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Cited by 268Wildlife Ecology and ConservationRangeland and Wildlife ManagementAnimal Ecology and Behavior Studies

Animal migration amid shifting patterns of phenology and predation: lessons from a Yellowstone elk herd

Open access
Middleton, Arthur D., Kauffman, Matthew J., McWhirter, Douglas E., Cook, John G., Cook, Rachel C., Nelson, Abigail A., Jimenez, Michael D., Klaver, Robert W.·2013·Ecology
DOI 10.1890/11-2298.1
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Abstract

Migration is a striking behavioral strategy by which many animals enhance resource acquisition while reducing predation risk. Historically, the demographic benefits of such movements made migration common, but in many taxa the phenomenon is considered globally threatened. Here we describe a long‐term decline in the productivity of elk (Cervus elaphus) that migrate through intact wilderness areas to protected summer ranges inside Yellowstone National Park, USA. We attribute this decline to a long‐term reduction in the demographic benefits that ungulates typically gain from migration. Among migratory elk, we observed a 21‐year, 70% reduction in recruitment and a 4‐year, 19% depression in their pregnancy rate largely caused by infrequent reproduction of females that were young or lactating. In contrast, among resident elk, we have recently observed increasing recruitment and a high rate of pregnancy. Landscape‐level changes in habitat quality and predation appear to be responsible for the declining productivity of Yellowstone migrants. From 1989 to 2009, migratory elk experienced an increasing rate and shorter duration of green‐up coincident with warmer spring–summer temperatures and reduced spring precipitation, also consistent with observations of an unusually severe drought in the region. Migrants are also now exposed to four times as many grizzly bears (Ursus arctos) and wolves (Canis lupus) as resident elk. Both of these restored predators consume migratory elk calves at high rates in the Yellowstone wilderness but are maintained at low densities via lethal management and human disturbance in the year‐round habitats of resident elk. Our findings suggest that large‐carnivore recovery and drought, operating simultaneously along an elevation gradient, have disproportionately influenced the demography of migratory elk. Many migratory animals travel large geographic distances between their seasonal ranges. Changes in land use and climate that disparately influence such seasonal ranges may alter the ecological basis of migratory behavior, representing an important challenge for, and a powerful lens into, the ecology and conservation of migratory taxa.

AI snapshot

Written from the paper’s full text.

TL;DR

A long-term study of the Clarks Fork elk herd found that migratory elk productivity declined while resident elk productivity increased, with the decline linked to drought-related changes in vegetation phenology and greater exposure to recovering grizzly bears and wolves. The results suggest that migration’s demographic advantages can weaken even in protected wilderness when climate and predation patterns shift.

Key findings

  • Migratory elk calf recruitment fell by 73.5% from 1989 to 2009, while resident recruitment declined to a breakpoint around 2002 and then increased. Over four winters, pregnancy was 70.6% for migrants (n = 75) versus 89.2% for residents (n = 65); the best model showed a quadratic age effect and an independent lower pregnancy probability for migratory status (P = 0.04).
  • Among migratory females aged 4–14, lactating elk had a 21.4% pregnancy rate (3/14) compared with 86.7% (13/15) for non-lactating elk (P < 0.001). Resident pregnancy did not differ by lactation status (86.7% vs. 100%, P = 0.57).
  • On the migratory summer range, green-up duration shortened by 1.3 days per year, totaling 27 days over 21 years, while peak NDVI and maximum NDVI increment increased. April–August temperatures rose, July temperature increased by about 4°C, and April–May precipitation declined.
  • Migratory elk were exposed to roughly four times as many grizzly bear groups and wolves as resident elk; average wolf numbers were 35.2 versus 8.1. In an overlapping study, bears caused 58–60% of calf deaths and wolves 15–17%.

