Royale National Park Research Articles

A historical contingency hypothesis for population ecology

Assessments of historical contingency have advanced our understanding of adaptive radiation and community ecology, but little attention has been given to assessing the importance of historical contingency in population ecology. An obstacle has been the unmet need to conceptualize historical contingencies for populations in a manner that allows for their explanatory power to be assessed and quantified so that it can be directly compared with the explanatory power of statistical models representing other hypotheses or theory-based explanations. Here we conceptualize historical contingencies as a series of random events characterized by (1) significant legacy effects that are comparable in length to the waiting time between such events, and (2) the disparate nature of individual events in the series. From that conceptualization, we present a simple quantitative framework for assessing the explanatory power of historical contingencies in population ecology and apply it to an existing long-term dataset on the predator-prey system in Isle Royale National Park. The population-level phenomenon that we focused on was predation rate because it is a synthesis of three basic elements in population ecology (predator abundance, prey abundance and kill rate). We also compared the explanatory power of models of the historical contingency hypothesis to a wide-range of alternative, theory-based, statistical models used to assess underlying mechanisms or forecast future dynamics. Models of the historical contingency hypothesis explained over half of the interannual variation in predation rate and performed similarly, or better than, the vast majority of alternative, theory-based, models. Those findings highlight the potential value of reconsidering the way that population ecologists traditionally attempt to explain phenomena. We also discuss how this new conceptualization of the historical contingency hypothesis can also be valuable for synthesizing several other important ecological concepts of broad significance, especially reddened spectra, tipping points, alternative stable states, and ecological surprises. If the historical contingency hypothesis were found to be broadly applicable, then it would likely explain why ecologists are conspicuously poor at forecasting future dynamics.

Communal aggregation of Brown Tree Snakes Boiga irregularis at the southern limit of their distribution

ABSTRACT On a remote sandstone outcrop within the Royal National Park, New South Wales, numerous instances were documented involving the aggregation of Brown Tree Snakes Boiga irregularis. Over the period from 2018 to 2023, a total of 8 visits to the site were logged, revealing 3 observed aggregations. Notably, the occurrences of these aggregations appeared to be influenced by seasonality, with each observation being made during late autumn or winter. The peak aggregation count documented involved six adult snakes.

Late Holocene hunting economies in coastal southeastern Australia: Insights from the archaeological fauna of Curracurrang 1 Rockshelter, Royal National Park

ABSTRACTCurracurrang 1 (1CU5) is a rockshelter site located in the Royal National Park (RNP) on the coast south of Sydney. Excavated from 1962 to 1966, the site's rich Holocene cultural deposit has become important for understanding regional Late Holocene developments in Australian lithic and shell technologies. Our comprehensive analysis of 1CU5's faunal remains is presented here, accompanied by new AMS radiocarbon dates and a reinterpretation of the site's occupation sequence. Much of the midden deposit spans from about 2500 BP to approximately 1850 AD, rather than only the last ∼1500 years as originally believed based on less comprehensive dating. A wide range of terrestrial and marine fauna were exploited at 1CU5, with the relative importance of the latter group increasing within the last ∼1500 years. Greater fish consumption during the later period may relate to use of novel hook and line fishing technology using hooks made from shellfish, but concurrent increases in seals, seabirds and marine invertebrates suggest a broader increased reliance on marine resources. By comparison, the earlier period, which coincides with the manufacture of backed microliths, displays relatively greater reliance on terrestrial marsupials. Taxonomic representation suggests occupation of the shelter from winter through spring, and potentially into summer. Analysis of the 1CU5 fauna marks an important contribution to the understanding of Late Holocene economies at the interface of the greater Sydney and NSW South Coast cultural and biogeographic regions.

