Which marine mammal uses sponges as tools to protect its nose while foraging?

The marine mammal that uses sponges as tools to protect its nose while foraging is the bottlenose dolphin.

This behavior, called sponging, has been observed in Indo-Pacific bottlenose dolphins in Shark Bay, Western Australia. A dolphin breaks off a marine sponge and carries it over the tip of its rostrum, the elongated structure commonly called its beak. The sponge likely protects the sensitive rostrum as the dolphin probes sandy seafloors for prey.

Sponging helps dolphins target bottom-dwelling fish that may hide in sediment and lack swim bladders, making them harder to detect with echolocation. The behavior is especially associated with female dolphins and appears to be learned socially, often passing from mother to daughter. That makes it an example of animal culture, not merely an individual trick.

A common mix-up is sea otters, which also use tools, especially rocks to open shellfish. However, the sponge-over-the-nose technique is specifically documented in bottlenose dolphins, and has only been observed in Shark Bay.