Seasonal marine nutrient subsidies to terrestrial predator-prey systems: wolves, salmon, and deer on BC’s Central Coast

Chris Darimont PhD Student Department of Biology PO Box 3020 University of Victoria Victoria, BC V8W 3N5 cdarimon@uvic.ca

Community processes and the niches of organisms are often affected seasonally and spatially by ecosystem linkages.  We are now recognizing the link between marine and terrestrial systems in the Pacific Northwest, one largely mediated by the annual migration of spawning salmon.  Our understanding of how salmon affect consumer and community ecology, however, remains poorly understood.  This knowledge is important given that salmon returns represent a fraction of the historical abundance and diversity. 

In the rainforests of the mid coast of British Columbia, the dominant terrestrial mammalian predator is the gray wolf (12).  Wolves occur on all landmasses in this archipelago (2, 6, 10).  They prey on Sitka black-tailed deer, moose, goat, and other terrestrial and marine resources (3, 4, 5, 7).  

In the fall, however, salmon can form a significant component of the diet of these terrestrial predators.  In earlier work, stable isotopic signatures from wolf hair identified a seasonal dietary shift in hair tissue grown during fall, the period of salmon availability (9).  We are continuing to use the technique we developed, and it may assist other studies in examining otherwise undetectable niche differentiation between hetero- or conspecifics.

Faecal samples from coastal areas during fall are also revealing salmon remains (7; unpublished data).  In addition, we have detailed behavioural observations of predation on salmon by wolves (8). 

Like bears, wolves are vectors that transport marine nutrients into terrestrial systems.  Abandoned carcasses feed a diversity of users (e.g. 11) and become important fertilizers in nutrient-limited coastal ecosystems.

The combination of more data from stable isotope analysis, direct observation, and examinations of scats shows promise to better understand the association among wolves, the annual migration of salmon, and ecosystem processes.  Salmon may disrupt the tight ecological association between wolves and ungulate (hoofed animal) prey thought to dominate this ecosystem and others.  This work should provide insight into predator-prey dynamics as they relate to seasonal shifts in resources in these taxa and others, as well as demonstrate the far-reaching effects of salmon as a nutrient subsidy to Pacific Northwest forests.

The above work also lead Dr. Reimchen and I to investigate the use of stable isotope analysis to examine the association between niche and fitness.  Using an intra-generational comparison of isotopic signatures of surviving and non-surviving deer over two years of predation by wolves, we detected resource-specific fitness differences among individuals.  We demonstrated that predation can be ecologically selective independent of age, sex, and nutritional condition, and specifically at the level of the individual niche (1). Understanding the ecological context of niche space is important; it allows insight into genetic, morphological, and behavioural variability within populations. 


My dissertation work is a component of the Rainforest Wolf Project, sponsored by the Raincoast Conservation Foundation  and directed by Dr. Paul Paquet. We work closely with the Heiltsuk First Nation in their Traditional Territory.

1. Darimont, C.T., P.C. Paquet, and T.E. Reimchen. 2007. Stable isotopic niche predicts fitness in a wolf-deer system. Biological Journal of the Linnean Society 90: 125–137.

2. Paquet, P.C., S.M. Alexander, P.L. Swan, and C.T. Darimont. 2006. The influence of natural landscape fragmentation and resource availability on connectivity and distribution of marine gray wolf (Canis lupus) populations on the Central Coast, British Columbia, Canada. Pp 130-156 In Connectivity Conservation (Ed. by Crooks, K. and M.A. Sanjayan). Society for Conservation Biology. Cambridge University Press.

3. Price, M.H.H., C.T. Darimont, N.N. Winchester, and P.C. Paquet. 2005. Facts from faeces: Prey remains in wolf faeces revise occurrence records for mammals of British Columbia’s Coastal Archipelago. Canadian Field-Naturalist 119:192-196.

4. Bryan, H., C.T. Darimont, T.E. Reimchen, and P.C. Paquet. In press. Early ontogenetic diet of wolves. Canadian Field-Naturalist.

5. Darimont, C.T., P.C. Paquet, T.E. Reimchen, and V. Crichton. 2005. Range expansion by moose into coastal temperate rainforests of British Columbia, Canada. Diversity and Distributions 11: 235-239.

6. Paquet, P.C., C.T. Darimont, F. M. Moola, and C. Genovali. 2005.  Connectivity where the land meets the sea; preserving the last of the best. Wild Earth 14: 21-25 (Peer edited).

7. Darimont, C.T., M.H.H. Price, N.N. Winchester, J. Gordon-Walker, and P.C. Paquet. 2004. Predators in natural fragments: Foraging ecology of wolves in British Columbia’s Central and North Coast Archipelago. Journal of Biogeography 31: 1867-1877.

8. Darimont, C.T., T.E. Reimchen and P.C. Paquet. 2003. Foraging behaviour by gray wolves on salmon streams in coastal British Columbia. Canadian Journal of Zoology 81: 349-353.

9. Darimont, C.T., and T.E. Reimchen. 2002. Intra-hair stable isotope analysis implies seasonal shift to salmon in gray wolf diet. Canadian Journal of Zoology 80: 1638-1642.

10. Darimont, C.T., and P.C. Paquet. 2002. The Gray Wolves, Canis lupus, of British Columbia’s Central and North Coast: distribution and conservation assessment. Canadian Field-Naturalist 116: 416-422.

11. Hocking, M.D., C.T. Darimont, K. S. Christie, and T.E. Reimchen. In press. Niche variation in burying beetles (Nicrophorus spp.) associated with Pacific salmon carcasses. Canadian Journal of Zoology.

12. McAllister, I., and C.T. Darimont. In press. Rainforest Wolves. The Last Wild Wolves. Douglas and MacIntyre/Greystone Books. Vancouver, BC. (Coffee Table Book)