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Demographic responses of threatened woodland caribou to annual variation in meteorological and phenological conditions
Craig DeMars
Climate change is expected to increasingly impact populations of woodland caribou and much focus has been placed on how a warming climate has facilitated the northward expansion of apparent competitors (e.g., white-tailed deer) and novel predators (e.g., coyotes). Climate change, however, may also exert effects on caribou populations that are not mediated by predation. Here, we used data from 21 populations in western Canada to assess the demographic response of woodland caribou to annual variation in a suite of meteorological and phenological metrics. Recent research on other ungulate populations suggests that climatic variation may have minimal direct impact on low-density populations such as woodland caribou because per-capita resources may remain sufficient even in “bad” years. We tested this prediction by relating climatic variation to juvenile recruitment and adult female survival, two vital rates with high influence on caribou demography. Contrary to the low-density/low-impact prediction, we recorded relatively strong effects in both rates, though explained variation across all demographic models was low, suggesting that factors other than adverse climatic conditions had a greater influence on caribou demography during our monitoring period (1994–2015). In general, juvenile recruitment was more affected by variation in growing season conditions in the year prior to birth, responding positively to longer, more productive growing seasons and negatively to those that were warmer and drier. Adult female survival, in contrast, was more affected by winter conditions, responding negatively to colder and more variable winters during the monitoring year and up to three years prior. Given these unexpected results, we discuss alternative explanations as to why these woodland caribou populations did not conform to the low-density/low-impact prediction. The demographic effects we recorded have direct implications for caribou conservation, highlighting the increased relevance of recovery actions when adverse climatic conditions are more likely to negatively affect caribou demography.
Wild forest reindeer returns to its historical range – first releases from breeding enclosures in a Finnish reintroduction project
Sakari Mykrä-Pohja, Milla Niemi & Pekka Kilpeläinen
The Finnish wild forest reindeer Rangifer tarandus fennicus occurred throughout Finland still in the 17th century. It was gradually hunted to nationwide extinction by the 1920s but started to re-establish in the 1950s. Nowadays it occurs in Finland and the Western parts of Russia. The total world population is about 4000 individuals. The overall trend has been negative. In 2016, Finland and the EU started a seven-year conservation project WildForestReindeerLIFE. One of the actions is a new reintroduction into two areas in the subspecies’ historical range. This will be carried out through captive breeding and soft releases. Founders both from zoos and from the wild have been moved into two enclosures since autumn 2017. The first calves were born in May 2018. During the autumn 2019, we released 17 individuals of varying age and origin. Eight of them were born in the enclosures. Based on the GPS-tracking, camera traps and field observations, the released animals have mainly stayed close (< 1 km) to the enclosures. In one site, young males made two short-term explorative trips about 20 km distance from the enclosure. In the other site, adult zoo-born female with her calf explored the landscape for some days before settling down near the enclosure. Especially young zoo-born males have been tamer than expected. Near the breeding enclosures, their flight distance could be as short as a few meters, whereas away from the enclosure it appears to be longer. We’ll follow the behavior of released animals in the coming years.
Seasonal patterns of mortality for boreal caribou in the southern Northwest Territories
Allicia Kelly
Seasonality is an important component in shaping the dynamics that influence ecosystems, including mortality. We investigated temporal patterns of mortality in the boreal ecotype of woodland caribou (Rangifer tarandus caribou) in the southern Northwest Territories. Survival data were collected from 423 adult female caribou tracked by radio collars between 2003 and 2018, 172 of which died during the study from predation (106), non-predation (i.e., starvation), (15), harvest (11), accidents (3), or unknown causes (37). We used generalized additive mixed models to evaluate temporal patterns of mortality across the year. We found that probability of mortality followed a trimodal pattern with three peaks, one during pre-calving, one in mid-summer, and a smaller peak in late autumn, with a 6-fold difference in mortality risk between the lowest and highest periods of the year. Mortality risk was higher overall from late spring (pre-calving) to mid-summer than it was from late summer until the end of winter, despite decreasing for about 6 weeks post-calving. We explored potential factors contributing to mortality risk at different times of the year.