Methods

  • The study compared migratory and resident subpopulations of the approximately 4,500-animal Clarks Fork elk herd using winter helicopter and ground surveys from 1989 to 2009, summer recruitment surveys from 2007 to 2009, and captures in 2007–2008 with GPS or VHF collars. Pregnancy was assessed by PSPB analysis or palpation, and body condition, rump fat, and chest girth were measured.
  • Analyses included piecewise regression, generalized linear mixed models with AIC selection, t tests, Kolmogorov-Smirnov tests, and Fisher’s exact tests. Vegetation phenology was measured with AVHRR NDVI from 1989 to 2009, climate data came from PRISM, and predator counts came from Interagency Grizzly Bear Study Team, National Park Service, and U.S. Fish and Wildlife Service time series.
  • Seasonal ranges were delineated using minimum convex polygons from GPS-collared migratory and resident elk; forested cover was excluded from NDVI sampling, and irrigated field use by resident elk was quantified from GPS locations.

Limitations

  • Stated: the authors did not directly estimate cause-specific calf mortality for their study population and instead assumed predation rates were similar to those from an overlapping 2003–2005 study. They also could not document population trends for black bears or mountain lions, and they were unsure why lower pregnancy among lactating migrants was not accompanied by lower body fat.
  • Evident: the design is observational and correlational, so the links among drought, phenology, predator abundance, and elk demography are not experimentally isolated. Migratory and resident elk differ in range, management exposure, and age structure, and predator abundance is used as an index rather than a direct measure of predation on the study animals.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1890/11-2298.1

Cites

60 of 60 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

19 of 77 cited sources checked · 7 supported · 0 flagged · accuracy not yet measured

  • Premisecitation

    Feeding on emergent vegetation at the onset of growing season is adaptive because it promotes fat gain and reproduction.

    “Following these periods of poor nutrition, feeding upon emergent vegetation at the onset of the growing season is adaptive because such highly digestible forage promotes fat gain and reproduction (Cook et al. 2004a, Parker et al. 2009).”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites Cook et al. 2004a source
    • cites Parker et al. 2009 source

      The ‘Minimizing the maximum detriment to free-ranging ungulates’ section describes emerging shoots as high-quality forage and says ungulates should select nutritious food in spring. The ‘Conclusion and perspectives’ and ‘Body fat’ sections link nutrient intake, fat reserves, and reproduction, but place replenishment of reserves chiefly in summer and autumn; they do not specifically establish that feeding on vegetation at the onset of spring promotes fat gain. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
  • Premisecitation

    Most attention on migration declines has focused on habitat degradation and physical barriers, which have reduced prominent migratory populations.

    “Most of this attention has focused on habitat degradation and conspicuous physical barriers to migration (e.g., fences and roads), which have reduced prominent migratory populations (Harris et al. 2009).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites Harris et al. 2009 source

      The Threats and Discussion sections identify habitat loss, fences, and transportation corridors as threats to migrations and migratory populations. The paper does not establish that most attention to migration declines has focused on those threats; it also identifies unsustainable hunting as a principal cause. Page numbers are unavailable in our copy. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
  • Premisecitation

    For temperate species, winter cold and deep snow cause steady body mass decline.

    “For temperate species, the cold temperatures and deep snow of winter cause a steady decline in body mass (Parker et al. 2009)”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Parker et al. 2009 source

      The Body Mass section says northern ungulates commonly lose body mass over winter, while the Energy Costs and Intake section describes increased movement costs in snow and cumulative energetic costs of cold. The paper does not establish that cold and deep snow cause a steady decline in body mass across temperate species specifically. The indexed passages do not provide page numbers. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
  • Premisecitation

    Much empirical evidence indicates pregnancy of temperate ungulates is influenced primarily by growing-season nutrition.

    “much empirical evidence indicates that pregnancy of temperate ungulates is influenced primarily by growing-season nutrition (Langvatn et al. 1996, Cook et al. 2004a, Parker et al. 2009).”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites Langvatn et al. 1996 source
    • cites Cook et al. 2004a source
    • cites Parker et al. 2009 source
  • Interpretationcitation

    A likely mechanism for climate-induced reduction in migratory elk reproductive performance is a mismatch between vegetation green-up and the lactation period.

