Landscape heterogeneity shapes predation in a newly restored predator–prey system

In the paper

“Native ungulates that have lived without predators are expected to become naı ¨ve and less vigilant, increasing their vulnerability to predation (Berger 1999;Berger et al. 2001;Sand et al. 2006).”

What the sources say

• ?Not checked — no full text of the sourcecites Berger 1999 source
• ?Not checked — no full text of the sourcecites Berger et al. 2001 source
• Supported

  The Introduction links predation to vigilance and says isolation from predators should select against costly anti-predator behaviour. It also predicts that Scandinavian moose unfamiliar with wolves will be relatively easier to kill; the Abstract reports higher wolf hunting success in Scandinavia than in North American populations continuously exposed to predators. Together these support the cited expectation, rather than a claim that reduced vigilance was directly measured. (LLM, conf=0.91)

  cites Sand et al. 2006 source

In the paper

“Several studies on Yellowstone's NR have suggested that wolves are affecting willow (Salix spp.), cottonwood (Populus spp.) and aspen (P.tremuloides) communities by changing the behaviour of elk that heavily browse these woody plants during winter (Ripple et al. 2001;Ripple & Beschta 2004;Beyer et al. 2007).”

What the sources say

• ?Not checked — no full text of the sourcecites Ripple et al. 2001 source
• Supported

  The “Northern winter range” section reports reduced elk browsing of willow and cottonwood at sites with higher wolf-predation risk after reintroduction. It also links wolf predation risk to elk foraging patterns and recruitment of woody plants including aspen, and describes winter browsing of these species on Yellowstone’s northern range. The claim appropriately presents this as a suggestion rather than an established effect across every site. (LLM, conf=0.90)

  cites Ripple & Beschta 2004 source
• ?Not checked — no full text of the sourcecites Beyer et al. 2007 source

In the paper

“Several studies have shown that elk respond to the risk of predation by wolves by increasing vigilance levels (Laundre et al. 2001) or shifting habitat use temporally (Creel et al. 2005;Gude et al. 2006).”

What the sources say

• Supported

  The Discussion reports that female elk increased vigilance in areas with wolves, supporting the claim attached to Laundré et al. (2001). The temporal habitat-use claim is attached to other citations, not this source. Page numbers are not provided in the supplied passages. (LLM, conf=0.94)

  cites Laundre et al. 2001 source
• ?Not matched

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

  cites Creel et al. 2005
• ?Not checked — no full text of the sourcecites Gude et al. 2006 source

In the paper

“During the 10 years since reintroduction, the NR wolf population increased from 14 wolves in three packs to 84 wolves in six packs (Fig. 1a).”

In the paper

“The bestfit landscape model included all landscape variables and vastly outperformed the elk + wolf encounter model (likelihood ratio v 2 ¼ 270.11, d.f.¼ 6, P < 0.0001; Table 1; Table S1).”

In the paper

“Similarly, the per-capita kill rate for wolves on the NR has not declined sharply over the study period (D.W. Smith, unpublished data), suggesting that wolf packs maintained a relatively constant annual kill rate.”

What the sources say

• ?Not matched

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

  cites D.W. Smith, unpublished data

In the paper

“A few large, competitively dominant packs retained access to the best hunting grounds over the 10 years, but the majority of pack territories shifted away from the best hunting grounds as wolf density increased.”

In the paper

“After controlling for pack size, a decline through time in the average catchability of elk within each pack's winter territory area was evident (multiple regression; pack size: t ¼ )2.48, P ¼ 0.0166; year: t ¼ )3.47, P ¼ 0.0011), with a significant pack size • time interaction (t ¼ 2.33, P ¼ 0.0238) whereby large packs had access to high-quality hunting grounds and small packs were relegated to po”

In the paper

“however, our findings indicate that risk is a function of both predator distribution and habitat features, with habitat playing the larger role at high predator densities.”

In the paper

“When first reintroduced, wolf pack distribution also strongly influenced predation risk (panel b), but this influence has largely diminished after 10 years of wolf population expansion.”

In the paper

“Spatial variation in predation risk is largely driven by landscape features, which create a limited number of hunting grounds where predation risk is often 10 times higher than the landscape average (a map value of 1 denotes average risk).”

In the paper

“Over this time period, 92% of the ungulate prey taken by wolves during winter have been elk (Smith et al. 2004).”

