Activity

  • Sebastian Thornton posted an update 3 days, 14 hours ago

    Our goals were: (i) to determine whether dive�Csurfacing patterns varied with habitat depth and water temperature in accordance with a priori expectations; (ii) to assess the extent to which variation in average dive and surface times could be predicted based on these easily measured features of the environment; and (iii) to infer the implications of neglecting nonrandom variation in the probability of being available for detection for analyses of survey data. Our analyses are not intended as a comprehensive study of factors influencing diving behaviour. Clearly, a diversity of physiological, ecological and environmental variables (e.g. body size, Schreer & Kovacs 1997; prey distribution, Croxall et?al. 1985; predation risk, Kramer, Manley & Bourgeois 1983; Heithaus & Frid 2003; reproductive status or breeding location, Hays et?al. 2002) influence dive and surface times. The question here Enzalutamide order is whether broad, predictable trends in average dive and surface times at the group level exist �C with uncertainty around the averages reflecting variation related to other factors �C and whether accounting for such trends can improve the reliability of abundance estimates, spatiotemporal comparisons and applications of at-sea survey data. Shark Bay, Western Australia (c. 25��45��S, 113��44��E), is a shallow (mostly <15?m), subtropical bay located c. 800?km north of Perth. Our study area in the bay��s Eastern Gulf is characterized by expansive shallow (6��0?m) sand-dominated habitat, with a tidal range of 1��2?m (Burling, Pattiaratchi & Ivey 2003). Sub-adult and adult green and loggerhead turtles use Shark Bay as a feeding ground year round. Green turtles may feed on a variety of seagrasses, algae, scyphozoan jellyfish and ctenophores (Heithaus et?al. 2002; Seminoff, Jones & Marshall 2006; Burkholder et?al. 2011), while loggerhead turtles in neritic foraging areas tend to feed on benthic invertebrates, particularly molluscs and crustaceans (Dodd 1988; Plotkin, Wicksten & Amos 1993; Limpus et?al. 2001; Lazar et?al. 2011; J. Thomson et al., unpublished data). Turtles were captured by hand (Heithaus, Frid & Dill 2002) during haphazard searches and transect surveys of the study area. Curved carapace length (CCL) was measured (��0��5?cm), and turtles were tagged using titanium flipper tags (Department of Environment and Conservation, Western Australia) applied to a proximal foreflipper scute. Turtles were considered male if the tail length was ��25��0?cm and unclassed, and which would include immature males and all females, if the tail length was <25��0?cm (Limpus, Couper & Read 1994a,b; Heithaus, Frid & Dill 2002). We used TDRs (MK9; Wildlife Computers, Redmond, WA, USA) to collect diving data. Tags recorded depth (��0��5?m) every second and temperature (reported to ��0��01?��C) every 60?s.

Skip to toolbar