Training
Before testing, the penguins were trained to voluntarily participate in the study:
First, they were desensitized to their head being in a confined space by receiving food through a large bucket until they remained comfortably inside.
Then, the experimental mask was introduced and the delay between inserting their head and receiving food was gradually increased.
Trials
During trials the spirometer was connected to the experimental mask and the penguin breathed spontaneously into it while either standing or lying.
The spirometer measured the airflow (blue line), and the software calculated the corresponding volumes (pink line):