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Spawning salmon disrupt trophic coupling between wolves and ungulate prey in coastal British Columbia.

Darimont CT, Paquet PC, Reimchen TE - BMC Ecol. (2008)

Bottom Line: Concordance of faecal and isotopic data suggests our intra-hair isotopic methodology provides an accurate proxy for salmon consumption, and might reliably track seasonal dietary shifts in other consumer-resource systems.Use of salmon by wolves as a function of its abundance and the adaptive explanations we provide suggest a long-term and widespread association between wolves and salmon.Seasonally, this system departs from the common wolf-ungulate model.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biology, Box 3020, Stn CSC, University of Victoria, Victoria, British Columbia, V8W 3N5, Canada. darimont@ucsc.edu

ABSTRACT

Background: As a cross-boundary resource subsidy, spawning salmon can strongly affect consumer and ecosystem ecology. Here we examine whether this marine resource can influence a terrestrial wolf-deer (Canis lupus-Odocoileus hemionus) predator-prey system in coastal British Columbia, Canada. Data on resource availability and resource use among eight wolf groups for three seasons over four years allow us to evaluate competing hypotheses that describe salmon as either an alternate resource, consumed in areas where deer are scarce, or as a targeted resource, consumed as a positive function of its availability. Faecal (n=2203 wolf scats) and isotopic analyses (n=60 wolf hair samples) provide independent data sets, also allowing us to examine how consistent these common techniques are in estimating foraging behaviour.

Results: At the population level during spring and summer, deer remains occurred in roughly 90 and 95% of faeces respectively. When salmon become available in autumn, however, the population showed a pronounced dietary shift in which deer consumption among groups was negatively correlated (r=-0.77, P<0.001) with consumption of salmon, which occurred in 40% of all faeces and up to 70% of faeces for some groups. This dietary shift as detected by faecal analysis was correlated with seasonal shifts in delta13C isotopic signatures (r=0.78; P=0.008), which were calculated by intra-hair comparisons between segments grown during summer and fall. The magnitude of this seasonal isotopic shift, our proxy for salmon use, was related primarily to estimates of salmon availability, not deer availability, among wolf groups.

Conclusion: Concordance of faecal and isotopic data suggests our intra-hair isotopic methodology provides an accurate proxy for salmon consumption, and might reliably track seasonal dietary shifts in other consumer-resource systems. Use of salmon by wolves as a function of its abundance and the adaptive explanations we provide suggest a long-term and widespread association between wolves and salmon. Seasonally, this system departs from the common wolf-ungulate model. Broad ecological implications include the potential transmission of marine-based disease into terrestrial systems, the effects of marine subsidy on wolf-deer population dynamics, and the distribution of salmon nutrients by wolves into coastal ecosystems.

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Study area and home ranges of wolf social groups. Study area in which wolves (Canis lupus) were sampled for hair and faeces on the central coast of British Columbia, 2001 to 2004. Home ranges estimated as 95% kernels based on re-sightings of individual wolves.
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Figure 1: Study area and home ranges of wolf social groups. Study area in which wolves (Canis lupus) were sampled for hair and faeces on the central coast of British Columbia, 2001 to 2004. Home ranges estimated as 95% kernels based on re-sightings of individual wolves.

Mentions: BC's central coast is a remote area, accessible only by boat or air, and only minimally modified by industrial activity [29]. Our study area is roughly 3,300 km2, and is centred on Bella Bella (52° 10' N, 128° 09' W; Figure 1).


Spawning salmon disrupt trophic coupling between wolves and ungulate prey in coastal British Columbia.

Darimont CT, Paquet PC, Reimchen TE - BMC Ecol. (2008)

Study area and home ranges of wolf social groups. Study area in which wolves (Canis lupus) were sampled for hair and faeces on the central coast of British Columbia, 2001 to 2004. Home ranges estimated as 95% kernels based on re-sightings of individual wolves.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2542989&req=5

Figure 1: Study area and home ranges of wolf social groups. Study area in which wolves (Canis lupus) were sampled for hair and faeces on the central coast of British Columbia, 2001 to 2004. Home ranges estimated as 95% kernels based on re-sightings of individual wolves.
Mentions: BC's central coast is a remote area, accessible only by boat or air, and only minimally modified by industrial activity [29]. Our study area is roughly 3,300 km2, and is centred on Bella Bella (52° 10' N, 128° 09' W; Figure 1).

Bottom Line: Concordance of faecal and isotopic data suggests our intra-hair isotopic methodology provides an accurate proxy for salmon consumption, and might reliably track seasonal dietary shifts in other consumer-resource systems.Use of salmon by wolves as a function of its abundance and the adaptive explanations we provide suggest a long-term and widespread association between wolves and salmon.Seasonally, this system departs from the common wolf-ungulate model.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biology, Box 3020, Stn CSC, University of Victoria, Victoria, British Columbia, V8W 3N5, Canada. darimont@ucsc.edu

ABSTRACT

Background: As a cross-boundary resource subsidy, spawning salmon can strongly affect consumer and ecosystem ecology. Here we examine whether this marine resource can influence a terrestrial wolf-deer (Canis lupus-Odocoileus hemionus) predator-prey system in coastal British Columbia, Canada. Data on resource availability and resource use among eight wolf groups for three seasons over four years allow us to evaluate competing hypotheses that describe salmon as either an alternate resource, consumed in areas where deer are scarce, or as a targeted resource, consumed as a positive function of its availability. Faecal (n=2203 wolf scats) and isotopic analyses (n=60 wolf hair samples) provide independent data sets, also allowing us to examine how consistent these common techniques are in estimating foraging behaviour.

Results: At the population level during spring and summer, deer remains occurred in roughly 90 and 95% of faeces respectively. When salmon become available in autumn, however, the population showed a pronounced dietary shift in which deer consumption among groups was negatively correlated (r=-0.77, P<0.001) with consumption of salmon, which occurred in 40% of all faeces and up to 70% of faeces for some groups. This dietary shift as detected by faecal analysis was correlated with seasonal shifts in delta13C isotopic signatures (r=0.78; P=0.008), which were calculated by intra-hair comparisons between segments grown during summer and fall. The magnitude of this seasonal isotopic shift, our proxy for salmon use, was related primarily to estimates of salmon availability, not deer availability, among wolf groups.

Conclusion: Concordance of faecal and isotopic data suggests our intra-hair isotopic methodology provides an accurate proxy for salmon consumption, and might reliably track seasonal dietary shifts in other consumer-resource systems. Use of salmon by wolves as a function of its abundance and the adaptive explanations we provide suggest a long-term and widespread association between wolves and salmon. Seasonally, this system departs from the common wolf-ungulate model. Broad ecological implications include the potential transmission of marine-based disease into terrestrial systems, the effects of marine subsidy on wolf-deer population dynamics, and the distribution of salmon nutrients by wolves into coastal ecosystems.

Show MeSH
Related in: MedlinePlus