What the sources say

• ?Not checked — no full text of the sourcecites Smith et al. 2004 source

In the paper

“In contrast, landscape factors strongly influenced kill sites, creating distinct hunting grounds and prey refugia.”

• Also stated in: § D I S C U S S I O N · hedged

  “Our study suggests that hunting grounds -habitat patches with physical features favourable to hunting success of wolvesexist on the NR, and that their distribution on the landscape influences both territorial space used by wolves and spatial variation in predation risk for elk.”

In the paper

“The history of introductions of exotic predators to predator-free islands illustrates that novel predators can markedly reduce populations of native prey and cause local extinctions (Fritts & Rodda 1998;Knapp et al. 2001;Blackburn et al. 2004).”

What the sources say

• ?Not checked — no full text of the sourcecites Fritts & Rodda 1998 source
• ?Not checked — no full text of the sourcecites Knapp et al. 2001 source
• ?Not checked — no full text of the sourcecites Blackburn et al. 2004 source

In the paper

“Wolves were reintroduced to YNP in 1995 after being extirpated from this ecosystem in the 1930s (Bangs & Fritts 1996).”

What the sources say

• ?Not matched

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

  cites Bangs & Fritts 1996

In the paper

“Theory suggests that native predator-prey systems persist over the long term due to heterogeneity in predation rates caused by prey refugia in space or time (Fryxell et al. 1988;Kareiva & Wennegren 1995;Ellner et al. 2001).”

What the sources say

• ?Not checked — no full text of the sourcecites Fryxell et al. 1988 source
• ?Not checked — no full text of the sourcecites Kareiva & Wennegren 1995 source
• ?Not checked — no full text of the sourcecites Ellner et al. 2001 source

In the paper

“Aerial relocations of wolf packs known to be on a kill were excluded from the UD estimation to reduce the spatial dependence of kill sites on pack territories.”

In the paper

“While an estimated 27% of total kills went undiscovered, the two survey efforts conducted simultaneously (45% of our kills were detected from the air, 71% from the ground and 17% by both survey methods) resulted in minimal detection bias with respect to the landscape features used in our analysis (Smith et al. 2004).”

What the sources say

• ?Not checked — no full text of the sourcecites Smith et al. 2004 source

In the paper

“This indicates that wolves were not simply making kills on the landscape in strict proportion to the distribution of elk, or their own spatial patterns of winter territory use.”

In the paper

“All landscape variables showed relatively low levels of collinearity (r < 0.43), except for SWE and elk, which were negatively correlated with r ¼ )0.80.”

In the paper

“Smith et al. (2004) used a double-count method to evaluate observation error in these surveys and found that ground crews are biased towards detecting wolf-killed elk in close proximity to the road system, with no kills found further than 7.23 km from the road.”

What the sources say

• ?Not checked — no full text of the sourcecites Smith et al. 2004 source

In the paper

“For example, in only 4 years at least 10 adult moose (Alces alces) fell prey to grizzly bears at the frontier of bear recolonization in the greater Yellowstone area as compared with no records of predation where both had existed for 100+ years (Berger et al. 2001).”

What the sources say

• ?Not checked — no full text of the sourcecites Berger et al. 2001 source

In the paper

“Unlike the highly vulnerable native prey of introduced predators, the heterogeneity of the landscape that elk historically shared with wolves should allow them to mediate their risk of predation from this newly restored predator.”

In the paper

“In wolf-ungulate systems, as in other large mammal systems (Sinclair & Arcese 1995), prime-age adult prey are largely invulnerable to predation, and predators are highly selective, targeting the young, old or weak (Mech & Peterson 2003).”

What the sources say

• ?Not checked — no full text of the sourcecites Sinclair & Arcese 1995 source
• ?Not matched

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

  cites Mech & Peterson 2003

In the paper

“This notion is supported by recent findings showing that elk move out of open areas when wolves are near (Creel et al. 2005) or likely to occur (Fortin et al. 2005), and aggregate in increasingly larger groups in open areas the longer wolves are absent (Creel & Winnie 2005).”

What the sources say

• ?Not matched

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

  cites Creel et al. 2005
• ?Not checked — no full text of the sourcecites Fortin et al. 2005 source
• ?Not matched

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

  cites Creel & Winnie 2005

In the paper

“These results have implications for the potential of restored predators to initiate trophic cascades by changing the habitat-selection patterns or foraging behaviour of their prey (i.e.behaviourally mediated trophic cascades; Schmitz et al. 2004).”

