Exploring Nature: The Big Rat

The people who live on Isla Natividad, a wide stretch of sand off Mexico’s Baja California Peninsula, are proud of the island’s many birds. There are auklets, cormorants, pelicans, ospreys and herons, just to name a few.

Most importantly, the four-mile-long island is home to the world’s largest colony of black-vented shearwaters, a gray seabird with a raspy cry. A whopping 95% of the species hatch on this island.

In 1919, a most unwelcome creature was spotted on the island: A big rat.

This odious rodent is responsible for about 40% of bird extinctions worldwide, so this was definitely bad news. Worse, it was feared the rat might be a pregnant female, in which case the rat population could multiply exponentially.

So the islanders took immediate action. More than 200 baited traps were set. A rat-sniffing dog was brought in which had been on duty at the island’s port to sniff out stowaway rats on commercial freighters and Navy vessels. The “super-dog” could not find the rat, but it did help identify the area where it was most active.

A camera trap and video surveillance documented that the big rat was still around and one particular bit of footage provided good news – the rat was a male. Phew.

Traps were baited with all sorts of things – long-lasting vanilla, reheated leftovers and essence of muskrat gonad. Nothing worked.

Finally, a trap was sprung and the rat was caught and killed. What was the bait that enticed the big rat to his death? Cheese. Sometimes you just can’t beat a classic.

Children on the island staged a burial and erected a tiny wooden cross on the rat’s grave and today, the birds of Isla Natividad squawk and fly about, clearly surviving and thriving.