Royale National Park Research Articles

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.

Exploring the Origins of Red Foxes (Vulpes vulpes) on Isle Royale

Isle Royale National Park is generally considered a pristine ecosystem, but the island archipelago has a long history of human impacts that have altered the island's mammal communities through extirpations and introductions. The origin of red foxes (Vulpes vulpes) on the islands are of particular interest given their ubiquity and uncertain colonization history. Red foxes were first reported on Isle Royale in 1925, shortly after the foundation of a small fox farm that began on Isle Royale in 1922. We sequenced two mitochondrial haplotypes from red fox scats collected on Isle Royale and compared them to haplotypes from the mainland surrounding Lake Superior, the predominant source of the island's other native mammals. Some Isle Royale foxes matched widespread haplotypes commonly found across Canada, but over half of our samples matched haplotypes previously detected only in Newfoundland. While we cannot conclude a singular origin, we offer a working hypothesis red foxes on Isle Royale are derived from a combination of natural colonization and human introduction. Specifically, we propose native red foxes may be admixed with fur-farmed foxes from an introduction in the early 20th century.

Emigration and First-Year Movements of Initial Wolf Translocations to Isle Royale

Canis lupis (Gray Wolf or Wolf) can move great distances with important consequences to the persistence of isolated populations. We used global position system (GPS) tracking technology to summarize the movements of 4 Wolves translocated to Isle Royale National Park, MI, in 2018–2019. We quantified aspects of movement behavior of individual Wolves following translocation to, and an emigration event from the Isle Royale ecosystem.

Skeletal and Dental Development Preserve Evidence of Energetic Stress in the Moose of Isle Royale

Food shortages can leave diagnostic, and in the case of the dentition, irreversible changes in mineralized tissue that persist into historical and fossil records. Consequently, developmental defects of tooth enamel might be used to track ungulate population irruptions or declines in resource availability but dental tissue’s capacity for preserving historical population density changes has yet to be investigated in wild populations. We test the ability of macroscopic enamel defects, mandible and metapodial lengths to track changes in the well-known insular moose population of Isle Royale National Park. Our study demonstrates that 1) a moose density threshold exists on the island above which there is a significant decrease in mandible and metatarsus length and a concomitant increase in enamel hypoplasias, 2) food limitation has a more pronounced effect on male than female skeletal and dental growth, and 3) combined data from tooth enamel hypoplasias and bone lengths reflect the relative density of this ungulate population, and should be broadly applicable to other ungulate osteological samples. Developmental defects in dental enamel were among the highest recorded in a wild population, and even during low-density intervals the population density of Isle Royale moose has been high enough to negatively impact skeletal and dental growth, indicating the comparatively poor health of this isolated century-old ecosystem.

Climate Change Is Likely to Alter Future Wolf – Moose – Forest Interactions at Isle Royale National Park, United States

We evaluated how climate change and variable rates of moose browsing intensity, as they relate to wolf predation, might impact the forests of Isle Royale National Park, MI USA by conducting a simulation modelling experiment. The experiment consisted of contrasting three different scenarios of wolf management and with a static (current conditions) and changing climate (high emissions). Our results suggest that the interactive effects of wolf predation and climate change are likely to be temporally variable and dependent on biogeographic and forest successional processes. During the first 50 years of simulations, when the effects of climate change were minor, higher simulated rates of predation by wolves reduced moose population densities, resulting in greater forest biomass and higher carrying capacities for moose. However, over the longer term, early successional and highly palatable aspen and birch forests transitioned to late successional spruce and fir forests, regardless of climate or predation intensity. After 50 years, the effects of climate change and predation were driven by effects on balsam fir, a late successional species that is highly palatable to moose. High-intensity predation of moose allowed balsam fir to persist over the long term but only under the current climate scenario. Climate change caused a reduction in balsam fir and the other boreal species that moose currently feed on, and the few temperate species found on this isolated island were unable to compensate for such reductions, causing strong declines in total forest biomass. The direct effects of moose population management via reintroduction of wolves may become increasingly ineffective as the climate continues to warm because the productivity of boreal plant species may not be sufficient to support a moose population at all, and the isolation of the island from mainland temperate tree species may reduce the likelihood of compensatory species migrations.

