Invasive Species on Nantucket
Island Science

Native or Washashore?

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• by Dr. Sarah Oktay, Director, University of Massachusetts Nantucket Field Station •

A Biological Search for the Indigenous Life on Nantucket

Not all readers of this column may know the term washashore which is used by natives to refer to newcomers who live on Nantucket who were not born here. Other historically used terms include “coof” and “round- pointers” to refer to coming round Brant Point for those of us who have wandered onto Nantucket’s shores. That same term can be applied to the many types of plants and animals that have made their way to Nantucket, often at the expense of native species. Nantucket is home to a huge variety of plants and animals, but I bet you’d be surprised to find out what does or doesn’t belong here. These species come over on boats, in ballast water or in many cases were imported by the colonists who missed their English gardens. Some were imported for hunting, to treat erosion issues or to act as windbreaks.

I decided to write this column because it never fails to amaze me that the humble earthworm, one of the most basic types of Nature is an imported species to this part of the country. Several of our native species such as garter snakes and the American woodcock eat earthworms. I have no idea how hungry they were before earthworms got here. From http://ecosystems.serc.si.edu/earthworm-invaders/, we learn that “Native earthworms all but disappeared more than 10,000 years ago, when glaciers from a Pleistocene ice age wiped them out. A few survived further south. But today, virtually all earthworms north of Pennsylvania are non-native. New earthworms began entering North America as early as the 1600s, with the first European settlers. They crossed over in root balls or the dry ballast of ships. As the British, French, Spanish and Dutch colonized the American continent, they were largely oblivious to another colonization going on under their feet. European earthworms thrived in the upper soils of forests and gardens. Native earthworms, if there were any, remained deeper underground. In the end Europe’s earthworms established an empire that would long outlive any built by its nations. Many of the earthworms most common in gardens today, including the familiar red worm (Lumbricus rubellus), trace their origins back to the Old World.”

And so up from the soil can spring the many many invasive plants that have migrated to our shores through bird poop or are carried over by unsuspecting humans. Not unlike a scene from the” Invasion of the Body Snatchers” or perhaps “ Frankenstein”, a seemingly innocent looking daisy can quickly overtake an island. Invasive plants can be accidentally or deliberately introduced via agriculture, as forage crops for sheep or cows, as ornamentals or escapees from botanical gardens and estate gardens, through aquatic gardens, erosion control techniques, storms, or via hitchhiking pollen and seeds delivered by migrating birds. Human actions are the primary means of invasive species introductions.  On Nantucket, the primary adverse effect perpetuated by invasive plants is ecological harm caused by habitat destruction as they out-compete other plants for nutrients, sunlight, water, and space.

As an example, the colorful and fragrant Rosa rugosa (saltspray rose or beach rose) which is practically synonymous with Nantucket beaches and shorelines is an introduced species brought over from Eastern Asia to slow erosion and build our dunes. As alluded to above, the quintessential summertime weedy wildflower, the Ox eye daisy (Leucanthemum vulgare), is also a washashore. Each flower head can produce up to 200 flat seeds that are 0.08 in. (2 mm) long. The Oxeye daisy is native to Europe and was introduced into the United States as an ornamental in the 1800s. Oxeye daisies can thrive in a wide variety of soil types and can grow in sun to partial shade. They are basically another super plant that can easily spread and take hold.

Deer: Native. Gray Seals Native (see the end of this article to learn how their populations have diminished and regrown). More Natives that might surprise you: Poison ivy (Toxicodendron radicans), Fox grape (Vitis labrusca), Scrub Oak (Quercus ilicifolia), Cattails (Typha latifolia), and the prickly pear cactus (Opuntia humifusa– on the Commonwealth’s endangered plant list).

Other washashores: many of the fish in our ponds are introduced (stocked) such as catfish, pickerel, and crappie. I love to fish so I don’t seem to mind this as much and they (so far) don’t seem to be adversely affecting the aquatic environment too much. Bull frogs are another introduced species that according to the state may have been introduced to Nantucket to control insects. You might remember our lab mascot, the insidiously invasive red eared slider turtle named Trawalney that I have written about in the past (“The Invader Came from Petworld” http://yesterdaysisland.com/2010/science/21.php ). Thankfully very few aquatic invasive plants and no invasive mussels are found here. In the harbor and marshes we have exotic invasive green crabs (Carcinus maenas) which are procreating like bunnies and pushing out native crabs such as the lady crabs and blue crabs. An invasive crab found extensively on the mainland, the Asian shore crab (Hemigrapsus sanguineus) can also be found here. Interestingly it looks like green crabs may be keeping native marsh crabs (Sesarma reticulatum) from destroying marshes by scaring them off before they shear down too much cordgrass (http://www.sciencedaily.com/releases/2013/04/130403122015.htm). This summer we will test that out here on island.

