Description
Synonymy - The name Mus decumanus was used by Fisher in 1896 (cited in Lee 1988). The other names were given to various European and Asian populations (Hall and Kelson 1959).
Similar Species - Rattus rattus is much rarer, with no recent records in Baltimore or Washington DC, but may be established in coastal areas from VA southwards. It is also the common rat of ships, especially from warmer regions (Hall and Kelson 1959; Paradiso 1969).
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Animalia | Chordata | Mammalia | Rodentia | Muridae | Rattus |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1799 | Established | Stable | Introduced | Regular Resident | Europe | East Asia | Shipping(unspecified) |
History of Spread
Rattus norvegicus (Norway Rats; Brown Rats), despite their name, were probably native to eastern Asia, and entered Europe around 1553 (Walker 1968), spreading into the British Isles in the 18th century, and largely replacing the smaller R. rattus (Black rat) (Taylor et al. 1990). Rattus norvegicus is thought to have arrived in North America in about 1775. In northern areas, it has largely replaced R. rattus (Hall and Kelson 1959). In some areas of the southeast US, both species may still coexist (Paradiso 1969; Taylor et al. 1990). Rattus norvegicus is now found on every continent and many islands; and tends to replace R. rattus in more temperate climates (Hall and Kelson 1959; Taylor et al. 1990; Walker 1968).
Rattus norvegicus are assumed to have arrived in the Chesapeake Bay region within a few years or decades of their arrival elsewhere in North America, although precise dates are unavailable. They were abundant and long-established in Maryland by 1895, according to an unpublished manuscript by William H. Fisher (Lee 1988). Rattus norvegicus are most abundant in populated areas; including port areas and docks, but also inhabit stream banks, marshes, fields, and shores (Handley and Patton 1947; Paradiso 1969). Tidal marshes at Bombay Hook National Wildlife Refuge (Delaware Bay) had a large rat population (McCallum 1971) and R. norvegicus are likely to be abundant in similar habitats around the Cheapeake region (in Spartina spp., Scirpus spp., and Phragmites australis stands, and on the shores of tidal rivers and inlets). Paradiso (1969) mentions large populations living in burrows along the shore of Loch Raven reservoir, north of Baltimore, and 'around government buildings and monuments' in Washington DC. Populations have been studied on St. Clements Island in the Potomac River (St. Marys County MD) (Lattanzio and Chapman 1980), and also noted on Assateague Island (Paradiso and Hardley 1965), Parramore, and Revel Islands (Dueser et al. 1979) on the Atlantic side of the Eastern Shore.
History References - Dueser et al. 1979; Hall and Kelson 1959; Handley and Patton 1947; Lattanzio and Chapman 1980; Lee 1988; McCallum 1971; Paradiso 1969; Paradiso and Hardley 1965; Taylor et al. 1990; Walker 1968
Invasion Comments
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | ||||
| Salinity (‰) | 35.0 | 0.0 | 0.0 | |
| Oxygen | ||||
| pH | ||||
| Salinity Range | fresh-eu |
Age and Growth
| Male | Female | |
|---|---|---|
| Minimum Adult Size (mm) | 392.0 | 391.0 |
| Typical Adult Size (mm) | 403.0 | 400.0 |
| Maximum Adult Size (mm) | 414.0 | 408.0 |
| Maximum Longevity (yrs) | 0.9 | 0.9 |
| Typical Longevity (yrs | 0.1 | 0.1 |
Reproduction
| Start | Peak | End | |
|---|---|---|---|
| Reproductive Season | |||
| Typical Number of Young Per Reproductive Event |
|||
| Sexuality Mode(s) | |||
| Mode(s) of Asexual Reproduction |
|||
| Fertilization Type(s) | |||
| More than One Reproduction Event per Year |
|||
| Reproductive Startegy | |||
| Egg/Seed Form |
Impacts
Economic Impacts in Chesapeake Bay
Rattus norvegicus (Norway Rats) are abundant in coastal areas of Chesapeake Bay, especially in disturbed urban waterfront areas, but also in wildlife refuges, (e.g. St. Clements Island, Potomac River) (Lattanzio and Chapman 1980). Their impact on human health and comfort is greatest away from water in poor urban neighborhoods and as agriculture pests in fields, food processing plants, and granaries. Control methods include cats, traps, and various poisons (Taylor et al. 1990).
