Bunny-proof? Not this fence!
QUESTION Is the barrier featured in the film Rabbit-Proof Fence still there?
yes, the fence is still standing — but it’s not rabbit-proof.
The 2002 Australian film was based on the 1996 book Follow The Rabbit-Proof Fence by Doris Pilkington Garimara.
It tells the story of the author’s mother, Molly, who, along with two other girls, Daisy and Gracie, are taken from their families in 1931 to be trained as servants.
They run away and set off on an epic j ourney home across the Outback, following the rabbit-proof fence bordering Western Australia while being pursued by the law and an Aboriginal tracker.
Rabbit-proof fence usually refers to No. 1 Fence, which crosses the state from north to south. It was the world’s longest unbroken fence when it was finished in 1907, stretching 1,139 miles.
Unfortunately, the rabbits bypassed the southern end of the barrier before it was completed. To contain them, No. 2 Fence was erected to the west and No. 3 Fence was built to connect the two, bringing the total length to 2,023 miles.
The state Barrier Fence, as the three of them were renamed, provides protection against mobs of migrating emus and wild dogs, but has done little to restrict the movement of rabbits.
There is evidence of rabbits arriving in Australia with settlers as far back as 1788. They were bred in farms and enclosures for meat.
They became a pest following the arrival of a shipment of the wild type in 1859. These were released on Barwon Park, the property of englishman Thomas Austin, near Geelong in Victoria.
He stated that ‘ the introduction of a few rabbits could do little harm and might provide a touch of home, in addition to a spot of hunting’.
He couldn’t have been more wrong. Interbreeding with f armed rabbits resulted in a particularly hardy variety. The numbers exploded and by the late 1940s there were 600 million.
This was partly due to a number of high rainfall years with subsequent good harvests, as well as World War II, which r educed manpower f or t r apping and fence maintenance. The cost to agriculture was devastating. The intentional introduction in the 1950s of myxomatosis, a rabbit-specific virus, saw a dramatic decline in numbers until the 1990s when immune rabbits began to dominate. Their numbers have since grown to 200 million.
The constant deterioration of the state Barrier Fence has meant there was almost always somewhere the rabbits could cross.
However, the fence continues to play an important role in protecting farmers’ livelihoods from emus that can destroy crops and from packs of wild dogs, which can each kill more than 20 sheep a day.
Long sections of the fence are maintained by individual landholders and regional councils.
Tom Davies, Gerringong, New South Wales.
QUESTION Could one kind of virus be used to
fight another?
VIRUses are not known to attack each other because they aren’t true living organisms and require living cells to be able to replicate or reproduce.
However, they might be used to attack each other indirectly. This has been considered in the fight against HIV.
The HIV-1 virus is able to dodge many of the standard medical interventions and a vaccine remains elusive. Drugs suppress viral growth, but not a cure because of latent infections in cells.
These failures have inspired proposals of novel interventions that take advantage of the long-term, chronic nature of HIV-1 infections. In a virus war, a therapeutic virus is introduced into the patient to dynamically limit or kill HIV-infected cells and thereby prevent the collapse of the immune system.
Another approach is to introduce a therapeutic virus that suppresses HIV-1 reproduction when both i nfect the same cell. This research is very much in its infancy.
K. Singh, Bedford.
QUESTION How do jumping beans work?
TecHNIcALLy not beans at all, they are the seed pods of Mexican shrub Sebastiana pavoniana that have been implanted with moth larvae.
In spring, when the plant begins to bloom i n the arid, rocky slopes of chihuahua and sonora, Mexico, the cydia saltitans moth lays her eggs on the flower capsules.
When the eggs hatch, the larvae eat their way into the capsules. As these capsules mature, they become brown and hard on the outside and bean-like in appearance.
safe and secure in the pod, the larva feasts on the capsule’s contents. eventually the pod falls from the bush on to the forest floor where the larva may move around, causing the bean to bounce.
To get jumping beans to move on demand, simply hold one in your hand. The small rise in temperature will result in the larva attempting to move itself and the seed pod away from a potentially dehydrating heat source.
To keep the larva alive, soak the beans (but don’t submerge them) in a little chlorine-free water for a few hours every couple of weeks. In their natural environment, monsoon rains keep them hydrated.
In the right conditions, larvae stay in the beans until the following spring, maturing into a pupa that will no longer spasm in response to heat.
Just before this, they eat an exit hole in the seed and plug it with a silken thread. Next, they spin a cocoon that connects via a silken pathway to this exit.
The matured moth has no jaws, so without this pre-made exit it would have no way out of the seed.
After emerging, a moth lives for just a few days — its sole purpose being to propagate its species.
Emilie Lamplough, Trowbridge, Wilts.
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