    “Therefore, one likely mechanism for a climateinduced reduction in the reproductive performance of migratory elk is a ''mismatch'' between vegetation greenup and the period of lactation (Post and Forchhammer 2008).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites Post and Forchhammer 2008 source

      The Introduction describes a potential mismatch between plant growth and the resource demands of lactation, and the Abstract reports reduced reproductive success associated with that mismatch. The study concerns migratory caribou in West Greenland, not elk, so it does not establish the proposed mechanism specifically for elk. (LLM, conf=0.87)

      Experimental — accuracy not yet measured
  • Classified as probably not a substantial claim. 21
  • May combine two claims. 37

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    High annual NDVI increments are negatively related to juvenile growth and survival.

    “high annual NDVI increments (i.e., rapid vegetation emergence) have been negatively related to juvenile growth and survival (Pettorelli et al. 2007).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Pettorelli et al. 2007 source

  • May combine two claims.

    Premisecitation

    Elk density and winter severity have been decreasing in the system for many years.

    “Indeed, elk density and winter severity have been decreasing in the system for many years (Wilmers andGetz 2005, Eberhardt et al. 2007).”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites Wilmers and Getz 2005 source

      The Weather Data Analysis and Discussion sections report declining winter snow depth and a shorter period of snow cover since 1948, supporting the winter-severity part of the claim. They do not report that elk density has been decreasing for many years; the Discussion instead predicts higher elk densities if snow levels continue to decline. Page numbers are not available in our copy. (LLM, conf=0.87)

      Experimental — accuracy not yet measured
    • cites Eberhardt et al. 2007 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Global declines in ungulate migration have raised concern, including in wildebeest, saiga, pronghorn, and caribou.

    “In recent years, however, concern has grown over global declines in ungulate migration, including such diverse species as wildebeest (Connochaetus taurinus), saiga (Saiga tatarica), pronghorn (Antilocapra americana), and caribou (Rangifer tarandus) (Berger 2004, Bolger et al. 2008, Festa-Bianchet et al. 2011).”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites Berger 2004 source
    • cites Bolger et al. 2008 source
    • cites Festa-Bianchet et al. 2011 source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Prior research has shown that recent drought has diverse effects on regional wildfire activity and snowpack, amphibian populations, and bat reproduction.

    “Prior research has revealed diverse influences of recent drought on the region's wildfire activity and snowpack (Westerling et al. 2006), amphibian populations (McMenamin et al. 2008), and bat reproduction (Adams 2010).”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites Westerling et al. 2006 source
    • cites McMenamin et al. 2008 source
    • cites Adams 2010

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In European migratory birds, a mismatch between spring arrival and breeding-range phenology may be linked to recent population declines.

    “In migratory birds in Europe, such a mismatch between the springtime arrival of migrants and the phenology of their breeding range may be linked to recent population declines (Both et al. 2006).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Both et al. 2006 source

      The supplementary Table 1A reports recent population declines in several pied flycatcher populations in the Netherlands and gives caterpillar peak dates for their breeding areas. The passages available from our copy do not establish a mismatch between spring arrival and breeding-range phenology or link that mismatch to the declines. (LLM, conf=0.78)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    Elk in Yellowstone do not strongly avoid wolves during winter and do not avoid foraging on willow and aspen even in high-risk areas.

    “This latter finding is consistent with the observations that elk in Yellowstone do not strongly avoid wolves during winter (Fortin et al. 2005, Mao et al. 2005) and do not avoid foraging on two preferred browse species, willow and aspen, even in high-risk areas of the ecosystem (Creel et al. 2009, Kauffman et al. 2010).”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites Fortin et al. 2005 source
    • cites Mao et al. 2005 source
    • cites Creel et al. 2009 source

      The Abstract reports that elk shifted from grazing to browsing when wolves were present, which supports the general point that they continued to browse. It does not identify willow or aspen, or establish that elk continued foraging on those species in high-risk areas. The winter wolf-avoidance clause is attributed to other citations in the citing sentence. (LLM, conf=0.82)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    In the only prior ungulate case known to the authors, recent Arctic warming advanced vegetation green-up more rapidly than female caribou advanced parturition, with negative effects on calf production.

    “In the only prior case for ungulates that we know of, recent arctic warming advanced vegetation green-up more rapidly than female caribou (Rangifer tarandus) advanced their parturition date, with negative effects on calf production (Post and Forchhammer 2008).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites Post and Forchhammer 2008 source

  • Classified as probably not a substantial claim.

