Data and code from: Impact evaluation shows that hunting without quotas has contrasting effects on deer harvest across management levels

Hunting is widely used to manage deer populations and their impacts on
ecosystems. Various management strategies can be used to ensure that the
hunting bag is of adequate size and composition to actually control
population growth, including the abolishment of hunting quotas. However,
the actual impacts of hunting without quotas on deer harvest are rarely
assessed. Here we evaluated the impact of hunting without quotas on roe
deer (Capreolus capreolus) in Schleswig-Holstein, Germany, by comparing
the hunting bag seven years before and after the abolishment of hunting
quotas in the federal state and state forests. We used linear mixed models
and a counterfactual approach to separate the impact of hunting without
quotas from confounding factors that also influence roe deer harvest. We
found no significant change in annual harvest densities (i.e., the number
of harvested roe deer per 100 ha) overall, but a significant increase in
harvest densities in state forests. This increase was most pronounced in
forest districts where the forest manager changed during the study.
Hunting without quotas altered the harvest sex ratio from a
female-dominated to a male-dominated one in both the state forests and the
entire state. Despite this decrease in relative number of females
harvested, hunting without quotas still led to an increase in the absolute
number of harvested females in the state forests, while fewer females were
harvested across the entire state. Synthesis and applications: Hunting
without quotas increased the total and female harvest density in state
forests, but actually decreased female harvest across the state. Thus,
such hunting could result in source-sink dynamics that make actual
reductions of roe deer densities in state forests challenging. Our study
illustrates the usefulness of counterfactual approaches to objectively
evaluate the effectiveness of hunting regulations as a wildlife management
tool. Such approaches could be applied more routinely in the future and
may be extended to evaluate the impact of hunting regimes on actual deer
densities and their effects on (forest) vegetation.