Isle Royale National Park Research Articles

Effects of increased concentrations of inorganic nitrogen and dissolved organic matter on phytoplankton in boreal lakes with differing nutrient limitation patterns

Global changes are currently contributing to increasing concentrations of nitrogen (N) and dissolved organic matter (DOM) in boreal lakes. While these changes can affect phytoplankton, the relative importance of each of these subsidies and how their effects vary with nutrient limitation patterns remain unclear. We investigated the effects of increasing N and DOM on phytoplankton in two relatively remote boreal regions of the northern US with lakes that differ in N and DOM concentrations: Acadia National Park (ACAD) in the northeastern US, and Isle Royale National Park (ISRO) in the north-central US. Nutrient enrichment assays were conducted in two lakes from each area first to assess nutrient limitation patterns. To determine the effects of increasing N and DOM, changes in phytoplankton biomass and community structure were examined in bioassay experiments using a N gradient combined with either DOM enrichment or DOM shading treatments. Algal biomass response indicated N limitation in ISRO and N&P co-limitation in ACAD. In the N gradient experiments, algal biomass in the N-limited lake increased along the N gradient, while it was unaffected in the N&P co-limited lake. Regardless of nutrient limitation pattern, algal biomass increased with DOM enrichment, with DOM additions primarily stimulating chlorophytes, diatoms, and chrysophytes. In contrast, shading with DOM had no effect on any phytoplankton response metrics. In boreal lakes, the effects of N enrichment were dependent on nutrient limitation status of the lake, whereas the effects of DOM enrichment were observed across lakes regardless of nutrient limitation status, suggesting that increasing DOM may have widespread effects on aquatic systems.

Injury Patterns at Isle Royale National Park: An Epidemiologic Review of Injuries and Illnesses Sustained in a Remote Environment

Isle Royale National Park is a remote island in northern Lake Superior that attracts 16,000 visitors annually. The epidemiology of injuries and illnesses sustained by Isle Royale׳s visitors has not been previously studied.The purpose of this study is to examine these data and evaluate them for injury patterns. This is a retrospective observational study examining the epidemiology of injuries and illnesses sustained during the period from 2008 to 2012. Incident reports completed by park rangers were reviewed and the data sorted according to time of year, time of day, type of medical encounter, and whether the patient was stable, unstable, or required transport. Two hundred and seventy patient care reports were obtained from the National Park Service. Sixty-four percent of encounters occurred in July and August, and most patients sought care in the afternoon. Care was provided by park rangers, the majority of whom were trained to the level of emergency medical technician. Fifty-eight percent of cases were trauma related, and 20% of all cases were evacuated. The majority of incidents were trauma related. The majority of the rangers on the island are trained to the level of emergency medical technician-B and appear to offer appropriate care to the island's many visitors, utilizing the National Park Service treatment protocols and comprehensive medical kits. In addition, access to advanced medical care is readily available by air and water evacuation.

Spatial arrangement and metrics of freshwater coastal rock pools applied to amphibian conservation

Coastal habitats are an ecotone between aquatic and terrestrial ecosystems. Depressions on volcanic bedrock shores of Lake Superior form small pool habitats that are influenced to various degrees by their spatial context and that relate to differences in mechanisms of disturbance. A total of 71,931 coastal pools were mapped and measured, and amphibian occupants were identified along 48 km of shoreline at Isle Royale National Park, where coastal rock pool habitats were abundant. Generally, mean depth of pools was 0.11 m, with a mean surface area of 0.6 m 2 , although maximum measurements were 1.5 m and 378 m 2 , respectively. Three strongly defined zones occurred, with bedrock near the lake having a low slope and more numerous, smaller, and shallower pools; bedrock near the forest edge had a steeper slope and fewer, larger, and deeper pools; and a median zone occurring between. A single offshore location, Passage Island, had nearly 63% of all pool abundance. Two amphibian species were typical of coastal pools, the chorus frog ( Pseudacris triseriata ) and blue-spotted salamander ( Ambystoma laterale ), while spring peeper ( Pseudacris crucifer ) was uncommon and probably incidental to coastal habitats. These three species were significantly more abundant in mid-shore pools. Four other amphibian species were only rarely detected. Both coastal habitat density and chorus frog abundance were highest at localities directly adjacent to an international shipping lane. As a result of intriguing spatial distributions and potential for impacts from coastal pollution, chorus frog in particular reveals that coastal ecology can be unique from inland contexts and have important management implications at the land–water interface.