Participatory study of policy process for wildlife conservation and ecotourism in Eswatini: A multiple streams analysis

By the 1950 s, overhunting in the African Kingdom of Eswatini drove most of its wildlife to extinction. In 2022, Eswatini has one of the most robust conservation success stories in all of Southern Africa and yet has received minimal scholarly attention. Using the Multiple Streams Framework, to understand a complex system, we analyze 40 interviews and 34 policy documents to study variation in problems, policy, and politics across four different types of conservation areas: Community Based Wildlife Protected Areas, a Royal National Park, a Parastatal National Park, and a Privately Managed Protected Area. Our research is participatory, meaning Eswatini conservation professionals played a role in shaping research design and questions and collecting data. We found that policy solutions common to all institutions include 1) the absolute decision-making power of the king, 2) the stringent wildlife protection law in the 1953 Game Act, and 3) a surprisingly conducive space for communities to enact community-based conservation amidst an authoritarian monarchy. The most important problems include economic challenges (e.g. poverty) and climate change. Politics play a role, with unprecedented, violent pro-democracy protests in the summer of 2021 with activists calling for increased human rights considerations, a problem that spills into the wildlife conservation sector. Findings can be used by policy-makers seeking to replicate conservation successes elsewhere, or to enact reforms in the Eswatini system to enable its proven system of wildlife conservation to adapt and endure.

The far-reaching effects of genetic process in a keystone predator species, grey wolves.

Although detrimental genetic processes are known to adversely affect the viability of populations, little is known about how detrimental genetic processes in a keystone species can affect the functioning of ecosystems. Here, we assessed how changes in the genetic characteristics of a keystone predator, grey wolves, affected the ecosystem of Isle Royale National Park over two decades. Changes in the genetic characteristic of the wolf population associated with a genetic rescue event, followed by high levels of inbreeding, led to a rise and then fall in predation rates on moose, the primary prey of wolves and dominant mammalian herbivore in this system. Those changes in predation rate led to large fluctuations in moose abundance, which in turn affected browse rates on balsam fir, the dominant forage for moose during winter and an important boreal forest species. Thus, forest dynamics can be traced back to changes in the genetic characteristics of a predator population.

Woody species response to altered herbivore pressure at Isle Royale National Park

AbstractHerbivores shape vegetative communities via numerous mechanisms, including browse. We used vegetation monitoring data from Isle Royale National Park to examine woody species change across a nine‐year interval, coinciding with herbivore escalation. Here, moose and snowshoe hare are the dominant herbivores, while the gray wolf is the apex predator. Our initial sampling period (2010) followed six years of low moose abundance, while our second sampling event (2019) followed a nine‐year escalation in moose density. We tested for change in both saplings and shrubs and compared diameter size distributions of common tree species in three island sections. We found a decline in large saplings of sugar maple, a species limited to the west section of the island. We also saw declines in small saplings of sugar maple, paper birch, and trembling aspen. For some species, including black spruce and white spruce, taxa that are unpalatable to moose, diameter distributions were proportionally larger (i.e., indicative of fewer small individuals) in 2019 than in 2010. In contrast, diameter distributions of black ash in the central section and trembling aspen in the central and east sections of the island were proportionally smaller (indicative of more small individuals) in 2019 than in 2010. We found that ~50% of common shrub taxa were more abundant during the second sampling event, while none declined. Our work here brings to light several unanticipated results. While we demonstrated partial recovery of trembling aspen, likely originating during the earlier period of low moose abundance, our results suggest further changes may be attributable to other island herbivores. The response of black ash, a hydric species, may be stemming from a sixfold increase in active beaver sites, while that of spruce may be attributable to a historic spike in snowshoe hare density. We currently have only a limited understanding of the impacts of the island's lesser studied herbivores on overstory regeneration. Further research on these linkages can inform decisions addressing controls on forest structure.

