (corticosteroid synthesis inhibitor) over chronic predator exposure in a 2 × 2 factorial design, we evaluated if tadpole anti-predator responses were mediated by corticosterone. Tadpoles were less active and more likely to exhibit a startle response when exposed to perceived predation risk, but direct and interactive effects of the metyrapone treatment on behaviour were negligible. Predator-exposed tadpoles grew larger and had deeper tail fins, whereas the metyrapone treatment resulted in smaller tadpoles with shallower tail fins. Tadpoles simultaneously exposed to metyrapone treatment and predation risk had reduced tail-fin depth and increased body:tail ratio compared to steroid-normal animals. Because both traits are implicated in tadpole vulnerability to predation, these results suggest that the corticosteroid pathway may mediate tadpole morphological response to perceived predation risk. We provide evidence supporting a possible role for corticosterone in anti-predator responses of amphibians specifically in terms of morphological responses. Our results suggest that corticosteroid adjustment may impact prey survival through phenotypic change upon exposure to predation risk and thereby suggest a possible functional role of this hormonal pathway in amphibian physiological ecology.

Nomenclature : Hillis, 1988.

We studied factors shaping the diversity and abundance of small mammals in temperate woodlands in northeastern Poland at local (within the forests) and regional (among the forests) scales. We compared diversity and abundance of rodents and insectivores in habitats covering the widest possible range of forest productivity in Central Europe, from dry coniferous to wet deciduous forests. Small mammals were live-trapped during summer (2004–2006) on 206 circular plots. On the regional scale, the number of small mammal (rodent and shrew) species positively correlated with the proportion of deciduous stands in the woodland's area. In all forests, the bank vole (Myodes glareolus) and the yellow-necked mouse (Apodemus flavicollis) dominated, and their joint proportion in the community increased with share of deciduous forest habitats. On the local scale, the number of species increased significantly with productivity of both capture site and the whole woodland. Variation in rodent abundance was influenced mainly by forest productivity at the capture site, productivity of the whole woodland, and month of capture. Only a minor part of the variation in shrew abundance was explained by habitat productivity. The relationship between forest productivity and small mammal diversity was linear and positive on both local and regional scales. The different responses of rodents and insectivores to increasing productivity could be due to a wider ecological niche of shrews and their competition for space with rodents.

Nomenclature: Mitchell-Jones et al., 1999; White, White & Walters, 2005; Wilson & Reeder, 2005; Seneta & Dolatowski, 2006.