Safety and nature versus tourists, athlets and residents in Sagarmatha National Park Nepal

The subject of this publication is Sagarmatha National Park located in Nepal, along with the consequences of its popularity among all worlds and the effects of using the environment on selected specific cases. The main purpose of the work is to illustrate the included natural and social conditions as well as the state and perspectives for the development of operational functions in the park. The economic situation of the country will also be presented, taking into account the conditions conducive to the development of inbound tourism.High mountains have now become one of the main collections of scientific research. One of the reasons is the intensive transformation available from the mass nature of qualified tourism or mountain climbing. The world has entered the multifaceted era of 'tourism'. The natural values of the environment are currently covered by one of the basic elements of the supply of the harvest. Man cannot be chased from the mountains! It is necessary to include his harmonized sport, tourism and economic interests with nature protection. Tourism supported and contributes to the development of various forms of nature and environmental protection, which are the first national parks and nature reserves: Yellowstone in the USA founded in 1872, the Royal National Park in Australia founded by the British in modern colonies in 1879 or the second historical Banff National Park in Canada created in 1885. Contemporary forms of environmental protection originate from the romantic west over wild nature and associated with progressive industrialization in the nineteenth century destroying natural ecosystems on an unprecedented scale. Although the ideas of nature protection may already be sought in antiquity for activities that will then be related to religious worship. In China, the first laws on nature protection were announced 4,000 years ago, and in India about 3,000 years ago. The declaration on the protection of forest resources was issued in 1671 by the Danish King Christian V, and 34 years later also by Russian Tsar Peter I. In Poland, the first symptoms of care for forest resources concern the place in 1337, during the reign of Casimir the Great, when he announced statutes prohibiting logging in other people's forests. Conscious protection of the disappearing species in the form of royal law takes place at the end of the 16th century, which provisions protect the forced turns as a result of cutting out large tracts of forests.In Nepal, ecological awareness of the power elites and local people has matured for a long time. Robbery of forest management was widely used, wood for fuel or land was obtained for arable crops. It wasn't until the mid-1960s that King Mahendra issued the first laws on nature protection and provided for penalties for its destruction. The descendant and heir to the throne of King Mahendra - Birendra permanently introduced the protection of natural resources to the country's development plans and in the first year of his reign (1973) he issued the Act on National Parks and Nature Conservation, which took care of a number of animal species and established the first Royal Chitwan National Park. In subsequent years, new national parks and reserves were created in naturally valuable areas. There are 8 national parks in Nepal. The protected areas cover a total of 13% of the area.The inspiration to write this study was data analysis and own observation of both the natural resources of the Sagarmatha National Park, as well as the attitude to the natural environment of its inhabitants as well as athletes and tourists.

Community Attitudes and Perceptions Concerning Rhinoceros Poaching and Conservation: A Case Study in Eswatini

Rhinoceros poaching has been recognized the world over as a conservation crisis, the result of the high price of horn and demand in Asian markets. The commitment and participation of local people in conservation activities, however, are crucial for conservation success. Here we assess attitudes and perceptions towards rhino poaching and conservation in light of surveys in two local communities adjacent to the Hlane Royal National Park in eSwatini where perhaps 100 black (Diceros bicornis) and white (Ceratotherium simum) rhino occur. Our survey of 60 households addressed perceptions and attitudes towards rhino conservation and willingness to participate in rhino poaching and conservation activities. No efforts have been made to involve local people in conservation activities, and the people do not benefit from the park's activities. About 20% of respondents expressed their willingness to help rhino poachers provided they are paid for their services. Of the remaining 80%, some mentioned that they would not help poachers for fear of being apprehended. Still, some mentioned that they would not help poachers because of their concern about poaching and believe its prevention is important. Park authorities here and elsewhere could invest in building better people–park relationships, and provide opportunities for local communities to participate in conservation activities. Conservation policies to co-manage the resources could be used to deter poaching and to conserve wildlife involving local community members in monitoring and enforcement strategies.

Red-eared Sliders Trachemys scripta elegans in southern Sydney, including new incursions

The invasive Red-eared Slider Trachemys scripta elegans has spread extensively, forming naturalised populations on all continents except Antarctica. Ranked among the 100 worst invasive species, there are biosecurity concerns that native turtles become outcompeted and displaced, as well as other speculative impacts. The actual ecological impacts in Australia have not been properly studied, however impacts shown in other countries are concerning. Incursions have presented in New South Wales, Queensland, Victoria, Western Australia and the Australian Capital Territory. A number of sightings have been reported from southern Sydney, including six sites where more than one slider has persisted. The incursions at Yeramba Lagoon in the Georges River National Park and the Centennial Parklands have been the most documented, whereas incursions in the Lime Kiln Bay Wetland, Rockdale Wetlands Corridor and Audley in the Royal National Park appear to have occurred recently. To date, breeding in southern Sydney has only been confirmed at Yeramba Lagoon. A range of removal techniques have been successfully applied to eradicate isolated incursions in Brisbane and Melbourne. However, these options are difficult to implement in southern Sydney sites where incursions occur in high visitation public lands.