Phenotypic variation in the molt characteristics of a seasonal coat color-changing species reveals limited resilience to climate change

The snowshoe hare (Lepus americanus) possesses a broad suite of adaptations to winter, including a seasonal coat color molt. Recently, climate change has been implicated in the range contraction of snowshoe hares along the southern range boundary. With shortening snow season duration, snowshoe hares are experiencing increased camouflage mismatch with their environment reducing survival. Phenological variation of hare molt at regional scales could facilitate local adaptation in the face of climate change, but the level of variation, especially along the southern range boundary, is unknown. Using a network of trail cameras and historical museum specimens, we (1) developed contemporary and historical molt phenology curves in the Upper Great Lakes region, USA, (2) calculated molt rate and variability in and among populations, and (3) quantified the relationship of molt characteristics to environmental conditions for snowshoe hares across North America. We found that snowshoe hares across the region exhibited similar fall and spring molt phenologies, rates and variation. Yet, an insular island population of hares on Isle Royale National Park, MI, completed their molt a week earlier in the fall and initiated molt almost 2weeks later in the spring as well as exhibited slower rates of molting in the fall season compared to the mainland. Over the last 100years, snowshoe hares across the region have not shifted in fall molt timing; though contemporary spring molt appears to have advanced by 17days (~ 4days per decade) compared to historical molt phenology. Our research indicates that some variation in molt phenology exists for snowshoe hares in the Upper Great Lakes region, but whether this variation is enough to offset the consequences of climate change remains to be seen.

Relation among Mercury, Selenium, and Biomarkers of Oxidative Stress in Northern Pike (Esox lucius).

Mercury (Hg) is a toxic environmental contaminant associated with oxidative stress in freshwater fish. A known antagonist to Hg, selenium (Se), may reduce the toxic effects of Hg. In this study, the relation among Se, methylmercury (MeHg), inorganic mercury (IHg), total mercury (THg), and the expression of biomarkers of oxidative stress and metal regulation in livers of northern pike were examined. Livers from northern pike were collected from 12 lakes in Isle Royale National Park, Pictured Rocks National Lakeshore, Sleeping Bear Dunes National Lakeshore, and Voyageurs National Park. The concentrations of MeHg, THg, and Se were measured in liver tissue, and the expression of superoxide dismutase (sod), catalase (cat), glutathione s-transferase (gst), and metallothionein (mt) was assessed. There was a positive relationship between the concentrations of THg and Se, with a Hg:Se molar ratio less than one in all livers examined. There was no significant relation between sod, cat, gst, or mt expression and Hg:Se molar ratios. cat and sod expression were significantly related to increases in percent MeHg, relative to THg; however, gst and mt expression were not significantly altered. This suggests that incorporating biomarkers containing Se may be a better indicator than non-selenium-containing proteins of assessing the long-term effect of Hg and the interactions between Hg and Se in the livers of fish, such as northern pike, especially when molar concentrations of Se are greater than Hg.

Temporal variation in translocated Isle Royale wolf diet

Wolves (Canis lupus) can exert top-down pressure and shape ecological communities through the predation of ungulates and beavers (Castor spp.). Therefore, understanding wolf foraging is critical to estimating their ecosystem-level effects. Specifically, if wolves are consumers that optimize tradeoffs between the cost and benefits of prey acquisition, changes in these factors may lead to prey-switching or negative-density dependent selection with potential consequences for community stability. For wolves, factors affecting cost and benefits include prey vulnerability, risk, reward, and availability, which can vary temporally. We described the wolf diet by the frequency of occurrence and percent biomass and characterized the diet using prey remains found in wolf scats on Isle Royale National Park, Michigan, USA, during May-October 2019 and 2020. We used logistic regression to estimate prey consumption over time. We predicted prey with temporal variation in cost (availability and/or vulnerability) such as adult moose (Alces alces), calf moose, and beaver (Castor canadensis) to vary in wolf diets. We analyzed 206 scats and identified 62% of remains as beaver, 26% as moose, and 12% as other species (birds, smaller mammals, and wolves). Adult moose were more likely to occur in wolf scats in May when moose are in poor condition following winter. The occurrence of moose calves peaked during June-mid-July following birth but before calf vulnerability declined as they matured. By contrast, beaver occurrence in wolf scat did not change over time, reflecting the importance of low-handling cost prey items for recently introduced lone or paired wolves. Our results demonstrate that the wolf diet is responsive to temporal changes in prey costs. Temporal fluctuation in diet may influence wolves' ecological role if prey respond to increased predation risk by altering foraging or breeding behavior.

