The Animals Of Delaware

Section 01

Why The Second Smallest State Matters Globally

Delaware is 96 miles long, never more than 35 miles wide, and has the lowest mean elevation of any state at about 60 feet. It has no mountains, no large forest wilderness, and only around 60 mammal species. On paper it is unremarkable.

What Delaware has is a bay. Delaware Bay hosts the largest spawning aggregation of horseshoe crabs on Earth, and that single fact makes the state internationally significant. On spring high tides around the new and full moons in May and June, hundreds of thousands of horseshoe crabs come ashore to lay eggs in the sand. Those eggs arrive precisely when hundreds of thousands of shorebirds, having flown from South America, need to refuel before continuing to the Arctic.

The red knot is the species that made this famous. It can nearly double its body weight in two weeks on horseshoe crab eggs, and it cannot complete its migration without them. When horseshoe crab harvest for bait and biomedical use reduced egg availability in the 1990s, the red knot population fell sharply, and the two species are now managed together as a single system. Delaware Bay is designated a Wetland of International Importance and a hemispheric site in the Western Hemisphere Shorebird Reserve Network.

Beyond the bay, Delaware is a boundary state. It sits where northern and southern species meet: bald cypress swamp reaches its northern limit in Sussex County, while some northern species reach their southern limit in the state's few remaining upland forests.

Section 02

Delaware's Official State Animals

The blue hen is not a wild bird. It is a fighting-gamecock breed, and the designation comes from Revolutionary War tradition: Delaware soldiers were said to carry blue hen gamecocks and to fight like them. It is a domestic breed honoured for military history, which makes Delaware one of a handful of states whose official bird is not a wild species. That is partly why the gray fox was later named the state wildlife animal, filling the gap.

Two of the symbols are quietly sophisticated. Naming the horseshoe crab the state marine animal in 2002 came directly out of the red knot crisis and the fight over harvest limits. And the stonefly designation is a genuinely unusual choice: stoneflies are among the most pollution-sensitive aquatic insects, so their presence in a stream is a direct measure of water quality. Delaware effectively made a bioindicator an official symbol.

Section 03

Habitats By Region, And Who Lives In Each

1. Piedmont, the northern sliver

Only the far northwest corner above Wilmington sits in the Piedmont, with rolling hills, rocky streams, and mature oak-tulip poplar forest. It holds species found nowhere else in the state: forest-interior songbirds like Louisiana waterthrush and hooded warbler, plus salamanders needing cold, rocky headwaters.

2. Coastal Plain uplands and Delmarva forest

Most of the state, low and flat, historically mixed oak and loblolly pine with a high water table. This is Delmarva fox squirrel country, and it holds white-tailed deer, coyote (which only arrived in Delaware in the 1990s, making it the last state in the continental US to be colonised), red and gray fox, and the state's small but growing bald eagle population.

3. Delmarva bays and freshwater wetlands

Shallow, seasonal depressions scattered across the coastal plain, sometimes called Delmarva bays or whale wallows. They fill in winter and dry in summer, which excludes fish and makes them ideal amphibian nurseries. Tiger salamanders, barking treefrogs, and several rare frogs depend on them, and they are among the state's most threatened habitats.

4. Bald cypress swamp, Great Cypress Swamp

In southern Sussex County, bald cypress reaches its northern range limit. The Great Cypress Swamp, once heavily logged and burned, is now the largest contiguous forest on the Delmarva Peninsula and holds breeding prothonotary warblers, barred owls, and a returning population of forest specialists.

5. Delaware Bay shore and salt marsh

Extensive tidal salt marsh, mudflat, and sand beach along the bay. This is the horseshoe crab and shorebird zone, and also holds saltmarsh sparrow, seaside sparrow, clapper rail, black rail, diamondback terrapin, and enormous numbers of wintering snow geese and ducks.

6. Atlantic coast and inland bays

Ocean beaches from Cape Henlopen to Fenwick Island, plus the shallow Rehoboth, Indian River, and Little Assawoman bays behind them. Piping plover and least tern nest on the beaches, bottlenose dolphins feed offshore in summer, and gray and harbour seals haul out in winter.

Section 04

The Horseshoe Crab And Shorebird System

This deserves its own section because it is the single most important wildlife event in the state and one of the great migration spectacles in the world.

Horseshoe crabs are not crabs. They are closer to spiders and scorpions, and the lineage is roughly 450 million years old, older than dinosaurs and largely unchanged. Females come ashore on spring tides, dig shallow nests, and lay tens of thousands of eggs each. Waves and later crabs dig up a large share of those eggs, and the surplus washes into the surf zone where birds can reach it.

The birds arriving to eat them have flown extraordinary distances. Red knots of the rufa subspecies winter as far south as Tierra del Fuego and breed in the central Canadian Arctic, a round trip that can exceed 18,000 miles. They reach Delaware Bay with depleted fat reserves and roughly two weeks to rebuild. Also present in large numbers: ruddy turnstone, semipalmated sandpiper, sanderling, dunlin, and short-billed dowitcher.

The conflict is that horseshoe crabs are valuable to people too. They have been harvested as bait for eel and conch fisheries, and their blue, copper-based blood contains Limulus amebocyte lysate, which detects bacterial contamination in vaccines and injectable drugs. Every batch of injectable medicine made in the US has historically been tested with it. Crabs are bled and returned to the water, with some mortality. More on that: how horseshoe crabs guard our vaccines.

Section 05

Mammals Of Delaware

Around 60 species, with no large predators and no bears. Delaware is one of only a few states with no established black bear population.