Recovery actions for woodland caribou: Predicting and testing the efficacy of habitat restoration
Melanie Dickie
Anthropogenic habitat alteration via land conversion directly reduces habitat availability and disrupts ecological processes. Western Canada’s boreal forest has undergone rapid landscape change as a result of human expansion and resource development. Resulting habitat loss and alteration is hypothesized to be the ultimate cause of boreal woodland caribou declines, one of the most high-profile species at risk in Canada’s boreal forest. While a variety of recovery actions are being employed to recover caribou populations, habitat restoration has been identified as a necessary and important management tool. Restoration is required to restore ecological processes to address the ultimate cause of caribou declines, habitat loss and alteration, as well as the proximate cause, unsustainable predation rates as a result of human-mediated changes to predator-prey dynamics. While the importance of conducting habitat restoration is clear, the effectiveness of restoration treatments is not well understood. Given the spatial extent of these disturbances and the cost of habitat restoration treatments, it behooves researchers and managers to predict and monitor the effectiveness of restoration treatments. Here we explore the predicted success of restoration for recovering caribou populations using predator-prey simulations, and empirically test the effectiveness of restoration treatments. We present a multiple-lines-of-evidence approach for understanding caribou, moose, wolf and bear response to habitat restoration treatments aimed to restore the functional and ecological processes in northeastern Alberta. Understanding behavioral and population-level responses to restoration treatments is necessary to ensure successful recovery and adaptive management.
Indigenizing Science
Morgan Hrycak
Environmental and biological sciences are often siloed from examining Indigenous-related concerns, which can compromise Indigenous rights. Learning about braiding Indigenous ways of knowing and Western Science can be an invaluable way to strengthen relationships and facilitate project support (e.g. on caribou conservation projects). This presentation series will provide perspectives on Indigenous Knowledge and bioethics, decolonizing genomic science, and harvesting rights.
- Part 1: Perspectives on Bioethics and Research Implications will focus on examples of Indigenous Knowledge, bioethical considerations of scientific research, governance of Indigenous community data, and science communication principles. By knowing these topics, Western scientists can better understand Indigenous concerns on-the-ground. For more information about references used in this presentation, please see the References for Indigenizing Science-Bioethics and Research Implications.
- Part 2: Chronic Wasting Disease will focus on the decolonization of genomic science, harvesting rights, and the science behind prion diseases. Chronic wasting disease is a fatal nervous system disorder affecting cervids, such as deer and moose. However, Canada’s caribou populations are considered at high risk for this disease. Due to Indigenous connections to the land, understanding chronic wasting disease from Indigenous perspectives can help in understanding and managing the spread of this disease.
Movement, energetics, and demography of Norwegian reindeer
Rebecca Viejou
In Norway, reindeer are fragmented into roughly 23 wild populations and 76 semi-domestic herding districts. The variation in forage quantity, migratory behaviour, and demography across these populations provide an opportunity to examine the causes and consequences of migration. In this presentation, I will summarize the results of three studies with the following research goals:
- Use forage biomass, digestibility and energy data, and previously defined landscape models of vegetation and geoclimatic variation to develop maps of summer and winter digestible energy across Norwegian reindeer ranges.
- Use GPS locations of 304 wild reindeer trajectories to test a series of predictions that follow from the forage quantity hypothesis for migration.
- Use 15 years of population data for 43 semi-domestic herding districts to test the basic assumption that migrations provide a demographic benefit.
The results of this work suggest that access to winter ranges with high digestible energy may be an important driver of the large-scale seasonal movements of reindeer, with measurable demographic consequences.
Science to inform policy: Linking population dynamics to habitat for threatened species in Canada
Cheryl Johnson
You can find the published manuscript for this presentation here.
Boreal forests provide numerous ecological services, including the ability to store large amounts of carbon, and are of significance to global biodiversity. Increases in industrial activities in boreal landscapes since the mid‐20th century have added to concerns over biodiversity loss and climate change. Boreal forests are home to dwindling populations of boreal caribou Rangifer tarandus caribou in Canada, a species at risk that requires large, undisturbed landscapes for persistence. In 2012, the Canadian government defined critical habitat for boreal caribou by relating calf recruitment to disturbances. Some have questioned whether the recruitment relationship can be extrapolated beyond the environmental conditions represented in the analysis.
We examined the effects of human disturbances and fire (alone and in combination) on variation in recruitment and adult female survival using data from 58 study areas in Canada. Top models were used in aspatial scenarios of landscape change to evaluate the efficacy of the critical habitat definition in achieving the recovery objectives for boreal caribou in two contrasting landscapes: Little Smoky, dominated by high levels of human disturbances, and the northern boreal shield of Saskatchewan (SK1), dominated by fire.
The top recruitment model suggested the negative effect of fire was three to four times smaller than human disturbances. The top adult female survival model included human disturbances only. These results re‐affirm that human disturbances are the primary factor contributing to boreal caribou declines.
Our aspatial scenarios suggested that undisturbed habitat would have to increase to ≥68% for Little Smoky to maintain a self‐sustaining population of boreal caribou with some degree of certainty. In contrast, the SK1 population was self‐sustaining with 40% undisturbed habitat when fire disturbance predominates, but could become vulnerable with increases in human disturbances (8%–9%).
