10 May 2011

Mark Carter goes in search of irrupting rats and rare kites in the Red Centre.

“Rat Plague Bears Down on Alice Springs” screamed the headline on the national ABC News website. A friend of mine in the Parks Service, source of the story, was unsettled: “It wasn’t really the angle we were hoping for”. I could sympathise; rather than an alarming tale of impending verminous doom which the media ran, the arrival of the Long-haired Rat Rattus villosissimus should really be seen as major cause for desert ecological-joy.

Long-haired Rat, photo by Peter J. Nunn. A very rare animal, there aren't many photos of these critters in the wild. Populations very occasionally irrupt, providing important food for birds like Letter-winged Kites.

My friend is a scientist with the NT Parks Service Biodiversity Unit and is a topgun field naturalist to boot. I have known him for a while but as we both lead fairly nomadic lives at times we often go long periods between meetings. Last year we had bumped into each other one dawn as he was dropped by chopper onto the mountain ridge I happened to be bushwalking on. He was checking traps he laid to search out Long-tailed Dunnarts and Critically Endangered Centralian Rock Rats, two spectacularly rare desert mountain mammals which hadn’t been recorded for years yet were expected to be benefiting from 2010’s massive rains.

A few weeks later I met him again on the heavily vegetated peak of Mount Sonder where he greeted me with a wide grin – he had found both species booming on top of this huge mountain. Sonder’s fire-ravaged lower slopes had protected an island of premium fire-sensitive mammal habitat from wildfires. This was the first time these creatures had been found alive this millennium in the southern NT, and in the case of the Rock Rat, proof the creature is not globally extinct … yet.

He had first told me of the villosissimus’s arrival in the centre a few weeks before the media mangled his biodiversity-good-news press release. We were in the pub swapping stories of wildlife encountered and telling of plans for trips to come. A handful of nocturnal sightings had occurred near Alice Springs but the best of the lot was of one animals allegedly rescued in broad daylight from outside the Post Office in the centre of town! This was very exciting news as villosisimus irruptions are rare events. The last time they reached Alice Springs from their remote homelands was a quarter of a century ago. They can also brings a very special creature in their wake- the near-mythical Letter-winged Kite.

A close relative of the common Black-shouldered Kite, the Letter-winged Kite is a strange and wonderful beast. It is a beautiful animal- ghostly white translucent wings with a stark black stripe on the underwing, a pale face with large dark eyes. It  is also largely nocturnal, a factor which certainly adds to the difficulty of finding this bird. It is locked in a remarkable boom and bust predator-prey relationship with the Long-haired villosisimus Rats in rather the same way that Arctic Lemmings and Snowy Owl’s fates are tied. Lemmings boom in years of high snowfall, and villosisimus Rats do the same in years of sustained high rainfall.

Image by Peter Waanders, Southern Birding Services Southern Birding Services

Letter-winged Kites. Their numbers closely follow population cycles of their prey, including Long-haired Rats.

In a ‘normal’ year these kites are restricted in range to the blacksoil tablelands where their rat prey find refuge and their numbers dwindle to a relict few. When the big rains come the grasses go into overdrive, the rats breed like the blazes and the kites do their best to keep up, knocking out as many chicks as they can. Eventually a mass of young rats sets out across the newly green landscape of the desert centre in search of new ground and the eager young kites follow.

In recent decades these birds have made it all the way to the Simpson Desert where they have been known to switch to another species of irruptive native rodent- the Plains Mouse Pseudomys australis. They’ve even made it as far as Melbourne!

A native-rodent enthusiast who shall remain nameless told me a story about the last Plains Mouse irruption over a decade ago: “We heard their were all over the place at a remote reserve in the Simpson Desert. It was a rodent I hadn’t yet ticked in the wild so I drove all day to get to the site. We got there at dusk and set to spotlighting but they had already moved off. All there was there were these funny birds of prey which looked as disappointed as we were and left pretty soon after we arrived.” Needless to say, he isn’t a birder. My jaw dropped as he told this story! His “funny birds of prey” were Letter-winged Kites, one of the desert birds which birders most want to find.

After hearing of the Post Office rat, I set to driving dirt roads around Alice Springs at dusk and into the night in the hope of finding villosissimus and their wonderful winged followers. This can be a fun way of finding critters- slowly cruising byways with the headlights on high, you sometimes only get a second to make an identification before a creature glides or bounds off into the bush. Our blooming desert is a busy place at night- expect an owl or nightjar every five minutes and scampering mini-mammals every minute, on the minute. These rat & kite hunting forays are never a chore.

The rats didn’t take long to find. One night, after a glorious sunset by a flooded claypan in the company of 40 twittering Bourke’s Parrots, I was crawling along back to town at 30km per hour with the truck’s lights on high-beam when a rodent far bigger than the various native mice I’d seen so far, galumphed out of the grass and across the road.

A hunchbacked chunky dude with a big head- there was no doubt about it- it was a real live villosisimus. I braked hard- a mistake as the cloud of dust that created could obscure an elephant. By the time it cleared my ratty friend had gone. Undeterred I quartered the surrounding grasslands with a handheld spotlight and glimpsed two more rats scuttling into the grass hummocks. Since that night I have done more runs whenever I can squeeze the time, hunched forward in my seat, craning my neck at every Barn Owl and Tawny Frogmouth clipped by my lights, just in case I glimpse that white translucent wing with a stark black stripe on the underwing…

I have returned to the rat site several times now and not found them again, and of course the kites have not materialised anywhere near Alice. The rats are appearing across the region in dribs and drabs but are nowhere in numbers. Its been three weeks now and I am having to face up to the possibility that the impending rat ‘plague’ has sadly been be a false alarm.

However, time spent looking is never time wasted. I have had a run of magical encounters in the process: several tiny carnivorous Kultarr- a rarely seen Jerboa-like marsupial, the drama of a fleet of Pseudomys desertor (native mice!) scurrying across the track suddenly attacked by a murderous wild-eyed Boobook, little gaggles of Bourke’s Parrots doing half-convincing Night Parrot impersonations on the roadside, all lit up by my headlights.

I have not heard from my scientist friend how his search is going but I haven’t been discouraged. I will keep on searching, widening my net as I get the chance. I shall of course inform my fellow birders if I strike lucky, but in the meantime I am having a lot of fun in this search for the rat plague and those fabled “funny birds of prey”.