Description
Potentially Misidentified Species - Caiman crocodilus is native from Mexico to Argentina (Ross 1989), and has 3 records from VA (Norfolk, Henrico, Arlington Counties) between 1964 and 1982. The specimens ranged from 'small' to 1.5 m. Juveniles of this species are sold in the pet trade (Mitchell 1994), but are much less likely to survive winters in our region, with lower lethal limits of 10-15 C. Breeding populations do exist in south FL (Brandt and Mazzotti 1990). A specimen of Crocodylus acutus (American Crocodile), was believed to have been captured illegally in its native southern FL and released in the Dismal Swamp in 1976 (Bonavita 1979; Mitchell 1994).
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Animalia | Chordata | Reptilia | Crocodilia | Crocodylidae | Alligator |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1944 | Failed | Contracting | Introduced | Regular Resident | North America | North America | Ornamental(Pet Release) |
History of Spread
Alligator mississippiensis (The American Alligator ) is native to southeastern North America, from the Rio Grande River north to AR and east to the Atlantic (Ross 1989). The probable northern boundary of A mississippiensis' natural range is the southern portion of Albermarle Sound NC (Mitchell 1994). There is no paleontological evidence that alligators ever occurred naturally in VA (Richmond 1963), and the scattered occurrences reported by Clarke (1953), Bonavita (1979), and Mitchell (1994) doubtless result from the release of pets. Alligators were often hunted to extermination, and 'baby alligators' were widely sold in the pet trade until 1969 when the interstate sales of the species was covered by the Lacey Act. The species received additional protection from the Endangered Species Act in 1973, leading to rapid recovery of stocks in FL and elsewhere in the southeast (Hines and Percival 1987). Unwanted specimens were frequently released, making it difficult for herpetologists to define the original range (Conant 1958).
Clarke (1953) described two specific records of A mississippiensis from southeast VA, and suggests that numerous other releases probably occurred, particularly at the Naval Amphibious Training Base, Princess Anne County, where alligators were depicted on the camp insignia, and frequently kept as pets and mascots by servicemen. Mitchell (1994) lists 5 records for VA from 1969 to 1982, three of which were in tidal creeks. Repeated sightings of individuals, as well as size of the animals (0.76-1.6 m), suggests that some of these animals survived at least one and as many as three winters (Clarke 1953). In Septermber,1996, an animal 1.6 m long was shot by police in a residental area at Fort Washington MD, on the Potomac (Vogel 1996). A specimen 1.5 m long shot near Pittsburgh PA in 1949 was believed to have survived 6 or 7 winters (Barton 1955). Physiological data from A mississippiensis in SC (Brisbin et al. 1982) suggest that winter weather in the Chesapeake region probably frequently exceeds this species' tolerances. Alligator mississippiensis becomes sexually mature at 1.9 m (Magnuson et al. 1989), larger than any of the reported Chesapeake Bay specimens. There are no reports of breeding in VA (Clarke 1953; Mitchell 1994).
History References- Barton 1955; Bonavita 1979; Brisbin et al. 1982; Clarke 1953; Conant 1958; Hines and Percival 1987; Mitchell 1994; Richmond 1963; Ross 1989; Vogel 1996
Invasion Comments
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | 5.0 | |||
| Salinity (‰) | 0.0 | 0.0 | ||
| Oxygen | ||||
| pH | ||||
| Salinity Range | fresh-meso |
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 |
|||
| 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
Alligator mississippiensis (American Alligator) has had no economic impacts in the Chesapeake Bay region, except for costs to police or wildlife agencies of trapping or shooting specimens in settled areas.
Economic Impacts Outside of Chesapeake Bay
Juvenile Alligator mississippiensis (American Alligators ) were once a popular item in the pet trade. A moratorium on hunting, and on the pet trade, led to rapid recovery of A. mississippiensis populations in the southeast United States, eventually leading to a resumption of regulated harvesting for skins and meat (Hines and Percival 1987).
References- Hines and Percival 1987
Ecological Impacts on Chesapeake Native Species
Alligator mississippiensis (Alligators ) never became established in Chesapeake Bay, and so had no widespread impact on aquatic communities. Given their size, however, and the fact that individuals survived for several years in Virginia (Clarke 1953), some significant local predatory impact on fish, turtles, mammals, etc. in the vicinity of the individual animal was likely.
References- Clarke 1953
Ecological Impacts on Other Chesapeake Non-Native Species
Alligator mississippiensis (Alligators) have probably had no significant impacts on introduced species. However, even one alligator is likely to have some localized effects on both introduced and native fish, crayfish, and turtle populations in its vicinity.
References
Barton, A. J. (1955) Prolonged survival of a released alligator in Pennsylvania, Herpetologica 11: 210Bonavita, Jimmi (1979) Virginia Gators?, Virginia Wildlife 40: 10-11
Brandt, Laura A.; Mazzotti, Frank J. (1990) The behavior of juvenile Alligator mississippiensis and Caiman crocodilus exposed to low temperatures., Copeia 1990: 867-891
Brisbin, I. Lehr; Standora, Edward A.; Vargo, Michael J. (1982) Body temperatures and behavior of American alligators during cold winter weather, American Midland Naturalist 107: 209-217
Clarke, Robert F. (1953) Alligator escapees in southeastern Virginia, Herpetologica 9: 71-72
Conant, Roger (1958) A field guide to reptiles and amphibians of the United States and Canada east of the 100th meridian., , Boston. Pp.
Hines, Tommy C.; Percival, H. Franklin (1987) Alligator management and value-added conservation in Florida., In: Decker, Daniel J., and Goff, Gary R.(Eds.) Valuing Wildlife - Economic and Social Perspectives.. , Boulder, CO. Pp. 164-173
Magnuson, William Ernest; Vliet, Ken A.; Pooley, A. C.; Whitaker, Romulus (1989) Reproduction, In: (Eds.) Crocodiles and Alligators. , New York. Pp. 118-127.
Mazzotti, Frank J.; Dunson, W. A. (1984) Adaptations of Crocodylus acutus and Alligator for life in saline water, Comparative Biochemistry and Physiology : 641-646
McNease, Larry; Joanen, Ted (1979) Alligator diets in relation to marsh salinity, Proceedings of the Annual Conference of the Southeast Association of Fish and Wildlife Agencies 31: 36-40
Mitchell, Joseph C. (1994) The Reptiles of Virginia., , Washington, D. C.. Pp.
Richmond, Neil D. (1963) Evidence against the existence of crocodiles in Virginia and Maryland during the Pleistocene, Proceedings of the Biological Society of Washington 76: 65-68
Ross, Charles A (1989) Crocodiles and Alligators, , New York. Pp.
September 7, 1996 Misguided gator makes jaws drop in P. G., Washington Post, B-1, Washngton, DC.