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1. Estimating encounter location distributions from animal tracking data

   https://doi.org/10.1111/2041-210X.13597  

   Noonan, Michael J. ; Martinez‐Garcia, Ricardo ; Davis, Grace H. ; Crofoot, Margaret C. ; Kays, Roland ; Hirsch, Ben T. ; Caillaud, Damien ; Payne, Eric ; Sih, Andrew ; Sinn, David L. ; et al ( May 2021 , Methods in Ecology and Evolution)

   Ecologists have long been interested in linking individual behaviour with higher level processes. For motile species, this ‘upscaling’ is governed by how well any given movement strategy maximizes encounters with positive factors and minimizes encounters with negative factors. Despite the importance of encounter events for a broad range of ecological processes, encounter theory has not kept pace with developments in animal tracking or movement modelling. Furthermore, existing work has focused primarily on the relationship between animal movement and encounterrateswhile the relationship between individual movement and the spatiallocationsof encounter events in the environment has remained conspicuously understudied.

   Here, we bridge this gap by introducing a method for describing the long‐term encounter location probabilities for movement within home ranges, termed the conditional distribution of encounters (CDE). We then derive this distribution, as well as confidence intervals, implement its statistical estimator into open‐source software and demonstrate the broad ecological relevance of this distribution.

   We first use simulated data to show how our estimator provides asymptotically consistent estimates. We then demonstrate the general utility of this method for three simulation‐based scenarios that occur routinely in biological systems: (a) a population of individuals with home ranges that overlap with neighbours; (b) a pair of individuals with a hard territorial border between their home ranges; and (c) a predator with a large home range that encompassed the home ranges of multiple prey individuals. Using GPS data from white‐faced capuchinsCebus capucinus, tracked on Barro Colorado Island, Panama, and sleepy lizardsTiliqua rugosa,tracked in Bundey, South Australia, we then show how the CDE can be used to estimate the locations of territorial borders, identify key resources, quantify the potential for competitive or predatory interactions and/or identify any changes in behaviour that directly result from location‐specific encounter probability.

   The CDE enables researchers to better understand the dynamics of populations of interacting individuals. Notably, the general estimation framework developed in this work builds straightforwardly off of home range estimation and requires no specialized data collection protocols. This method is now openly available via thectmm Rpackage.

    

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2. Extreme site fidelity as an optimal strategy in an unpredictable and homogeneous environment

   https://doi.org/10.1111/1365-2435.13390  

   Gerber, Brian D. ; Hooten, Mevin B. ; Peck, Christopher P. ; Rice, Mindy B. ; Gammonley, James H. ; Apa, Anthony D. ; Davis, Amy J. ; Lemaître, ed., Jean‐François ( July 2019 , Functional Ecology)

   Animal site fidelity structures space use, population demography and ultimately gene flow. Understanding the adaptive selection for site fidelity patterns provides a mechanistic understanding to both spatial and population processes. This can be achieved by linking space use with environmental variability (spatial and temporal) and demographic parameters. However, rarely is the environmental context that drives the selection for site fidelity behaviour fully considered.

   We use ecological theory to understand whether the spatial and temporal variability in breeding site quality can explain the site fidelity behaviour and demographic patterns of Gunnison sage‐grouse (Centrocercus minimus). We examined female site fidelity patterns across multiple spatial scales: proximity of consecutive year nest locations, space‐use overlap within and across the breeding and brooding seasons, and fidelity to a breeding patch. We also examined the spatial and temporal variability in nest, chick, juvenile and adult survival.

   We found Gunnison sage‐grouse to be site faithful to their breeding patch, area of use within the patch and generally where they nest, suggesting an “Always Stay” site fidelity strategy. This is an optimal evolutionary strategy when site quality is unpredictable. Further, we found limited spatial variability in survival within age groups, suggesting little demographic benefit to moving among patches. We suggest Gunnison sage‐grouse site fidelity is driven by the unpredictability of predation in a relatively homogeneous environment, the lack of benefits and likely costs to moving across landscape patches and leaving known lek and breeding/brooding areas.

   Space use and demography are commonly studied separately. More so, site fidelity patterns are rarely framed in the context of ecological theory, beyond questions related to the win‐stay:lose‐switch rule. To move beyond describing patterns and understand the adaptive selection driving species movements and their demographic consequences require integrating movement, demography and environmental variability in a synthetic framework.

   Site fidelity theory provides a coherent framework to simultaneously investigate the spatial and population ecology of animal populations. Using it to frame ecological questions will lead to a more mechanistic understanding of animal movement, spatial population structuring and meta‐population dynamics.

   A freePlain Language Summarycan be found within the Supporting Information of this article.

    

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3. Predation risk drives long‐term shifts in migratory behaviour and demography in a large herbivore population

   https://doi.org/10.1111/1365-2656.14022  

   Williams, S. ; Hebblewhite, M. ; Martin, H. ; Meyer, C. ; Whittington, J. ; Killeen, J. ; Berg, J. ; MacAulay, K. ; Smolko, P. ; Merrill, E. H. ( November 2023 , Journal of Animal Ecology)

   Migration is an adaptive life‐history strategy across taxa that helps individuals maximise fitness by obtaining forage and avoiding predation risk. The mechanisms driving migratory changes are poorly understood, and links between migratory behaviour, space use, and demographic consequences are rare.

   Here, we use a nearly 20‐year record of individual‐based monitoring of a large herbivore, elk (Cervus canadensis) to test hypotheses for changing patterns of migration in and adjacent to a large protected area in Banff National Park (BNP), Canada.

   We test whether bottom‐up (forage quality) or top‐down (predation risk) factors explained trends in (i) the proportion of individuals using 5 different migratory tactics, (ii) differences in survival rates of migratory tactics during migration and whilst on summer ranges, (iii) cause‐specific mortality by wolves and grizzly bears, and (iv) population abundance.

