Challenges of collecting blow from small cetaceans

Abstract

We trialed the collection of blow samples using a waterproof electric multirotor (quadcopter) drone from two free‐ranging dolphin species, the abundant and approachable bottlenose dolphin (Tursiops aduncus) and the less common and boat shy humpback dolphin (Sousa sahulensis). This drone was fast, maneuverable, and quiet compared to other drones commonly used in studies of cetaceans and relative to their hearing thresholds. We were successful in collecting blow samples from four individual dolphins (three bottlenose dolphins and one humpback dolphin) in two groups. The success of obtaining samples was dependent on the individual dolphin's activity. We were successful in sampling when dolphins were resting and socializing but found that socializing dolphins were not predictable in their surfacing and direction and therefore do not recommend drone sampling socializing dolphins. The suitability and preference of the sampling technique over biopsy sampling is highly dependent on the dolphin activity. We also attempted to extract DNA from the blow samples with the aim of assessing the feasibility of using blow sampling by drone for population genetic studies. We were unsuccessful in extracting DNA and recommend that others attempting to sample dolphin blow with a drone should prioritize collecting a larger volume of blow that may yield adequate concentrations of DNA to be amplified. Blow sample volume could potentially be increased by sampling with more absorbent materials.

Operational Protocols for the Use of Drones in Marine Animal Research

“…Among odontocetes, to the authors' knowledge, drones have only been implemented to study a few species of dolphins. Example applications have included identifying dolphin presence and habitat use [137][138][139][140][141][142].…”

“…Two main types of drones have been used to study free-ranging dolphins; (1) existing off-the-shelf drone technology (e.g., DJI multirotors and (2) specifically designed, custom-built drone technology [142]. Off-the-shelf drones have been the type most frequently used to study dolphins.…”

“…In contrast, customised drones allow for more dedicated research to be conducted but requires more specialised piloting experience. For example, custom appendages have been implemented on multirotor drones to allow the collection of dolphin microbiome to study dolphin health [141,142].…”

The use of Unmanned Aerial Vehicles (UAVs) to sample the blow microbiome of small cetaceans

“…The sampling tool used in this study was developed and the methodology adapted to bottlenose dolphins maintained in an aquarium, considering both sampling success and safe distance from the animals, that did not compromise their normal behavior. Our results, despite being acquired from a small number of animals, suggest that this approach could represent a first step in overcoming the difficulties, already reported in other studies, associated with a drone-based sampling technique for wild small cetaceans [15]. A major limitation with using UAVs for blow sampling is the impossibility to match the samples with the individuals because bottlenose dolphin groups are relatively large, densely concentrated and highly dynamic, with frequent changes in group size and composition of individuals [26].…”

“…A major limitation with using UAVs for blow sampling is the impossibility to match the samples with the individuals because bottlenose dolphin groups are relatively large, densely concentrated and highly dynamic, with frequent changes in group size and composition of individuals [26]. The contemporary use of a sampling tool with a camera mounted on the UAV, as already tested by Raudino and colleagues (2019) [15], was not possible in our study; this technical limitation should be addressed in future studies by using different and more proficient UAVs. Another potential method to link blow samples to individual animals could be searching for the host DNA in the blow sample, which could provide a genetic individual identification.…”