Cost-effective eDNA methods for monitoring wild crocodiles

eDNA sampling has emerged as an attractive, noninvasive method for monitoring the planet’s increasingly threatened biodiversity. Sophisticated technologies have been developed to maximize eDNA collection, yet some of these methods are cost prohibitive, demonstrating the need for accessible, creative collection methods. We use crocodiles as a system to demonstrate the utility of simplified collection strategies: water filtered through standard paper coffee filters, sediment samples, and more traditional eDNA water filters from Thermo Scientific. Crocodiles are top predators and widely revered across cultures. Therefore, monitoring them can pose logistical challenges, necessitating the development of effective noninvasive tools. We show that both coffee filters and sediment samples successfully collected amplifiable crocodile DNA from a field site in Madagascar. We also tested Thermo Fisher eDNA filters exclusively from different sites but did not retain detectable crocodile DNA from these samples. This study introduces an accessible option for researchers and conservation practitioners everywhere, while facilitating easy community engagement in the monitoring of a powerful, spiritually significant species.