When pets go rogue: the link between the wildlife trade and exotic species
New Zealand puts considerable effort into managing the impacts of invasive species. And with good reason: invasive species wreak havoc on the environment and pose significant threats to animal health. The commitment to managing such pests and reducing their impacts is well exemplified by the Department of Conservation’s ‘Battle for our Birds’campaigns to achieve environmentally driven goals. A second example is the control of possums by TBfree NZ, with the aim of eradicating bovine tuberculosis, an animal health-driven goal. More recently the launch of initiatives to eradicate some predators from the mainland by 2050 has put New Zealand at the global forefront of the battle against invasive species.
These management initiatives concentrate on exotic species that have established self-sustaining populations and spread throughout New Zealand. The presence of these invasive species is mainly a legacy of ‘acclimatisation societies’, which made it their goal to establish exotic species for human delight and use. Luckily such acclimatisation societies are no longer active in New Zealand, though that does not necessarily imply that releases of potentially invasive species have ceased: the purposeful release of animals is being replaced by more subtle pathways of transport and the introduction of new and emergent exotic species. This shift has occurred in recent times in countries around the world and has been driven by concomitant changes in the relationships between humans and animals.
In this new context most species are transported into countries either intentionally (e.g. trading to satisfy the demand for animal products) or unintentionally (e.g. species hitching a ride in containers shipped from one country to another). Unlike the goals of acclimatisation societies, these new pathways rarely if ever have the explicit objective of establishing exotic species. Rather, some species escape or are released into new environments where they may be capable of forming self-sustaining populations.
Mounting evidence reveals the key role played by the pet trade in shaping the new national pool of exotic species. Globally a large variety of species are traded to supply and meet the demand for pets. This demand is causing significant environmental problems. In their native range the exploitation of populations is leading to over-harvesting and population declines; in the recipient regions some of the imported and traded species may pose an untenable risk of becoming invasive species.
The rise in the relevance of the pet trade has also changed the type of exotic species transported worldwide. Where in the past there was an emphasis on mammals and some birds, nowadays the pool of potential exotic species is dominated by ornamental fish, amphibians, reptiles, and cage birds. New and emergent exotic species pose new threats to native biota. For example, exotic amphibians may carry emergent diseases such as the chytrid fungus and ranaviruses, which can imperil native frog species. Earlier this year a snake was intercepted on an incoming flight at Auckland airport. The introduction of snakes to New Zealand environments, where native communities are naïve due to their natural absence, could lead to an ecosystem-scale disaster akin to that caused by introduced brown tree snakes in Guam.
Preventing the introduction and establishment of exotic species is the best way to avoid potential detrimental impacts, but to be effective, preventive strategies need to be based on good evidence. So, what is known about the risks of the pet trade in New Zealand? Trading in ornamental and aquarium fish has been highlighted as increasingly contributing to new introductions of exotic fish across the world. In New Zealand almost a quarter of the exotic fish present in 2012 were ornamental species (23.8%, or 5 out of 21). This proportion may further increase in the near future due to the growing numbers and diversity of exotic fish imported into the country.
Reptiles have also gained prominence as emerging exotic species. There is good information about exotic reptiles in the New Zealand pet trade thanks to the research of Heidy Kikillus in 2010, although an update would be welcome. Heidy reported 12 species of exotic reptiles found in the pet trade, with individuals of four species found at large (although none have established populations). It is not surprising that the most common pet reptile was the red-eared slider turtle, a species that has been traded in massive numbers globally. As in countless other countries, slider turtles are often found in the wild in New Zealand waterways, particularly around Wellington and Auckland. Rapid responses by governmental agencies to remove such animals have prevented their establishment in the wild, but these incursions represent a warning of the potential risks of pets.
Pablo García-Díaz has researched the role of the pet trade here as a source of new and emergent exotic species. Existing biosecurity arrangements, coupled with risk assessment tools for exotic imports (e.g. NIWA’s fish risk assessment model), should help protect New Zealand from emergent exotic species. Pablo does not, however, argue for a blanket ban on the pet trade in New Zealand. Instead, he contends that we need a more nuanced and up-to-date knowledge of the biosecurity risk currently posed by this trade. The need to comprehend the nature of such novel biosecurity risks to manage the new generation of potentially exotic species effectively is clear-cut. Otherwise New Zealand may need to deploy ‘Predator Free 2050-like’ initiatives in perpetuity to deal with an ever-increasing number of newly established exotic species.
This work was funded by the Invasive Animals CRC, Australia