The Edge of the Range

If density steps at a range boundary, the factor controlling the boundary's position is likely a substrate or physical barrier.

“should density step at the range boundary, the factor controlling the position of the boundary is likely to be a substrate or physical barrier (Caughley et al. 1988).”

A ramp effect can arise when a density attribute is low at the periphery and increases gradually toward the core of a species' distribution.

“A ramp effect could occur if an attribute such as density is low at the periphery but rises progressively towards the core of distribution (Caughley et al. 1988).”

In Manitoba, physical barriers such as lakes produce a steeper ramp or step effect.

“where the presence of physical barriers (lakes) produces a steeper ramp, or 'step' effect (Caughley et al. 1988).”

The negative relationship between coyote:fox ratio and distance from the southern boundary of wolf range is more consistent with a ramp effect from low wolf densities at the periphery than with other explanations.

“However, the strong negative linear relationship between the coyote : fox ratios and distance to the southern edge of wolf distribution is more suggestive of a 'ramp' effect due to very low densities of wolves on the periphery of their distribution (Caughley et al. 1988).”