Habitat selection by green turtles in a spatially heterogeneous benthic landscape in Dry Tortugas National Park, Florida
Ikuko Fujisaki, Kristen M. Hart, Autumn R. Sartain-Iverson
ABSTRACT: We examined habitat selection by green turtles Chelonia mydas at Dry Tortugas National Park, Florida, USA. We tracked 15 turtles (6 females and 9 males) using platform transmitter terminals (PTTs); 13 of these turtles were equipped with additional acoustic transmitters. Location data by PTTs comprised periods of 40 to 226 d in varying months from 2009 to 2012. Core areas were concentrated in shallow water (mean bathymetry depth of 7.7 m) with a comparably dense coverage of seagrass; however, the utilization distribution overlap index indicated a low degree of habitat sharing. The probability of detecting a turtle on an acoustic receiver was inversely associated with the distance from the receiver to turtle capture sites and was lower in shallower water. The estimated daily detection probability of a single turtle at a given acoustic station throughout the acoustic array was small (<0.1 in any year), and that of multiple turtle detections was even smaller. However, the conditional probability of multiple turtle detections, given at least one turtle de tection at a receiver, was much higher despite the small number of tagged turtles in each year (n = 1 to 5). Also, multiple detections of different turtles at a receiver frequently occurred within a few minutes (40%, or 164 of 415, occurred within 1 min). Our numerical estimates of core area overlap, co-occupancy probabilities, and habitat characterization for green turtles could be used to guide conservation of the area to sustain the population of this species.
Acoustic telemetry · Co-occupancy · Habitat selection · Satellite telemetry
<p>AQUATIC BIOLOGY
Aquat Biol
Vol. 24: 185–199, 2016
doi: 10.3354/ab00647
Published online February 22
INTRODUCTION
Habitat selection in response to spatial hetero-
geneity is a common theme in landscape, population,
and evolutionary ecology, and is important for habi-
tat conservation (Morris 2003a,b). Both abiotic and
biotic factors can dictate habitat selection; the physi-
cal environment is considered a primary factor in -
fluencing resource availability, but species’ fitness is
also dependent on population density and inter -
actions, such as competition (Rosenzweig 1991). Ani-
mals may use information such as proximity to con-
specifics in both positive (attraction) and negative
(avoidance) ways (Dall et al. 2005), and understand-
ing how individuals position themselves relative to
others could improve our ability to conserve wildlife
populations (Ward & Schlossberg 2004).
Most conspecific habitat selection studies have
predominantly centered on terrestrial species (e.g.
birds by Ward & Schlossberg 2004; reptiles by
Stamps 1991), while a comparably small number of
studies exist in the marine realm (e.g. turtles by
Schofield et al. 2006, 2007; fish by Lecchini et al.
2007). This is likely due to the challenges involved in
observing individuals during experiments. Experi -
mental mani pulation is particularly difficult for highly
© The authors 2016. Open Access under Creative Commons by
Attribution Licence. Use, distribution and reproduction are un -
restricted. Authors and original publication must be credited.
Publisher: Inter-Research · www.int-res.com
*Corresponding author: ikuko@ufl.edu
Habitat selection by green turtles in a
spatially heterogeneous benthic landscape
in Dry Tortugas National Park, Florida
Ikuko Fujisaki1,*, Kristen M. Hart2, Autumn R. Sartain-Iverson3
1University of Florida, Ft. Lauderdale Research and Education Center, Davie, FL 33314, USA
2US Geological Survey, Wetland and Aquatic Research Center, Davie, FL 33314, USA
3Cherokee Nation Technologies, contracted to US Geological Survey,