Search

Dryad Logo
Data from: Quantifying individual heterogeneity and its influence on life-history trajectories: different methods for different questions and contexts
Hamel, Sandra; Gaillard, Jean-Michel; Douhard, Mathieu; Festa-Bianchet, Marco; Pelletier, Fanie; Yoccoz, Nigel G. — 2017-09-21 Heterogeneity among individuals influences the life-history trajectories we observe at the population level because viability selection, selective immigration and emigration processes, and ontogeny change the proportion of individuals with specific trait values with increasing age. Here, we review the two main approaches that have been proposed to account for these processes in life-history trajectories, contrasting how they quantify ontogeny and selection, and proposing ways to overcome some of their limitations. Nearly all existing approaches to model individual heterogeneity assume either a single normal distribution or a priori known groups of individuals. Ontogenetic processes, however, can vary across individuals through variation in life-history tactics. We show the usefulness of describing ontogenetic processes by modelling trajectories with a mixture model that focuses on heterogeneity in life-history tactics. Additionally, most methods examine individual heterogeneity in a single trait, ignoring potential correlations among multiple traits caused by latent common sources of individual heterogeneity. We illustrate the value of using a joint modelling approach to assess the presence of a shared latent correlation and its influence on life-history trajectories. We contrast the strengths and limitations of different methods for different research questions, and we exemplify the differences among methods using empirical data from long-term studies of ungulates.
Dryad Logo
Merging indigenous and scientific knowledge links climate with the growth of a large migratory caribou population
Gagnon, Catherine A.; Hamel, Sandra; Russell, Don E.; Powell, Todd; Andre, James; Svoboda, Michael Y.; Berteaux, Dominique — 2019-12-23 <p>1. Climate change in the Arctic is two to three times faster than anywhere else in the world. It is therefore crucial to understand the effects of weather on keystone arctic species, particularly those such as caribou (Rangifer tarandus) that sustain northern communities. Bridging long-term scientific and indigenous knowledge offers a promising path to achieve this goal, as both types of knowledge may complement one another. 2. We assessed the influence of environmental variables on the spring and fall body condition of caribou from the Porcupine Caribou Herd. This herd ranges in the Yukon and Northwest Territories (Canada) and Alaska (USA), and is the only large North American herd that has not declined since the 2000s. Using observations recorded through an indigenous community-based monitoring program between 2000-2010, we analyzed temporal trends in caribou condition and quantified the effects of weather and critical weather-dependent variables (insect harassment and vegetation growth), on spring (n = 617 individuals) and fall (n =711) caribou condition. 3. Both spring and fall body condition improved from 2000 to 2010, despite a continuous population increase of ca. 3.6% per year. Spring and fall caribou condition were influenced by weather on the winter and spring ranges, particularly snow conditions and spring temperatures. Both snow conditions and spring temperatures improved during our study period, likely contributing to the observed caribou population increase. Insect harassment during the previous summer and the frequency of icing events also influenced caribou condition. 4. Synthesis and applications. Our study first shows how untangling the relative influences of seasonal weather variables allows a much better understanding of variation in seasonal body condition in Rangifer populations. Second, it indicates that a large migratory caribou population can grow and improve body condition in a global context of caribou decline and climate warming, thereby warning against generalizations about the influence of climate on all Rangifer populations. Finally, it testifies how data from indigenous community-based monitoring on a large spatiotemporal scale can remarkably improve ecological understanding of wildlife sustaining human communities. We recommend that management practices promote indigenous community-based ecological monitoring whenever feasible.</p>
Dryad Logo
Climate, caribou and human needs linked by analysis of Indigenous and scientific knowledge
Gagnon, Catherine A.; Hamel, Sandra; Russell, Don E.; Andre, James; Buckle, Annie; Haogak, David; Pascal, Jessi; Schafer, Esau; Powell, Todd; Svoboda, Michael Y.; Berteaux, Dominique — 2023-01-24 <p><span lang="EN-US">Migratory tundra caribou are ecologically and culturally critical in the circumpolar North. However, they are declining almost everywhere in North America, likely due to natural variation exacerbated by climate change and human activities. Yet, the interconnectedness between climate, caribou, and human well-being has received little attention. To address this gap, we bridged</span><span lang="EN-US"> </span><span lang="EN">Indigenous and scientific knowledge in a single model, using as an example the Porcupine caribou herd social-ecological system. Our analysis, involving </span><span lang="EN-US">688 (fall season) and 616 (spring season) interviews conducted over nine years with 405 (fall season) and 390 (spring season) Indigenous hunters </span><span lang="EN-CA">from nine communities, demonstrates that </span><span lang="EN-US">environmental conditions, </span><span lang="EN-CA">large-scale temporal changes associated with caribou demography, and cultural practices </span><span lang="EN-US">affect hunters’ capacity to meet their needs in caribou. </span><span lang="EN">Our quantitative approach </span><span lang="EN-US">bolsters our understanding of the complex relationships between ecosystems and human welfare in environments exposed to rapid climate change and shows </span><span lang="EN">the benefits of long-term participatory research methods implemented by Indigenous and scientific partners.</span></p> https://creativecommons.org/publicdomain/zero/1.0/
