Bristles are found on pig breeds instead of fur on most mammals. Because the density is less than with fur, pigs are vulnerable to sunburn. One breed, the Tamworth Pig is endowed with a very dense bristle structure such that sunburn damage to skin is minimized. Animals named for their bristles include bristlebirds, the Bristle-thighed Curlew, the Bristle-spined Porcupine, and the Trinity bristle snail. Bristles also anchor worms to the soil to help the worm move.