Anas platyrhynchos (bird)

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General Impact Anas platyrhynchos hybridizes with endemic duck species, some of which are now threatened with extinction. Species experiencing hybridization with mallards include the New Zealand grey duck (Anas superciliosa), American black duck Anas rubripes, Mexican duck (Anas platyrhynchos diazi), the 'Endangered (EN)' Hawaiian Duck (see Anas wyvilliana in IUCN Red List of Threatened Species), African black duck (Anas sparsa), yellow-billed duck (Anas undulatta), and the 'Endangered (EN)' Meller's duck (see Anas melleri in IUCN Red List of Threatened Species) (AEWA, 2003; Kulikova et al, 2005; Uyehara, 2007). Studies have recently indicated that A. platyrhynchos is thought to be a long-distance vector for the highly pathogenic avian influenza virus (HPAIV) (H5N1), a serious concern to the poultry industry and public health. Spread of the virus in conjuction with migratory routes and waterfowl infection indicate them as probable vectors. Experiments have shown that mallards are the prime candidate for being the long-distance vector of HPAIV (H5N1) since they excrete significantly higher proportions on the virus than other ducks while they are seemingly immune to its debilitating effects in both studies and wild bird die-offs from HPAIV in Europe and Asia. Furthermore, their extremely wide range and large populations, its presence in nearly every type of wetland, and tolerance to humans provide a potential link to wild waterfowl, domestic animals, and humans rendering it a perfect vector of the deadly HPAIV. Although human infection is rare, this virus has a high fatality rate in infected patients. The possibility of mutation to a more human infectable form and a human-to-human means of transmission, poses a tremendous threat of pandemic proportions. Additionally, captive reared mallards are believed to increase incidence of some other diseases such as Duck Virus Enteritis (DVE) in wild populations (Keawcharoen, 2008; Weber and Stilianakis, 2007; AEWA, 2003). Finally, high mallard populations are associated with algal bloom, deoxygenation, and loss of aquatic plants in overpopulated wetlands which can lead to botulism (RSPB, 2008).          Location Specific Impacts: Australia   Hybridisation: Mallards hybridize with Australia native Pacific black duck (Anas superciliosa). In locations such as Lord Howe Island no pure populations of A. superciliosa remain (Tracey et al, 2008). India   Competition: The mallard is believed to compete with native waterfowl in India (Williams, undated). Grand Terre Is. (New Caledonia) (New Caledonia (Nouvelle Calédonie))     Competition Hybridisation: Anas platyrhynchosis is larger and more prolific than the indigenous Pacific grey duck (see Anas superciliosa in IUCN Red List of Threatened Species). Products of hybridisation with the indigenous duck were observed in New Caledonia (in Pascal et al.., 2006). New Zealand     Hybridisation: In New Zealand, Anas platyrhynchosis is deemed to have caused severe declines in populations of the native Pacific grey duck (see Anas superciliosa in IUCN Red List of Threatened Species) through genetic introgression. As agricultural regions are now largely dominated by the introduced mallard A. superciliosa has become increasingly restricted to undeveloped areas (Rhymer et al.., 1994, 2004; BirdLife International 2004). South Africa   Hybridisation: Anas platyryhnchos hybridise with native Yellow-billed duck (A. undulata) in South Africa establishing a potential threat (AEWA, 2003). Western Cape (South Africa)   Hybridisation: Anas platyryhnchos hybridise with native Yellow-billed duck (A. undulata) in West Cape, South Africa where it is considered a major problem (AEWA, 2003). United States (USA)   Hybridisation: In North America, Anas platyrhynchos hybridizes with mottled ducks (Anas fulvigula), black ducks (Anas rubripes), and Pacific black ducks (Anas superciliosa) which have experienced decline believed to be a result of this hybridization (Kulikova, 2005; Muno-Fuentez, 2007; Rhymer et al, 1994; Snyder, 1993). Hawaii (United States (USA))   Hybridisation: Anas platyrhynchos threatens the endemic 'Endangered (EN)' Hawaiian Duck (see Anas wyvilliana in IUCN Red List of Threatened Species). Hybridization between the mallard and Hawaiian duck have greatly depleted pure stocks of Hawaiian ducks to the point they face extinction if it continues Threat to endangered species: Anas platyrhynchos threatens the endemic 'Endangered (EN)' Hawaiian Duck (see Anas wyvilliana in IUCN Red List of Threatened Species). Hybridization between the mallard and Hawaiian duck have greatly depleted pure stocks of Hawaiian ducks to the point they face extinction if it continues