text: When the mud layer is exposed at the tidal fringe, mudflats result affording a unique ecotone that affords numerous shorebird species a safe feeding and resting habitat.  Because the muds function much like quicksand, heavier mammalian predators not only cannot gain traction for pursuit, but would actually become trapped in the sinking muds. The muds are also an important substrate for primary marsh productivity including eelgrass, cordgrass and pickleweed. Furthermore, they are home to a large variety of molluscs and estuarine arthropods. Richardson Bay, for example, exposes one third of its areal extent as mudflat at low tide, which hosts a productive eelgrass expanse and also a large shorebird community.
  Mammals such as the Harbor seal may use mudflats to haul out of estuary waters; however, larger mammals such as humpback whales may become accidentally stranded at low tides. Note that normally humpback whales do not frequent estuaries containing mudflats, but at least one errant whale, publicized by the media as Humphrey the humpback whale, became stuck on a mudflat in San Francisco Bay at Sierra Point in Brisbane, California.