Material & Methods

Experiments were done with two bottlenose dolphins, a male (M1) and a female (F1) at the dolphinarium in Loro Parque, Tenerife, Spain.

The transparency of the water allowed us for direct visual observations of the swimming behavior and sound recording of the acoustic behavior of the animals during the discrimination task. Trials for each animal were run in sessions with a maximum of 5 trials per session and up to three sessions per day. I had four different target solid spheres made of four different materials: Aluminum, PVC, brass and steel.

Experimental setup from the side view of the pool
Experimental setup from an aerial view

I investigated the detailed swimming and biosonar behaviour in bottlenose dolphins while the animal actively moved towards and selected between two targets of different materials. I recorded the dolphins swimming across the pool and approaching the targets by measuring the received signal at two hydrophones placed above each target, as well as by filming the animal’s swimming movements during the trials.

Data collection started in November 2021 and was completed in January 2022 for both dolphins

-The dolphins wore opaque gelatin eyecups to prevent their use of vision while solving the tasks.

-Both dolphin and trainer were 13 m away from the targets, waiting for the experimenter to be ready.

-The trial started when the trainer gave a hand touch signal to the dolphin to indicate it to swim and locate the targets.

-The trial ended when the dolphin touched one of the targets with its rostrum

Screenshot of the video analysis program with a fixed known distance of 1m between each target, and head orientation from the blowhole to beak indicated by an arrow. The red circle indicated the location of the blowhole.