Population Ecology

, Volume 54, Issue 1, pp 19–30 | Cite as

Spatial synchrony of recruitment in mountain-dwelling woodland caribou

  • Troy M. HegelEmail author
  • David Verbyla
  • Falk Huettmann
  • Perry S. Barboza
Original Article


Spatial synchrony in population dynamics is a ubiquitous feature across a range of taxa. Understanding factors influencing this synchrony may shed light on important drivers of population dynamics. Three mechanisms influence the degree of spatial synchrony between populations: dispersal, shared predators, and spatial environmental covariance (the Moran effect). We assessed demographic spatial synchrony in recruitment (calf:cow ratio) of 10 northern mountain caribou herds in the Yukon Territory, Canada (1982–2008). Shared predators and dispersal were ruled out as causal mechanisms of spatial recruitment synchrony in these herds and therefore any spatial synchrony should be due to the Moran effect. We also assessed the degree of spatial synchrony in April snow depth to represent environmental variability. The regional average spatial synchrony in detrended residuals of April snow depth was 0.46 (95% CI 0.37 to 0.55). Spatial synchrony in caribou recruitment was weak at 0.13 (95% CI −0.06 to 0.32). The spatial scale of synchrony in April snow depth and caribou recruitment was 330.2 km (95% CI 236.3 to 370.0 km) and 170.0 km (95% CI 69.5 to 282.8 km), respectively. We also investigated how the similarity in terrain features between herds influenced the degree of spatial synchrony using exponential decay models. Only the difference in elevation variability between herds during calving was supported by the data. Herds with more similar elevation variability may track snowmelt ablation patterns in a more similar fashion, which would subsequently result in more synchronized predation rates on calves and/or nutritional effects impacting juvenile survival. Interspecific interactions with predators and alternate prey may also influence spatial synchrony of recruitment in these herds.


Moran effect Rangifer tarandus caribou Snow depth Terrain Yukon Territory 



Caribou recruitment and snow depth data were provided by Environment Yukon, Fish and Wildlife and Water Resources Branches, respectively. This research would not have been possible if it were not for the numerous biologists, technicians, and pilots who collected these data over nearly three decades, and particularly R. Farnell who managed the Yukon caribou program during much of this time. The support and assistance of numerous First Nations, Renewable Resources Councils, and community observers who participated in these surveys is also acknowledged. T. Jung, M. Lindberg, R. Maraj, H. Wittmer, E. Post, and one anonymous reviewer provided valuable comments on earlier versions of this manuscript. This is EWHALE publication number 105.

Supplementary material

10144_2011_275_MOESM1_ESM.pdf (93 kb)
Supplementary material 1 (PDF 93 kb)


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Copyright information

© The Society of Population Ecology and Springer 2011

Authors and Affiliations

  • Troy M. Hegel
    • 1
    • 2
    Email author
  • David Verbyla
    • 3
  • Falk Huettmann
    • 1
  • Perry S. Barboza
    • 1
  1. 1.Institute of Arctic BiologyUniversity of Alaska FairbanksFairbanksUSA
  2. 2.Fish and Wildlife BranchEnvironment YukonWhitehorseCanada
  3. 3.Department of Forest SciencesUniversity of Alaska FairbanksFairbanksUSA

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