Other beautiful wildflowers introduced here that have spread indiscriminately and now are part of the landscape: sheep sorrel (Rumex acetosella) Queen Anne’s lace or wild carrot (Daucus carota), several thistle species and purple loosestrife( Lythrum salicaria). The bane of every conservation group on island’s existence might be the Common Reed ((Phragmites australis) or its even more annoying friend, Japanese knotweed (Fallopia japonica). Each year the Nantucket Conservation Foundation, Massachusetts Audubon Society, Nantucket Land Bank and the Nantucket Land Council along with the Department of Public Works strive mightily to keep some of the exotic invasives at bay. When you remove them from your yard, you should take them to the digester at the DPW Waste Options site for proper disposal. This link includes one of the first lists of invasive plants created for Nantucket as a group project between UMass Boston and the Maria Mitchell Association http://efg.cs.umb.edu/nantucket/

Introduced invasive plants, almost too many to count. They include the honeysuckle, privet , scotch broom, many of these are ornamental plants that escaped from their original locations The Nantucket Conservation Foundation staff wrote an excellent article on invasive weeds which can be found here: http://ncfscience.wordpress.com/2014/04/16/the-weed-wars-nantucket-skirmishes-with-invasive-plants/

Obvious introductions: guinea hens, pheasants and quail. Wild turkeys were likely here several hundreds of years ago but not much research has been done to establish the ebb and flow of that populations. Helmeted Guineafowl (Numida meleagris) has been used as a “folk” defense against ticks acting as vectors for Lyme disease on Shelter Island, New York, and on the islands of Martha’s Vineyard and Nantucket, Massachusetts.

Mute swans (Cygnus olor) have become such an issue for Nantucket that the members of the Nantucket Biodiversity Initiative (www.nantucketbiodiversityinitiative.org) have started to keep track of them on our ponds each winter and are contemplating how to best deal with their increasing population.

The Nantucket Conservation Foundation excellent blog page gives us more details about the dangers of introduced swans: “The mute swan is the largest waterfowl species found on Nantucket but is actually not a native species to the United States. Valued for its beauty and aesthetic appeal, it was brought here from its native Eurasia and was introduced to parks, zoos and private estates in the New York area during the late 1870s. By the early 1890s, it had escaped captivity and was breeding in the wild. Since then, populations have been expanding all along the east coast and year round populations now occur as far west as Montana. On Nantucket, large resident populations occur on Hummock, West Hummock, Miacomet and Long Ponds.” [From http://ncfscience.wordpress.com/2013/01/16/mute-swans-cygnus-color/]

All those bunnies you see? Yup, not native, although we think we still have a native species here. The wall to wall cute as pie bunnies you see everywhere are Eastern cottontail (Sylvilagus floridanus, J.A. Allen, 1890) which is a New World cottontail rabbit, a member of the family Leporidae. It is one of the most common rabbit species in North America. It is native to many states in America, but not to New England and as an introduced species, it has pushed out its brethren, the New England cottontail. Like many other creatures found on Nantucket, rabbits were brought to Nantucket for hunting reasons. In fact, Eastern Cottontails were first introduced to New England on Nantucket in the 1880s. Snowshoe hares were also introduced to the island by hunters. In the past 3-4 decades acquired some bushy tailed friends for the bunnies, the common Gray Squirrel (Sciurus carolinensis), which probably makes all of our raptors happy.

When you go to the Massachusetts Division of Fisheries & Wildlife’s web page mammal web page (http://www.mass.gov/eea/agencies/dfg/dfw/fish-wildlife-plants/mammal-in-mass.html), you’ll find a list of every mammal species found in the state. This is a fascinating list showing a variety of hair-brained introductions (European Hare and European Rabbit) across the state and short lived heydays for various creatures (wolves and cougars). And it includes our aquatic mammals too. You’ll see a lot of “except in Nantucket County” entries on the right hand column of the table. Introduced Rodentia nuisance species include the house mouse (Mus musculus), brown or “Norway” rat (Rattus norvegicus) common on Nantucket and famous denizen of seedy parts of the cities, the black rat (Rattus rattus) which has been eradicated statewide. The Commonwealth of Massachusetts produces a list each year of invasive plants and animals which can be found here http://massnrc.org/pests/factsheets.htm. We just scratched the surface of the “Native or Washashore” game, hopefully you found it fun.

To learn more, check out these earlier articles.

Articles by Date from 2012