Nature’s lawnmower

Goats – so destructive, and yet, so many reasons to love them.

Goats (Capra hircus) have ravaged some of the most diverse and rare ecosystems.  Those garbage disposals on legs will eat anything green, thorns and all. And for the sake of our stomachs, humans did the best we could to spread them around, because goats are easy to feed, and conveniently, tasty (mmmm, cabrito..). In the 1700s, sailors would intentionally leave behind breeding pairs on islands, to act as a four-legged larders – nothing is fresher than still alive and reproducing. Feral goat populations have run amok around the world. In Australia, they are estimated to cost in control efforts $1.2 million AUD/year, in addition to degrading sensitive habitat (Animal and Plant Control Commission, South Australia, 1996). Goats have also had a massive impact on evolutionary biology’s poster child, the Galapagos Islands. Once introduced there, the goats did what they do best, and grazed the flora of the island to the ground, resulting in native plant species decline, erosion, and loss of habitat for rare native fauna. By 2000, the mountain sides of Santiago Island were covered with thousands upon thousands of goats, while endangered giant tortoises routinely fell in to volcanic craters, trying to reach the last of the food on eroding soil. Utter chaos! And so began the most ambitious invasive animal removal project to date. After 4 years of concerted effort and more of monitoring, and $6.1 million, 80,000 goats were cleared from Santiago Island (58,500 hectares), and more from Isabela Island (459,000 hectares), in an impressive feat of determination.

And yet, when they are not feral and free-living, goats have their uses. It seems cosmically just, that one of the most cost effective and efficient way to clear many invasive plants from an area is by goat. Goats eat everything! Which means they eat Himalayan blackberry, English Ivy, Scotch broom, Canada thistle (actually from Europe), and all manner of invasive plant. Of course, they are a bit of a nuclear option, best for areas with nothing herbaceous left besides weeds. There is a burgeoning economy in North America in goat rental for weed removal purposes, gaining them cultural icon status. In some instances, people even bring the weeds to the goats!

And so the goat, unlike many invasives, is an animal you pay to borrow, and you pay to eradicate.

ResearchBlogging.org

Marris, E. (2009). Goodbye Galapagos goats Nature DOI: 10.1038/news.2009.61

Guo, J. (2006). INVASIVE SPECIES: The Galapagos Islands Kiss Their Goat Problem Goodbye Science, 313 (5793), 1567-1567 DOI: 10.1126/science.313.5793.1567

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