Policy implications. Boreal caribou are listed as threatened under Canada’s Species at Risk Act. Our results suggest that the 65% undisturbed critical habitat designation in Canada’s boreal caribou Recovery Strategy may serve as a reasonable proxy for achieving self‐sustaining populations of boreal caribou in landscapes dominated by human disturbances. However, some populations may be less or more vulnerable, as illustrated by the scenarios in a landscape dominated by fire (SK1). Continued population monitoring will be essential to assessing the effectiveness of land management strategies developed for boreal caribou recovery, especially with climate change.
Let it grow? Moose response to habitat disturbance in caribou ranges
Laura Finnegan
Boreal caribou winter range in the Central Mackenzie Valley, NWT: What is it, where is it, and how can we manage for it proactively?
Jesse Tigner
Using forecasting tools to inform recovery actions for woodland caribou: a comparison of the tested and the untested
Mariana Nagy-Reis & Chris Johnson
A recurring challenge for resource managers and decision makers is quantifying the trade-offs associated with alternative recovery actions for species-at-risk. Provincial and federal agencies have either employed or planned to employ recovery actions to halt precipitous declines in woodland caribou populations. Nonetheless, testing the efficacy of such actions on the ground is difficult due to insufficient time and limited replication. Here we showcase two modeling approaches developed independently to quantify trade-offs associated with tested and untested recovery actions for woodland caribou, including Linear Feature Restoration/Deactivation, Maternal Penning, Predator Exclosure, Conservation Breeding, Wolf Reduction, and Moose Reduction. More specifically, we compare the estimated costs and demographic benefits associated with each action and discuss knowledge gaps, limitations of tested recovery actions, and uncertainties associated with untested actions. The two case studies demonstrate the utility of forecasting tools to inform recovery actions and guide decisions by explicitly estimating trade-offs associated with actions, which ultimately can be used in structured-decision making approaches to help bridge the gap between management and science.
Application of integrated population models for conservation of at-risk caribou populations
Mark Hebblewhite
Population monitoring can take many different forms, and monitoring elusive and endangered species frequently involves a variety of sparse data from different sources. Small populations are often hard to sample precisely and without bias, so when estimates of vital rates like survival or recruitment point to conflicting population trends, it can be hard to determine which is more correct. Integrated Population Models (IPM) provide an applied statistical framework to reconcile different types of data together in a unified population model. IPM’s help reconcile discrepancies between different data types, missed years, and often lead to increased precision in trend estimates as well. IPM models can also be used to evaluate efficiency of recovery actions. Finally, the process of developing IPM’s also often improves the science of database management, sampling designs, and highlights challenging assumptions and ways of improving efficiency. In this webinar, we highlight three case studies of the application of IPM modeling to the question of trend monitoring of threatened or endangered caribou (Rangifer tarandus caribou) in Alberta, Jasper National Park, and the Central Group of Southern Woodland caribou. All three case studies brought together dozens of biologists, managers, data scientists, and modelers to developed customized Bayesian IPM models to aid trend estimation, and reconcile differences amongst conflicting trends from different data types. In Alberta, we developed a R Shiny App (Eacker et al. Wildlife Society Bulletin) to aid Alberta caribou biologists in the data management processes to efficiently estimate caribou trends across the province using the Hatter-Bergerud R-M Equation. In Jasper National Park, we worked with Park Biologists to integrate data from data from juvenile recruitment surveys, telemetry-based survival, aerial population counts/mark-resight data, and non-invasive capture-recapture DNA data to better understand population status and trend of the South Jasper Local Population Unit. Finally, in the Central Group, we worked with local biologists and First Nations to develop IPMs for the Quintette and Klinse Za that helped test for efficacy of management and recovery actions. IPMs provide a useful, flexible tool for biologists to monitor populations and provides a valuable example of the benefits of integrated population modeling approaches for endangered species management and recovery.
30 years of change: Linking habitat, predators and alternative prey to explain recruitment variations of an endangered caribou population
Martin-Hugues St-Laurent
Woodland caribou populations suffer from habitat modifications and most are currently in decline. It has been suggested that the conversion of old-growth coniferous forests into early-seral stages has increased cervid abundances, which have, in turn, stimulated a numerical response of predator populations, ultimately threatening caribou populations via a habitat-mediated apparent competition mechanism. Using a long-term dataset (1984-2012) of the Atlantic-Gaspésie caribou population, we quantified changes in habitat structure and in interspecific interactions triggered by apparent competition between moose and caribou via the responses of two incidental predators, coyote and black bear. We also documented calf recruitment rates and analysed temporal trends in this vital rate. Our results show that the loss of high-quality habitat for caribou in the area surrounding the Gaspésie National Park varied from -30 to -56%, while the gain of preferential habitat for predators varied from +3 to +66%, mainly driven by logging. Inter-annual variations in autumn calf recruitment were mostly affected by the proxy of regional abundance of coyotes, which was highly correlated with moose and black bear proxies of abundance. The increase in coyote abundance in the Gaspésie Peninsula following anthropogenic habitat modifications seems to be the main mechanism responsible for the current decline in this caribou population. Our analyses revealed some impacts of habitat alteration and the complexity of the resulting trophic cascades. Moreover, we pointed out that an 802-km2 protected area is not enough to prevent the decline of a caribou herd if we drastically increase the disturbance level in the surrounding matrix.
