Limits...
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.

Show MeSH

Related in: MedlinePlus

Seasonal isotopic shifts in wolf hair. Seasonal isotopic shifts in δ13C and δ15N in wolf (Canis lupus) hair, collected in coastal British Columbia, 2001 to 2004. Seasonal shifts calculated by subtracting values in distal (summer-grown) hair segments from basal (fall-grown) hair segments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2542989&req=5

Figure 4: Seasonal isotopic shifts in wolf hair. Seasonal isotopic shifts in δ13C and δ15N in wolf (Canis lupus) hair, collected in coastal British Columbia, 2001 to 2004. Seasonal shifts calculated by subtracting values in distal (summer-grown) hair segments from basal (fall-grown) hair segments.

Mentions: Three tests revealed that most marine-derived isotopic enrichment was incorporated during fall and associated with salmon. First, δ13C values in whole hair samples were correlated with seasonal (fall minus summer) isotopic shifts in δ13C in the same hair (r = 0.54, n = 15, P = 0.038). Second, most individuals showed positive seasonal isotopic shifts between summer and fall, occupy the region of isotopic niche space defined by greater δ13C and δ15N signatures during fall compared with summer (χ2 = 56.13, df = 3, n = 60, P < 0.001; Figure 4). Third, we examined 'group years' with both faecal data during fall (n range: 9 to 92; mean = 54.0 faeces/group) and group-averaged δ13C seasonal isotopic shifts from wolf hair grown during that same year among members of those same groups (n range: 1 to 6; mean = 3.4 hair samples/group); cases with higher O/I salmon during fall showed greater average seasonal isotopic shifts in δ13C (r = 0.78, n = 10, P = 0.008, Figure 5).


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

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

Seasonal isotopic shifts in wolf hair. Seasonal isotopic shifts in δ13C and δ15N in wolf (Canis lupus) hair, collected in coastal British Columbia, 2001 to 2004. Seasonal shifts calculated by subtracting values in distal (summer-grown) hair segments from basal (fall-grown) hair segments.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Seasonal isotopic shifts in wolf hair. Seasonal isotopic shifts in δ13C and δ15N in wolf (Canis lupus) hair, collected in coastal British Columbia, 2001 to 2004. Seasonal shifts calculated by subtracting values in distal (summer-grown) hair segments from basal (fall-grown) hair segments.
Mentions: Three tests revealed that most marine-derived isotopic enrichment was incorporated during fall and associated with salmon. First, δ13C values in whole hair samples were correlated with seasonal (fall minus summer) isotopic shifts in δ13C in the same hair (r = 0.54, n = 15, P = 0.038). Second, most individuals showed positive seasonal isotopic shifts between summer and fall, occupy the region of isotopic niche space defined by greater δ13C and δ15N signatures during fall compared with summer (χ2 = 56.13, df = 3, n = 60, P < 0.001; Figure 4). Third, we examined 'group years' with both faecal data during fall (n range: 9 to 92; mean = 54.0 faeces/group) and group-averaged δ13C seasonal isotopic shifts from wolf hair grown during that same year among members of those same groups (n range: 1 to 6; mean = 3.4 hair samples/group); cases with higher O/I salmon during fall showed greater average seasonal isotopic shifts in δ13C (r = 0.78, n = 10, P = 0.008, Figure 5).

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