Growth rates and variances of unexploited wolf populations in dynamic equilibria

ABSTRACTSeveral states have begun harvesting gray wolves (Canis lupus), and these states and various European countries are closely monitoring their wolf populations. To provide appropriate perspective for determining unusual or extreme fluctuations in their managed wolf populations, we analyzed natural, long‐term, wolf‐population‐density trajectories totaling 130 years of data from 3 areas: Isle Royale National Park in Lake Superior, Michigan, USA; the east‐central Superior National Forest in northeastern Minnesota, USA; and Denali National Park, Alaska, USA. Ratios between minimum and maximum annual sizes for 2 mainland populations (n = 28 and 46 yr) varied from 2.5–2.8, whereas for Isle Royale (n = 56 yr), the ratio was 6.3. The interquartile range (25th percentile, 75th percentile) for annual growth rates, N t +1/N t , was (0.88, 1.14), (0.92, 1.11), and (0.86, 1.12) for Denali, Superior National Forest, and Isle Royale respectively. We fit a density‐independent model and a Ricker model to each time series, and in both cases we considered the potential for observation error. Mean growth rates from the density‐independent model were close to 0 for all 3 populations, with 95% credible intervals including 0. We view the estimated model parameters, including those describing annual variability or process variance, as providing useful summaries of the trajectories of these populations. The estimates of these natural wolf population parameters can serve as benchmarks for comparison with those of recovering wolf populations. Because our study populations were all from circumscribed areas, fluctuations in them represent fluctuations in densities (i.e., changes in numbers are not confounded by changes in occupied area as would be the case with populations expanding their range, as are wolf populations in many states). © 2014 The Wildlife Society.

Chironomidae (Diptera) in Freshwater Coastal Rock Pools at Isle Royale, Michigan

Chironomid pupal exuviae were collected from coastal rock pools at Isle Royale National Park, Michigan, from April to October in 2009 and 2010. Pools in bedrock depressions were separated into those higher on the shore, where desiccation is likely an important disturbance, and lower on the shore, where wave-wash from Lake Superior is likely a fundamental influence. The 102 species collected represent 42 genera in six subfamilies. The distribution and ecology of each species is summarized. Also included are remarks on species with significant range expansions, either with Palearctic or Nearctic disjunct ranges, or novel habitat use among species that are typically considered lotic but occur in splash zone pools at Isle Royale.

Trophic Cascades in a Multicausal World: Isle Royale and Yellowstone

Questions of whether trophic cascades occur in Isle Royale National Park (IRNP) or Yellowstone National Park's northern range (NR) cannot lead to simple, precise, or definitive answers. Such answers are limited especially by multicausality in the NR and by complex temporal variation in IRNP. Spatial heterogeneity, contingency, and nonequilibrium dynamics also work against simple answers in IRNP and NR. The existence of a trophic cascade in IRNP and NR also depends greatly on how it is defined. For example, some conceive of trophic cascades as entailing essentially any indirect effect of predation. This may be fine, but the primary intellectual value of such a conception may be to assess an important view in community ecology that most species are connected to most other species in a food web through a network of complicated, albeit weak, indirect effects. These circumstances that work against simple answers likely apply to many ecosystems. Despite the challenges of assessing the existence of trophic cascades in IRNP and NR, such assessments result in considerable insights about a more fundamental question: What causes population abundance to fluctuate?

Field philosophy: dualism to complexity through the borderland

For 5 years, we have taught an interdisciplinary experiential environmental philosophy—field philosophy—course in Isle Royale National Park. We crafted this class with a pedagogy and curriculum guided by the ethic of care (Goralnik et al. in J Experiential Education 35(3):412–428, 2012) and a Leopold-derived community-focused environmental ethic (Goralnik and Nelson in J Environ Educ 42(3):181–192, 2011) to understand whether and how wilderness experience might impact the widening of students’ moral communities. But we found that student pre-course writing already revealed a preference for nonanthropocentric and nonutilitarian ethics, albeit with a naive understanding that enabled contradictions and confusion about how these perspectives might align with action. By the end of the course, though, we recognized a recurrent pattern of learning and moral development that provides insight into the development of morally inclusive environmental ethics. Rather than shift from a utilitarian or anthropocentric ethic to a more biocentric or ecocentric ethic, students instead demonstrated a metaphysical shift from a worldview dominated by dualistic thinking to a more complex awareness of motivations, actions, issues, and natural systems. The consistent occurrence of this preethical growth, observed in student writing and resulting from environmental humanities field learning, demonstrates a possible path to ecologically informed holistic environmental ethics.

