Any cat owner knows that cats haven’t lost their hunting instincts in the 12,000 years since they were first domesticated. But it’s not just your toes under the bed sheets that are at risk—cats kill at least 1.3 billion birds and 12 billion mammals per year in the US alone, and have been implicated in the extinction of 63 species and the endangerment of hundreds more. Some cities are taking unusual action: implementing cat curfews. Husavik, Iceland was one of the first towns to institute a cat curfew—more than a decade ago—telling owners to keep cats inside after 10 p.m., and now other Icelandic towns are following suit. Several municipalities in Australia have also enacted curfews, enforceable with fines, though attempts to pass 24-hour bans have failed. Supporters of the bans also point out that keeping cats inside decreases their risk of injury from dangers like cars.  Some researchers say that cat bans make the most sense in rural areas with large nesting sites for coastal birds ...