Largest animal-made fishing nets

Certain humpback whales (Megaptera novaeangliae), a marine mammal with a worldwide distribution, have learned to create "bubble nets" to help catch their food, using perhaps one of the most ephemeral kinds of eco-engineering that lasts no more than a couple of minutes. Formed by a group of whales, coordinated by vocalizations, the nets can span anywhere from 3 to 30 metres (10-98 feet) in diameter. It is an apparently learned behaviour known by only some humpback pods that is passed down the generations. The technique involves a group of whales first circling a school of small fish or krill. One whale begins blowing bubbles via its blowhole as it circles the school; others join in, corralling the prey, then one whale gives a signal – a feeding call. At this point, the humpbacks break formation and swim upwards inside the "net" with their mouths wide open, gulping down the amassed quarry along with up to 15,000 gallons (56,780 litres) of seawater. The whales filter out the food against their baleen plates and expel the water.

As far as we know, only humpback whales and dolphins make bubble nets, though by nature of size whale nets are far bigger. However, "net-making" as a technique to capture food is used by numerous animals from spiders and caddisflies that spin silk, pelagic snails that use a net made of mucus, and, of course, humans, who for millennia have used a variety of natural or man-made materials to serve this purpose when hunting.