(Yellow-billed Duck), but currently there are low levels of introgression of
A. platyrhynchos genes into A. undulata (Stephens et al. 2020). Introgression
could become more extensive in the future if A. platyrhynchos populations are not
controlled (Stephens et al. 2020; Davies et al. 2020, Chap. 22). Pycnonotus jocosus
have been shown to damage crops, spread weeds, prey on native species and
compete with them elsewhere (Mo 2015), but their impact in South Africa is
unknown. Similarly, Psittacula krameri (Ring-necked Parakeet) is thought to compete for breeding holes with bats and other birds in other alien ranges leading to
population declines of affected species. It has a very limited but expanding distribution in South Africa, and only ancedotal observations of impacts have been
reported so far (Hart and Downs 2014). The species is a conflict species because it
has both societal benefits (as a pet) and negative impacts (see Zengeya et al. 2017;
Shackleton et al. 2020, Chap. 25).
17.2.1.6 Mammals
There are 42 alien mammal species that have been recorded outside of captivity in
South Africa (van Wilgen and Wilson 2018), eleven of which have formal globalscale EICAT assessments. All of these species cause large impacts in their invasive
range globally (Hagen and Kumschick 2018). For example, several alien rodent
species such as Rattus rattus (Black Rat), Rattus norvegicus (Norwegian Rat) and
Mus musculus (House Mouse) have caused local extinctions of native species of
invertebrates, birds, bats and rodents on several islands through predation, competition for food, and disease transmission (e.g. Steadman 1995; Marris 2000;
Courchamp et al. 2003). The feral species Capra hircus (Goat), Equus asinus
(Donkey) and Sus scrofa (Pig) cause massive impacts through competition with
native species for food, altering the structure and composition of plant communities
by grazing and rooting (e.g. Kurdila 1998; Campbell and Donlan 2005; Means and
Travis 2007). This has led to habitat loss, resulting in local extinction of some native
species and accelerated soil erosion. Other domestic species such as Felis catus (Cat)
can cause major impacts through predation leading to population declines, and in
some cases local extirpation, of native mammals, reptiles, and birds (Fitzgerald and
Veitch 1985; Winter and Wallace 2006).
For a few species, impacts have been recorded in South Africa. For example, M.
musculus and F. catus have caused major impacts on offshore islands (Berruti 1986;
Greve et al. 2017, 2020, Chap. 8). Mus musculus was introduced on Marion Island
before 1818, likely as a stowaway on ships whose crews were engaged in seal
hunting (Watkins and Cooper 1986). On the island, it preys on invertebrates (Jones
and Ryan 2010; Dilley et al. 2016) and this changed the population densities,
reproduction strategies and growth rates of some invertebrates on the island (Treasure and Chown 2014). Similarly, declines in albatross populations have been
ascribed to predation of chicks by M. musculus (Dilley et al. 2016). Felis catus
was introduced onto Marion Island in 1949 to control M. musculus (Bester et al.
2002). Although F. catus fed on M. musculus, it also preyed on seabirds and this
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T. A. Zengeya et al.
A. platyrhynchos genes into A. undulata (Stephens et al. 2020). Introgression
could become more extensive in the future if A. platyrhynchos populations are not
controlled (Stephens et al. 2020; Davies et al. 2020, Chap. 22). Pycnonotus jocosus
have been shown to damage crops, spread weeds, prey on native species and
compete with them elsewhere (Mo 2015), but their impact in South Africa is
unknown. Similarly, Psittacula krameri (Ring-necked Parakeet) is thought to compete for breeding holes with bats and other birds in other alien ranges leading to
population declines of affected species. It has a very limited but expanding distribution in South Africa, and only ancedotal observations of impacts have been
reported so far (Hart and Downs 2014). The species is a conflict species because it
has both societal benefits (as a pet) and negative impacts (see Zengeya et al. 2017;
Shackleton et al. 2020, Chap. 25).
17.2.1.6 Mammals
There are 42 alien mammal species that have been recorded outside of captivity in
South Africa (van Wilgen and Wilson 2018), eleven of which have formal globalscale EICAT assessments. All of these species cause large impacts in their invasive
range globally (Hagen and Kumschick 2018). For example, several alien rodent
species such as Rattus rattus (Black Rat), Rattus norvegicus (Norwegian Rat) and
Mus musculus (House Mouse) have caused local extinctions of native species of
invertebrates, birds, bats and rodents on several islands through predation, competition for food, and disease transmission (e.g. Steadman 1995; Marris 2000;
Courchamp et al. 2003). The feral species Capra hircus (Goat), Equus asinus
(Donkey) and Sus scrofa (Pig) cause massive impacts through competition with
native species for food, altering the structure and composition of plant communities
by grazing and rooting (e.g. Kurdila 1998; Campbell and Donlan 2005; Means and
Travis 2007). This has led to habitat loss, resulting in local extinction of some native
species and accelerated soil erosion. Other domestic species such as Felis catus (Cat)
can cause major impacts through predation leading to population declines, and in
some cases local extirpation, of native mammals, reptiles, and birds (Fitzgerald and
Veitch 1985; Winter and Wallace 2006).
For a few species, impacts have been recorded in South Africa. For example, M.
musculus and F. catus have caused major impacts on offshore islands (Berruti 1986;
Greve et al. 2017, 2020, Chap. 8). Mus musculus was introduced on Marion Island
before 1818, likely as a stowaway on ships whose crews were engaged in seal
hunting (Watkins and Cooper 1986). On the island, it preys on invertebrates (Jones
and Ryan 2010; Dilley et al. 2016) and this changed the population densities,
reproduction strategies and growth rates of some invertebrates on the island (Treasure and Chown 2014). Similarly, declines in albatross populations have been
ascribed to predation of chicks by M. musculus (Dilley et al. 2016). Felis catus
was introduced onto Marion Island in 1949 to control M. musculus (Bester et al.
2002). Although F. catus fed on M. musculus, it also preyed on seabirds and this
498
T. A. Zengeya et al.