German submarines were a terror of the seas for most of World War I. At first, anti-submarine efforts were limited mainly to mines and to metal nets strung across the mouths of harbors or areas at sea where submarines were predicted to be. Things began to look up for the Allies in 1916 with the development of the depth charge, which could be set to explode at a predesignated depth, and by 1917 the British had developed the convoy system, which dropped ship losses from 25 percent to less than 1 percent.
But before the development of the depth charge and convoy system, the British Navy was getting desperate for solutions, so they enlisted the help of scientists and the general public to come up with anti-submarine ideas. Not surprisingly, plenty of strange and unusual ideas were suggested, but two that gained some interest from the Admiralty were using sea lions and seagulls to locate submarines.
When the Navy decided to try using sea lions to locate submarines, they enlisted the help of sea lion trainers from the entertainment industry. The goal was to muzzle the sea lions and train them to avoid the fish around them in favor of a reward sound, which would signal that they would receive a treat. The trainers then planned to use the sound of a submarine as the reward sound, so that when the sea lions heard one, they would come to the surface and the British could spot them and thus the submarines. The trials went relatively well in pools and small lakes, but once the sea lions were taken to the open sea, they got too distracted and their performance was unreliable.
The Admiralty also commissioned trials with seagulls. The idea was that seagulls could be trained to locate submarines by teaching them to equate the periscopes with food. However, this idea never got off the ground, since the submarine that was to be provided for testing was needed elsewhere, and the Navy eventually abandoned the idea. Around the same time, the wealthy Thomas Mills became obsessed with the idea of using seagulls and tried to convince the Admiralty to carry out trials. They found his idea and methods too problematic and rejected his proposal. This upset Mills because he was convinced of the brilliance of his idea, so he spent the rest of the war and the years after paying for trials with his own money and trying to no avail to convince various groups to develop the use of seagulls in anti-submarine efforts.