Plant community development of Isle Royale’s moose-spruce savannas

In Isle Royale National Park, heavy moose browsing over the past 100 years has suppressed the regeneration of many tree species, gradually resulting in a shift towards more open forests and savannas. By 1996, 16% of the forests at the southwestern end of Isle Royale had become savanna and another 20% of forests were starting to have canopy breakup. The changes in understory vegetation brought about by savanna formation have received little attention, even though the future of moose and wolf populations on Isle Royale is tied to these vegetation changes. This study examined the vegetation of savannas ranging in age (date since formation) from <10 years to 80 years to examine how the ground flora changes over time from initial forest canopy breakup, to extensive grassland, and finally to a zootic subclimax dubbed “moose-spruce savanna.” Ordination techniques were used to describe plant communities and to identify environmental variables that influence vegetation development. Nonparametric multiplicative regression was used to predict how these variables influenced individual plants and structure within the communities. Plant communities had a notable shift from forest herbs to ruderal species, especially non-native plants. This succession was influenced strongly by the underlying bedrock and hydrology-altering moisture regimes and plant communities. Picea glauca (Moench) Voss. and Poa pratensis L. competed in a dynamic inhibitory relationship. The former facilitated forest plants while the latter out-competed other plants and promoted open swards. These interactions are dramatically changing the character of Isle Royale’s upland plant communities and will have important trophic consequences for the island.

Genetic rescue in Isle Royale wolves: genetic analysis and the collapse of the population

While genetic rescue is known to benefit population viability, the duration of that benefit is poorly understood. We document what appears to be the waning benefit of genetic rescue after approximately 2–3 generations for the wolf population in Isle Royale National Park. The fitness benefit of genetic rescue declined because of inbreeding and population abundance declined when the inbred individuals exhibited low reproduction and survival. Only detailed studies of other cases will reveal what aspects of these dynamics represent general features of genetic rescue. We also present evidence indicating that numerous past immigration events have likely gone undetected. This finding is of particular significance because the Isle Royale wolf population has maintained good population viability for decades even though it was small and thought to be isolated from the mainland population of wolves. Past gene flow also suggests that human-assisted gene flow is necessary to conserve the ecosystem services associated with predation, since climate warming has reduced the frequency of ice bridges and with it the only opportunity for unassisted gene flow.

Where Wolves Kill Moose: The Influence of Prey Life History Dynamics on the Landscape Ecology of Predation

The landscape ecology of predation is well studied and known to be influenced by habitat heterogeneity. Little attention has been given to how the influence of habitat heterogeneity on the landscape ecology of predation might be modulated by life history dynamics of prey in mammalian systems. We demonstrate how life history dynamics of moose (Alces alces) contribute to landscape patterns in predation by wolves (Canis lupus) in Isle Royale National Park, Lake Superior, USA. We use pattern analysis and kernel density estimates of moose kill sites to demonstrate that moose in senescent condition and moose in prime condition tend to be wolf-killed in different regions of Isle Royale in winter. Predation on senescent moose was clustered in one kill zone in the northeast portion of the island, whereas predation on prime moose was clustered in 13 separate kill zones distributed throughout the full extent of the island. Moreover, the probability of kill occurrence for senescent moose, in comparison to prime moose, increased in high elevation habitat with patches of dense coniferous trees. These differences can be attributed, at least in part, to senescent moose being more vulnerable to predation and making different risk-sensitive habitat decisions than prime moose. Landscape patterns emerging from prey life history dynamics and habitat heterogeneity have been observed in the predation ecology of fish and insects, but this is the first mammalian system for which such observations have been made.

