Name: Izabella Brunelli Andrade
Type: MSc dissertation
Publication date: 04/12/2020

Namesort descending Role
Agnaldo Silva Martins Advisor *

Examining board:

Namesort descending Role
Agnaldo Silva Martins Advisor *
Cecília Baptistotte External Examiner *
João Batista Teixeira External Alternate *
Sarah Maria Vargas Internal Examiner *
Yuri Luiz Reis Leite Internal Alternate *

Summary: Chelonia mydas (green turtle) is an emblematic group of animals threatened with extinction.
Among the various anthropogenic threats, the most growing and one of the most dangerous
currently is the debris ingestion. There are several studies related to the debris ingested by the
green turtles, however there is a difficulty in understanding how this solid waste is consumed by
these animals. Thus, in this work it was possible to demonstrate, through aerial images, a
foraging behavior not yet described, called “subsurface swimming”, which can increase the
susceptibility of debris ingestion by the turtles bringing consequences for the conservation of the
species. The data were obtained with the use of a drone in a region recognized as a feeding area
for juveniles of Chelonia mydas. Through the analysis of the recordings, two foraging behaviors
were identified, subsurface and bottom swimming, and also two events of interaction between
green turtles and garbage. During subsurface swimming, the animal swam close to the water
surface, ventilating and periodically capturing suspended material for feeding. In the background
foraging, the animal was seen foraging near the rocky bottom, regularly going to the surface to
ventilate and returning to the bottom. It was observed that the respiratory rate during bottom
foraging was double when compared to subsurface swimming. In addition, during the subsurface
swim, the green turtles captured food at least once in 85% of the total observations. The use of a
drone was fundamental in this work, allowing the description of a behavior that has not been
verified yet. Subsurface swimming requires less energy since the food is available in suspension
and the animal has fewer breathing events. In addition, subsurface swimming can facilitate the
access of green turtles to ingest plastic debris, as there is an enormous availability of this floating
material in coastal areas around the world, and it can also increase the likelihood of these
animals being hit by boats and fishing nets. With this, it is evident the need for protection and
monitoring of Chelonia mydas foraging areas by boats or fishing, as well as the control of solid
waste that arrive at the coast.

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