    Premisecitation

    Recent work found no differences in body fat levels and pregnancy rates of Yellowstone elk before and after wolf reintroduction.

    “recent work found no differences in the body fat levels and pregnancy rates of Yellowstone elk before and after wolf reintroduction (White et al. 2011).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites White et al. 2011 source

      The Abstract reports nearly identical age-adjusted body fat before and after wolf restoration, and the Results report similar pregnancy rates for elk aged 4–9 years. But the Results also report higher post-wolf body fat and pregnancy rates for elk older than 9 years. Thus, saying there were no differences across Yellowstone elk overgeneralizes the findings. (LLM, conf=0.89)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Some caribou declines may be linked to subtler changes in plant phenology, fire regimes, accessibility to predators, and densities of alternative prey.

    “some caribou declines may be linked to subtler changes in plant phenology, fire regimes, the accessibility of caribou to their predators, and densities of alternative prey (Vors andBoyce 2009, Festa-Bianchet et al. 2011).”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites Vors and Boyce 2009 source
    • cites Festa-Bianchet et al. 2011 source

      The Boreal and Mountain caribou section links declines to habitat changes, predation, altered alternative-prey abundance, and wolves’ travel efficiency; it also says increasing fire events could reduce recruitment and survival. The Migratory Tundra caribou section discusses changing plant-growth timing, but says that change may benefit caribou rather than linking it to declines. No page numbers were available in our copy. (LLM, conf=0.82)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Bird population declines may be linked to trophic mismatch.

    “population declines may be linked to trophic mismatch (Both et al. 2006)”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Both et al. 2006 source

      The supplementary table lists pied flycatcher population trends and caterpillar peak dates, but does not say that a mismatch between breeding and food availability is linked to the declines. Searches for “mismatch” and for breeding timing relative to caterpillar peaks found no decisive passage; the main article text appears absent from our copy. (LLM, conf=0.70)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Findingown data

    We detected no influence of density dependence or winter severity on calf:cow ratio.

    “we detected no influence of density dependence (regression of calf : cow ratio on abundance, F 1,12 ¼ 1.0, P ¼ 0.34) or winter severity (regression of calf : cow ratio on cumulative snow water equivalent [Wolverine Creek SNO-TEL, 10 km northwest of the core winter range of migrants], F 1,21 ¼ 3.02, P ¼ 0.1).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The green-up changes coincided with warmer spring-summer temperatures and reduced spring precipitation.

    “coincident with warmer spring-summer temperatures and reduced spring precipitation”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Resident elk recently showed increasing recruitment and a high pregnancy rate.

    “In contrast, among resident elk, we have recently observed increasing recruitment and a high rate of pregnancy.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Long-term monitoring revealed a shift in spatial distribution of the population over 21 years, driven by high recruitment and eastward expansion of residents.

    “Long-term monitoring has revealed an associated shift in the spatial distribution of the population over 21 years, driven by high recruitment levels (see Fig. 2A) and eastward expansion in the resident subpopulation (Appendix A).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    A similar warming trend occurred on resident elk year-round range, but no change in spring precipitation.

    “We detected a similar warming trend on the year-round range of resident elk, but no change in spring precipitation (Appendix D).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Some resident females spent 47-52% of their time in irrigated fields during July and August, though irrigated fields are 0.01% of their range.

    “Though only 0.01% of the residents' year-round range is irrigated, 23% (3/13) of resident females spent 47-52% of their time in irrigated fields during July and August.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Calf recruitment of resident elk declined to a breakpoint in 2002, then steadily increased.

    “Calf recruitment of resident elk declined to a breakpoint (2002 6 1.5, P , 0.001), then steadily increased (F 1,19 ¼ 5.71, P ¼ 0.007; Fig. 2A).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The resident elk calf:cow ratio declined to a breakpoint in 2002 and then steadily increased.

    “The calf : cow ratio of resident elk (gray circles) declined to a breakpoint (2002 6 1.5, P , 0.001) and then steadily increased (F 1,21 ¼ 5.71, P ¼ 0.007).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    From 1989 to 2009, maximum NDVI increment did not change on the resident range but increased on the migratory range.