An integrated assessment of polycyclic aromatic hydrocarbons (PAHs) and benthic macroinvertebrate communities in Isle Royale National Park

Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent organic pollutants that are known carcinogens and mutagens. This research used the sediment quality triad, an integrated weight-of-evidence approach, to evaluate sediment PAH concentrations, sediment toxicity, and benthic community structure at marina and reference sites in Isle Royale National Park, USA. The highest PAH concentrations were measured at marina locations and exceeded threshold effect concentrations (161μg PAH/g TOC) at one site. Marina locations were dominated by pyrogenic PAHs, indicating anthropogenic sources of these compounds. Survival of the amphipod Hyalella azteca was significantly reduced (p=0.0320) when exposed to sediments from marinas. Although macroinvertebrate abundance and species richness were similar at marina and reference sites, results of multivariate analyses showed that composition of benthic communities varied among sites. In particular, abundance of the PAH-sensitive amphipod, Diporeia spp. was significantly lower at marina sites compared to reference sites. In contrast to patterns observed for organochlorines (e.g., PCBS, dioxins), biota-sediment accumulation factors for PAHs measured in the burrowing mayfly Hexagenia limbata decreased with increasing Kow values, suggesting that the more lipophilic compounds were being metabolized. Increased PAH concentrations, shifts in community composition, low survival of H. azteca, and reduced abundances of Diporeia spp. at marina sites were consistent with the hypothesis that PAHs impacted these areas; however, across all sites these effects were relatively subtle. These results emphasize the need to use a weight-of-evidence approach when investigating effects of environmental contaminants that occur at relatively low concentrations.

The Forests of Isle Royale National Park: Can We Preserve This Pristine Wilderness in the Face of Climate Change?

Isle Royale National Park (IRNP) is an archipelago in west central Lake Superior. In 2010, the National Park Service Great Lakes Inventory and Monitoring Network initiated a long-term monitoring program at IRNP with the goals being to: (1) determine the current forest structure, (2) assess how succession and climate change will impact species assemblages, and (3) develop realistic management targets related to climate change impacts on IRNP forests. Five forest types were identified, with three of these (sugar maple (Acer saccharum Marsh.)/birch, eastern white cedar (Thuja occidentalis L), and balsam fir (Abies balsamea (L.) Mill.)) being climax types with little likelihood of succeeding into any other type over the next two to three decades. Two forest types (white spruce (Picea glauca (Moench) Voss),/trembling aspen (Populus tremuloides Michx.), and paper birch (Betula papyrifera Marsh.)) were in a state of transition. The long-term (> 50 year) successional pathways of all five forest types will be influenced by climate change, species' migration abilities, and disease. Many dominant species currently on the island, including balsam fir, black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.), and white spruce, are expected to become extirpated, while the abundance of other common species, including paper birch and trembling aspen, is expected to decline. The 21 km distance between the mainland and the islands will prohibit timely immigration of new species onto the island in the face of climate change. Immigration will likely be led by avian-dispersed species (Prunus spp., exotic Lonicera spp., and Rhamnus cathartica, another exotic species) with dispersal of other taxa relying on stochastic events or human transport. Managers should consider assisted migration to ensure that species assemblages remain congruent; otherwise, stable ecosystems dominated by a few non-native taxa may result. This is especially relevant on the eastern side of the island where balsam fir forests dominate in shallow, bedrock-derived soils.

The influence of winter severity, predation and senescence on moose habitat use

Habitat use is widely known to be influenced by abiotic and biotic factors, such as climate, population density, foraging opportunity and predation risk. The influence of the life-history state of an individual organism on habitat use is less well understood, especially for terrestrial mammals. There is good reason to expect that life-history state would affect habitat use. For example, organisms exhibiting poor condition associated with senescence have an increased vulnerability to predation and that vulnerability is known to alter habitat use strategies. We assessed the influence of life-history stage on habitat use for 732 moose (Alces alces) killed by wolves (Canis lupus) over a 50-year period in Isle Royale National Park, an island ecosystem in Lake Superior, USA. We developed regression models to assess how location of death was associated with a moose's life-history stage (prime-aged or senescent), presence or absence of senescent-associated pathology (osteoarthritis and jaw necrosis), and annual variation in winter severity, moose density and ratio of moose to wolves, which is an index of predation risk. Compared to senescent moose, prime-aged moose tend to make greater use of habitat farther from the shoreline of Isle Royale. That result is ecologically relevant because shoreline habitat on Isle Royale tends to provide better foraging opportunities for moose but is also associated with increased predation risk. During severe winters prime-aged moose tend to make greater use of habitat that is closer to shore in relation to senescent-aged moose. Furthermore, moose of both age classes were more likely to die in riskier, shoreline habitat during years when predation risk was lower in the preceding year. Our results highlight a complicated connection between life history, age-structured population dynamics and habitat-related behaviour. Our analysis also illustrates why intraspecific competition should not be the presumed mechanism underlying density-dependent habitat use, if predation risk is related to density, as it is expected to be in many systems.

