urban areas and loss of genetic integrity and identity in these taxa. However, recent
genetic studies have shown that introgression occurs from A. undulata into
A. platyrhynchos (Stephens et al. 2020). The presence of A. platyrhynchos on
farms and in rural settings also suggests that their populations should be reduced.
Because of the widespread distribution of both A. platyrhynchos and A. undulata in
South Africa, eradication is not an objective of this programme.
As A. platyrhynchos often swim in groups with A. undulata, the control
programme opted to feed target mallards and putative hybrids bread soaked with
anaesthetic (alpha-chloralose). All ducks in the urban area are habituated to people
feeding them bread. Once ducks have succumbed to the anaesthetic, they are
collected by kayakers waiting in the water, and transferred to a nearby facility
where a duty vet euthanises A. platyrhynchos and hybrids. The carcasses are then
sampled for DNA and removed by the City of Cape Town. The majority of birds
removed (63%) were found to be hybrids (Stephens et al. 2020). The programme
was efficiently identifying and removing hybrids, with 5% being pure yellow-billed
ducks (Stephens et al. 2020). The goal of this project is containment—the removal of
A. platyrhynchos and their hybrids in areas of high abundance of both alien and
native ducks in order to conserve the genetic integrity of A. undulata.
22.9 Mammals
22.9.1 Hemitragus jemlahicus (Himalayan Tahr)
An isolated population of Hemitragus jemlahicus is established on Table Mountain
in Cape Town (Measey et al. 2020, Chap. 5). Despite originating from only a few
zoo escapees, 330 individuals were counted during a survey in the 1970s (Lloyd
1975; Skead et al. 2011). The broad dietary preferences of these animals, along with
their tendency to aggregate, resulted in significant environmental degradation and
erosion at high densities (Lloyd 1975). As such, the authorities in charge of
Table Mountain (Department of Nature and Environmental Conservation, now
CapeNature, followed by SANParks from 1998), have conducted Himalayan Tahr
removal programmes since the early 1970s, with the view to restoring populations of
native ungulates in their place (Lloyd 1975; Gaertner et al. 2016). Public concerns
over animal welfare of the tahrs have received significant media attention over the
years (Gosling 2002; Skead et al. 2011).
Management interventions reduced tahr densities to a point that sightings became
a newsworthy occurrence (Skead et al. 2011). However, complete eradication has
not been achieved. The rugged and inaccessible mountainous terrain, exacerbated by
low detectability of individuals at low population densities, make it difficult to
implement management interventions. Tahrs have also been introduced to
New Zealand, where they are established and have been well-studied (e.g. Forsyth
and Tustin 2001; Cruz et al. 2017). However, no research has been published on the
ecology, space use or management of this species on Table Mountain. Research is
22 Alien and Invasive Animal Control Projects
649
genetic studies have shown that introgression occurs from A. undulata into
A. platyrhynchos (Stephens et al. 2020). The presence of A. platyrhynchos on
farms and in rural settings also suggests that their populations should be reduced.
Because of the widespread distribution of both A. platyrhynchos and A. undulata in
South Africa, eradication is not an objective of this programme.
As A. platyrhynchos often swim in groups with A. undulata, the control
programme opted to feed target mallards and putative hybrids bread soaked with
anaesthetic (alpha-chloralose). All ducks in the urban area are habituated to people
feeding them bread. Once ducks have succumbed to the anaesthetic, they are
collected by kayakers waiting in the water, and transferred to a nearby facility
where a duty vet euthanises A. platyrhynchos and hybrids. The carcasses are then
sampled for DNA and removed by the City of Cape Town. The majority of birds
removed (63%) were found to be hybrids (Stephens et al. 2020). The programme
was efficiently identifying and removing hybrids, with 5% being pure yellow-billed
ducks (Stephens et al. 2020). The goal of this project is containment—the removal of
A. platyrhynchos and their hybrids in areas of high abundance of both alien and
native ducks in order to conserve the genetic integrity of A. undulata.
22.9 Mammals
22.9.1 Hemitragus jemlahicus (Himalayan Tahr)
An isolated population of Hemitragus jemlahicus is established on Table Mountain
in Cape Town (Measey et al. 2020, Chap. 5). Despite originating from only a few
zoo escapees, 330 individuals were counted during a survey in the 1970s (Lloyd
1975; Skead et al. 2011). The broad dietary preferences of these animals, along with
their tendency to aggregate, resulted in significant environmental degradation and
erosion at high densities (Lloyd 1975). As such, the authorities in charge of
Table Mountain (Department of Nature and Environmental Conservation, now
CapeNature, followed by SANParks from 1998), have conducted Himalayan Tahr
removal programmes since the early 1970s, with the view to restoring populations of
native ungulates in their place (Lloyd 1975; Gaertner et al. 2016). Public concerns
over animal welfare of the tahrs have received significant media attention over the
years (Gosling 2002; Skead et al. 2011).
Management interventions reduced tahr densities to a point that sightings became
a newsworthy occurrence (Skead et al. 2011). However, complete eradication has
not been achieved. The rugged and inaccessible mountainous terrain, exacerbated by
low detectability of individuals at low population densities, make it difficult to
implement management interventions. Tahrs have also been introduced to
New Zealand, where they are established and have been well-studied (e.g. Forsyth
and Tustin 2001; Cruz et al. 2017). However, no research has been published on the
ecology, space use or management of this species on Table Mountain. Research is
22 Alien and Invasive Animal Control Projects
649