Abstract
BackgroundWhile cetaceans have been extensively studied around the world, nocturnal movements and habitat use have been largely unaddressed for most populations. We used satellite telemetry to examine the nocturnal movements and habitat use of four bottlenose dolphins (Tursiops truncatus) from a well-studied population in a complex estuary along the east coast of Florida. This also enabled us to explore the utility of satellite tracking on an apex predator within a very narrow and convoluted ecosystem. Our objectives were to evaluate (1) nocturnal home ranges and how individual dolphins moved within them, (2) nocturnal utilization of habitats surrounding ocean inlets, (3) nocturnal movements outside of the population’s known range (i.e., the study area), and (4) nocturnal use of select environmental variables.ResultsSatellite tags were active between 129 and 140 days (136 ± 4.99) during nocturnal hours (summer/fall 2012), yielding 3.3 ± 1.4 high-quality transmissions per night. Results indicated substantial individual variation among the four tagged dolphins, with home ranges varying in length from 53.9 to 83.6 km (x̅ = 71.9 ± 12.9). Binomial tests and MaxEnt models revealed some dolphins preferred habitats surrounding inlets, seagrass habitats, and various water depths, while other dolphins avoided these areas. All dolphins, however, showed substantial movement (x̅ = 5.8 ± 7.4 km) outside of the study area, including travel into rivers/canals and the adjoining ocean (6.0–8.6% and 0.8–2.9% of locations per dolphin, respectively).ConclusionsThis study was the first to utilize satellite telemetry on Indian River Lagoon dolphins and provided the first detailed insights into the nocturnal movements and habitat use of this population. Our findings suggest that while individual dolphin home ranges may overlap, they use different foraging strategies, feed on different prey, and/or exhibit intraspecific resource partitioning. In contrast with a prior study, all tagged dolphins showed considerable movement into the adjoining ocean and freshwater sources. This suggests this population has a much larger range than previously thought, which is important to consider for future research and conservation efforts.
Highlights
While cetaceans have been extensively studied around the world, nocturnal movements and habi‐ tat use have been largely unaddressed for most populations
We present findings from a satellite telemetry study of bottlenose dolphin nocturnal ranging patterns and habitat use in a shallow, estuarine system on the east coast of Florida, USA: the Indian River Lagoon (IRL) (Fig. 1)
Satellite tags remained active between 129 and 140 days (136 ± 4.99) and tag failure was due to either battery failure or delrin pin shearing/nut loss
Summary
While cetaceans have been extensively studied around the world, nocturnal movements and habi‐ tat use have been largely unaddressed for most populations. We used satellite telemetry to examine the nocturnal movements and habitat use of four bottlenose dolphins (Tursiops truncatus) from a well-studied population in a complex estuary along the east coast of Florida. This enabled us to explore the utility of satellite tracking on an apex predator within a very narrow and convoluted ecosystem. In a Hartel et al Anim Biotelemetry (2020) 8:13 number of recent studies on small cetaceans, nocturnal habits were sometimes found to differ substantially from diurnal behavior [1,2,3]. Nocturnal and diurnal movements and behaviors may differ or overlap, depending upon the population and perhaps the available habitat and/or prey species. Satellite telemetry is potentially a powerful tool in the study of the nocturnal habits of small cetaceans, but few such studies have been published to date [2]
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