Such an approach requires that goals and plans for evaluations are incorporated into the construction schedule. Step 5: Determine sampling scheme Several key questions Afatinib mouse related to data collection should now be addressed: (1) How long should sites be monitored before and after road mitigation? (2) How often should sites be monitored? (3) How many replicates are needed? As these decisions are unlikely to be independent, we recommend conducting model-based power analyses to optimize the sampling design (see, e.g., van der Grift et al. 2009b). For example, Fig. 2 illustrates the relationship between mitigation

effectiveness (the expected effect size) on the degree of temporal replication needed for adequate statistical power. Similar graphs can be produced for other design variables such as sampling frequency and the number of replicate sites. Note that either pilot studies or pre-existing data on anticipated effect sizes are needed to conduct this type of analysis. Fig. 2 Hypothetical Selleckchem LY2606368 relation between the probability of detecting an effect of road selleck chemicals llc mitigation and the duration of monitoring after the mitigation measures are put in place. The three scenarios illustrate variations in the expected effectiveness of mitigation, e.g. road mitigation is expected to reduce the

road effect by 100, 75 or 50 %. The figure shows that if we want to achieve statistical power of 80 % we should measure the response variable for 3, 6 and 12 years in scenarios 1, 2, and 3, respectively. This figure assumes that the effect of the mitigation measure on the population is

immediate. However, response Low-density-lipoprotein receptor kinase times of the population to both the road and the mitigation measures also have to be considered The sampling scheme is related to the chosen measurement endpoint and the characteristics of the studied species. For example, for a highly mobile species with a long lifespan, monitoring over a longer period would be required to assess a change in population density than that required to detect a change in movement. Similarly, a shorter monitoring period would be required to assess a change in road-kill numbers for a species that crosses roads frequently than for a species that crosses roads infrequently. For some measurement endpoints, such as changes in population size/density, higher levels of replication will allow a quicker evaluation of effectiveness. A study with three replicates will need to be continued for longer than a study with ten replicates, because with more replication the uncertainty in effect size will be reduced, thus allowing a reliable decision to be reached sooner. The rate of use of wildlife crossing structures often increases over time (e.g., Clevenger and Waltho 2003; Ford et al. 2010) due to habituation or gradual improvement in the quality of the crossing structure (e.g., vegetation succession on wildlife overpasses).