Over 450 species of amphibians, reptiles, fish, birds, and mammals, and a myriad of invertebrate animals, depend on the diversity of upland, wetland, and coastal ecosystems found at Cape Cod National Seashore. Depending on the species, the park may provide habitat year round, or only during nesting season, migration, or the winter time. Park wildlife includes marine mammals and turtles; the familiar gulls, terns, and waterbirds of beaches and salt marshes; and a great variety of animals that inhabit the park's woodlands, heathlands, grasslands, swamps, marshes, and vernal ponds. Twenty five federally-protected species occur in the park, most prominently the threatened piping plover. The Seashore is a significant site for this species with roughly 5% of the entire Atlantic coast population nesting here. Cape Cod National Seashore also supports 32 species that are rare or endangered in the state of Massachusetts. Some of these, such as the common tern, are conspicuous; far less noticeable is the elusive spadefoot toad which spends most its life buried in the sand, emerging only on warm nights with torrential rainfall.
While Cape Cod National Seashore provides significant protection to wildlife and their habitats, there are concerns. For example, changes due to sea level rise or fire suppression may alter habitats, making them less suitable for some species. Disturbance, development, and road mortality may also take its toll on park wildlife. With a program of long-term inventory and monitoring, knowledge of park wildlife continues to grow, and with it, efforts to ensure its survival.