Dryad Logo
Coping with seasonality: dynamics of adult body mass and survival in an alpine hibernator
Carrier, Béatrice; Hamel, Sandra; Garel, Mathieu; Côté, Steeve — 2022-03-03 <p><span style="font-size:12.000000pt;font-family:'TimesNewRomanPSMT';">Alpine mammals are highly vulnerable to current and projected climate change because they are confined to a certain elevation range. Physiological and behavioural adaptations in burrowing species, such as finding shelter in burrows when the summer conditions are unfavorable and hibernating in winter during the stressful period of resource shortage, could partly buffer the negative impacts of these forecasted changes. We studied the links between environmental factors and annual variations in adult mass and survival over 14 years in hoary marmots. We hypothesized that annual variation in seasonal environmental factors determines individual mass and survival through direct effects on food quality and availability, expecting greater survival when marmots reach higher mass before hibernation. We found that harsh winters decreased mass at emergence from hibernation by 47% compared with mild winters. Nonetheless, adult marmots had a greater mass gain in summers following harsh winters and reached a similar mass at the end of the summer compared with summers following mild winters. This result suggests individuals can adopt a resource allocation strategy that allows maximizing summer mass gain to survive hibernation. Earlier springs also increased summer mass gain by 15 g/day, and tended to increase apparent adult survival by 23%, compared with late springs. While these findings suggest a warming climate could have positive effects on summer mass gain and survival, survival also tended to decrease by 24% in summers with more precipitation. This result suggests the forecasted changes in precipitation extremes could also trigger considerable</span><span style="font-size:11.000000pt;font-family:'Calibri';"> </span><span style="font-size:12.000000pt;font-family:'TimesNewRomanPSMT';">negative effects on the demography of burrowing species in the long term. Our study shows</span><span style="font-size:11.000000pt;font-family:'Calibri';"> </span><span style="font-size:12.000000pt;font-family:'TimesNewRomanPSMT';">that, although burrowing and hibernating behaviours could buffer responses to</span><span style="font-size:11.000000pt;font-family:'Calibri';"> </span><span style="font-size:12.000000pt;font-family:'TimesNewRomanPSMT';">environmental changes, these behaviours are not an indefectible shield against climate</span><span style="font-size:11.000000pt;font-family:'Calibri';"> </span><span style="font-size:12.000000pt;font-family:'TimesNewRomanPSMT';">change.</span></p>
Dryad Logo
Predation risk and mountain goat reproduction: Evidence for stress-induced breeding suppression in a wild ungulate
Dryad
Dulude-de Broin, Frédéric; Hamel, Sandra; Mastromonaco, Gabriela F.; Côté, Steeve D. — 2020-02-03 <p>Abstract</p> <p>1. Non-consumptive effects of predation can strongly impact reproduction and demography of prey species. Still, the underlying mechanisms that drive non-consumptive effects are not fully understood, and the circumstances under which chronic physiological stress may mediate these effects remain unclear.</p> <p>2. Benefiting from over 23 years of environmental, physiological and demographic data, we tested the hypothesis that predation risk may impair reproduction of mountain goats through chronic elevation of physiological stress. We conducted path analyses to assess the relationships between predation risk, faecal glucocorticoid metabolites and hair cortisol concentration, and reproduction, while taking into account the potential effects of age class, sex, body mass, season, and within individual variation in glucocorticoid concentration.</p> <p>3. Predation risk had a direct positive effect on the average annual faecal glucocorticoid concentration in the population, which in turn negatively affected the proportion of reproductive females. The same pattern was observed with hair cortisol concentration, but these results were inconclusive potentially due to methodological challenges in estimating annual average of hair cortisol at the population level.</p> <p>4. Our study presents one of the first robust evidence that stress-mediated breeding suppression can occur in a wild ungulate following increased predation risk, thereby providing a major insight on the mechanisms underlying non-consumptive effects of predation in wild mammals.</p>

Map search instructions

1.Turn on the map filter by clicking the “Limit by map area” toggle.
2.Move the map to display your area of interest. Holding the shift key and clicking to draw a box allows for zooming in on a specific area. Search results change as the map moves.
3.Access a record by clicking on an item in the search results or by clicking on a location pin and the linked record title.
Note: Clusters are intended to provide a visual preview of data location. Because there is a maximum of 50 records displayed on the map, they may not be a completely accurate reflection of the total number of search results.

(Author: Hamel, Sandra)

Limit by:

Clear all

to