invertebrates, decomposition and peat formation have changed on Marion Island
(Smith 2008). More specifically, the reduction in decomposer invertebrates has
resulted in lower breakdown of plant litter, lowering the availability of nutrients
and slowing the growth rates of plants. This, in turn, is thought to result in slower
accumulation of peats (Smith 2008).
Additionally, the burrowing activities of M. musculus affect geomorphic processes on Marion Island: soils are destabilised, erosion around burrows increases and
temperatures around and in burrows increases (Eriksson and Eldridge 2014).
Rodents have been successfully eradicated from a number of islands (Howald
et al. 2007), including several sub-Antarctic islands (Towns and Broome 2003;
Martin and Richardson 2017; Springer 2018; http://milliondollarmouse.org.nz/).
Given the wide-reaching, and seemingly increasing impacts of M. musculus on the
terrestrial ecosystems of Marion Island, it is encouraging that a House Mouse
(M. musculus) eradication programme for Marion Island is planned to be undertaken
in 2021.
A second invasive mammal that had significant impacts on the island ecosystem
did, for some years, occur on Marion Island: Felis catus (the Domestic Cat) (Zengeya
et al. 2020, Chap. 17, Sect. 17.3). Felis catus were intentionally introduced in 1948
to control M. musculus populations in the meteorological station, but soon became
feral. The diet of F. catus consisted mainly of burrowing petrels (M. musculus made
up only app. 16% of their diet, van Aarde 1980), and it was therefore responsible for
causing major declines in burrowing seabird populations, and the local extinction of
at least one species (Bester et al. 2002). Felis catus was successfully eradicated from
Marion Island in 1991 through a combination of hunting, trapping, poisoning, and
biological control with a feline virus (Bester et al. 2002).
Other vertebrate species that were intentionally introduced to Marion Island to
provide fresh food for sealers, or, more recently, for overwinterers after the establishment of the South African meteorological station, include Sus scrofa domesticus
(Domestic Pig), Ovis aries (Sheep), Capra hircus (Goat) and Gallus gallus
domesticus (Chicken) (Watkins and Cooper 1986; Greve et al. 2017). Additionally,
Canis lupus familiaris (Domestic Dog) and two parrots were kept on Marion Island
for companionship in the 1960s (Watkins and Cooper 1986). All these species either
did not establish in the wild, or were subsequently removed from the island (Watkins
and Cooper 1986; de Villiers and Cooper 2008; Greve et al. 2017). Based on
evidence from other islands, it is highly likely that some of these species could
have caused significant damage, had they persisted as self-sustaining populations
(Frenot et al. 2001; Courchamp et al. 2003; Lecomte et al. 2013).
8.3.2 Free-living Invertebrates
The first summary of invasive insects of Marion Island was made by Crafford et al.
(1986); this account listed nine species that were classified as alien and ‘naturalised’.
Currently, a total of 27 invasive terrestrial invertebrate species is known from the
PEIs (Greve et al. 2017). As with the continental areas of South Africa (Janion212
M. Greve et al.
(Smith 2008). More specifically, the reduction in decomposer invertebrates has
resulted in lower breakdown of plant litter, lowering the availability of nutrients
and slowing the growth rates of plants. This, in turn, is thought to result in slower
accumulation of peats (Smith 2008).
Additionally, the burrowing activities of M. musculus affect geomorphic processes on Marion Island: soils are destabilised, erosion around burrows increases and
temperatures around and in burrows increases (Eriksson and Eldridge 2014).
Rodents have been successfully eradicated from a number of islands (Howald
et al. 2007), including several sub-Antarctic islands (Towns and Broome 2003;
Martin and Richardson 2017; Springer 2018; http://milliondollarmouse.org.nz/).
Given the wide-reaching, and seemingly increasing impacts of M. musculus on the
terrestrial ecosystems of Marion Island, it is encouraging that a House Mouse
(M. musculus) eradication programme for Marion Island is planned to be undertaken
in 2021.
A second invasive mammal that had significant impacts on the island ecosystem
did, for some years, occur on Marion Island: Felis catus (the Domestic Cat) (Zengeya
et al. 2020, Chap. 17, Sect. 17.3). Felis catus were intentionally introduced in 1948
to control M. musculus populations in the meteorological station, but soon became
feral. The diet of F. catus consisted mainly of burrowing petrels (M. musculus made
up only app. 16% of their diet, van Aarde 1980), and it was therefore responsible for
causing major declines in burrowing seabird populations, and the local extinction of
at least one species (Bester et al. 2002). Felis catus was successfully eradicated from
Marion Island in 1991 through a combination of hunting, trapping, poisoning, and
biological control with a feline virus (Bester et al. 2002).
Other vertebrate species that were intentionally introduced to Marion Island to
provide fresh food for sealers, or, more recently, for overwinterers after the establishment of the South African meteorological station, include Sus scrofa domesticus
(Domestic Pig), Ovis aries (Sheep), Capra hircus (Goat) and Gallus gallus
domesticus (Chicken) (Watkins and Cooper 1986; Greve et al. 2017). Additionally,
Canis lupus familiaris (Domestic Dog) and two parrots were kept on Marion Island
for companionship in the 1960s (Watkins and Cooper 1986). All these species either
did not establish in the wild, or were subsequently removed from the island (Watkins
and Cooper 1986; de Villiers and Cooper 2008; Greve et al. 2017). Based on
evidence from other islands, it is highly likely that some of these species could
have caused significant damage, had they persisted as self-sustaining populations
(Frenot et al. 2001; Courchamp et al. 2003; Lecomte et al. 2013).
8.3.2 Free-living Invertebrates
The first summary of invasive insects of Marion Island was made by Crafford et al.
(1986); this account listed nine species that were classified as alien and ‘naturalised’.
Currently, a total of 27 invasive terrestrial invertebrate species is known from the
PEIs (Greve et al. 2017). As with the continental areas of South Africa (Janion212
M. Greve et al.