fatalityCMR: capture-recapture software to correct raw counts of wildlife fatalities using trial experiments for carcass detection probability and persistence time

Abstract

Many industrial and agricultural activities involve wildlife fatalities by collision, poisoning or other involuntary harvest: wind turbines, highway network, utility network, tall structures, pesticides, etc. Impacted wildlife may benefit from official protection, including the requirement to monitor the impact. Carcass counts can often be conducted to quantify the number of fatalities, but they need to be corrected for carcass persistence time (removal by scavengers and decay) and detection probability (searcher efficiency). In this article we introduce a new piece of software that fits a superpopulation capture-recapture model to raw count data. It uses trial data to estimate detection and daily persistence probabilities. A recurrent issue is that fatalities of rare, protected species are infrequent, in which case the software offers the option to switch to an ‘evidence of absence’ mode, i.e., estimate the number of carcasses that may have been missed by field crews. The software allows distinguishing between different turbine types (e.g. different vegetation cover under turbines, or different technical properties), as well between two carcass age-classes or states, with transition between those classes (e.g, fresh and dry). There is a data simulation capacity that may be used at the planning stage to optimize sampling design. Resulting mortality estimates can be used 1) to quantify the required amount of compensation, 2) inform mortality projections for proposed development sites, and 3) inform decisions about management of existing sites.