Density-dependent social behaviour: from individuals in groups to populations
Quinn Webber
Density dependence is a key population ecology parameter that can influence variation in life-history, morphology, and behaviour. Caribou population density is known to fluctuate through space and time. In Newfoundland, caribou occupy approximately 14 distinct sub-populations, and since the late 1990s, nearly all of these sub-populations have experienced declines in population size. In this talk, we outline three potential behavioural outcomes of the drastic change in population density observed for Newfoundland caribou. First, based on a thirty-year dataset of caribou group size observations collected during aerial surveys, we found that groups varied in size both spatially and temporally. In contrast to our expectation, groups decreased in size as a function of increasing population density, while groups tended to be larger in winter compared to summer, presumably as a result of seasonal access to foraging opportunities. Second, we examined the role of the social environment to determine whether reproductive success varies for caribou that form calving aggregations during parturition compared to those that give birth solitarily. We found that approximately 80% of caribou in the Middle Ridge herd give birth within a social calving aggregation, but there was no difference in reproductive success between animals that gave birth on, or off, the calving ground. However, when only considering caribou on the calving ground, we found that animals living closer to the periphery of the social aggregation had lower reproductive success than those at the core of the social aggregation. Finally, we found that social network strength and habitat specialization were density-dependent, while more social individuals were habitat generalists. However, habitat specialization had a greater effect on fitness, where habitat specialists had higher fitness than habitat generalists, but only at high density. Our work on caribou in Newfoundland addresses questions about the density and context dependence of social behaviour and provides a theoretical framework for future studies to address similar questions. We broadly integrate aspects diverse ecological fields, including socioecology, spatial ecology, movement ecology, and conservation biology.
Habitat loss on seasonal migratory range imperils an endangered ungulate: implications for redefining critical habitat for mountain caribou
Sara Williams
Using a telemetry location dataset spanning 1981 – 2018, we tested for changes in prevalence of migratory tactics (resident, migrant) over time, switching between tactics, shifts in seasonal space-use including migration corridors, and survival consequences of migrant and resident tactics for 237 adult female endangered woodland mountain caribou in one population in western Canada. Over more than three decades, the proportion of individuals displaying annual migration to the low elevation forested winter range declined from nearly 100% to 38%. Correspondingly, there was a strong switch away from being migrant to being year-round residents at high elevation. These behavioral changes corresponded to abandonment of low elevation winter ranges in association with increasing levels of anthropogenic land uses, including forestry and oil and gas developments. Furthermore, there were no identifiable migration corridors to target for migratory route protection. Shifts in migratory behavior translated to lower survival rates, particularly for caribou demonstrating resident tactics, consistent with recent declines of the caribou population. That migrants switched to residency in their largely undisturbed summer range, despite lower survival, indicates maladaptive habitat selection consistent with recent patterns of mountain caribou extirpations.
Continental and regional patterns in caribou resource selection across a wide gradient of fire frequency
Eric Palm
Boreal caribou living in an area shaped by natural disturbances: insights into the ecology and conservation of the species from where we know the least
Clara Superbie
The decline of boreal and mountain caribou (Rangifer tarandus caribou) is widely believed to be a result of anthropogenic and natural disturbance by means of disturbance-mediated apparent competition (DMAC). Here, landscape disturbance increases the abundance of browsing ungulates by reducing the seral age of forests, promoting predator numbers, and in turn heightening predation risk to caribou. However, research on the species has mostly focused on where caribou have been impacted by significant industrial disturbances, in relatively productive southern boreal and mountain systems. Yet, about 2/3 of the Canadian caribou population exists principally in northern taiga and shield habitat where logging is absent, and where other industrial activities are quasi-inexistent. In such wildfire-dominated ecoregions of low productivity, we know very little of how DMAC acts as a limiting factor to caribou. Here, we propose to summarize some of the results coming out of 6-years of research on the ecology of caribou living in the northern boreal shield of Saskatchewan. We propose to discuss if DMAC applies as a threat in this population and investigate how caribou and their predators respond to fire but extremely low levels of linear features. Put in perspectives with recently published studies on the topics, we raise questions about how to best protect northern caribou units which may serve as sources to southern caribou populations. Answers to these questions are important to both theoretical and applied ecology, including how we might improve caribou conservation.