were also initiated. The implementation of control measures related to these instruments might have reduced introductions through some pathways (for examples see
Boxes 12.1 and 12.5), however, this is difficult to prove and changing fashions or
other socio-economic factors could have played a role (see Box 12.1).
Box 12.4 Escaped Pets
More than a billion ornamental fish are traded as pets globally each year
(Whittington and Chong 2007), while the trade in other animals is dominated
by birds, reptiles and relatively fewer mammals (Bush et al. 2014). The pet
trade is known to have caused some important and high impact invasions
globally. This can occur when the pet itself is released or escapes from
captivity; examples include Python bivittatus (Burmese Python) in the Everglades in Florida (e.g. Dove et al. 2011); Felis catus (Domestic Cat), which is
generally regarded as one of the worst invaders globally but which has been
most devastating on islands (e.g. Nogales et al. 2004); and Carassius auratus
(Goldfish), which is an aquatic ecosystem engineer that can increase turbidity
and nutrient loading in rivers and lakes (Crooks 2002). However, the pet trade
can also contribute to invasions when the organisms that are associated with
some pets are introduced alongside them [for example, amphibians that are
infected with the devastating chytrid fungus (Scheele et al. 2019)] or when
associated organisms are sold [e.g. plants sold, often with fish, in the aquarium
trade (Martin and Coetzee 2011)].
The pet trade in South Africa consists of many vertebrates, of which fish,
amphibians and reptiles have been studied in the greatest detail (van Wilgen
et al. 2008; van der Walt et al. 2017), but also invertebrates like tarantulas
[~200 species (Shivambu 2018)], insects, scorpions and gastropods [~35
species (Nelufule 2018)]. For some groups the number of individuals and
species imported for the pet trade has increased over time (van Wilgen et al.
2010), and there has been an increase in the number of pet taxa that have
escaped or have been released from captivity (first figure below). Given the
high impacts caused by some introduced pets elsewhere in the world, it seems
surprising that the importance of the pet trade as a source for major invaders
seems to be relatively minor in South Africa, besides the classical examples of
Cats and Dogs that have caused massive impacts on local fauna where they
have been introduced (Hagen and Kumschick 2018). Many vertebrates and
invertebrates in the pet trade (e.g. second figure below) have not established
populations outside of captivity or are not (yet) problematic (van Wilgen et al.
2008; Measey et al. 2020, Chap. 5, Sect. 5.2). For example, Psittacula krameri
(Rose-ringed Parakeet), is known to cause high impacts in other areas where
introduced, but has only recently established populations in Durban (Hart and
Downs 2014) and Johannesburg (Measey et al. 2020, Chap. 5, Sect. 5.3.2).
(continued)
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K. T. Faulkner et al.
Boxes 12.1 and 12.5), however, this is difficult to prove and changing fashions or
other socio-economic factors could have played a role (see Box 12.1).
Box 12.4 Escaped Pets
More than a billion ornamental fish are traded as pets globally each year
(Whittington and Chong 2007), while the trade in other animals is dominated
by birds, reptiles and relatively fewer mammals (Bush et al. 2014). The pet
trade is known to have caused some important and high impact invasions
globally. This can occur when the pet itself is released or escapes from
captivity; examples include Python bivittatus (Burmese Python) in the Everglades in Florida (e.g. Dove et al. 2011); Felis catus (Domestic Cat), which is
generally regarded as one of the worst invaders globally but which has been
most devastating on islands (e.g. Nogales et al. 2004); and Carassius auratus
(Goldfish), which is an aquatic ecosystem engineer that can increase turbidity
and nutrient loading in rivers and lakes (Crooks 2002). However, the pet trade
can also contribute to invasions when the organisms that are associated with
some pets are introduced alongside them [for example, amphibians that are
infected with the devastating chytrid fungus (Scheele et al. 2019)] or when
associated organisms are sold [e.g. plants sold, often with fish, in the aquarium
trade (Martin and Coetzee 2011)].
The pet trade in South Africa consists of many vertebrates, of which fish,
amphibians and reptiles have been studied in the greatest detail (van Wilgen
et al. 2008; van der Walt et al. 2017), but also invertebrates like tarantulas
[~200 species (Shivambu 2018)], insects, scorpions and gastropods [~35
species (Nelufule 2018)]. For some groups the number of individuals and
species imported for the pet trade has increased over time (van Wilgen et al.
2010), and there has been an increase in the number of pet taxa that have
escaped or have been released from captivity (first figure below). Given the
high impacts caused by some introduced pets elsewhere in the world, it seems
surprising that the importance of the pet trade as a source for major invaders
seems to be relatively minor in South Africa, besides the classical examples of
Cats and Dogs that have caused massive impacts on local fauna where they
have been introduced (Hagen and Kumschick 2018). Many vertebrates and
invertebrates in the pet trade (e.g. second figure below) have not established
populations outside of captivity or are not (yet) problematic (van Wilgen et al.
2008; Measey et al. 2020, Chap. 5, Sect. 5.2). For example, Psittacula krameri
(Rose-ringed Parakeet), is known to cause high impacts in other areas where
introduced, but has only recently established populations in Durban (Hart and
Downs 2014) and Johannesburg (Measey et al. 2020, Chap. 5, Sect. 5.3.2).
(continued)
334
K. T. Faulkner et al.