Arduinos have been used to collect parameters associated with water quality. Here's a project that studied water quality at a catfish farm. https://iopscience.iop.org/article/10.1088/1742-6596/1751/1/012067/meta #osidccasestudy

Here's a cute project to build an #arduino-powered mousetrap. I can imagine using similar techniques to simply monitor small animal movements using a tube with the ultrasonic sensor and a camera. You could also do it with a NearIR camera. It might be interesting to see whether you get different results (ie, I've always wondered whether the near IR illumination would bias the results).
https://hackaday.com/2023/09/02/arduino-powered-trap-hopes-to-catch-mice/ #osidccasestudy

The TRACEPaw project uses a camera and machine learning to infer information about the ground based on the deformation of a silicone hemisphere. And it uses a microphone to get more info about the substrate. What a cool project! https://www.cnx-software.com/2023/08/24/tracepaw-sensorized-paw-helps-legged-robots-feel-the-floor-with-arduino-nicla-vision/ #osidccasestudy