Thursday, November 19, 2015

With Cats Away, the Mice Will Prey

photo: "Feral Kitty" by Avi, via Flickr, (CC BY-SA 2.0)
We read it in the media all the time: feral cats must be eradicated because they're wiping out birds. Reports claim that if we just get rid of the cats, the world will be a utopia for birds. It's as if no forests are being razed, no tall glass buildings or giant wind turbines are being built, climate change is not altering habitats and migration routes, and there are no other predatory risks for birds out there.

Unfortunately, in some cases fear and misinformation have won out, and feral cats have been eradicated. But how often do we hear about what happens after the cats are gone?

The truth does trickle into the press now and then, and we've recently heard about problems on Marion Island, off the coast of South Africa. According to a new report, mice have become a plague on the island and are killing scores of seabird chicks. "Speculation is that the mouse population explosion on Marion Island is linked to the warmer, drier climate - as well as to the absence of the feral cats" the report says (emphasis added.) The irony is that the South African government spent millions of dollars and 19 years[i] eradicating feral cats from the island, in order to protect seabirds from predators! 

Nowhere has killing cats been a foolproof solution for protecting birds, and Marion Island is only one example. It took 15 years and millions of dollars to eradicate 2,500 cats from Macquarie Island[ii], off the southern coast of Australia. What happened next was an explosion of the population of rabbits, rats and mice. Sound familiar? The World Wildlife Fund says, "Severe overgrazing by more than 100,000 rabbits has caused landslides that have destroyed seabird nesting habitat. Rats and mice also attacked nests to eat eggs, and killed both chicks and adult birds."[iii]

It is very important to protect threatened bird populations, but we see time and again that killing cats for the supposed sake of birds does not work. Non-lethal population management techniques, like trap-neuter-return for feral cats, should be employed instead of trapping, shooting, and poisoning, which just leave holes in ecosystems that other predators fill. And more resources should be devoted to emerging chemical sterilization techniques that could help control feral cat populations in remote areas where doing surgery is a challenge. It's well past time we learn from our experiences on these islands, put the unsuccessful killing campaigns behind us, and embrace a future of humane management that protects threatened species without punishing others.



[i] Bester, M. N. et al., "A Review of the Successful Eradication of Feral Cats from Sub-Antarctic Marion Island, Southern Indian Ocean." South African Journal of Wildlife Research 32.1 (2002): p-65. Print.
[ii] Bester, M.N. et al., 2002.
[iii] http://www.wwf.org.au/our_work/saving_the_natural_world/oceans_and_marine/priority_ocean_places/antarctica_and_southern_ocean/macquarie_island/

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