RCrab: An R Analytics Tool to Visualize and Analyze the Movement of Horseshoe Crabs in Long Island Sound

Abstract

Mark-recapture programs are important for studying the ecology and population dynamics of wildlife. An R shiny analytics tool was developed to track the movement of horseshoe crabs in Long Island Sound based on tag and re-sight data. The crabs were tagged and recaptured by volunteers of Project Limulus, a community-based research program. The dataset contains tag and recapture location information for 14,065 horseshoe crabs over 18 years. The dataset was initially cleaned by removing records with missing, duplicate or incorrect data. A new data structure was developed to save the data and simplify processing: Three dimensions were used, one for the original horseshoe crab tag data, the second for the recapture data, and the third for the mating behavior data recorded both when originally tagged and when found during the recaptures. The R tools enables scientists and the general public to easily produce charts and movement maps based on the dataset. To study horseshoe crab movement, the Long Island Sound area was divided into five major tagging activity areas. Our results show that horseshoe crabs can cross the Sound (from CT to NY and back) and an interesting trend of movement towards the northern and eastern parts of Long Island Sound which correlates with less pollution and human disturbance.