Wildfire is the most important disturbance regime in North American boreal forest communities, driving forest composition and structure across this region. Recent climate models predict that increasing fire intensity and frequency will result in a shift from a largely coniferous forest to one with a greater dominance by deciduous species. We investigated how an iconic predator of the boreal system, the Canada lynx (Lynx canadensis), moves through a range of burn scars (2-78 years old) and if these movements reflect habitat selection of their main prey, the snowshoe hare (Lepus americanus). Using GPS collars at 4-h fix rates, we fitted integrated step selection models to lynx movements across an 80-year post-fire chronosequence to assess habitat selection in both deciduous and coniferous forests. We predicted that lynx would primarily select intermediately-aged spruce, but young deciduous stands, mirroring the habitat selection of snowshoe hares. We found, however, that lynx habitat selection peaked at intermediately aged stands in both forest types. We hypothesize that this difference is driven by selection for habitats that maximize capture probability as opposed to simply representing the highest hare density. This idea is supported by observed seasonal changes in peak selection in deciduous stands, with selection for younger stands in winter, when leaf loss reduces cover. There was no seasonal change in coniferous stands as they experience little change in cover across seasons. Together these results show that lynx can be resilient to short-term shifts toward intermediate-aged stands. However, these benefits will likely diminish in the longer term as the decrease in fire return interval may reduce the prevalence of intermediate-age stands.

Climate warming can cause arthropods to express plastic and/or evolved changes in morphology. Previous studies have demonstrated that body sizes of Arctic butterflies are influenced by the temperatures experienced as larvae. To investigate whether this was occurring among Alaskan butterflies, we analyzed temporal trends in the wing sizes of three Holarctic species, Colias hecla, Boloria chariclea, and Boloria freija, using museum specimens collected in Arctic tundra regions of Alaska between 1971 and 1995. Wing length was compared to accumulated growing degree days (GDD) during both the spring of the year collected and the previous year’s summer during the normal period of larval development. We used mixed-effects models to test if spring and summer temperatures affected adult morphology. Results show that for every 1°C increase in average seasonal temperature, wingspans decreased between 0.7 millimeters and 5 millimeters, with B. freija the most strongly affected. Our results suggest that the morphological sensitivity of Arctic butterflies to warming is the outcome of interactions between life-history traits and regional climate, with all species sensitive to warming the summer before the flight year as well as warming the spring of the flight year. B. freija, which overwinters as late instar larvae that do not feed before pupation the following spring, was particularly strongly affected by summer warming.

An individual’s size in early stages of life may be an important source of individual variation in lifetime reproductive performance, as size effects on ontogenetic development can have cascading physiological and behavioral consequences throughout life. Here, we explored how natal size influences subsequent reproductive performance in grey seals (Halichoerus grypus) using repeated encounter and reproductive data on a marked sample of 363 females that were measured for length at ~4 weeks of age and eventually recruited to the Sable Island breeding colony. Two reproductive traits were considered: provisioning performance (mass of weaned offspring), modeled using linear mixed effects models; and reproductive frequency (rate at which a female returns to breed), modeled using mixed-effects multistate mark-recapture models. Mothers with the longest natal lengths produced pups 8 kg heavier and were 20% more likely to breed in a given year than mothers with the shortest lengths. Correlation in body lengths between natal and adult life stages, however, is weak: longer pups do not grow to be longer than average adults. Thus covariation between natal length and future reproductive performance appears to be a carry-over effect, where the size advantages afforded in early juvenile stages may allow enhanced long-term performance in adulthood.

1. Recent empirical studies have quantified correlation between survival and recovery by estimating these parameters as correlated random effects with Bayesian multivariate mixed effects models fit to tag-recovery data. In these applications, increasingly negative correlation between survival and recovery indicates increasingly additive harvest mortality. The power of mixed effects models to detect non-zero correlations has rarely been evaluated and these few studies have not focused on a common data type in the form of tag recoveries. 2. We assessed the power of multivariate mixed effects models to estimate negative correlation between annual survival and recovery. Using three priors for multivariate normal distributions, we fit mixed effects models to a mallard (Anas platyrhychos) tag-recovery dataset and to simulated data with sample sizes corresponding to different levels of monitoring intensity. We also demonstrate a method of calculating effective sample size for capture-recapture data. 3) Different priors lead to different inference about additive harvest when we fit our models to the mallard data. Our power analysis of simulated data indicated most prior distribution and sample size combinations resulted in correlation estimates with substantial bias and imprecision. Many correlation estimates spanned the available parameter space (–1,1) and were biased towards zero. Only one prior combined with our most intensive monitoring scenario allowed our models to consistently recover negative correlation without bias. Underestimating the magnitude of correlation coincided with overestimating the variability of annual survival, but not annual recovery. 4) The inadequacy of prior distributions and sample size combinations typically assumed adequate for robust inference represents a concern in the application of Bayesian mixed effects models for the purpose of informing harvest management. Our analysis approach provides a means for examining prior influence and sample size on mixed-effects models fit to capture-recapture data while emphasizing transferability of results between empirical and simulation studies.