Genetic analysis reveals spatial structure in an expanding introduced rusa deer population

Context Rusa deer (Cervus timorensis), originally introduced in the 1860s, are still spreading in eastern Australia. The expanding peri-urban rusa deer population in the Illawarra region of New South Wales, Australia is having undesirable impacts on human and ecological communities, but the spatial structure of this population has not been investigated. Genetic information on invasive species is potentially useful in identifying management units to mitigate undesirable impacts. Aims The aim of this study was to investigate population structure, characterise dispersal, and determine if natural and human-made landscape features affected gene flow in rusa deer invading the Illawarra region of New South Wales. Methods We used reduced representation sequencing (DArT-Seq) to analyse single nucleotide polymorphisms distributed throughout the genomic DNA of rusa deer culled during a management program. We used admixture and Principal Component Analyses to investigate population structure with respect to natural and human-made landscape features, and we investigated whether our genetic data supported the presence of sex-biased dispersal. Key results Genetic diversity was highest in the north, near the original introduction site. A railway line demarcated restricted gene flow. Surprisingly, the Illawarra escarpment, a prominent landscape feature, did not restrict gene flow. There was no evidence of sex-biased dispersal and seven individuals were identified as genetic outliers. Conclusions The genetic structure of the Illawarra rusa deer population is consistent with individuals spreading south from their introduction site in Royal National Park. The population is not panmictic, and a landscape feature associated with urbanisation was associated with increased spatial genetic structure. Outliers could indicate hybridisation or secondary incursion events. Implications Rusa deer can be expected to continue invading southwards in the Illawarra region, but landscape features associated with urbanisation might reduce dispersal across the landscape. The genetic structuring of the population identified three potential management units on which to prioritise ground shooting operations.

Practical application of disease risk analysis for reintroducing gray wolves (Canis lupus) to Isle Royale National Park, USA

AbstractEvaluation of disease risks associated with wildlife translocations is important for minimizing unintended harm and achieving conservation goals. A framework for disease risk analysis (DRA) has been developed by the World Organization for Animal Health and International Union for Conservation of Nature, but applications for planning and implementation in wildlife conservation projects are limited. To fill this gap, we describe a DRA we conducted to identify, assess, and mitigate disease risks associated with reintroduction of gray wolves (Canis lupus) to Isle Royale National Park (IRNP). A total of 19 wolves were translocated from multiple locations within the Great Lakes Region to IRNP between September 2018 and September 2019. Integration of the DRA into project planning and use of diverse expertise among project personnel enabled a timely and cost‐effective process that facilitated multidisciplinary and cross‐cultural collaboration, transparent communication about risks and uncertainties, and practical management of disease risks for wildlife and personnel. Engaging disease experts and experienced field biologists in the assessment also helped to identify and account for potential sources of bias. We hope practical examples like this encourage wider adoption of DRA principles in translocations of wildlife for conservation purposes.

Matlab Open Source Code: Noise-Assisted Multivariate Empirical Mode Decomposition Based Causal Decomposition for Causality Inference of Bivariate Time Series.

Causality inference has arrested much attention in academic studies. Currently, multiple methods such as Granger causality, Convergent Cross Mapping (CCM), and Noise-assisted Multivariate Empirical Mode Decomposition (NA-MEMD) are introduced to solve the problem. Motivated by the researchers who uploaded the open-source code for causality inference, we hereby present the Matlab code of NA-MEMD Causal Decomposition to help users implement the algorithm in multiple scenarios. The code is developed on Matlab2020 and is mainly divided into three subfunctions: na_memd, Plseries, and cd_na_memd. na_memd is called in the main function to generate the matrix of Intrinsic Mode Functions (IMFs) and Plseries can display the average frequency and phase difference of IMFs of the same order in a matrix which can be used for the selection of the main Intrinsic Causal Component (ICC) and ICCs set. cd_na_memd is called to perform causal redecomposition after removing the main ICC from the original time series and output the result of NA-MEMD Causal Decomposition. The performance of the code is evaluated from the perspective of executing time, robustness, and validity. With the data amount enlarging, the executing time increases linearly with it and the value of causal strength oscillates in an ideally small interval which represents the relatively high robustness of the code. The validity is verified based on the open-access predator-prey data (wolf-moose bivariate time series from Isle Royale National Park in Michigan, USA) and our result is aligned with that of Causal Decomposition.

