There's also a small population of Brush Tailed Rock Wallabies living in Kalihi valley on the island of O`ahui, Hawaii. The are descended from a pair that escaped from a private zoo in 1916 [1].
Estimates on the population vary, but the state estimated it reached as high as 75 animals in the 90's [2].
Occasionally someone will snap a photo of one, such as this one in 2013 [3].
[1] http://en.wikipedia.org/wiki/Brush-tailed_rock-wallaby#Intro... [2] http://archives.starbulletin.com/2007/08/18/news/whatever.ht... [3] http://www.hawaiinewsnow.com/story/22589173/woman-snaps-pict...
Time to introduce a couple of California cougars to the mix :-)
Marsupials are generally good breeders so eventually there will need to be a cull, but because they aren't hooved herbivores some of the normal destructions doesn't happen, like with goats or pigs.
Why warming up for their test match of course: http://www.rugby.com.au/wallabies/GameDay/2014Fixtures.aspx