Abstract. Animal habitat selection is a process that functions at multiple, hierarchically structured spatial scales. Thus multi-scale analyses should be the basis for inferences about factors driving the habitat selection process. Vertebrate herbivores forage selectively on the basis of phytochemistry, but few studies have investigated the influence of selective foraging (i.e., fine-scale habitat selection) on habitat selection at larger scales. We tested the hypothesis that phytochemistry is integral to the habitat selection process for vertebrate herbivores. We predicted that habitats selected at three spatial scales would be characterized by higher nutrient concentrations and lower concentrations of plant secondary metabolites (PSMs) than unused habitats. We used the Greater Sage-Grouse (Centrocercus urophasianus), an avian herbivore with a seasonally specialized diet of sagebrush, to test our hypothesis. Sage-Grouse selected a habitat type (black sagebrush, Artemisia nova) with lower PSM concentrations than the alternative (Wyoming big sagebrush, A. tridentata wyomingensis). Within black sagebrush habitat, Sage-Grouse selected patches and individual plants within those patches that were higher in nutrient concentrations and lower in PSM concentrations than those not used. Our results provide the first evidence for multi-scale habitat selection by an avian herbivore on the basis of phytochemistry, and they suggest that phytochemistry may be a fundamental driver of habitat selection for vertebrate herbivores.

For herbivores, nutrient intake is limited by the relatively low nutritional quality of plants and high concentrations of potentially toxic defensive compounds (plant secondary metabolites, PSMs) produced by many plants. In response to phytochemical challenges, some herbivores selectively forage on plants with higher nutrient and lower PSM concentrations relative to other plants. Pygmy rabbits (Brachylagus idahoensis) are dietary specialists that feed on sagebrush (Artemisia spp.) and forage on specific plants more than others within a foraging patch. We predicted that the plants with evidence of heavy foraging (browsed plants) would be of higher dietary quality than plants that were not browsed (unbrowsed). We used model selection to determine which phytochemical variables best explained the difference between browsed and unbrowsed plants. Higher crude protein increased the odds that plants would be browsed by pygmy rabbits and the opposite was the case for certain PSMs. Additionally, because pygmy rabbits can occupy foraging patches (burrows) for consecutive years, their browsing may influence the nutritional and PSM constituents of plants at the burrows. In a post hoc analysis, we did not find a significant relationship between phytochemical concentrations, browse status and burrow occupancy length. We concluded that pygmy rabbits use nutritional and chemical cues while making foraging decisions.

Quantifying long‐term, low reproductive metrics indicative of an ungulate population's low nutritional status can help spur action to manage for moderate densities in contrast to unsustainable, high densities. We previously ranked the moose (Alces alces gigas) population described here as having the lowest nutritional status among 14 moose populations in Alaska, USA, primarily using reproductive indices (1996–2005) from moose with ages estimated by counting cementum annuli. Here, we detailed lifetime reproductive metrics from a subset of known‐age female moose initially radio‐collared at 9–10 months of age (7 cohorts; 1996–2002); we renewed radio‐collars as necessary. We radio‐tracked and circled these moose via aircraft at 24‐ or 48‐hour intervals to detect the presence of newborns during the 1998–2018 calving seasons, with meaningful annual sample sizes during 2000–2014. The number of snow‐free days in the year preceding parturition had a subtle positive effect on parturition probability, but we found no evidence for effects of the preceding February and March immobilization, cohort affiliation, or the preceding winter's snow cover on the probability of a female being parturient. The probability of twinning declined as the calving season progressed. Compared with moose production in populations with improved nutrition, our study population experienced low production primarily as a result of delayed maturation, occasional pauses in reproduction, and low twinning rates. Reproductive senescence occurred at normal advanced ages despite nutritional stress. We recorded a 28% parturition rate among 144 females 3 years of age (min. age of reproduction). Parturition rates were stable from 4 to 13 years of age (truex¯ = 77%), declined at 14 years of age, and peaked at 15 years of age. Females first twinned at 5 years of age (5%), and the twinning rate increased with age, peaking at 13 years of age (25%). Overall, 136 radio‐collared females with complete reproductive histories produced a mean of 5.3 calves/lifetime while being monitored a mean of 7.1 years at ages ≥3 years, although variability in individual production was high. Delaying or pausing reproduction increased the parturition rate at 4 and 5 years of age. However, females that delayed first reproduction produced fewer calves/lifetime on average compared with moose that first produced at 3 years of age. Virtually all moose regularly gave birth with occasional 1‐year pauses that acted to enhance production the subsequent year; the incidence of 2 consecutive nonparturient years was 2.8% (24/844). Moose experienced relatively stable, low nutritional status during 2000–2014 based upon low population‐wide twinning rates from annual aerial transect surveys (no telemetry) flown a few days after the median annual calving dates. Detailed understanding of low reproductive metrics encouraged empowered stakeholders to allow liberal harvests of female moose (2.0–4.4% of prehunt moose population numbers) and encouraged land managers to allow wildfires to burn 25% of ...

Conservation and management of habitat is central to the conservation of grouse. Identifying thresholds of biotic and abiotic risks that may reduce habitat quality is therefore a component of habitat management of grouse. We propose that dietary phytochemicals, specifically plant secondary metabolites (PSMs), represent an ecological risk to grouse, which are not often considered in the management of grouse. Most species of grouse consume PSMs, which have negative consequences at some concentration. Moreover, several studies provide evidence that the risks posed by PSMs will likely increase under projected climate change scenarios. We discuss potential risks of PSMs for grouse and propose theoretical models, which can be used to test current and future physiological, behavioural and ecological risks of PSMs. We propose that dose-response thresholds can be used to predict and monitor the synergistic risks of PSMs and climate change for grouse. We further suggest that identifying dose-response thresholds to PSMs is needed in the management of vertebrate herbivores in general.

The effects of hunting on wildlife populations vary dramatically, depending on the timing and magnitude of harvest, and population-specific states and vital rates. We examined the hypothesis that spatially and seasonally concentrated harvest decreases annual survival probabilities of willow ptarmigan (Lagopus lagopus). We estimated survival of radio-marked willow ptarmigan at 2 categories of sites: those where ptarmigan were easily accessible and heavily hunted and those that were remote and received little or no hunting pressure in Alaska, USA. We predicted that seasonal survival estimates during the willow ptarmigan hunting season would be lower in access corridors than at remote sites and that this would result in lower annual survival unless subsequent seasonal compensatory mortality occurred. Consistent with our prediction, annual survival was higher at remote sites (adult males: 0.50, 95% credible interval [CrI] = 0.42-0.57; adult females: 0.36, 95% CrI = 0.26-0.46; juveniles: 0.39, 95% CrI = 0.29-0.50) than at accessible sites (adult males: 0.36, 95% CrI = 0.26-0.46; adult females: 0.23, 95% CrI = 0.12-0.32; juveniles: 0.25, 95% CrI = 0.13-0.37) for all demographic groups. Concentrated harvest occurred in accessible sites during the hunting season (Aug-Mar). During the post-breeding season (Aug-Nov), when willow ptarmigan were near their breeding sites and the hunting season was open, survival was higher for those from remote sites than for those from accessible sites when accounting for demographic group (adult male, adult female, juvenile). In contrast, during winter (Dec-Mar), when willow ptarmigan had

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