Lepidosperma prospectum (Cyperaceae), a new species from Sydney coastal heath and notes on usage of sword sedges

Lepidosperma prospectum G.T.Plunkett & R.L.Barrett (Cyperaceae tribe Schoeneae) is here described as a new species in the Sydney region of New South Wales. It is highly restricted in distribution, occurring at Manly (Sydney Harbour National Park), Kamay Botany Bay National Park and Royal National Park in dense coastal shrublands behind coastal cliffs. These locations are within the traditional lands of the Gamaragal, Gweagal and Dharawal people respectively. Joseph Banks and Daniel Solander were the first Europeans to explore the flora of New South Wales in 1770 around Botany Bay but they did not collect this species. Lepidosperma prospectum is superficially similar to L. sieberi Kunth, which occurs in adjacent habitats, but molecular data have shown that it is more closely allied to Western Australian species. A brief review of recorded indigenous and European knowledge and utilisation of the genus Lepidosperma Labill. is presented to highlight the varied uses of the genus.

The Role of Wolves in Regulating a Chronic Non-communicable Disease, Osteoarthritis, in Prey Populations

It is widely accepted that predators disproportionately prey on individuals that are old, weak, diseased or injured. By selectively removing individuals with diseases, predators may play an important role in regulating the overall health of prey populations. However, that idea is seldom tested empirically. Here we assess the extent that wolves (Canis lupus) select adult moose (Alces alces) in Isle Royale National Park on the basis of age-class and osteoarthritis, a chronic, non-communicable disease. We also assess how temporal variation in kill rates (on moose by wolves) were associated with the subsequent incidence of osteoarthritis in the moose population over a 33-year period (1975–2007). Wolves showed strong selection for senescent moose and tended to avoid prime-aged adults. However, the presence of severe osteoarthritis, but not mild or moderate osteoarthritis, appeared to increase the vulnerability of prime-aged moose to predation. There was weak evidence to suggest that senescent moose with osteoarthritis maybe more vulnerable to wolves, compared to senescent moose without the disease. The incidence of osteoarthritis declined following years with higher kill rates–which is plausibly due to the selective removal of individuals with osteoarthritis. Together those results suggest that selective predation plays an important role in regulating the health of prey populations. Additionally, because osteoarthritis is influenced by genetic factors, these results highlight how wolf predation may act as a selective force against genes associated with developing severe osteoarthritis as a prime-aged adult. Our findings highlight one benefits of allowing predators to naturally regulate prey populations. The evidence we present for predation’s influence on the health of prey populations is also relevant for policy-related arguments about refraining from intensively hunting wolf populations.

Interspecific Killing of Vulpes vulpes (Red Fox) Kits at a Den Site by Canis lupus (Gray Wolf) in Isle Royale National Park, Michigan

Canis lupus (Gray Wolf or Wolf) have killed subordinate canids that scavenge on Wolf-killed prey, but little evidence is available for antagonistic behavior of Wolves toward other canids at interspecific den sites. We investigated clusters of locations from a global positioning system (GPS)collared male Wolf, translocated to Isle Royale National Park, MI, on 23 March 2019. On 17 May 2019, we investigated a GPS cluster of the Wolf and observed 3 Vulpes vulpes (Red Fox) kit carcasses at an excavated Red Fox den site. We report details from this event and evidence for interspecific aggression and implications for Wolf–Red Fox interactions. To our knowledge, this represents the first reported killing of Red Fox kits at their den by a Wolf. Limited reports of interspecific killings by Wolves of Red Foxes suggests this interaction was opportunistic and rare.