    “From 1989 to 2009, maximum NDVI increment (C) did not change on the resident range but (D) increased on the migratory range”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Over the same period, green-up duration did not change on the resident range but decreased on the migratory range.

    “Over the same period, green-up duration (E) did not change on resident range but (F) decreased on migratory range”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Lactating females were pregnant at a lower rate than non-lactators in the migratory population, whereas lactation did not affect the pregnancy rate of residents.

    “Lactating females were pregnant at a lower rate than non-lactators in the migratory population, whereas lactation did not affect the pregnancy rate of residents.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Several wolf packs now occupy the year-round range of migratory elk, but only one pack has occupied the resident elk range.

    “Several wolf packs now occupy the year-round range of migratory elk (pack numbers shown above bars), but only one pack has occupied the resident elk range.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The body fat of lactating migrants was significantly lower than that of non-lactating migrants, but did not differ from that of lactating residents.

    “The body fat (mean þ SE) of lactating migrants was significantly lower than that of non-lactating migrants, but did not differ from that of lactating residents.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    A one-sided K-S test indicated that migratory elk had a higher proportion of older individuals than residents, consistent with recent reductions in calf recruitment.

    “A one-sided K-S test (see Results) indicated that migratory elk had a higher proportion of older individuals than the residents, consistent with recent reductions in calf recruitment.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The number of grizzly bear groups counted during summer observation flights within the year-round range of migratory elk increased over 21 years, and no grizzlies were observed in flights over the resident elk range.

    “The number of grizzly bear (Ursus arctos) groups (shown with fitted solid line and 95% CI in dashed lines) counted during summer observation flights from 1990 to 2008 within the year-round range of migratory elk increased over 21 years (no grizzlies were observed in flights over the range of resident elk).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Peak protein intake of temperate mountain ungulates coincides with annual maximum NDVI increment.

    “Peak protein intake of temperate mountain ungulates has been shown to coincide with the annual maximum increment in NDVI (Hamel et al. 2009)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Hamel et al. 2009 source

  • Classified as probably not a substantial claim.

    Study design and conductcitation

    Agency observations were classified at subpopulation level based on winter range associations established previously via VHF telemetry and validated through GPS collaring during 2007-2010.

    “Agency observations were classified at the subpopulation level based on winter range associations of migratory and resident elk established previously via very high frequency (VHF) telemetry (Rudd et al. 1983), and validated through our own Global Positioning System (GPS) collaring during 2007-2010.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Rudd et al. 1983

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Migration evolved in ungulates because it provides prolonged access to high-quality forage and can reduce predator exposure in seasonal environments.

    “Migration is thought to have evolved in ungulates because in seasonal environments it affords prolonged access to high-quality forage and can reduce predator exposure (Fryxell and Sinclair 1988).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Fryxell and Sinclair 1988

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Migrations of Serengeti wildebeest, Greater Yellowstone elk, and mule deer track vegetation green-up.

    “Accordingly, the migrations of species such as Serengeti wildebeest, and Greater Yellowstone elk (Cervus elaphus) and mule deer (Odocoileus hemonius) track vegetation green-up (Holdo et al. 2009, White et al. 2010, Sawyer and Kauffman 2011).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Holdo et al. 2009

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites White et al. 2010

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Sawyer and Kauffman 2011 source

  • May combine two claims.

    Interpretationreasoning

    Resident elk are likely subsidized by removal of large carnivores and by irrigated agriculture, contributing to their recent expansion.

    “In contrast, resident elk are likely subsidized by the removal of large carnivores and by irrigated agriculture, contributing to their recent expansion.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Reduced mortality due to predation is thought to benefit migratory individuals by increasing juvenile survival.

    “Thus, reduced mortality due to predation is thought to benefit migratory individuals by increasing juvenile survival (Bolger et al. 2008).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Bolger et al. 2008 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In relatively pristine landscapes, fitness benefits of migration have promoted abundance of migratory ungulates, which can outnumber residents by an order of magnitude.

    “In relatively pristine landscapes, such fitness benefits have promoted the abundance of migratory ungulates, which can outnumber their resident counterparts in some cases by an order of magnitude (Fryxell et al. 1988).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Fryxell et al. 1988

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Premisecitation

    In Serengeti, predation was lower for migratory than resident wildebeest; in Alberta, migratory elk reduced wolf exposure by 70% compared with residents.

