Dataloggers geven inzicht in leefwijze karetschildpadden
Bericht uitgegeven door Dutch Caribbean Nature Alliance (DCNA) [land] op [publicatiedatum]
Om meer te weten te komen over het gedrag en habitatgebruik van karetschildpadden (Eretmochelys imbricata) in Lac Bay op Bonaire, heeft Sea Turtle Conservation Bonaire verspreidingsonderzoek gedaan naar de dieren. Daarnaast hebben ze, met sponsoring van Wageningen IMARES UR, vier schildpadden uitgerust met een datalogger op hun schild. Deze dataloggers meten iedere vijf seconden de diepte, en leggen de GPS coördinaten vast van de plekken waar de schildpadden ademhalen. Uit de eerste resultaten blijkt dat de karetschildpadden regelmatig de baai in- en uitgaan. De onderzoekers wisten nog niet dat de schildpadden ook in de baai verblijven en zich bij dichte zeegrasvelden en in de buurt van het mangrovebos voeden met sponzen. Het is vooralsnog onduidelijk of de schildpadden de mangroven ook wel eens ingaan.
Lees verder in het Engels......
In an attempt to learn more about the behavioural patterns and habitat use of Hawksbill turtles (Eretmochelys imbricata) at Lac Bay, Bonaire, Sea Turtle Conservation Bonaire (STCB) performed abundance surveys and, with funding from Wageningen IMARES UR, deployed dataloggers on the carapace of four Hawksbill turtles in 2012.
Three of these dataloggers were retrieved by the end of 2012 and showed some valuable results. In January 2013, one more Hawksbill was fitted with a datalogger and that one has been retrieved in July and is being analysed now. A preliminary assessment of the data seems to confirm the patterns found with the other three turtles.
The dataloggers are programmed to record depth every five seconds and obtain GPS coordinates whenever the animal comes up to the surface to breathe. The three dataloggers already recovered in 2012 were analysed and yielded detailed data on Hawksbill behaviour in and around Lac Bay, revealing that these turtles regularly move in and out of the bay. When outside the bay, the animals adhere to a diurnal pattern of resting at night and activity during the day. When inside Lac, such a diurnal pattern is more difficult to perceive due to the shallow waters and limitations concerning depth resolution of the dataloggers, but it appears that a similar pattern is maintained.
Of particular interest to STCB researchers is this new evidence that Hawksbills appear to reside inside Lac Bay and feed where dense seagrass beds are and near the mangroves, presumably eating organisms, such as sponges, associated with the seagrass stands and the mangrove roots. It remains unclear whether Hawksbills actually enter the mangroves to any extent.
Text: Sea Turtle Conservation Bonaire (STCB)
Photos: Sea Turtle Conservation Bonaire; Google Earth Pro - DigitalGlobe
Published by: Dutch Caribbean Nature Alliance (DCNA)
Source: BioNews August 2013 edition, DCNA
Nederlandse inleiding: Sara Mulder, De Natuurkalender