Human introduction of invasives

When my best friend's family decided to up sticks and move to Australia, she was gutted to find that as well as leaving all her friends behind, “Rodney” the guinea pig couldn’t journey with them either. Whilst some pets are welcomed with (relatively) open arms in Australia, poor Rodney along with many other animals was not. This is because the introduction of pets is one of the main ways which humans can facilitate the transport of invasives. Historically before tight controls were implemented, it was not uncommon for adventurers to take their pets with them; sealers for example would travel with cats and dogs to oceanic islands (Taylor, 1979). 

Without prior knowledge of the potential negative impact of  invasives, this behaviour from our ancestors is understandable. Some rationale behind the deliberate introduction of species however, is just downright crazy. For example at the end of the 19^th century, The American Acclimatization Society decided that it was completely reasonable to try and introduce all of the birds ever mentioned in a play written by William Shakespeare to North America (Mirsky, 2008). This movement as a whole was inevitably unsuccessful however, the European Starling is now well established across the USA.  

Perhaps more sensibly, species may be introduced to a new location to act as a biological control. Biological controls reduce the population of other species that are having a negative effect on the environment. But biological controls have the potential to get out of control! The Cane Toad is an excellent example of a species that was introduced to Australia in 1935 to control the cane beetle population, and in turn has had catastrophic effects on native organisms (Shine, 2010).   

Despite man kind’s best effort to limit the spread of species from their native range in the 21^st Century, accidents do happen, and certain organisms can be little rascals. The small size of some animals and seeds enable them to be easily transported; hiding in cargo travelling across the globe e.g. rats (Atkinson, 1985), in the ballast water of boats (Roberts, 1990), or even on the bottom of your shoes.

On that note I feel that it is perfect time to introduce one of the most notorious species of this topic, behold the Zebra Mussel:

 (Wildlife Forever/ North America Fishing Club, 2013)