Invasive Species

A Case Study in Invasive Species: The European Rabbit on Destruction Island, WA

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The European rabbit is considered a major, invasive threat on islands worldwide where it's often introduced as a pet and stays for good to take over the landscape and alter the habitat permanently, just as it did on Destruction Island, WA, where it's thought to have been brought to the island as a pet of the lighthouse keeper's daughter and escaped, and the rest, as they say, is history (Welch 2012). The presence of the European rabbit on Destruction Island is a huge threat to tufted puffin populations for many reasons, including that the rabbit is an invasive species and Destruction Island is one of few remaining viable breeding grounds for tufted puffins in Washington state. In 2007 it was one of only 12 out of 25 historical burrows that were still occupied, and in 2008 it was one of only 17 out of 32, both rates of about 50% (Pearson et al 2011), which shows that it's an area where it's important to focus some of the conservation efforts for tufted puffin populations in Washington, such as by attempting to eradicate the European rabbit. Other reasons that the European rabbit poses a concern as an invasive species include that their mere presence can be enough to deter the notoriously skittish tufted puffin from entering their burrows if a rabbit is nearby, and thus not allowing the puffin to tend to their young which decreases fledgling success. It is also known to have happened in rare cases where rabbits will enter the burrows of tufted puffins and other seabirds to drive them out directly (Hokum 2014). The presence of the European rabbits has also caused an increase in the number of bald eagles on Destruction Island as they are one of the bald eagle's main prey sources. As was described above, bald eagles are also a predator of the tufted puffin, though it's thought that their biggest impact here is scaring the tufted puffins away from their burrows, sometimes permanently, which leads to malnourishment of their chicks and decreased fledgling success (Welch 2012). Another way this rabbit species affects the tufted puffins is through their ravenous consumption of the native perennial grasses on the island which were once thigh-high

Map depicting occupation of historical breeding colonies (Pearson et all 2011).
Destruction Island is the third black circle up on the left.

but have now been decimated and replaced by nonnative annual grasses that are kept short by the rabbit's constant consumption of them. The problem with the shortness of these annual grasses is that they're no longer capable of stabilizing steep, muddy hillsides that now collapse faster than they ever have before, destroying habitat that the tufted puffin requires for its burrows (Welch 2012). For all of these reasons, the European rabbit is a pesky invasive species that must be eradicated from the island if tufted puffins are to stand a chance at rebounding their population numbers. A proposal to remove the rabbits from the island is currently in the planning stages, however in the past there has been opposition from the public that has stopped other such plans, so it is hoped and expected that the plan can actually be carried out this time around, as similar plans have shown success in the past on the Farallon Islands in California in the 1970's where tufted puffin populations rebounded after European rabbits were removed and the tufted puffins were able to reclaim burrows the rabbits had taken over (Ainley and Boekelheide 1990).