Becoming Wilderness: Nature, History, and the Making of Isle Royale National Park by Amalia Tholen Baldwin (review)

Becoming Wilderness: Nature, History, and the Making of Isle Royale National Park by Amalia Tholen Baldwin (review)

Becoming Wilderness: Nature, History, and the Making of Isle Royale National Park. By Amalia Tholen Baldwin. Houghton: IRKPA Press, 2011. vi + 90 pp. Illustrations, map, notes, and bibliography. Paper $12.95.

Previous articleNext article No AccessBOOK REVIEWSBecoming Wilderness: Nature, History, and the Making of Isle Royale National Park. By Amalia Tholen Baldwin. Houghton: IRKPA Press, 2011. vi + 90 pp. Illustrations, map, notes, and bibliography. Paper $12.95.Francis M. CarrollFrancis M. Carroll University of Manitoba Search for more articles by this author PDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 17, Number 2April 2012 Published for the American Society for Environmental History and the Forest History Society Views: 12Total views on this site Article DOIhttps://doi.org/10.1093/envhis/ems008 Views: 12Total views on this site HistoryPublished online February 22, 2012 © 2012 The Author. All rights reserved.PDF download Crossref reports no articles citing this article.

Temperature, recreational fishing and diapause egg connections: dispersal of spiny water fleas (Bythotrephes longimanus)

The spiny water flea (Bythotrephes longimanus) is spreading from Great Lakes coastal waters into northern inland lakes within a northern temperature-defined latitudinal band. Colonization of Great Lakes coastal embayments is assisted by winds and seiche surges, yet rapid inland expansion across the northern states comes through an overland process. The lack of invasions at Isle Royale National Park contrasts with rapid expansion on the nearby Keweenaw Peninsula. Both regions have comparable geology, lake density, and fauna, but differ in recreational fishing boat access, visitation, and containment measures. Tail spines protect Bythotrephes against young of the year, but not larger fish, yet the unusual thick-shelled diapausing eggs can pass through fish guts in viable condition. Sediment traps illustrate how fish spread diapausing eggs across lakes in fecal pellets. Trillions of diapausing eggs are produced per year in Lake Michigan and billions per year in Lake Michigamme, a large inland lake. Dispersal by recreational fishing is linked to use of baitfish, diapausing eggs defecated into live wells and bait buckets, and Bythothephes snagged on fishing line, anchor ropes, and minnow seines. Relatively simple measures, such as on-site rinsing of live wells, restricting transfer of certain baitfish species, or holding baitfish for 24 h (defecation period), should greatly reduce dispersal.

Genomic sweep and potential genetic rescue during limiting environmental conditions in an isolated wolf population

Genetic rescue, in which the introduction of one or more unrelated individuals into an inbred population results in the reduction of detrimental genetic effects and an increase in one or more vital rates, is a potentially important management tool for mitigating adverse effects of inbreeding. We used molecular techniques to document the consequences of a male wolf (Canis lupus) that immigrated, on its own, across Lake Superior ice to the small, inbred wolf population in Isle Royale National Park. The immigrant's fitness so exceeded that of native wolves that within 2.5 generations, he was related to every individual in the population and his ancestry constituted 56 per cent of the population, resulting in a selective sweep of the total genome. In other words, all the male ancestry (50% of the total ancestry) descended from this immigrant, plus 6 per cent owing to the success of some of his inbred offspring. The immigration event occurred in an environment where space was limiting (i.e. packs occupied all available territories) and during a time when environmental conditions had deteriorated (i.e. wolves' prey declined). These conditions probably explain why the immigration event did not obviously improve the population's demography (e.g. increased population numbers or growth rate). Our results show that the beneficial effects of gene flow may be substantial and quickly manifest, short-lived under some circumstances, and how the demographic benefits of genetic rescue might be masked by environmental conditions.