    “For instance, in the Serengeti Ecosystem, predation was found to be lower for migratory than for resident wildebeest (Sinclair 1984), and in Alberta, migratory elk reduced their wolf exposure by 70% in comparison with resident elk (Hebblewhite and Merrill 2007).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Sinclair 1984

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Hebblewhite and Merrill 2007 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The influence of differential carnivore recovery and predation on partially migratory elk performance has previously been investigated in and around Banff National Park.

    “The influence of differential carnivore recovery and predation on the performance of partially migratory elk has previously been investigated in and around Banff National Park (BNP) in Alberta, Canada.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The early-winter low pregnancy rates suggest a summer influence on the probability of conception, which conflicts with the proposed winter nonconsumptive-effect mechanism.

    “suggesting a summer influence on the probability of conception that is at odds with the proposed mechanism.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Sexual maturity was delayed in European red deer populations that experienced warmer springs and advanced phenology, probably due to reduced growth rates among calves and yearlings.

    “For instance, sexual maturity was delayed in populations of European red deer (Cervus elaphus) that experienced warmer springs and advanced phenology (Langvatn et al. 1996), probably because of reduced growth rates among calves and yearlings (Cook et al. 2004a).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Langvatn et al. 1996 source
    • cites Cook et al. 2004a source

  • May combine two claims.

    Premisecitation

    Fluctuations in short-term energy balance are known to influence pregnancy probability of domestic ungulates and may occur without large changes in body fat.

    “Fluctuations in short-term energy balance are known to influence the pregnancy probability of domestic ungulates (e.g., National Research Council 1985, Fitz-Rodriguez et al. 2009), and may occur without large changes in body fat levels.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites National Research Council 1985

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Fitz-Rodriguez et al. 2009 source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Recent studies describe regional climatic changes as anomalous in millennial and longer contexts and as consistent with anthropogenic forcing.

    “recent studies have described regional climatic changes as anomalous (within 1000-year [Pederson et al. 2011] and 14 000-year [Shuman 2011] contexts) and consistent with anthropogenic forcing (Barnett et al. 2008, Shuman 2011).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Pederson et al. 2011 source
    • cites Shuman 2011

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Barnett et al. 2008 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The caribou climate effect was thought to be mediated by nutritional limitation on lactating females, similar to recent findings in Rocky Mountain bats including migratory populations.

    “The latter climate effect was thought to be mediated by a nutritional limitation on lactating females, similar to recent findings among Rocky Mountain bats, including migratory populations (Adams 2010).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Adams 2010

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Premisecitation

    Newly reintroduced wolves caused 15-17% of calf deaths, favoring young calves in summer.

    “Additionally, newly reintroduced wolves caused 15-17% of calf deaths, favoring young calves in summer (Barber-Meyer et al. 2008).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Barber-Meyer et al. 2008 source

  • May combine two claims.

    Interpretationreasoning

    Recent increases in resident elk recruitment are consistent with a likely nutritional subsidy from irrigated fields coupled with lower rates of calf predation by grizzlies and wolves.

    “Recent increases in the recruitment of resident elk are consistent with a likely nutritional subsidy from irrigated fields, coupled with lower rates of calf predation by grizzlies and wolves.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: In the year-round habitats of resident elk, large carnivores are limited by management removals following livestock depredations, and bears may be further limited by low tolerance for human activity.

  • May combine two claims.

    Interpretationown data

    An additional factor contributing to reduced pregnancy rate of migratory subpopulation was its older age structure, likely a result of sustained low recruitment.

    “An additional factor contributing to the reduced pregnancy rate of the migratory subpopulation was its older age structure (Fig. 3B), a likely result of sustained low recruitment in recent years.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    A secondary reason proposed for the historical dominance of migratory ungulates is that seasonal movements reduce exposure to predation.