The nutritional condition of moose co‐varies with climate, but not with density, predation risk or diet composition

A fundamental question about the ecology of herbivore populations pertains to the relative influence of biotic and abiotic processes on nutritional condition. Nutritional condition is influenced in important, yet poorly understood, ways by plant secondary metabolites (PSMs) which can adversely affect a herbivore's physiology and energetics. Here we assess the relative influence of various abiotic (weather) and biotic (intraspecific competition, predation risk and diet composition) factors on indicators of nutritional condition and the energetic costs of detoxifying PSMs for the moose population in Isle Royale National Park (USA). Specifically, we observed interannual variation in the ratio of urea nitrogen to creatinine (UN:C), an indicator of nutritional restriction, over 29 years and the ratio of glucuronic acid to creatinine (GA:C), an indicator of energetic investment in detoxifying PSMs, over 19‐years. Both UN:C and GA:C were measured in samples of urine‐soaked snow. Most importantly, climatic factors explained 66% of the interannual variation in UN:C, with moose being more nutritionally stressed during winters with deep snow and during winters that followed warm summers. None of the biotic factors (density, predation, diet composition) were useful predictors of UN:C or GA:C. The absence of a relationship between diet composition and either UN:C or GA:C suggests that the nutritional ecology of wild herbivores is probably complicated by fine‐scale variation in protein content and concentrations of PSMs amongst plants of the same species. UN:C increased with GA:C at both the individual and population‐level. That result is consistent with detoxification being energetically costly, such that it impairs nutritional condition and also highlights how spatio‐temporal variation in the intake and detoxification of PSMs may influence population dynamics. Lastly, because we observed interannual variation in nutritional condition over three decades and detoxification over two decades these findings are relevant to concerns about how herbivore populations respond to climate change.

Winter Tick Burdens for Moose Are Positively Associated With Warmer Summers and Higher Predation Rates

Climate change is expected to modify host-parasite interactions which is concerning because parasites are involved in most food-web links, and parasites have important influences on the structure, productivity and stability of communities and ecosystems. However, the impact of climate change on host–parasite interactions and any cascading effects on other ecosystem processes has received relatively little empirical attention. We assessed host-parasite dynamics for moose (Alces alces) and winter ticks (Dermacentor albipictus) in Isle Royale National Park over a 19-year period. Specifically, we monitored annual tick burdens for moose (estimated from hair loss) and assessed how it covaried with several aspects of seasonal climate, and non-climatic factors, such as moose density, predation on hosts by wolves (Canis lupus) and wolf abundance. Summer temperatures explained half the interannual variance in tick burden with tick burden being greater following hotter summers, presumably because warmer temperatures accelerate the development of tick eggs and increase egg survival. That finding is consistent with the general expectation that warmer temperatures may promote higher parasite burdens. However, summer temperatures are warming less rapidly than other seasons across most regions of North America. Therefore, tick burdens seem to be primarily associated with an aspect of climate that is currently exhibiting a lower rate of change. Tick burdens were also positively correlated with predation rate, which could be due to moose exhibiting risk-sensitive habitat selection (in years when predation risk is high) in such a manner as to increases the encounter rate with questing tick larvae in autumn. However, that positive correlation could also arise if high parasite burdens make moose more vulnerable to predators or because of some other density-dependent process (given that predation rate and moose density are highly correlated). Overall, these results provide valuable insights about interrelationships among climate, parasites, host/prey, and predators.

