[5] It is found in shallow water on the west coast of North America, between southern Oregon and Baja California,[6] where it forms a U-shaped burrow in the sediment and feeds on plankton using a mucus net.

[4] Shallow water in the northeastern Pacific Ocean is the habitat of U. caupo; its range extends from southern Oregon to northern Baja California.

The worm draws water through its burrow by peristaltic contractions of its body and as food particles pass through the net they adhere to it.

[9] These include the California softshell clam (Cryptomya californica), pea crabs, shrimps and scaleworms.

[2] The arrow goby (Clevelandia ios) uses the entrance of the burrow as a refuge into which it can dash if danger threatens.