Dyke Marsh supports a diversity of animals, including gray squirrels, cottontail rabbits, shrews, field mice, river otters, red fox, little brown bats and whitetail deer. Evidence of beaver activity is often visible along the Haul Road and boardwalk. Beavers and muskrats can be seen swimming in the marsh in the early evening. Fish include carp, bullhead, chain pickerel, shad, striped bass and shiners. Reptiles such as snapping turtles and northern water snakes and amphibians such as frogs are also common. The table at right lists all the mammals observed in Dyke Marsh over more than 30 years as documented in the FODM sponsored study The Dyke Marsh Preserve Ecosystem by David W. Johnston.

Virginia Oppossum (Didelphis virginiana)
Northern Short-tailed Shrew (Blarina brevicauda)
Eastern Mole (Scalopus aquaticus)
Star-nosed Mole (Condylura cristata)
Little Brown Myotis (Myotis lucifugus)
Northern Red Bat (Lasiurus borealis)
Hoary Bat (Lasiurus cinereus)
Silver-haired Bat (Lasionycteris noctivagans)
Eastern Pipistrelle (Pipistrellus subflavus)
Big Brown Bat (Eptesicus fuscus)
Evening Bat (Nycticeius humeralis)
Eastern Cottontail (Sylvilagus floridanus)
Eastern Chipmunk (Tamias striatus)
Woodchuck (Marmota monax)
Eastern Gray Squirrel (Sciurus carolinensis)
Southern Flying Squirrel (Glaucomys volans)
American Beaver (Castor canadensis)
Marsh Rice Rat (Oryzomys palustris)
Eastern Harvest Mouse (Reithrodontomys humulis)
White-footed Mouse (Peromyscus leucopus)
Deer Mouse (Peromyscus maniculatus)
Eastern Woodrat (Neotoma floridana)
House Mouse (Mus musculus)
Norway Rat (Rattus norvegicus)
Black Rat (Rattus rattus)
Meadow Vole (Microtus pennsylvanicus)
Common Muskrat (Ondatra zibethicus)
Red Fox (Vulpes vulpes)
Common Gray Fox (Urocyon cinereoargenteus)
Common Raccoon (Procyon lotor)
Mink (Mustela vison)
Striped Skunk (Mephitis mephitis)
Northern River Otter (Lutra canadensis)
White-tailed Deer (Odocoileus virginianus)

FODMer Laura Sebastianelli is monitoring beavers in the western part of Dyke Marsh, behind River Towers. On May 1, she spotted two families, two adults and a kit and two adults and two kits nursing. At one point, she saw five adults and three kits on top of the lodge (see photo) and at least one beaver swimming around. Thank you, Laura. This is a very special, little-visited part of Dyke Marsh.

FODM member Deborah Hammer led a group of 35 on a frog and bat walk in the western part (photo, left) of the Dyke Marsh Wildlife Preserve on the evening of May 1. Deborah is a bat educator and rehabilitator. She lives nearby and has observed frogs and bats in this part of Dyke Marsh for the last 13 years. She is concerned that she is not hearing many spring peepers or seeing as many bats as she used to. “The sky used to be filled with them,” she commented.

Deborah told the group that frogs and toads need still water like ephemeral pools upland to lay eggs and hatch tadpoles. Bats need woodland trees upland of wetlands for nesting and marsh areas for hunting for food. She is concerned that development proposed for Westgrove Park to the west of Dyke Marsh could destroy or degrade the little nearby suitable habitat that remains. “It’s all interconnected,” she commented.

She offered many interesting facts, among them these:

• The most common native frogs here are the green frog, bullfrog, spring peeper and southern leopard frog. Dyke Marsh is the southern leopard frog’s northernmost habitat.
• Bats can live 20 years on average, are the only mammal that flies and can eat 3,000 insects a night.
• There are 16 bat species in Virginia and 10 in Fairfax County. (Little brown bat, photo by Rick Reynolds.)

Birds are perhaps the most visible and accessible animal species of the marsh. Bird-watching, or birding has made the Dyke Marsh Wildlife Preserve a popular attraction for many visitors. There are resident species in every habitat from emergent wetlands to upland forests as well as migratory species that visit the marsh each spring and fall. FODM has conducted several studies and surveys on birds and bird life and has documented over 270 species in Dyke Marsh. For a complete list including seasonal occurrence, see our Bird List page and see our Breeding Bird Survey page for a report on birds that breed in Dyke Marsh. These studies help to monitor the overall health of the marsh by documenting trends in bird populations such as in The Marsh Wren – Loss of Habitat, Loss of Birds below. FODM also participates in the annual Christmas Bird Count and leads a weekly Sunday morning bird walk all year.

At least three species of owls have been observed in the Dyke Marsh Wildlife Preserve over the years – barred owl (Strix varia), Eastern screech owl (Megascops asio) and the great horned owl (Bubo virginianus).

FODM President Glenda Booth has written an article in the January-February 2019 Virginia Wildlife magazine, titled “Virginia’s Most Mysterious Birds.” You can read the entire article here.

Butterfly checklist - Friends of Dyke Marsh volunteers conduct butterfly surveys from April to October every year. Working with staffers from the National Park Service, George Washington Memorial Parkway unit, we have prepared a butterfly checklist for our members and visitors. The checklist includes butterflies you could observe in Dyke Marsh and many of their host plants. Thank you to the following for helping produce this brochure: Jessica Strother, Jim Waggener, Mark Maloy and Brent Steury.

You can read the checklist here.

