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Spatial synchrony of recruitment in mountain-dwelling woodland caribou

TitleSpatial synchrony of recruitment in mountain-dwelling woodland caribou
Publication TypeJournal Article
Year of Publication2012
AuthorsHegel, TM, David, V, Huettmann, F, Barboza, PS
JournalPopulation Ecology

Spatial synchrony in population dynamics is aubiquitous feature across a range of taxa. Understandingfactors influencing this synchrony may shed light onimportant drivers of population dynamics. Three mechanismsinfluence the degree of spatial synchrony betweenpopulations: dispersal, shared predators, and spatial environmentalcovariance (the Moran effect). We assesseddemographic spatial synchrony in recruitment (calf:cowratio) of 10 northern mountain caribou herds in the YukonTerritory, Canada (1982–2008). Shared predators and dispersalwere ruled out as causal mechanisms of spatialrecruitment synchrony in these herds and therefore anyspatial synchrony should be due to the Moran effect.We alsoassessed the degree of spatial synchrony in April snow depthto represent environmental variability. The regional averagespatial synchrony in detrended residuals of April snow depthwas 0.46 (95% CI 0.37 to 0.55). Spatial synchrony in caribourecruitment was weak at 0.13 (95% CI -0.06 to 0.32). Thespatial scale of synchrony in April snow depth and caribourecruitment was 330.2 km (95% CI 236.3 to 370.0 km) and170.0 km (95% CI 69.5 to 282.8 km), respectively. We alsoinvestigated how the similarity in terrain features betweenherds influenced the degree of spatial synchrony usingexponential decay models. Only the difference in elevationvariability between herds during calving was supported bythe data. Herds with more similar elevation variability maytrack snowmelt ablation patterns in a more similar fashion,which would subsequently result in more synchronizedpredation rates on calves and/or nutritional effects impactingjuvenile survival. Interspecific interactions with predatorsand alternate prey may also influence spatial synchrony ofrecruitment in these herds.