   We found dramatic shifts in migration consistent with behavioural plasticity in individual choice of annual migratory routes. Shifts were inconsistent with exposure to the bottom‐up benefits of migration. Instead, exposure to landscape gradients in predation risk caused by exploitation outside the protected area drove migratory shifts. Carnivore exploitation outside the protected area led to higher survival rates for female elk remaining resident or migrating outside the protected area.

   Cause‐specific mortality aligned with exposure to predation risk along migratory routes and summer ranges. Wolf predation risk was higher on migratory routes than summer ranges of montane‐migrant tactics, but wolf predation risk traded‐off with heightened risk from grizzly bears on summer ranges. A novel eastern migrant tactic emerged following a large forest fire that enhanced forage in an area with lower predation risk outside of the protected area.

   The changes in migratory behaviour translated to population abundance, where abundance of the montane‐migratory tactics declined over time. The presence of diverse migratory life histories maintained a higher total population abundance than would have been the case with only one migratory tactic in the population.

   Our study demonstrates the complex ways in which migratory populations change over time through behavioural plasticity and associated demographic consequences because of individuals balancing predation risk and forage trade‐offs.

    

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4. Stable isotopes reveal limited Eltonian niche conservatism across carnivore populations

   https://doi.org/10.1111/1365-2435.13266  

   Manlick, Philip J. ; Petersen, Shelby M. ; Moriarty, Katie M. ; Pauli, Jonathan N. ; McArthur, ed., Clare ( January 2019 , Functional Ecology)

   Niche conservatism—the retention of ecological traits across space and time—is an emerging topic of interest because it can predict responses to global change. The conservation of Grinnellian niche characteristics, like species‐habitat associations, has received widespread attention, but the conservation of Eltonian traits such as consumer–resource interactions remains poorly understood.

   The inability to quantify Eltonian niches through space and time has historically limited the assessment of Eltonian niche conservatism and the dynamics of foraging across populations. Consequently, the relative influence of endogenous factors like phylogeny versus exogenous features like environmental context has rarely been addressed.

   We tested Eltonian niche conservatism using a paired design to compare foraging among four populations of American martensMartes americanaand Pacific martensMartes caurina, morphologically and ecologically similar sister taxa that are allopatrically distributed throughout western North America. We developed a three‐stage isotopic framework and then quantified dietary niche overlap between the sister species and paired island‐mainland sites to assess the relative influence of endogenous (i.e., species) versus exogenous (i.e., environment) factors on Eltonian niches. First, we calculated pairwise dietary overlap in scaled δ‐space using standard ellipses. We then estimated proportional diets (“p‐space”) for individuals using isotopic mixing models and developed a novel utilization distribution overlap approach to quantify proportional dietary overlap. Lastly, we estimated population‐level proportional diets and quantified the differential use of functional prey groups across sites.

   We detected no pairwise overlap of dietary niches in δ‐space, and distributions of individual diets in p‐space revealed little overlap in core diets across populations. All pairwise comparisons of individuals revealed significant differences in diet, and population‐level comparisons detected contrasting use of functional prey groups.

   We developed a multi‐faceted isotopic framework to quantify Eltonian niches and found limited evidence of Eltonian niche conservatism across carnivore populations. Our findings are consistent with the growing recognition of dietary plasticity in consumers and suggest that consumer–resource dynamics are largely driven by exogenous environmental factors like land cover and community composition. These results illustrate the context‐dependent nature of foraging and indicate consumer functionality can be dynamic.

   Aplain language summaryis available for this article.

    

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5. Longitudinal dynamics and behavioural correlates of telomeres in male wire‐tailed manakins

   https://doi.org/10.1111/1365-2435.13715  

   Vernasco, Ben J. ; Dakin, Roslyn ; Majer, Ariana D. ; Haussmann, Mark F. ; Brandt Ryder, T. ; Moore, Ignacio T. ; Angelier, ed., Frédéric ( December 2020 , Functional Ecology)

   Building on the predictions of state‐dependent life‐history theory, telomeres are hypothesized to either correlate with or function as an adaptive, proximate mediator of an individual's behaviour and life‐history strategy. To further understand the relationship between telomeres, behaviour and life‐history strategies, we measured male behaviour, telomere lengths and telomere dynamics in a free‐living population of known‐age, male wire‐tailed manakinsPipra filicauda.

   Male wire‐tailed manakins perform coordinated displays with other males at leks and these displays form the basis of long‐term coalition partnerships. Males exhibit consistent individual differences in the number of social partners within their social network and the frequency of social interactions. Male sociality is also positively correlated with both social rise and reproductive success.

   We measured male behaviour using a telemetry‐based, proximity datalogging system and blood telomere lengths were quantified using qPCR. We examined the relationships between telomere length, telomere dynamics, social status, and male behaviour. We also quantified the repeatability of telomere lengths, examined age‐related changes in telomere length, and tested for instances of telomere elongation that exceed residual error in telomere length.

   Telomere length was found to be highly repeatable. More social males exhibited shorter telomeres and higher rates of telomere attrition. Telomeres did not significantly vary with age within or between individuals in either of the male social classes. Two out of 25 individuals exhibited patterns telomere elongation that exceeded residual error in telomere measurements.

   Here we show that telomeres consistently vary between male wire‐tailed manakins and these differences are related to variation in male social behaviour. In this relatively long‐lived species, telomeres appear to be flexible traits that can increase or decrease in length. Overall, this study provides observational support for the hypothesis that telomeres act as a molecular marker that relates to behaviour in a state‐dependent manner. We also provide insight into the molecular consequences of individual variation in male social behaviour.

   A freePlain Language Summarycan be found within the Supporting Information of this article.

    

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