Invasiveness is linked to greater commercial success in the global pet trade

Abstract

The pet trade has become a multibillion-dollar global business, with tens of millions of animals traded annually. Pets are sometimes released by their owners or escape, and can become introduced outside of their native range, threatening biodiversity, agriculture, and health. So far, a comprehensive analysis of invasive species traded as pets is lacking. Here, using a unique dataset of 7,522 traded vertebrate species, we show that invasive species are strongly overrepresented in trade across mammals, birds, reptiles, amphibians, and fish. However, it is unclear whether this occurs because, over time, pet species had more opportunities to become invasive, or because invasive species have a greater commercial success. To test this, we focused on the emergent pet trade in ants, which is too recent to be responsible for any invasions so far. Nevertheless, invasive ants were similarly overrepresented, demonstrating that the pet trade specifically favors invasive species. We show that ant species with the greatest commercial success tend to have larger spatial distributions and more generalist habitat requirements, both of which are also associated with invasiveness. Our findings call for an increased risk awareness regarding the international trade of wildlife species as pets.

Keywords: biological invasions; exotic pets; human-mediated dispersal; internet trade; wildlife trade.

Fig. 1.

Invasive species are overrepresented in the global pet trade. Patterns of overrepresentation of invasive species (i.e., species that have established outside of their natural range) in traded mammals (3, 21), birds (3, 21, 22), reptiles (3, 17, 21), amphibians (3, 17, 23), and fish (–26). For each taxon, pie charts represent the proportion of invasive (red) and noninvasive (gray) species in the global and traded species pools. The exact percentage of invasive species is indicated in the center and the geographic origin of the data (and its reference) on the bottom left of each pie chart (see SI Appendix, Table S1 and Fig. S1 for details; silhouettes are from phylopic.org).

Fig. 2.

The global trade in ants as pets. (A) Geographical flows. The arrows link the ecozones that source (species’ native range) and receive (location of the online sellers) traded ant species; arrow width is proportional to the number of species traded (SI Appendix, Table S4). (B) Temporal trend in the number of websites selling ants. Sixty-five websites selling ant colonies were detected. Ninety-two percent of the detected websites went online during the last 10 y (i.e., 2007–2017). (C) Invasive species are overrepresented among traded ant species. (D) Invasive species are sold by 1.7 times more sellers than noninvasive species. Squares and vertical lines represent mean ± 99.5% CI estimations of the average number of sellers for each group. Each point represents a traded ant species.

Fig. 3.

Three ecological characteristics associated with greater invasiveness also increase commercial success. (A) Habitat generalism and range size are positively linked to both commercial success and invasiveness. Worker body size is also positively linked to commercial success but is negatively linked to invasiveness (invasive ant species are smaller than noninvasive species). (B) Marginal effects (mean ± 95% CI) of each ecological characteristic linked to both invasiveness and commercial success according to the best-fitting negative binomial model explaining ant species commercial success (see SI Appendix, Table S5 for statistical details).