Something gruesome is afoot on Midway Atoll: As reported by the US Fish and Wildlife Service (FWS), and now picked up by the Washington Post, mice there appear to be attacking nesting albatrosses and causing them to bleed fairly profusely. Why? Well, one speculative interpretation is that they’re drinking their blood.
Understandably, this has caused some concern. Midway Atoll is the largest albatross colony in the world, and history has taught conservation biologists that there’s little worse than an invasive species.
“The majority of seabird extinctions around the world have been caused by invasive mammals, in particular, non-native rodents,” the FWS communique emphasizes.
The common house mouse has been present on Midway Atoll for around 75 years now. Introduced with the black rat back in the day, their larger evolutionary cousins have since been exterminated, leaving the mice to proliferate without much competition.
These omnivorous scavengers are happy to get their jaws around anything that’ll provide them with energy or sustenance, and weirdly, the fairly sizeable albatrosses appear to be a new target.
First seen in the 2015 hatching season, mice are causing open wounds on the heads and necks of these seabirds, creatures that clearly have been taken by surprise. They’ve quickly learned to attack the birds from behind, where they’re most vulnerable.
“Mice attacks have increased from just a few incidents to hundreds of wide-spread attacks on albatross that result in injury, nest abandonment, and death,” the post notes.
Strikingly, Dr Alex Bond, a conservation biologist and expert on marine birds from London's Natural History Museum, told IFLScience that this incident isn’t isolated – and worse has been seen elsewhere.
“On Gough Island, Tristan da Cunha, mice eat Tristan albatross chicks alive,” Bond added, something that’s been studied and documented. “The same is happening on subantarctic Marion Island,” where it appears mice are essentially scalping their prey.
“So rather than ‘blood-sucking’ mice, this is part of their routine predation.”
This incident is initially reminiscent of the behavior of another bloodthirsty critter, this time found on the Galapagos Islands: the so-called vampire finch. Found on the barren, dry Wolf Island, this bird sometimes survives by stabbing the oil gland-rich tail end of booby chicks until blood is drawn, which is used to quench their considerable thirst.
Is the behavior of these Midway mice, then, somewhat similar? It’s possible. An ecologist, speaking to the Washington Post, suggests that during full-blown droughts, mice were seeking hydration through any means possible.
Bond suggests that a direct comparison isn’t possible though, with these finches or other similarly behaving birds, like oxpeckers in Africa.
Unlike the newly invasive mice on Midway, “these all concern native species, where such predation has either evolved naturally, or has existed for centuries or millennia as predator and prey adapt in a sort of evolutionary arms race.”
Having lived largely free of rodents since they’ve been nesting there, seabirds on Midway Atoll are clearly unequipped to deal with mice. Not only do they instinctively not fear them, but they don’t possess any defense mechanisms that can help them out.
Nesting albatrosses are particularly vulnerable, as they’ll refuse to evade the mice and will instead stay put and guard their young.
Worryingly, the reproductive cycle of albatrosses is far slower than that of mice. Far from just meaning that mice are quickly going to outnumber their victims here, this also means that any losses they suffer from such attacks will have knock-on effects for their population for generations to come.
It’s not surprising, then, that the FWS is now planning to remove the mice from the island, although the debate as to how best to do this is still underway.