Description
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Animalia | Chordata | Mammalia | Perissodactyla | Equidae | Equus |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1800 | Established | Stable | Introduced | Boundary Resident | Europe | Eurasia | Agriculture(Agricultural Weed) |
History of Spread
Equus caballus (Horse, Pony) became extinct in North America after the Pleistocene, but was re-introduced with European colonization. Feral horses became established on the plains of Western North America, and on several Atlantic Islands: Sable Island, Nova Scotia, Assateague Island MD-VA, and Shackleford Banks NC (Keiper 1985a).
The likeliest source of the Assateague Pony populations is the release by farmers of surplus animals, probably beginning in the 18th century. However, shipwrecks are another possible source of the animals. By the late 1700s, annual roundups had begun in order to brand animals to establish ownership, and return some ponies for farm use. It is probable that many releases of horses on Assateague Island, through the 19th and early 20th centuries, have altered the genetic makeup and appearance of the pony population. Introduction of some Shetland ponies in the early 20th century has altered the prevailing color pattern from solid to piebald. The small size of the island ponies may result from the source stock, natural selection, and/or the limited diet on the island (Keiper 1985a).
Currently two herds are managed on Assateague Island, in different ways, by the two Federal agencies which control the island: the National Park Service, and the United States Fish and Wildlife Service. Horses roam freely in Assateague National Seashore on the northern half (MD)of the Island, but are regulated by fences in the Chincoteague National Wildlife Refuge (VA), on the southern end. The VA herd is controlled by annual 'pony pennings' or roundups (Keiper 1985a).
History References- Keiper 1985a
Invasion Comments
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | ||||
| Salinity (‰) | 0.0 | 0.0 | ||
| Oxygen | ||||
| pH | ||||
| Salinity Range | fresh-eu |
Age and Growth
| Male | Female | |
|---|---|---|
| Minimum Adult Size (mm) | ||
| Typical Adult Size (mm) | ||
| Maximum Adult Size (mm) | ||
| Maximum Longevity (yrs) | ||
| Typical Longevity (yrs |
Reproduction
| Start | Peak | End | |
|---|---|---|---|
| Reproductive Season | |||
| Typical Number of Young Per Reproductive Event |
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| Sexuality Mode(s) | |||
| Mode(s) of Asexual Reproduction |
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| Fertilization Type(s) | |||
| More than One Reproduction Event per Year |
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| Reproductive Startegy | |||
| Egg/Seed Form |
Impacts
Economic Impacts in Chesapeake Bay
Wild populations of Equus caballus (Horse, Pony) in the Chesapeake Bay region are limited to Assateague Island (MD/VA). Other populations of horses on Atlantic coastal islands occur on Sable Island, Nova Scotia, and the Outer Banks (NC).
Aesthetic - The Assateague Island ponies (Equus caballus) are one of the region’s major tourist attractions. Most visitors to Assateague Island expect to see the ponies. Management of horse-human interactions is a major task of rangers on the Island (Keiper 1985a).
Habitat Change, Fisheries - The density of ponies is carefully managed, although in different ways, by the 2 Federal agencies which control the island: the National Park Service, and the United States Fish and Wildlife Service. Horses roam freely in Assateague National Seashore on the northern half of the Island, but are regulated by fences in the Chincoteague National Wildlife Refuge, on the southern end. Pony grazing has definite impacts on salt marshes and other vegetation areas (Keiper 1985a; Keiper 1990). Compaction of the soil by the horses' hooves adversely affects fiddler crabs and other invertebrates (Grant et al. 1991; Walther and Rebach 1997). Ponies can be expected to have effects on saltmarsh use by fish and waterfowl. The population is controlled by annual roundups and auctions of the animals (Keiper 1985a).
References - Grant et al. 1991; Keiper 1985a; Keiper 1990; Walther and Rebach 1997
Economic Impacts Outside of Chesapeake Bay
Populations of Equus caballus (feral horses) occur in coastal regions, on Sable Island, Nova Scotia, and the Outer Banks (NC), on Unalaska Island AK, on a Greek island, and probably many other places around the world (Lever 1985). These animals may be important as tourist attractions, in more accessible places. They may also represent a genetic and scientific resource for understanding the evolution and behavior of an economically important domestic animal (Keiper 1985a).
References- Keiper 1985a; Lever 1985
Ecological Impacts on Chesapeake Native Species
Wild populations of Equus caballus (Horse, Pony) in the Chesapeake Bay region are limited to Assateague Island (MD/VA). Other populations of wild horses on Atlantic coastal islands occur on Sable Island Nova Scotia, and the Outer Banks (NC).
Herbivory- Exclosure experiments indicate significant impacts on plant biomass in salt marshes, on Assateague Island. In 1983 experiments, vegetation biomass in grazed areas was about three quarters that in exclosures (Keiper 1990).
Habitat change- Differences in Uca sp. (fiddler crab) density were seen due to sediment compaction in grazed versus ungrazed areas, of Assateague Island (Walther and Rebach 1997). Possible effects of feral horse activity on benthos composition were seen on Shackleford Banks NC (Grant et al. 1991) . These impacts were not easily distinguishable from abiotic variables.
References- Grant et al. 1991; Keiper 1990; Walther and Rebach 1997
Ecological Impacts on Other Chesapeake Non-Native Species
Wild populations of Equus caballus (Horse, Pony) in the Chesapeake Bay region are limited to Assateague Island (MD/VA). Other populations of wild horses on Atlantic coastal islands occur on Sable Island Nova Scotia, and the Outer Banks (NC).
Competition- Competition with Cervus nippon (Sika Deer) is possible, but has not been studied carefully (Keiper 1990).
Herbivory- Assateague Island ponies graze on exotic grasses, including Polypogon monspeliensis (Rabbitsfoot Grass) as well as native species (Hill 1986).
References- Hill 1986; Keiper 1990
References
Bailey, John (1946) The Mammals of Virginia, In: (Eds.) . , Richmond, VA. Pp.Grant, D. C.; Ligibel, J. A.; Nowacek, D. P.; Horseburgh, S. E.; Link, M. A.; Ngu, M. N.; Furr, K. I.; Hall, C. M. (1991) Impact of feral horse migration on soft bottom infaunal community structure, Journal of the Elisha Mitchell Scientific Society 107: 13-20
Hill, Steven R. (1986) An annotated checklist of the vascular flora of Assateague Island (Maryland and Virginia), Castanea 51: 265-305
Keiper, Ronald R. (1985) The Assateague Ponies, , Centreville, MD. Pp.
Keiper, Ronald R. (1990) Biology of large grazing mammals on the Virginia Barrier Islands, Virginia Journal of Science 41: 352-363
Lever, Christopher (1985) Naturalized mammals of the world., In: (Eds.) . , London. Pp.
Putman, R. J. (1991) The Handbook of British Mammals, , London. Pp. 486-491
Walker, Ernest P. (1968) Mammals of the World, , Baltimore, MD. Pp.
Walther, Shelly M.; Rebach, Steve (1997) Habitat-related variations in fiddler crab populations due to feral horse activity., , Portland ME. Pp. 99