FODM participated in the National Park Service’s (NPS) Spotlight on Resources research conference on October 7 and 8, 2020. Jessica Strother and Bob Veltkamp prepared a poster describing our almost five years of volunteer surveys of dragonflies, damselflies and butterflies in Dyke Marsh. The poster, which includes 11 photographs, documents the species surveyed from 2016 through 2019: butterflies, 49 species; damselflies, 12 species; dragonflies, 36 species. Click here to view the poster. Our thanks to the dedicated volunteers and to NPS for the opportunity to share our work.

Since 2016, volunteers from FODM and the Audubon Society of Northern Virginia have conducted surveys of butterflies, dragonflies and damselflies in Dyke Marsh from April to October, led by Jim Waggener and Jessica Strother.

2020 marked the fifth consecutive year. Their volunteer efforts built on previous surveys by Dr. Ed Barrows, Georgetown University, and Christopher Hobson, Virginia Department of Conservation and Recreation, Division of Natural Heritage in 2016.

The surveyors covered a defined area around the Belle Haven Marina and the Haul Road trail, using the same methodology each year, except in 2020, volunteers followed covid-19 pandemic protocols for their protection.

2020 Results

In 15 surveys totaling 33 field hours, the volunteers documented 33 butterfly species and 19 dragonfly species. They added two butterfly species to the previous list: the American snout (Libytheana carinenta) and the great spangled fritillary (Speryeria cybele). They added three species to the dragonfly/damselfly list: the twelve-spotted skimmer (Libellula pulchella), the shadow darner (Aeshna umbrosa) and the swift river cruiser (Macromia illinoiensis illinoiensis) .

A few highlights:

• Butterfly species outnumbered dragonflies (51 to 39), but far more individual dragonflies and damselflies were counted than butterflies.
• The group found new species each year.
• The group observed a more positive trend in monarch butterflies than in the first year of the survey, 2016.
• Species and overall numbers of dragonflies continue to decline.

To read the report covering all five years of surveys, click here. To see the species checklist showing species identified over the five years, click here. To reach the FODM butterfly and host plant checklist, click here.

Eastern tiger swallotail

Eastern tiger swallowtail(Papilio glaucus), black form. Photo by Glenda Booth

Editor’s note: FODM volunteers are working to control invasive plants and add more native plants, especially at the native plant site on the Haul Road trail. Insects and plants co-evolve and insects like butterflies depend on certain native or host plants for food and shelter. We assume that more aggressively controlling non-native plants like English ivy and porcelain berry could provide more support for native insects, like those that these surveys target.

The Friends of Dyke Marsh send athank you to the following volunteers: Jim Waggener, Jessica Strother, Ed Eder, Larry Cartwright, Margaret Fisher, Joel Goldman, Su Kim, Joan Haffey, Ken Larsen, Joanne and Powell Hutton, Larry Meade, Rusty Moran, Gary Myers, Dave Nichols, Kristi Odom, Fred Siskind and Dixie Sommers. Thanks too to Brent Steury, George Washington Memorial Parkway, Natural Resources Program Manager.

FODM volunteers have conducted lepidoptera and odonata (butterflies, dragonflies and damselflies) surveys from April to October ever year since 2016. Here are the total species observed from 2016 to 2019: Butterflies - 49 species; Damselflies - 12 species; Dragonflies - 36 species.

Chris Hobson, with the Virginia Department of Conservation and Recreation, Division of Natural Heritage, conducted a four-day field survey, sponsored by FODM, in 2011 by boat and on foot between May and September.  Dr. Edd Barrows, a Georgetown University entomologist, has identified four additional species. 

Hobson identified the following 16 species in 2011:

Common Green Darner (Anax junius), Orange Bluet (Enallagma signatum), Big Bluet (Enallagma durum), Prince Baskettail(Epitheca princeps), Common Pondhawk (Erythemis simplicicollis), Eastern Forktail (Ischnura verticalis), Fragile Forktail (Ischnura posita), Slaty Skimmer (Libellula incesta), Needham’s Skimmer (Libellula needhami), Great Blue Skimmer (Libellula vibrans), Wandering Glider (Pantala flavescens), Blue Dasher (Pachydiplax longipennis), Eastern Amberwing (Perithemis tenera), Common Whitetail (Plathymis lydia), Russet-tipped Clubtail (Stylurus plagiatus), Black Saddlebags (Tramea lacerate).

On July 22, 2013, Hobson added four more species to the survey:

Widow Skimmer (Libellula luctuosa), Twelve-spot Skimmer (Libellula pulchella), Halloween Pennant (Celithemis eponina), River Cruiser (Macromia sp.).

Any survey is a “snapshot” at a given time and place, not a comprehensive inventory. Total numbers seen on any day can vary tremendously, depending on the weather and time of year. Hobson saw more than 1,000 of one species in one day and hundreds of another during a short paddling trip, for example. His report notes that “there seems to be a core group of species that can be found consistently in and around the marsh” and that a number of other resident and migratory species could occur in the marsh.

Dragonflies and damselflies are in the order Odonata. These insects have two pairs of wings and three pairs of legs, among other characteristics. Dragonflies typically spread their wings to their sides when they land and are typically larger and more robust. Damselflies are usually smaller and they typically hold their wings together over their abdomen. Their eyes are separated. To identify specific species, experts study their wings, wing patterns, colors, tail, thorax, abdomen, genitalia and other features, some under a microscope. Some have bright, lustrous hues and diaphanous wings. Behavior is another important factor in identification of Odonata.

Dragonflies and damselflies are found around rivers, wetlands, seeps, bogs, springs, streams, ponds and lakes because their larvae, known as nymphs, are aquatic. Adults can be from half an inch to five inches long. Some species migrate south and return to Virginia in the spring. In Virginia, at least 194 species of dragonflies and damselflies have been identified. The best time to see them is from April to October.

Hobson submitted a report to FODM and to the National Park Service.