Wolves modulate soil nutrient heterogeneity and foliar nitrogen by configuring the distribution of ungulate carcasses

Mechanistic links between top terrestrial predators and biogeochemical processes remain poorly understood. Here we demonstrate that large carnivores configure landscape heterogeneity through prey carcass distribution. A 50-year record composed of > 3600 moose carcasses from Isle Royale National Park, Michigan, USA, showed that wolves modulate heterogeneity in soil nutrients, soil microbes, and plant quality by clustering prey carcasses over space. Despite being well utilized by predators, moose carcasses resulted in elevated soil macronutrients and microbial biomass, shifts in soil microbial composition, and elevated leaf nitrogen for at least 2-3 years at kill sites. Wolf-killed moose were deposited in some regions of the study landscape at up to 12x the rate of deposition in other regions. Carcass density also varied temporally, changing as much as 19-fold in some locations during the 50-year study period. This variation arises, in part, directly from variation in wolf hunting behavior. This study identifies a top terrestrial predator as a mechanism generating landscape heterogeneity, demonstrating reciprocal links between large carnivore behavior and ecosystem function.

Declines in moose population density at Isle Royle National Park, MI, USA and accompanied changes in landscape patterns

Ungulate herbivores create patterns of forage availability, plant species composition, and soil fertility as they range across large landscapes and consume large quantities of plant material. Over time, herbivore populations fluctuate, producing great potential for spatio-temporal landscape dynamics. In this study, we extend the spatial and temporal extent of a long-term investigation of the relationship of landscape patterns to moose foraging behavior at Isle Royale National Park, MI. We examined how patterns of browse availability and consumption, plant basal area, and soil fertility changed during a recent decline in the moose population. We used geostatistics to examine changes in the nature of spatial patterns in two valleys over 18 years and across short-range and long-range distance scales. Landscape patterns of available and consumed browse changed from either repeated patches or randomly distributed patches in 1988–1992 to random point distributions by 2007 after a recent record high peak followed by a rapid decline in the moose population. Patterns of available and consumed browse became decoupled during the moose population low, which is in contrast to coupled patterns during the earlier high moose population. Distributions of plant basal area and soil nitrogen availability also switched from repeated patches to randomly distributed patches in one valley and to random point distributions in the other valley. Rapid declines in moose population density may release vegetation and soil fertility from browsing pressure and in turn create random landscape patterns.

Scaling the effects of moose browsing on forage distribution, from the geometry of plant canopies to landscapes

Landscape heterogeneity influences large herbivores by altering their feeding rates, but as herbivores attempt to maximize feeding rates they also create spatial heterogeneity by altering plant growth. Herbivore feeding rates thus provide a quantitative link between the causes and consequences of spatial heterogeneity in herbivore‐dominated ecosystems.The fractal geometry of plant canopies determines both the density and mass of twigs available to foraging herbivores. These properties determine a threshold distance between plants (d*) that distinguishes the mechanisms regulating herbivore intake rates. When d* is greater than the actual distance between plants (d), intake is regulated by the rate of food processing in the mouth. But when d* < d, intake is regulated by the rate at which the herbivore encounters new plants. Alterations to plant geometry due to past browsing could change the rate at which herbivores encounter and process bites of plant tissue, modify d* relative to d, and thus change intake rates and the distribution of mechanisms regulating it across landscapes.We measured changes in the geometry of aspen (Populus tremuloides) and balsam fir (Abies balsamea) saplings along gradients of moose browsing from 2001 to 2005 at Isle Royale National Park, Michigan, USA. For aspen saplings, fractal dimension of bite density, bite mass, and forage biomass responded quadratically to increasing moose browsing and were greatest at ∼3–4 g·m−2·yr−1 consumption. For balsam fir, in contrast, these same measures declined steadily with increasing moose browsing.The different responses of plant canopies to increased browsing altered d* around plants. In summer, d* ≥ d for aspen saplings at all prior consumption levels. Food processing therefore regulated summer moose feeding rates across our landscapes. In winter, changes in bite mass due to past browsing were sufficient to cause d* < d for aspen and balsam fir. Therefore, travel velocity and food processing jointly regulated intake rate during winter. Browsing‐induced changes in the small‐scale geometry of plant canopies can determine intake rate at larger spatial scales by changing d* relative to d and, hence, which mechanisms determine intake rate, essentially altering how herbivores sense the distribution of their food resources.