Small-Scale Movement Patterns, Activity Budgets, and Association Patterns of Radio-Tagged Indian River Lagoon Bottlenose Dolphins (Tursiops truncatus)

Information on movement patterns and habitat selection for critical activities are fundamental to understanding and managing animal populations. While bottlenose dolphins (Tursiops truncatus) inhabiting the Indian River Lagoon (IRL), Florida, are known to exhibit long-term residency, data regarding short-term movement and association patterns, habitat use, and activity budgets are limited. These parameters and the percentage of time dolphins occurred within a predetermined survey strip were evaluated utilizing VHF radio-telemetry. A total of nine IRL dolphins (eight males and one female) were captured and fitted with radio transmitters (summers of 2007 and 2010). Focal follows utilized instantaneous scan samples and standardized behavioral categories. Conspecifics were identified, and the half-weight index was utilized to evaluate association patterns. Radio tags remained adhered for 15 to 97 days (mean: 45.8 +/- 25.3 days), and the tag attachment site influenced attachment longevity. The linear distances traversed by tagged dolphins ranged between 13.4 to 39.4 km (mean: 28.1 +/- 9.49 km). While shallow water (< 1 m) habitats were frequently utilized (42.8% observations), dolphins selected deeper waters based on availability. Activity budgets differed between individuals and age-classes and were associated with water depth. Foraging and play behavior were observed significantly more in the shallowest water (<= 1 m). Dolphins exhibited a high number of low-level associations (mean: 25.0 +/- 14.58; range: 8 to 43 marked individuals), while one male individual exhibited a high-level male association (coefficient of association [COA] = 0.88) and a moderately high-level female association (COA = 0.67). This study represents the most extensive radio-tracking effort for IRL dolphins; it established radio-telemetry as a useful method to evaluate seasonal ranging patterns and provided important baseline data on short-term association patterns, activity budgets, and habitat use. Future studies that incorporate remote tracking capabilities, increased time and sample sizes, and nocturnal behavior are warranted to expand our understanding of movement patterns and habitat utilization.