Whodunnit? The great lemon heist

An absent-minded human burglar with a taste for lemons? Not likely - I've been struggling to give away lemons and limes lately, as most of our friends and neighbours have their own laden trees. Also - tellingly - one of the lemons was half eaten.

This leaves a host of suspects. Blacktail wallabies are extremely fond of lemons. They dextrously use both paws to pick them, usually the fattest and juiciest fruit. Those teeth marks might well have been wallabies'. But wallabies don't gather fruit into a pile. They tend to pick, take a bite or two, then lose interest. Wombats may taste a fallen lemon, but unless they're very hungry, won't eat them.

Foxes, on the other hand, do eat lemons - and apples and peaches and many other fruits too. I've even watched them climb peach and apple trees to do so. Foxes also make store cupboards of fruit, especially if they have cubs, though usually foxes only take one fruit at a time, hide them in their lair then come back for more.

Rats? Not the fluffy bush rats, but the introduced black rat, or roof rat. Roof rats gather quite substantial larders of food to eat later. They're fond of nuts, fruit or even snails - one rat nest I discovered had more than 30 snail shells in it, though the snail eradication didn't make me feel any friendlier to the rat.

Whoever stole the lemons is also probably the culprit who ate every single bell pepper from the two large bushes near the lemon tree, and ate all the parsley too. This might still leave rats as the guilty party - black rats will eat just about anything, including parsley. The rats were also certainly the corn thieves who ate most of our crop in a single night.

The main suspect, however, is Possum X, an extremely large male possum who has also just eaten all but four of our Seville oranges. I'm pretty sure he's the culprit there, as the oranges that are left are right at the tip of the branches which wouldn't take the weight of a sturdy possum, but would be quite accessible to a black rat. But do possums ever make piles of fruit 'for later'? The ones here just have a fruit eating orgy on the spot, then head to their nests to sleep it off.

The answer might be a combination of culprits. Possum X may have knocked the fruit off the tree and a rat gathered it, then found the lemons too heavy to carry up to the nest, though come to think of it, the local rats probably have low nests under logs or rocks at the moment, as we've pruned back the vines where they'd made nests high up in the post-bushfire growth, and have been using small animal traps to stop them invading the roof spaces or sheds.

Small animal traps don't kill the animal that's lured in there. The trap door shuts as soon as they begin to nibble on the bait or step on the platform the bait sits on. Live traps seem by far the best way to deal with rodent problems. For every trap we put out, we caught a rat each night. Now we catch maybe one rat once a week, and a mouse every day or two. We check the traps every morning, so the animals don't have to stay there long - not much longer than it takes to eat the sliced apple, peanut butter and other bait we've left there. If you are going to condemn a rat or mouse it deserves a good last meal.

Trapped rats or mice can be disposed of in many ways, some humane and some not, though it is hard to think of a less humane way than poison baits, especially the ones that kill dogs, cats, eagles, goshawks, owls and anything else that might feel like a rat snack. Poison baits are ecocide. In an area like ours, where we have native rats and native mice as well as the introduced ones, the live traps also mean we can make sure we are only getting rid of the invaders, and giving the native species a better chance to survive. Do make sure though that you put the traps in a spot where the cat won't investigate it, or you may have an angry cat, or only put the traps out at night when cats should be indoors.

You may even decide not to kill the rat or mouse racing round the cage, but release them instead - preferably where they won't compete with native rats or mice. They would also make a good meal for a python, but the local pythons are hibernating in the cold.

As there are now a couple of small animal traps in the vegie garden too, the rat problem there should be solved in a few weeks.

But what if the culprit is Possum X? The traps we've put out are too small for a full grown ringtail possum, nor could I bring myself to relocate Possum X even if we captured him. This is his home, and possums will trek 20 kilometres or more to get back to their own territory, or can be killed by possums whose home turf they invade. The best anti-Possum X protection is probably to put fruit fly netting over the remaining parsley. A rat might crawl underneath the netting, but Possum X doesn't like handling fine mesh with his claws. The Seville orange is about to be pruned, the lower branches removed and a 'possum collar' placed on the trunk, wide enough to make it impossible for a possum to clamber over it.

From now on Possum X can stick to lemons.