mort: An R package to conservatively identify mortalities and shed tags in passive telemetry arrays

Telemetry is commonly employed to track animals and support ecological inferences, yet the possibility that tagged animals have died or shed their tags is often not fully considered. Neglecting to consider mortality and/or tag shedding can lead to biases in the interpretation of results. We introduce the R package mort, developed to identify potential mortalities or shed tags in passive telemetry arrays. mort was designed for aquatic acoustic receivers with primarily non-overlapping detection radii, but the methods can be applied to any telemetry study that uses passive tracking (i.e. stationary receivers). We describe the primary functions and key options that are supported, provide guidance on the general use of the package, and demonstrate use with three case studies. The thresholds to identify mortalities are either user-defined or derived from the dataset itself (using observed durations of residences of animals that are known to be alive). This flexibility, along with numerous customizable options, allows application to multiple species and systems. mort fills an important gap in standardized workflows when processing and analysing passive telemetry data. The R package is a useful tool and will improve reproducibility in ecological research and management decisions that rely on results from passive telemetry.