• White-tailed deer: abundant and the state's only large wild mammal, dense enough to damage forest regeneration and crops.
• Gray fox: the state wildlife animal, and the only North American canid that routinely climbs trees.
• Red fox: more common in open farmland, and largely descended from European stock introduced for hunting.
• Coyote: the newest arrival, first confirmed breeding in the 1990s and still at low density compared with neighbouring states.
• Delmarva fox squirrel Sciurus niger cinereus: a large, silvery squirrel endemic to the Delmarva Peninsula. It was federally endangered from 1967, recovered through habitat protection and translocation, and was delisted in 2015, one of the clearer endangered species successes on the East Coast.
• River otter, mink, muskrat, beaver, raccoon, Virginia opossum, striped skunk, woodchuck, eastern cottontail, gray squirrel, southern flying squirrel: all widespread.
• Nutria: an invasive South American rodent that was the target of a large Delmarva eradication programme.
• Bats: nine species, with the northern long-eared bat federally endangered and little brown bats sharply reduced by white-nose syndrome.
• Marine mammals: bottlenose dolphin in summer, harbour and gray seals in winter, plus humpback and North Atlantic right whales offshore. Right whales pass through Delaware's offshore waters on migration and are among the most endangered whales on Earth.

Bobcat, black bear, elk, wolf, and mountain lion are all absent, extirpated in the colonial and early industrial periods. Occasional bobcat and bear wanderers are reported from Maryland and Pennsylvania.

Section 06

Birds Of Delaware

More than 420 species have been recorded in a state of under 2,000 square miles, a density explained entirely by position on the Atlantic Flyway.

• Waterfowl: Bombay Hook and Prime Hook refuges winter very large numbers of snow geese, Canada geese, northern pintail, American black duck, and green-winged teal. Snow goose flocks can number in the tens of thousands.
• Wading birds: great blue heron, great and snowy egrets, glossy ibis, black-crowned and yellow-crowned night-herons, and one of the region's notable heronries at Pea Patch Island in the Delaware River.
• Raptors: bald eagle, which grew from a handful of pairs to well over 100 nesting pairs, plus osprey on nearly every channel marker, northern harrier over marsh, and short-eared owl in winter.
• Marsh specialists: saltmarsh sparrow, seaside sparrow, clapper and Virginia rails, and the very secretive black rail, which has declined severely.
• Beach nesters: piping plover, least tern, American oystercatcher, and black skimmer, all requiring beach closures during nesting.

Section 07

Reptiles, Amphibians, And Fish

Delaware has around 25 reptile and 20 amphibian species. Only one snake is venomous.

Snakes: the northern copperhead occurs only in the northern Piedmont sliver and is uncommon. Every other snake in the state is harmless, including eastern rat snake, black racer, northern water snake, eastern kingsnake, corn snake, and eastern garter snake. Timber rattlesnakes were extirpated from Delaware long ago.

Turtles: diamondback terrapin in brackish creeks, eastern box turtle, spotted turtle, mud and musk turtles, painted turtle, red-bellied turtle, snapping turtle, plus loggerhead, green, Kemp's ridley, and leatherback sea turtles offshore. See the seven sea turtle species.

Amphibians: eastern tiger salamander (state endangered and dependent on Delmarva bays), marbled and spotted salamanders, four-toed salamander, eastern newt, plus barking treefrog, carpenter frog, southern leopard frog, spring peeper, wood frog, and Fowler's toad.

Fish: weakfish is the state fish, and the estuary is a nursery for summer flounder, striped bass, bluefish, and blue crab, which is culturally and economically central to the region. Atlantic sturgeon spawn in the Delaware River and are federally endangered; the river's population is one of the most closely watched on the coast. American shad and river herring runs are the focus of dam removal and fish passage work.

Section 08

Dangerous Animals In Delaware

Delaware is close to the safest state in the country for wildlife encounters. There are no bears, no big cats, no alligators, and one uncommon venomous snake in one corner of the state.

• Ticks: the real risk. Lyme disease incidence in Delaware is among the highest per capita in the nation, and lone star ticks also transmit ehrlichiosis and cause alpha-gal syndrome.
• White-tailed deer: vehicle collisions are the leading source of wildlife-related injury.
• Northern copperhead: northern Piedmont only, uncommon, and bites are rare and rarely serious.
• Mosquitoes and greenhead flies: salt marsh greenheads are a genuine summer nuisance, and mosquitoes carry West Nile virus and eastern equine encephalitis.
• Jellyfish and stingrays: sea nettles in the inland bays in late summer; shuffle your feet in shallow water.
• Rabies: raccoons, foxes, skunks, and bats are the vectors. Do not handle wild mammals.

Section 09

Endangered And Protected Species

Sea level rise is the defining threat in Delaware in a way it is not in most states. With the lowest mean elevation in the country and extensive tidal marsh, the state is losing high marsh to open water, and species like saltmarsh sparrow and black rail that nest just above normal high tide have very little margin. Marsh migration inland is blocked by roads and development in many places.

Section 10

Where To See Wildlife In Delaware

• Bombay Hook National Wildlife Refuge: the state's premier site, with a wildlife drive through impoundments and marsh. Snow geese in winter, shorebirds in spring, waders all summer.
• Prime Hook National Wildlife Refuge: marsh restoration in progress, excellent for waterfowl and marsh birds.
• Mispillion Harbour and Slaughter Beach: the classic horseshoe crab spawning and red knot viewing sites in May.
• Cape Henlopen State Park: seabirds, seals in winter, dolphins in summer, and migrant songbirds.
• Great Cypress Swamp: northern-limit bald cypress and forest interior birds.
• Pea Patch Island, via Fort Delaware: one of the region's largest wading bird colonies.
• White Clay Creek State Park: the Piedmont species that occur nowhere else in the state.