Diving behaviour during the internesting interval for loggerhead turtles Caretta caretta nesting in Cyprus

Abstract

Time depth recorders were used to assess the patterns of depth utilisation by 2 loggerhead turtles Caretta caretta in Cyprus, eastern Mediterranean. Dives to the seabed accounted for 59% (171 h) and 75% (215 h) of the internesting interval, respectively, with most dives being shallow (< 20 m), suggesting the turtles remained close to the shore. These benthic dives decreased markedly in the days following or prior to a nesting event, suggesting that the behaviours associated with nesting may be protracted. This importance of the seabed for loggerhead turtles in Cyprus contrasts with the far more extensive use of mid-water resting dives recently reported for this species in Japan. Our evidence suggests that this dichotomy may reflect differences in the amount of time spent travelling, with mid-water resting occurring when turtles are travelling and, conversely, when little time is spent travelling turtles opt to remain predominantly on the seabed.

Inferring vertical and horizontal movements of juvenile marine turtles from time-depth recorders

“…foraging, resting) from being consistently assigned to individual dives based on dive profile shape (see Houghton et al 2002). We could, however, identify a strong diel signal in dive behaviour.…”

Seasonal variability in voluntary dive duration of the Mediterranean loggerhead turtle, <i>Caretta caretta </i>

“…Thus, it can be assumed that their behaviour was affected only by the confined space of the tanks, not by the conditions of the surrounding medium. Houghton et al (2002) also found that inter-nesting loggerhead turtles from Cyprus, Eastern Mediterranean, generally dived for less than 40 min in water of 27 to 28°C. The dive duration observed in this study may therefore reflect closely the seasonal variations in dive duration of free-ranging loggerhead turtles.…”

“…Investigations using transmitting-or data-logging devices attached to the turtle's carapace are undertaken mainly during the nesting season, when the females go on land to lay eggs (e.g. in the Mediterranean: Hochscheid et al, 1999;Houghton et al 2002). However, information about their movements and preferred locations during the winter are mainly derived from occasional sightings or fisheries bycatch (but see Epperly et al, 1995).…”

Flow simulation along a seal: the impact of an external device

“…It is essential to minimise drag by reducing the frontal area of the device and streamlining its shape. The development and use of short deployment devices should be considered, like those already applied for turtles (Houghton et al 2002) and cetaceans (Aguilar Soto et al 2008).…”