Aquatic Macrophytes are Seasonally Important Dietary Resources for Moose

Moose (Alces alces) are generalist herbivores, but are important aquatic-terrestrial ecotone specialists. Aquatic macrophytes are a high-quality food source for moose during summer, but the importance of aquatic food sources to the moose diet is difficult to study. We used stable isotope analysis of carbon and nitrogen from moose hooves and forage (terrestrial plants, aquatic macrophytes, and arboreal lichen) to assess the diet of moose at Isle Royale National Park, Michigan, USA, using Bayesian mixing models. We also evaluated the isotopic variability along chronologies of serially sampled hooves. Overall, our mixing models indicate that 13%–27% of the summer moose diet was aquatic in origin. Among moose that died during winter, body condition was impaired and hoof 15N was higher where aquatic habitats were sparse. Although isotope chronologies preserved in hooves could significantly enhance our understanding of ungulate foraging ecology, interpretation of such chronologies is presently limited by our lack of knowledge pertaining to hoof growth rate and seasonal growth variability related to age and health. Distinct isotopic values among terrestrial plants, aquatic macrophytes, and arboreal lichens indicate that continued methodological advances in stable isotope ecology will lead to more precise estimates of the contribution of aquatic feeding to moose population dynamics and other ungulates.

Negative frequency-dependent foraging behaviour in a generalist herbivore (Alces alces) and its stabilizing influence on food web dynamics.

Resource selection is widely appreciated to be context-dependent and shaped by both biological and abiotic factors. However, few studies have empirically assessed the extent to which selective foraging behaviour is dynamic and varies in response to environmental conditions for free-ranging animal populations. Here, we assessed the extent that forage selection fluctuated in response to different environmental conditions for a free-ranging herbivore, moose (Alces alces), in Isle Royale National Park, over a 10-year period. More precisely, we assessed how moose selection for coniferous versus deciduous forage in winter varied between geographic regions and in relation to (a) the relative frequency of forage types in the environment (e.g. frequency-dependent foraging behaviour), (b) moose abundance, (c) predation rate (by grey wolves) and (d) snow depth. These factors are potentially important for their influence on the energetics of foraging. We also built a series of food-chain models to assess the influence of dynamic foraging strategies on the stability of food webs. Our analysis indicates that moose exhibited negative frequency dependence, by selectively exploiting rare resources. Frequency-dependent foraging was further mediated by density-dependent processes, which are likely to be predation, moose abundance or some combination of both. In particular, frequency dependence was weaker in years when predation risk was high (i.e. when the ratio of moose to wolves was relatively low). Selection for conifers was also slightly weaker during deep snow years. The food-chain analysis indicates that the type of frequency-dependent foraging strategy exhibited by herbivores had important consequences for the stability of ecological communities. In particular, the dynamic foraging strategy that we observed in the empirical analysis (i.e. negative frequency dependence being mediated by density-dependent processes) was associated with more stable food web dynamics compared to fixed foraging strategies. The results of this study indicated that forage selection is a complex ecological process, varying in response to both biological (predation and moose density) and abiotic factors (snow depth) and over relatively small spatial scales (between regions). This study also provides a useful framework for assessing the influence of other aspects of foraging behaviour on the stability of food web dynamics.

Detecting dynamic system regime boundaries with Fisher information: the case of ecosystems

The direct measurement of the resilience (resistance to disturbances) of an ecosystem’s current regime (or “alternative stable state”) remains a key concern for managing human impacts on these ecosystems and their risk of collapse. Approaches which utilize statistics or information theory have demonstrated utility in identifying regime boundaries. Here, we use Fisher information to establish the limits of the resilience of a dynamic regime of a predator–prey system. This is important because previous studies using Fisher information focused on detecting whether a regime change has occurred, whereas here we are interested in determining how much an ecological system can vary its properties without a regime change occurring. We illustrate the theory with simple two species systems. We apply it first to a predator–prey model and then to a 60-year wolf–moose population dataset from Isle Royale National Park in Michigan, USA. We assess the resilience boundaries and the operating range of a system’s parameters without a regime change from entirely new criteria for Fisher information, oriented toward regime stability. The approach allows us to use system measurements to determine the shape and depth of the “cup” as defined by the broader resilience concept.Graphic abstractThe direct measurement of the resilience (resistance to disturbances) of an ecosystem’s current regime remains a key concern for managing human impacts on these ecosystems and their risk of collapse. Here, we use Fisher information to establish the limits of stability of a dynamic regime of a predator–prey system. The region of stability is represented by the “floor of the canyon” in the adjacent graphic. While the theory is illustrated with an ecosystem example, it is applicable in its present form to dynamic systems in general.