Fisheries (Wildlife)- Rattus norvegicus are predators on eggs and young of waterfowl (Figley and Van Druff 1982), although at Bombay Hook National Wildlife Refuge, experimental rat removal had no effect on nesting success (McCallum 1971).
Aesthetic- Rattus norvegicus is 'almost universally hated and detested by Western man' (Taylor et al. 1990). Most people strongly dislike rats, and sighting of rats in a neighborhood, on a beach or in a park, would probably detract from property values or the enjoyment of a recreation area. However, because they are usually nocturnal, rat populations may be abundant in beach areas, dwelling among rocks in jetties, or in marshes, but be rarely seen by visitors except at dawn and dusk (Fofonoff, personal observation.).
Health - Rattus norvegicus are one of the more serious health problems in urban areas, as a vector of a wide range of diseases including leptospirosis, and in other parts of the world, typhus and bubonic plague (Taylor et al. 1990). In the Chesapeake Bay context, the biggest risks are probably to dockworkers, construction workers, and others who regularly work in rat-infested urban waterfront areas. The presence of rats in beach and park areas probably is usually more of an aesthetic than a health problem.
Agriculture- Rattus norvegicus is a major agricultural pest, especially to root and grain crops, in the field and during storage, and transport (Taylor et al. 1990).
References- Figley and Van Druff 1982; Lattanzio and Chapman 1980; McCallum 1971; Taylor et al. 1990
Economic Impacts Outside of Chesapeake Bay
Rattus norvegicus (Norway Rat) is a major pest worldwide, but is rare in low-altitude urban areas in the tropics and subtropics, where R. rattus (Black Rat) predominates. In less developed nations, it is a vector of diseases such as bubonic plague and typhus (Taylor et al. 1990).
References- Taylor et al. 1990
Ecological Impacts on Chesapeake Native Species
Rattus norvegicus (Norway Rat) has become a common inhabitant of both urbanized and undeveloped coastal areas (McCallum 1971; Paradiso 1969; Lattanzio and Chapman 1980; Taylor et al. 1990). Because of its swimming ability, generalized diet, high reproductive rate, and general adaptability, R. norvegicus have had major ecological impacts through much of their introduced range, particularly on islands where few other mammals may be present.
Competition - Rattus norvegicus 'will eat virtually anything' (Paradiso 1969). Its diet is likely to overlap with that of several other omnivorous mammals common in coastal areas, including Didelphis virginicus (Opossum), Procyon lotor (Raccoons ), Mephitis nigra (Striped Skunks ) as well as rodents of similar size including Microtus pennsylvanicus (Meadow Voles ) and Oryzomys palustris (Marsh Rice Rats) (Bailey 1946; McCallum 1971; Taylor et al. 1990; White 1989).
Predation- Rattus norvegicus in coastal areas may eat a variety of marine invertebrates, including crabs, amphipods and molluscs (Taylor et al. 1990). Rattus rattus and R. norvegicus have been reported as predators on intertidal molluscs in Oregon, Chile, and South Africa (Zamorano 1986). Rattus norvegicus are also potential predators on eggs and nestlings of birds and are implicated in the decline of CA populations of Rallus longirostris californicus (Clapper Rail) (Cohen and Carlton 1995) and are likely to pose a threat to many birds nesting on islands, marshes, and other coastal areas. However, McCallum (1971) did not detect predation by rats on nesting waterfowl in Bombay Hook National Wildlife Refuge; DE. Experimental rat removal had no effect on nesting success of birds (McCallum 1971) .
Herbivory- Rattus norvegicus eat a wide variety of plant foods, especially seeds, and are reported to graze on Spartina spp. in English salt marshes (Taylor et al. 1990).
Control methods for rats have potential impacts on native fauna. Rat traps may kill native rodents. Domesticated cats which are rat predators, also kill a wide variety of birds and small mammals. Some acute rat poisons may seriously affect predators, but widely used decoagulant poisons pose smaller risks (Taylor et al. 1990).
References - Bailey 1946; Cohen and Carlton 1995; McCallum 1971; Paradiso 1969; Taylor et al. 1990; White 1989; Zamorano 1986
Ecological Impacts on Other Chesapeake Non-Native Species
Rattus norvegicus (Norway Rat) is now a common predator on developed and 'wild' waterfronts, affecting other introduced biota, as well as native species.
