Data from: Integrating encounter theory with decision analysis to evaluate collision risk and determine optimal protection zones for wildlife

1. Better understanding human-wildlife interactions and their links with
management can help improve the design of wildlife protection zones. One
important example is the problem of wildlife collisions with vehicles or
human-built structures (e.g. power lines, wind farms). In fact, collisions
between marine wildlife and watercraft are among the major threats faced
by several endangered species of marine mammals. Natural resource managers
are therefore interested in finding cost-effective solutions to mitigate
these threats. 2. We combined abundance estimators with encounter rate
theory to estimate relative lethal collision risk of the Florida manatee
(Trichechus manatus latirostris) from watercraft. We first modeled
seasonal abundance of watercraft and manatees using a Bayesian analysis of
aerial survey count data. We then modeled relative lethal collision risk
in space and across seasons. Finally, we applied decision analysis and
Linear Integer Programming to determine the optimal design of speed zones
in terms of relative risk to manatees and costs to waterway users. We used
a Pareto efficient frontier approach to evaluate the performance of
alternative zones, which included additional practical considerations
(e.g. spatial aggregation of speed zones) in relation to the optimal zone
configurations. 3. Under the various relationships for probability of
death given strike speed that we considered, the current speed zones
reduced the relative lethal collision risk by an average of 51.5% to 70%
compared to the scenario in which all speed regulations were removed (i.e.
the no-protection scenario). We identified optimal zones and near-optimal
zones with additional management considerations that improved upon the
current zones in terms of cost or relative risk. 4. Policy Implications:
Our analytical framework combines encounter rate theory and decision
analysis to quantify the effectiveness of speed zones protecting manatees
while accounting for uncertainty. Our approach can be used to optimize the
design of protection zones intended to reduce conflicts between human
waterborne activity and marine mammals. This framework could be extended
to address many other problems of human-wildlife interactions, such as the
optimal placement of wind farms to minimize collisions with wildlife or
the optimal allocation of ranger effort to mitigate poaching threats.