    “A secondary reason put forth for the historical dominance of migratory ungulates is that their seasonal movements reduce their exposure to predation (Fryxell et al. 1988, Fryxell andSinclair 1988).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Fryxell et al. 1988

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Fryxell and Sinclair 1988

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Premisecitation

    During that study, bears, primarily grizzlies, caused 58-60% of calf deaths, more than three times the proportion estimated 15 years earlier in the same area.

    “During that study, bears (primarily grizzlies) caused 58-60% of calf deaths (Barber-Meyer et al. 2008), more than three times the proportion estimated 15 years earlier in the same area 1).(Singer et al. 1997).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Barber-Meyer et al. 2008 source
    • cites Singer et al. 1997 source

  • May combine two claims.

    Interpretationown data

    The study's findings newly connect the region's drought to changes in vegetation phenology and to the demographic benefits of ungulate migration.

    “Our findings newly link the region's drought to changes in vegetation phenology and the demographic benefits of ungulate migration.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisenone given

    In the year-round habitats of resident elk, large carnivores are limited by management removals following livestock depredations, and bears may be further limited by low tolerance for human activity.

    “By contrast, in the year-round habitats of resident elk, large carnivores are limited by management removals following livestock depredations, and bears may be further limited by a low tolerance for human activity.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: In the year-round habitats of resident elk, large carnivores are limited by management removals following livestock depredations, and bears may be further limited by low tolerance for human activity.

  • May combine two claims.

    Interpretationreasoning

    The decline in demographic benefits of migration coincided with growing large carnivores and severe drought that appears to have reduced habitat quality.

    “This apparent decline in the demographic benefits of migration coincided with growing numbers of large carnivores that prey on elk calves and a severe, long-term drought that appears to have reduced habitat quality.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    The low pregnancy rate of migrants resulted in part from poor reproduction of young and lactating females, consistent with prior study of ungulates under nutritional limitation.

    “The low pregnancy rate of migrants resulted in part from poor reproduction of young and lactating females (Fig. 3B, C), consistent with prior study of ungulates under nutritional limitation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Warmer temperatures and reduced precipitation appear to facilitate rapid vegetation growth and reduce its availability to Yellowstone migrants on summer range.

    “Overall, warmer temperatures and reduced precipitation appear to facilitate rapid growth of vegetation and reduce the time in which it is available to Yellowstone migrants on their summer range.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Female elk under nutritional stress may give birth to lighter calves with reduced growth rates, which can increase the window of calf vulnerability and risk of calf mortality.

    “Female elk under nutritional stress may give birth to lighter calves with reduced growth rates, which can increase the window of calf vulnerability and risk of calf mortality (Singer et al. 1997, White et al. 2010).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Singer et al. 1997 source
    • cites White et al. 2010

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Birds are known to benefit from abundant resources and reduced predation risk on disparate seasonal ranges.

    “Though birds are also known to benefit from abundant resources (Levey and Stiles 1992) and reduced predation risk (McKinnon et al. 2010) on disparate seasonal ranges”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Levey and Stiles 1992 source
    • cites McKinnon et al. 2010 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Human influences on seasonal resource availability and nest predation have long been a concern in studies of Neotropical migratory birds.

    “human influences on seasonal resource availability and nest predation have long been a concern in studies of Neotropical migratory birds (Robinson et al. 1995).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Robinson et al. 1995 source

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    As land migrants, ungulates appear particularly vulnerable to physical obstruction of their migration routes compared with other migratory taxa.

    “As land migrants, ungulates appear particularly vulnerable to the physical obstruction of their migration routes in comparison with other migratory taxa.”
    Quote in the paperNot a substantial claim
53 of 53

  • The paper relies on this without support.

    Many migratory elk calve before their spring migration.

    “many migratory elk calve prior to their spring migration”

  • The paper relies on this without support.

    The observed decline in migratory elk productivity is not primarily due to other predators or unmeasured factors.

    “Although black bears (Ursus americanus) and mountain lions (Puma concolor) also occur in the study area, we were unable to document trends for these species.”

  • The paper relies on this without support.

    The grizzly bear group observation time series is a valid index of grizzly abundance on the migratory elk range.

    “To evaluate patterns of grizzly abundance, we used a time series of bear group observations conducted in mid-summer flights by the Interagency Grizzly Bear Study Team (IGBST).”

  • The paper relies on this without support.

