Lord Howe Island was declared free of rodents in 2019, but the celebration may have been premature. The recent appearance of nearly 100 rats has conservationists wondering if these intruders are survivors or newcomers to the island, which is a UNESCO World Heritage Site home to various endangered species.
This past April, a local woman spotted a rat near Ned’s Beach Cemetery. It marked the first time since 2019 that a rat had been seen anywhere on Lord Howe Island, located 780 km northeast of Sydney, Australia. An ensuing investigation resulted in the capture of two rats: a juvenile male and a pregnant female.
But this was just the beginning, as The Guardian reports. A total of 96 black rats have been captured and killed this year, raising concerns that the controversial, A$17 million Rodent Eradication Program (REP) didn’t actually work, or least not to the expected degree. Officials are now trying to figure out if the rats are leftovers from the original population or if a new population has somehow taken root on the island.
An estimated 150,000 rats and 210,000 mice lived on the island at the outset of the eradication program. That’s a lot of rodents for an island measuring just 14.55 square kilometres in size. It’s so small that a maximum of 400 tourists are allowed on the island at any given time.
Mice were inadvertently brought here by ships in the mid-19th century, while the sinking of a ship near the coast in 1918 is blamed for the introduction of rats. These invaders have inflicted tremendous damage onto the island ecosystem, resulting in the extinction of five bird species and 13 invertebrate species, while threatening another 70 species, according to the Sydney Morning Herald.
To exterminate the troublesome rats and mice, REP officials placed poisoned cereal pellets into 22,000 lockable traps. Helicopters then dropped the deadly bait (44 tons of it, per The Guardian) in inaccessible places to protect people on the island, a territory of New South Wales. A detector dog flushed out the last remaining rat in 2019, or so it seemed.
The discovery of nearly 100 rats since April has inspired a series of new measures, including the strategic placement of 250 motion-detecting cameras and the deployment of teams with specially trained dogs from New South Wales and New Zealand. Encouragingly, no rat has been seen on the island since the first week of August. Genetic tests are being carried out on the newly discovered rats to determine their origin, the results of which are expected by the end of this year, The Guardian reports.
Should no more rats be detected, the program can shift to preventative biosecurity measures. But the effort, despite the recent sightings, appears to be working.
Indeed, native animals are rebounding on the island, including a significant boost in the number of endangered Lord Howe Island woodhens. Other animals poised to make a comeback include the kermadec petrel, masked booby, and white-bellied storm petrel, along with land snails and various ground lizards. Plants are also expected to rebound, including the critically endangered little mountain palm. Excitingly, plans are in the works to reintroduce the world’s rarest insect — the Lord Howe Island phasmid — to the island. These gigantic flightless insects can measure over 12 cm in length.
But this assumes the rats are truly gone. Only time will tell, as will diligent efforts to keep the Lord Howe Island rodent free.
More: The Helicopter Pilots Who Carpet-Bomb Islands to Battle Invasive Rats.