When Companions Become Pests

The annual trade in exotic vertebrates as pets – that is, pets without a long history of domestication, unlike dogs, cats, or horses – is a multi-billion-dollar global business. This business involves the shipping of thousands of species, and tens of millions of individual animals, both internationally and within different countries. 

The majority of animals involved in the exotic pet trade remain in captivity for the duration of their lives, but many individuals escape confinement or are released – perhaps due to difficulty in providing care for large, old, aggressive, or sick animals. The research highlights that this had caused a substantial worldwide growth in the number of non-native and invasive animal populations. For instance, one study showed that, of the 140 non-native reptiles and amphibians that have been introduced in Florida, nearly 85% arrived via the pet trade. 

Keeping vertebrate animals as household companions is becoming increasingly popular throughout the world. It has been reported that in the U.S., Australia, and the U.K., over 50% of all households have at least one pet. In the U.S., approximately 50% of pets can be considered “exotic” and ownership of reptiles and amphibians more than doubled between 1994 and 2012.

The trade in exotic pets can be legal, illegal, or both, as a species’ status may change as it moves across political boundaries within the commodity chain.  Most countries do not keep comprehensive records of the species imported as pets, and of those that do, large numbers of imports are often listed as “unidentified” or are misidentified and/or mislabelled. Despite this, a variety of sources indicate that the market for exotic pets is enormous. 

Which exotic pets will establish non-native populations next?

Predicting which exotic pet species will establish new non-native populations is a fundamental component of biosecurity policy. There are several factors to be taken into account: 

1. The introduced exotic pet must be able to physiologically tolerate local environmental conditions. E.g. marine fishes released into fresh water are unlikely to survive and establish non-native populations. 
2. The number of individuals released and the number of release events, which together are known as “propagule pressure”. Propagule pressure and establishment success is higher when, all else being equal, a larger number of individuals are sold in a region, as this means that a larger number would be accidentally or deliberately introduced. 
3. The differing popularity of exotic pet species. It has been reported that there is a consistent pattern in pet trade import data where a few species constitute the majority of individuals imported and sold, and these species are also the ones that are commonly introduced and regularly become established 

Knowledge gaps:

It is important that advocates continue trying to understand how the exotic pet trade contributes to invasions. To do this, more research is required in relation to:

1. The motivations and practices associated with pet-keeping in different cultures.
2. Market demand, consumer behavior, species’ traits, and why people purchase pets and what motivates them to release them. 
3. The economic interest in maintaining a healthy and growing exotic pet trade. 
4. The black market. The costs to participants of wildlife crime include the direct cost of illicit transport, probability of detection by authorities, and legal consequences if caught. To discourage illegal trade, costs could be increased, or benefits decreased. 

Increasing knowledge on the above points, is a challenging task which involves social perceptions, market forces, and ecology. Interdisciplinary efforts are needed to understand the exotic pet trade and create strategies that mitigate its potential harmful effects. It is important that advocates keep striving to increase their knowledge and ultimately protect both native and non-native species.