‘Little blighters’ that drive me barking mad


Two years ago, we transplanted 20 cherry saplings cloned from an ancient and historical tree (see Old Nic’s Notebook; May, 1, 2003) here where I live in Kurohime, Nagano Prefecture. We then raised the saplings with loving care in our own little nursery for six years, before replanting them at the entranceway to our Afan Woodland Trust.

All the trees survived the first winter and thrived through the following spring, summer and autumn. Then, as the snow melted, we discovered to our horror that all 20 had been ravaged by mice, which had chewed off all the bark at the bottom of the trees and, in some cases, had eaten all the roots as well. These trees were 2 meters and more high, and without the mice they had an excellent chance of growing to maturity and giving a lot of people pleasure when they bloomed — and nice little black cherries for the birds.

Ever since we started planting in the woods, we’ve had trouble with mice, especially with cherry saplings, maples and oaks. A friend tried to console me the other day by reminding me that in a natural forest, out of thousands of saplings only one or two would survive to become mature trees. That is true, but it’s still galling as we strive to upgrade the trust’s ravaged, neglected woodland that, before we took over, had lost a lot of its plants because of choking, crowding and disease.

In some cases we’ve surrounded the roots and bottoms of saplings with fine mesh, and although that keeps the mice off, the wire is not good for the roots. Oh well, we’ll just have to keep going! As it is, there are several 16-year-old cherry trees around our ponds that need to be thinned a bit, so we’ll replant some of them near the entranceway. Mice don’t attack the bigger trees.

The biggest tree-chewer in our woods is the little aka nezumi (wood mouse), which burrows and hoards its food underground. In snow country, these mice make a maze of interlocking half-tunnels in the ground, the top half being snow. Its favorite foods are acorns and walnuts, of which we have lots — so why the little blighters need to chew young tree roots and bark I just don’t know, unless it’s just for fun or a bit of a change.

Like most mice, though, these wood mice will go for a lot of things, and Mr. Matsuki, our woodsman who regularly gets them in his shed, often catches them with a nasty old-fashioned spring trap, baited with peanut butter.

Apart from Mr. Matsuki and his traps, the wood mouse’s major enemies are our owls, especially when they’re raising young. This year we’ve set a miniature camera in the owl’s nest box to hopefully improve our data on their rodent body-count. Previously, we waited until the young left the nest, then cleaned it out and counted the skulls in the regurgitated owl pellets.

Along with owls, snakes are great mouse-controllers. However, we see far fewer snakes around here now than, say, 20 years ago. Both Mr. Matsuki and I believe a major reason for this is the increase in the number of concrete culverts.

A waterway separates our woods and the national forest higher up the hillside, and most of this channel was made more than 100 years ago out of clay reinforced in places with rocks. This waterway diverts a stream to deliver water to local paddy fields, and the old part is home to char, firefly, caddis and dragonfly larvae. A snake would have no problem crossing it. Part of the waterway has, though, been relined with smooth concrete, which char cannot swim up and in which other water creatures cannot live.

One day I saw a snake, about 120 cm long, being washed down this culvert, even though there was only a couple of centimeters of water running in it. The snake was writhing helplessly, unable to get out. As I’ve said before, although these concreted waterways kill a lot of young birds and small animals, more and more of them are replacing natural streams and eco-friendly waterways all over Japan. I’m sure that there’s a concrete-culvert madman somewhere high in the government with an evil plot to deplete the land of snakes, encourage a wood mouse population explosion — and drive Mr. Matsuki and me batty with frustration when the damn mice chew our young trees.

Anyway, whether you like snakes or not, they’re great for controlling mouse numbers, and I really wish we had more.

Mice have pestered and plagued me in camps and field headquarters all over the world. In my Simien Mountain National Park house in Ethiopia (ONN, Aug. 25, 2002), not only would mice nibble on saddlery and any stores, but one even chewed through the hose that went through the wall from a gas stove to a cylinder outside. Damn nearly blew the kitchen up!

This year I’m going to reconstruct a mouse trap I used in a cabin in the woods of northern Canada. There, I cut the top off one of those large, square tin cans used for oil. Then I took a small round soup can and ran a wire through it, end to end. Next I strung the wire and can lengthwise across the top of the square tin so the can in the middle would revolve, and smeared it with peanut butter. After also dabbing a little peanut butter on a sloping wooden gangway that I propped up against the rim of the can — and pouring 15 cm of water into the tin — I left the trap on the kitchen floor and awaited its first victim.

I didn’t have to wait long. It seemed like mice were lining up to climb the sloping gangway then jump onto the can smeared in peanut butter. Unfortunately for them, this would then roll round and drop them in the water. One night, we even managed a rodent body count of 16 in the bottom of the tin! The only drawback was that our cook was kept awake by squeaking, splashing mice, scrabbling at the smooth metal walls until they succumbed.

Mind you, there were a lot of mice around. One got into my rucksack, which I took home to Winnipeg with me. It lived in the house for a month, and we could not discover its hiding place. Then, when I finally got around to cleaning out the bag on the vacuum cleaner, there it was inside. It had made a nest in all the hair and fluff, no doubt gorging itself on the food debris dropped by three kids.

Anyway folks, Mr. Matsuki has plans too, so I’ll let you patient readers know who finally designed the better mouse trap.