    The wolf number time series from NPS and USFWS is a valid index of wolf abundance on the elk ranges.

    “To evaluate patterns of wolf abundance, we used a time series from the National Park Service (1996)(1997)(1998) and U.S. Fish and Wildlife Service (1999-2009; available online).”

  • The authors state this as an assumption.

    Rates of calf predation are very similar for the migratory elk studied.

    “Here, we are assuming that rates of calf predation are very similar for the migratory elk we studied.”

  • The paper relies on this without support.

    In the year-round habitats of resident elk, large carnivores are limited by management removals following livestock depredations, and bears may be further limited by low tolerance for human activity.

    “By contrast, in the year-round habitats of resident elk, large carnivores are limited by management removals following livestock depredations, and bears may be further limited by a low tolerance for human activity.”
6 of 6

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • The same resident-elk trend has two denominator degrees of freedom

    Minor

    The results and Fig. 2 caption give different denominator degrees of freedom, 19 and 21, for the same F statistic and P value.

  • Fourfold predator comparison cannot apply to grizzly bears

    Minor

    The abstract applies a fourfold migrant-to-resident comparison to both grizzly bears and wolves, but the results report no grizzlies on resident range. A fourfold comparison with a zero grizzly count is not supported.

  • Grizzly-bear observation period differs between results and caption

    Minor

    The results describe grizzly-bear observations from 1989 to 2009, whereas the Fig. 5 caption dates the observation flights from 1990 to 2008. The caption also calls its shorter interval 21 years.

3 of 3

Cites

Flagged first, then by citations

Research works printed but not linked: 2

  1. Rudd W. J, 1983, Do split hunting seasons influence elk migration from Yellowstone National Park?, Wildlife Society Bulletin, 11, 328
  2. Sinclair A. R. E, 1984, Dynamics of the Serengeti ecosystem: pattern and process, Serengeti: dynamics of an ecosystem, 1

Cited by

Sorted by citations

Related

Authors
Middleton, A. D., Kauffman, M. J., McWhirter, D. E., Cook, J. G., Cook, R. C., Nelson, A. A., Jimenez, M. D., & Klaver, R. W.
Affiliations
  • University of Wyoming (US)
  • Wyoming Game and Fish Department (US)
  • National Council for Air and Stream Improvement (US)
  • United States Fish and Wildlife Service (US)
  • United States Geological Survey (US)
Corresponding author
Middleton, Arthur D.
ORCID
Venue
Ecology
Publisher
Wiley
Published
2013-06
Volume
94
Issue
6
Pages
1245-1256
ISSN
  • 0012-9658 (ISSN-L)
  • 1939-9170
DOI
10.1890/11-2298.1
OpenAlex
W1985547247
Cited by
268
References
60
Citations by year
2026: 11 · 2025: 15 · 2024: 22 · 2023: 18 · 2022: 20 · 2021: 17 · 2020: 22 · 2019: 28 · 2018: 25 · 2017: 21 · 2016: 23 · 2015: 18 · 2014: 9 · 2013: 16 · 2012: 3
FWCI
19.40
Type
journal article
Language
en
Open access
Licence
onlinelibrary.wiley.com/termsAndConditions#vor (vor)
Locations
  • Ecology (publishedVersion)
  • PubMed (publishedVersion)
  • Iowa State University Digital Repository (Iowa State University) (submittedVersion)
Funders
Rocky Mountain Elk Foundation
Topics
  • Physical Sciences › Environmental Science › Ecology › Wildlife Ecology and Conservation
  • Physical Sciences › Environmental Science › Ecology › Rangeland and Wildlife Management
  • Physical Sciences › Environmental Science › Ecology › Animal Ecology and Behavior Studies
Keywords
animal migration, elk, red deer, Yellowstone National Park, predation risk, drought, grizzly bear, wolf, recruitment (biology), pregnancy rate, climate change, habitat quality
MeSH terms
Altitude, Animals, Ursidae, Deer, Environmental Monitoring, Female, Humans, Human Activities, Male, Population Dynamics, Predatory Behavior, Time Factors, Wyoming, Ecosystem, Wolves, Animal Migration

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-09-29.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-09-29.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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