The relative effect of top-down versus bottom-up forces in regulating and limiting ungulate populations is an important theme in ecology. Untangling these effects is important for basic understanding of trophic dynamics and is critical for effective management. We integrated two independent sources of observations to compare the drivers of moose abundance across 55 replicated populations. Across populations, moose declined by nearly 20% over 20 years. At high density, moose were regulated by intraspecific competition. Predation primarily limited population growth, except at low density, where it was regulating. Harvest was largely additive and potentially contributed to population decline. Our results provide strong evidence for density dependent predation, highlighting that population dynamics are context dependent and vary strongly across gradients in climate, forest type and predator abundance. Consequently, management of moose would be optimized by taking different strategies across populations in accordance with their population trajectories and abundance of predators.

The relative effect of top-down versus bottom-up forces in regulating and limiting wildlife populations is an important theme in ecology. Untangling these effects is critical for basic understanding of trophic dynamics and effective management. We examined the drivers of moose abundance by integrating two sets of observations to create one of the largest existing spatiotemporal datasets on ungulate population dynamics globally. We documented a 20% population decline. At high density, moose were regulated by intraspecific competition. Predation primarily limited population growth, except at low density, where it was regulating. Harvest was largely additive and contributed to population decline. Our results provide strong evidence for density dependent predation, highlighting that population dynamics are context dependent and vary strongly across gradients in climate, forest type and predator abundance. These results clarify longstanding questions in population ecology and highlight the complex relationships between natural and human-caused mortality in driving ungulate population dynamics.

The range of the Canada lynx (Lynx canadensis) has contracted substantially from its historical range prior to the 19th century. Using harvest records, we found that the southern range of the lynx in Ontario in the late 1940s collapsed and then in a short period of time increased to its largest extent in the mid-1960s where the lynx range spread south of the boreal forest for a decade. After this expansion the southern range contracted northwards beginning in the 1970s. Most recently, there has been a slight expansion between 2010-2017. We have attributed these dynamics on the southern range periphery to the fluctuation of the boreal lynx population in the core of the species’ range. In addition, connectivity to boreal lynx populations and snow depth seemed to condition whether the lynx expanded into an area. However, we did not find any evidence that would suggest that these changes were due to anthropogenic disturbances or competition. The boreal lynx population does not reach numbers as it once did, consequently we likely will not see large expansions of the southern lynx range as in the mid-1960s. Our results suggest that southern lynx range in Ontario have been driven by the magnitude of the boreal lynx population cycle, connectivity to the boreal forest and snow conditions. Therefore, it is quite unlikely that southern lynx population in the Great Lakes will ever recover, since the warming climate and forestry practices are causing a northward contraction of the boreal forest and likely with it the core lynx populations.