Long-term tracking reveals the influence of body size and habitat type on the home range of Antillean manatees (Trichechus manatus manatus)

Abstract

Antillean manatees (Trichechus manatus manatus) are endangered coastal, marine, and riverine megaherbivores with high environmental plasticity, constrained by tidal and seasonal water level cycles that affect access to food and fresh water. Accurate quantification of the species' habitat requirements, typically achieved through home range (HR) estimation, is required to implement area-based conservation initiatives. In this study, we used GPS tracking data from 38 wild and captive-rehabilitated released manatees to estimate HR using autocorrelated kernel density estimators (AKDE) and average time speed. We investigated whether body size, habitat type, sex and behavioural group influence home range size due to energy requirements, resources availability, a scramble-competitive polygyny mating system, and adaptation to the wild. Eighteen manatees exhibited range-resident behaviour, with a mean 95% home range of 72.96 km² (± 218.52) and a median of 10.69 km². The mean daily speed was estimated to be 13.47 km/day (± 4.16). Home range and body size were positively correlated, consistent with HR allometry theory. Long-term tracked individuals showed a trend of increasing HR over time. Only four released animals (17.4%) were range-resident, suggesting that they may need additional time to establish a home range. Individuals using only the marine environment had larger home ranges compared to mixed (marine and estuarine) and estuarine environments, probably due to freshwater availability. Our study contributes to the understanding of the factors driving manatee movement and provides more accurate estimates of area requirements, which can inform the establishment and zoning of marine protected areas.