Ethology, the study of animal behavior, is essential for assessing the response of an animal to changes in its environment and insight into potential impacts of human activity on a given population. A behavioral response can either increase an individual’s fitness and lead to success of the species or it can lead to a decrease in fitness that makes the animal struggle to adapt to the new habitat. This is especially true for marine mammals – specifically cetaceans – that need to acclimate to changing sea levels, changing sea temperatures, and frequent anthropogenic activity such as tourism and fishing. Therefore, it is vital to have an effective system in place to document the behaviors being displayed to infer if the population is struggling or thriving.
Cetacean behavior is divided into two different categories: states and events. States are long-term behaviors measured by its duration (ex: swimming, feeding, resting…), whereas events are short-term behaviors measured by how frequent the animal exhibits them (ex:breaching, leaping, changing direction…). Cetaceans may display these behaviors as a form of communication or in reaction to boat presence, which can be a positive reaction (the animal swims towards the boat), a negative reaction (the animal swims away from the boat), or a neutral reaction (the animal maintains its original direction). Other useful parameters to note are the way in which dolphins are grouped, whether it be in one large group, smaller sub-groups, or dispersed, as well as their movement formation, which include a front (swimming side-by-side), a line (one in front of the other), or a semi-circle.
The goal for this project is to classify the main behavioral states and events of the cetaceans within the eastern Aegean Sea, with a specific focus on the effect of boat traffic on common dolphins (Delphinus delphis). The other two studied dolphin species are striped dolphin (Stenella coeruleoalba) and bottlenose dolphins (Tursiops truncatus). Since the common dolphin is an endangered species and the population around the Mediterranean is still declining, it is crucial to gather more data pertaining to their behavior around human activity. Furthermore, different behavioral states will be matched to the dolphin’s vocalisation (clicks, whistles and burst pulses) collected by the Bioacoustics Team to understand if the sound’s frequency changes during specific behaviors.
Behavioral data is recorded in multiple ways. The first way is through a hard-copy data sheet, on which other important information such as the time, date, coordinates, and presence of other boats or species are noted. The other technique is video recording the sighting via handycam, after which the videos are analyzed using BORIS (Behavior Observation Research Interactive Software), a computer program that catalogues the behaviors exhibited by the dolphins in sequential order.
To date we have analyzed videos using BORIS from June 2017 – November 2018 and matched behavioral states to the dolphins’ sounds from August 2017 – November 2018. For the common dolphins, no significant effect was found pertaining to boat presence, number of boats or type of boats on the duration of behavioral states, but more data needs to be collected for more powerful statistical analysis.
Aaron Crasnick
Marine Mammal Researcher
Wildlife Ecology & Conservation, University of Delaware,USA