Competition - Rattus norvegicus is widely believed to have outcompeted and eliminated R. rattus (Black Rat) from much of the latter's introduced range, particularly in temperate areas. Where the two species coexist, R. rattus, the better climber of the two, is likely to be on roofs and upper floors of builidings (Bailey 1946; Taylor et al. 1990). However, the evidence for competition and species replacement is open to dispute, since these events occurred at a time when scientific observations were very limited (Paradiso 1969). Paradiso (1969) considered climate preferences to be the primary factor limiting R. rattus and favoring R. novegicus in temperate areas.
Predation - Rats destroyed some nests of introduced Anas platyrhynchos (Mallard Duck) in NJ coastal marshes (Figley and Van Druff 1982).
References - Bailey 1946; Figley and Van Druff 1982; Paradiso 1969; Taylor et al. 1990
References
Bailey, John (1946) The Mammals of Virginia, In: (Eds.) . , Richmond, VA. Pp.Childs, James E.; Glass, Gregory E.; Korch, George W.; LeDuc, James E. (1989) Effects of hantaviral infection on survival, growth, and fertility in wild rat (Rattus norvegicus) populations of Baltimore, Maryland, Journal of Wildlife Diseases 25: 469-476
Cohen, Andrew N.; Carlton, James T. (1995) Nonindigenous aquatic species in a United States estuary: a case study of the biological invasions of the San Francisco Bay and Delta, , Washington DC, Silver Spring MD.. Pp.
Dueser, Raymond D; Brown, William C.; Hogue, Gregory S.; McCaffrey, Cheryl; McCuskey, Sue; Hennesey, Gerald J. (1979) Mammals on the Virginia Barrier Islands, Journal of Mammalogy 60: 425-429
Figley, William K.; VanDruff, Larry W. (1982) The ecology of urban Mallards, Wildlife Monographs 81: 1-40
Glass, G. E.; Childs, J. E.; Korch, G. W.; LeDuc, J. W. (1989) Comparative ecology and social interactions of Norway Rat (Rattus norvegicus) populations in Baltimore, Maryland, Occasional papers of the Museum of Natural History, The University of Kansas 130: 1-33
Glass, Gregory E.; Korch, George W.; Childs, James E. (1988) Seasonal and habitat differences in growth rates of wild Rattus norvegicus, Journal of Mammalogy 69: 587-592
Hall, E. Raymond; Kelson, Keith R. (1959) The Mammals of North America, , New York. Pp.
Handley, Charles O, Jr.; Patton, Clyde P. (1947) Wild Mammals of Virginia, , Richmond VA. Pp.
Lattanzio, Richard M; Chapman, Joseph A. (1980) Reproductive and physiological cycles in an island population of Norway Rats, Bulletin of the Chicago Academy of Sciences 12: 1-68
Lee, David S. (1988) Wm. H. Fisher's 'Mammals of Maryland': a previously unknown compilation of the state's fauna, Maryland Naturalist 32: 9-37
1971 An investigation of factors influencing waterfowl productivity of the tidal marsh of Bombay Hook National Wildlife Refuge.
Mills, Edward L.; Leach, Joseph H.; Carlton, James T.; Secor, Carol L. (1993) Exotic species in the Great Lakes: a history of biotic crises and anthropogenic introductions., Journal of Great Lakes Research 19: 1-54
Mills, Edward L.; Scheuerell, Mark D.; Carlton, James T.; Strayer, David (1997) Biological invasions in the Hudson River: an inventory and historical analysis., New York State Museum Circular 57: 1-51
Paradiso, John L. (1969) Mammals of Maryland, , Washington, D.C.. Pp.
Paradiso, John L.; Handley, Charles O. (1965) Checklist of mammals of Assateague Island, Chesapeake Science 6: 167-171
Taylor, K. D. (1990) Ship Rat: Rattus rattus., , Oxford. Pp. 255-259
Taylor, K. D.; Fenn, M. G.; MacDonald, D. W. (1990) Common Rat: Rattus norvegicus., , Oxford. Pp. 248-255
Walker, Ernest P. (1968) Mammals of the World, , Baltimore, MD. Pp.
White, Christopher P. (1989) Chesapeake Bay- Nature of the estuary: A field guide, , Centreville MD. Pp.
Zamorano, Juan H. (1986) Rattus rattus, un depredador intermareal poco conocido., Medio Ambiente 8: 58-62