Status and movement of adfluvial brook trout Salvelinus fontinalis at Isle Royale, Michigan, Lake Superior

Adfluvial brook trout Salvelinus fontinalis populations in the Lake Superior basin have suffered declines over the last century due to habitat degradation and exploitation. Natural resources agencies throughout the basin have restored habitat and implemented restrictive angling regulations as tools to protect remnant coaster brook trout populations, but the success of these practices is unknown in some locations. We used electrofishing and passive integrated transponder (PIT) tag movement data from 2008 to 2020 to describe population characteristics, temporal trends, and adfluvial life history of coaster brook trout in Washington Harbor, Isle Royale National Park, Lake Superior after implementation of catch-and-release regulations in 2004. Our results document the presence of an adfluvial coaster brook trout population in Washington Harbor, Isle Royale. Temporal trends indicate that brook trout abundance and distribution in Washington Harbor increased since earlier observations in the late 1990s and early 2000s likely due to enactment of protective regulations, and increased stream flows and water levels observed in recent years in both Washington Creek and Lake Superior, respectively. Annual tag detection of Washington Harbor brook trout in Washington Creek at the antenna arrays varied from 25% in 2009 to 100% in 2011 and 2013, and averaged 60.7% throughout the study. Peak in adfluvial brook trout use of Washington Creek was from August – October with few detections occurring outside of the presumed spawning period. This study provides valuable insight into the population characteristics, movement patterns, and temporal increase in abundance of an adfluvial brook trout population in Lake Superior.

Negative frequency-dependent prey selection by wolves and its implications on predator–prey dynamics

Many species exhibit selective foraging behaviour, where consumers use a nonrandom subset of available food types. Yet little is known about how selective foraging behaviour varies with environmental conditions and the community level consequences of such selection dynamics. We examined selective foraging by wolves preying primarily on elk in Yellowstone National Park (YNP) over a 12-year period and on moose in Isle Royale National Park (IRNP) over a 47-year period. Specifically, we assessed how selection for calves and senescent adults varied with their frequency in the environment, wolf abundance and winter severity. Selection for senescent adults decreased as the relative abundance of senescent prey increased (i.e. negative frequency-dependent selection) in both study sites. In IRNP, selection for calves was also negatively frequency dependent and declined with increasing wolf abundance. These results are inconsistent with the pattern of positive frequency-dependent selection expected under the prey-switching hypothesis. These results suggest that selection is primarily driven by intraspecific differences in prey vulnerability and wolves’ interest in minimizing their risk of injury, as opposed to maximizing intake rates. Lastly, we ran simulations to evaluate how predator–prey dynamics were influenced by dynamic patterns of selection, like those observed in YNP and IRNP. The simulations indicated that predators are more efficient (i.e. steeper slope of the numerical response) when selection for calves is negatively frequency dependent, which results in a lower mean abundance of prey. More importantly, predation is a stronger destabilizing force when selection for calves is negatively frequency dependent. That stronger destabilizing force is indicated by greater variability in the abundance of prey and predators, prey populations being less resilient and a steeper negative slope of the relationship between predation rate and prey population growth rate. As such, our simulation analyses suggest that some of the observed patterns of negative-frequency dependent selection may have important consequences for predator–prey dynamics. • Wolves showed negative frequency-dependent selection for calves and senescent prey. • Wolves did not exhibit prey-switching behaviour when preferred prey became rare. • Selection is likely driven by the predator's interest to reduce their risk of injury. • Selection for calves may result in more efficient predators and less resilient prey.

The effects of access restrictions and communication strategies for divisive environmental management

In 2018, the U.S. National Park Service announced a controversial plan to translocate 20−30 gray wolves (Canis lupus) to Isle Royale National Park to increase genetic diversity and ultimately the dwindling wolf population. Media were restricted physical access during the translocations, citing safety concerns for the wolves and management team, as well as logistical challenges because of the remoteness of the park. Given these restrictions, we used interviews and quantitative analyses of news stories and press releases to examine what communication strategies the National Park Service and its partners deployed and how access restriction affected the way news outlets covered the events. By identifying source diversity groups, we found U.S. government sources were predominately featured with few other source types included, and that coverage heavily relied on press release information. We discuss the implications of this communication strategy and potential consequences for access restrictions when covering divisive events in remote locations.