What the sources say

• ?Not checked — no full text of the sourcecites Schmitz et al. 2004 source

In the paper

“Our finding of strong landscape effects on predation suggests that landscape features may often Ôtip the balanceÕ in predator-prey encounters, thus influencing post-encounter outcomes.”

In the paper

“Such habitat features can influence spatial patterns of predation by influencing either pre-or post-encounter interactions between predators and prey (Hebblewhite et al. 2005), and we believe both mechanisms play a role in conferring riskiness to the NR hunting grounds.”

What the sources say

• ?Not checked — no full text of the sourcecites Hebblewhite et al. 2005 source

In the paper

“Wolves are inefficient predators with generally low hunting success (»20%; Smith et al. 2000) due, in part, to the large size and defensive capabilities of their prey.”

What the sources say

• ?Not checked — no full text of the sourcecites Smith et al. 2000 source

In the paper

“Hopcraft et al. (2005) found similar patterns for Serengeti lions (Panthera leo), whereby lion kills were more closely associated with good hunting habitats (in this case, stalking cover) than areas of high prey abundance.”

What the sources say

• ?Not checked — no full text of the sourcecites Hopcraft et al. 2005 source

In the paper

“In Minnesota, boundaries between wolf pack territories appear to function as buffers where most interpack killings occur (Mech 1994) and where ungulate prey densities are elevated (Hoskinson & Mech 1976).”

What the sources say

• ?Not checked — no full text of the sourcecites Mech 1994 source
• ?Not checked — no full text of the sourcecites Hoskinson & Mech 1976 source

In the paper

“In a study that was able to decompose the stages of predation, Hebblewhite et al. (2005) found that topographic features determined patterns of wolf-elk encounters, while habitat (i.e.vegetation) mediated postencounter outcomes.”

What the sources say

• ?Not checked — no full text of the sourcecites Hebblewhite et al. 2005 source

In the paper

“Streams and roads provide convenient travel corridors that likely increase prey encounter rates (Kunkel & Pletscher 2000), while open habitats likely facilitate prey detection (Kunkel & Pletscher 2000;Creel et al. 2005).”

What the sources say

• ?Not checked — no full text of the sourcecites Kunkel & Pletscher 2000 source
• ?Not matched

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

  cites Creel et al. 2005

In the paper

“Predator distribution has been commonly used as a surrogate for predation risk in ecological studies (e.g.Ripple et al. 2001;Creel et al. 2005;Fortin et al. 2005);”

What the sources say

• ?Not checked — no full text of the sourcecites Ripple et al. 2001 source
• ?Not matched

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

  cites Creel et al. 2005
• ?Not checked — no full text of the sourcecites Fortin et al. 2005 source

In the paper

“Instead, the relative high density of wolf and elk populations on the NR and the strong landscape influence on predation success interact to create a pattern of high territorial overlap where the best hunting opportunities exist.”

In the paper

“These results are consistent with our hypothesis that individual wolf packs shifted their winter territories away from but adjacent to the best hunting grounds, thus decoupling kill locations from wolf distribution.”

In the paper

“The mosaic of risky and safe habitat patches available to NR elk suggests that elk can reduce their risk of wolf predation by making movements on the order of 1-2 km, easily achieved within daily movements (Fortin et al. 2005).”

What the sources say

• ?Not checked — no full text of the sourcecites Fortin et al. 2005 source

In the paper

“Because we found a strong influence of landscape variables on kill-site occurrence after accounting for the distribution of predator and prey, we believe that habitat mediates predation by influencing the occurrence or outcome of wolf-elk encounters.”

In the paper

“In fact, wolf territory locations were a positive predictor of elk habitat use (i.e.wolf and elk distributions closely overlap).”

What the sources say

• ?Not checked — no full text of the sourcecites Mao et al. 2005 source

In the paper

“How elk perceive and manage the trade-off between food and safety will ultimately determine the existence and strength of a behaviourally mediated trophic cascade in the NR system.”

In the paper

“Our study makes clear that NR elk in winter face a clear trade-off between forage quality and predation risk: most of these browse communities are found in open, flat areas near rivers and roads, which are risky places for elk.”