Response of boreal lakes to changing wind strength: Coherent physical changes across two large lakes but varying effects on primary producers over the 20th century

AbstractNear‐surface wind speeds have changed over recent decades, raising questions about the extent to which these changes are altering the vertical thermal structure of lakes and affecting lake food webs. Neo‐ and paleolimnological techniques were used to assess wind‐driven changes in lake thermal habitat and resulting effects on primary producers in two lakes in Isle Royale National Park, an island archipelago located in Lake Superior, where wind speed has increased in recent decades. Responses in Siskiwit Lake, a large (16 km2 surface area), deep (Zmax = 49 m), oligotrophic lake, were compared to those of Lake Desor, a moderately large (4.3 km2) but shallower (Zmax = 13 m), mesotrophic lake. High‐frequency sensor data suggested that changes in wind speed affected epilimnion thickness in both lakes synchronously (ρ = 0.7, p < 0.001). Diatom‐inferred mixing depths suggested a coherent shift in both lakes to deeper mixing (an increase of 3 and 6 m) since 1920 (ρ = 0.8), which was correlated with an increase in regional wind speed during the 20th century at the decadal‐scale in Lake Desor and Siskiwit Lake (ρ = 0.6 and 0.4, respectively). In Lake Desor, algal biomass declined as mixing deepened from 1920 to 1980, and then cyanobacteria and cryptophyte pigments increased from 1980 to present, a period of inferred stable and deep mixing. Algal pigment concentrations in Siskiwit Lake were unchanged as mixing depth deepened. Although changes in wind speed altered lake physical structure similarly, the ecological consequences of these changes differed between lakes and were most likely influenced by lake‐specific variability in nutrient and light availability.

Activity patterns of insectivorous bats during a seasonal transition period from hibernation to reproduction

Bat activity is influenced by fluctuating environmental variables. It may also be influenced by energetic pressures related to pregnancy, lactation, and emergence following winter inactivity. We evaluated nightly changes in relative bat activity at Royal National Park in response to Julian date, ambient temperature, precipitation, wind speed and moon phase on a nightly scale for six weeks during spring, as insectivorous bats move out of hibernation or frequent, prolonged torpor, and into the maternal season. Interestingly, later Julian date (reflecting seasonal transition) was the sole variable that best predicted total nightly activity. In addition, we opportunistically assessed bat activity in response to a severe storm, considered a Category 1 cyclone, resulting in 96.4mm of rain in one night and wind speeds up to 94km h–1. Only one species of bat, Chalinolobus gouldii, was active during the storm, with activity restricted to the latter part of the evening when precipitation had reduced, indicating rapid resumption of activity following severe weather. The results of this research can be used as an indicator of emergence from winter inactivity and highlight activity patterns of bat species in relation to environmental variables to inform timing of monitoring programs, bat surveys, and targeted research.

The relative roles of dispersal and establishment for shaping whole-lake aquatic macrophyte richness, diversity, and community structure in hemiboreal lakes

ABSTRACTAquatic macrophyte diversity and structure play an important role in freshwater communities, yet little research on macrophytes has focused on native communities in the undisturbed hemiboreal lakes of North America. We used data collected from 15 inland lakes on Isle Royale National Park (Michigan, USA) to identify relationships among macrophyte metrics that describe dispersal and introduction potential (richness, diversity, community structure via growth form, and connectivity) and lake metrics that control establishment and growth potential. Results from partial least square regression analyses found that the most important and recurring predictors were those corresponding to establishment and growth. Alkalinity was the major contributor to the variation seen in richness, Shannon evenness, and Simpson inverse diversity metrics. Sediment phosphorus also contributed significantly to richness and diversity, but negatively. For growth form, half of the variation in submersed species related to alkalinity while almost half of variation in emergent species related to alkalinity and water color. Most of the variation in floating-leaved species was negatively related to alkalinity and water color. Our results suggest a high relative importance of establishment and growth metrics compared to introduction and dispersal metrics for understanding native macrophyte communities in North American hemiboreal lakes.