Do moose and other forest ungulates browse less near roads and houses, giving young trees a better chance to grow?

Details

Like large carnivores, hunters both kill and frighten ungulates, so they might indirectly affect plants through trophic cascades. The researchers hypothesized that intensive hunting and lasting fear of humans lead moose and other forest ungulates to partly avoid areas near human infrastructure because of perceived hunting risk, with positive cascading effects on tree recruitment.

In an observational study using Norwegian forest inventory data, they found lower browsing pressure and higher tree recruitment closer to roads and houses, where ungulates are more likely to encounter humans. Browsing and recruitment were negatively related, but reduced browsing accounted for only a small proportion of the higher tree recruitment near human infrastructure.

The researchers suggest that this apparently weak cascading effect may arise because recorded browsing pressure only partly reflects long-term browsing intensity near humans. Tree recruitment was also related to the density of small trees 5–10 years earlier; that earlier density was higher near human infrastructure. If small-tree density reflects past browsing pressure, the cascading effect is probably stronger than their estimates suggest.

The researchers interpret reduced browsing near roads and houses as most consistent with animals avoiding risk because they fear humans—a behaviorally mediated effect—rather than excessive hunting locally reducing ungulate density, a density-mediated effect.