Detectability and impact of repetitive surveys on threatened West African crocodylians.

West African crocodylians are among the most threatened and least studied crocodylian species globally. Assessing population status and establishing a basis for population monitoring is the highest priority action for this region. Monitoring of crocodiles is influenced by many factors that affect detectability, including environmental variables and individual- or population-level wariness. We investigated how these factors affect detectability and counts of the critically endangered and the newly recognized . We implemented 195 repetitive surveys at 38 sites across Côte d'Ivoire between 2014 and 2019. We used an occupancy-based approach and a count-based GLMM analysis to determine the effect of environmental and anthropogenic variables on detection and modeled crocodile wariness over repetitive surveys. Despite their rarity and level of threat, detection probability of both species was relatively high (0.75 for and 0.81 for . ), but a minimum of two surveys were required to infer absence of either species with 90% confidence. We found that detection of .  was significantly negatively influenced by fishing net encounter rate, while high temperature for the previous 48 h of the day of the survey increased .  detection. Precipitation and aquatic vegetation had significant negative and positive influence, respectively, on .  counts and showed the opposite effect for .  counts. We also found that fishing encounter rate had a significant negative effect on .  counts. Interestingly, survey repetition did not generally affect wariness for either species, though there was some indication that at least .  was more wary by the fourth replicate. These results are informative for designing future survey and monitoring protocols for these threatened crocodylians in West Africa and for other endangered crocodylians globally.