During periods of high tide most of the animals found on the muddy base are marine and many of these will burrow into the mud or cling to the base of some plants when the water recedes. Between the tides terrestrial animals move in. Wading and wetland birds are almost always present.
Small mammals, small fishes, birds, insect-eating bats insects, spiders, and marine invertebrates are found in salt marshes. Marine invertebrates include amphipods, isopods, anemones, shrimps, crabs, limpets, molluscs and gastropods.
Most of the gastropods eat rotting plant material. This helps recycle nutrients. Some snails eat the saltmarsh plants and the layer of microscopic algae growing on the mud's surface. Snails are an important food sources for fish and many other animals.
Insects are also abundant in the salt marsh. Most of these salt marsh invertebrates consume living plants, or fluids secreted by the plants. Some insects also feed on detritus, though the importance of their role in the food web as grazers and detritus feeders is small compared to their importance to the abundant species of birds which depend on them for food. The undigested grass eaten by insects is deposited as faeces on the marsh surface where it becomes part of the detrital food web.