Keeping electronic tags on our roaming wildlife

Weevil and tracker
Image caption Each tracker is the size of a large grain of rice

There is a surprising amount we don't know about all sorts of animals, birds and even insects. But these gaps in our knowledge are being filled by ever advancing tracking technology.

Slap a tiny tracking gizmo on your creature of choice and it will happily reveal everything about its movements.

Over the years, we have tracked everything from sooty terns on the Ascension Islands to adders in the Wyre Forest using a variety of different approaches but now, we bring you the smallest living thing we've tracked, the vine weevil.

Just 1cm (0.4inch) long, the vine weevil is a real pest for gardeners and farmers alike so the researchers at Harper Adams University College are trying out various methods to control them. That means they have to track them first.

To do this they glue tiny trackers to the backs of the weevils. The weevils themselves are then released into a crop of strawberry plants and their every movement monitored. The aim is to see how far the insects roam and learn more about the potential for pest control using a natural pathogen.

Weevils scanned

Each tracker is the size of a large grain of rice and is a fifth of the weight of an adult weevil. But in extensive tests it seems the added weight doesn't stop the weevils moving about as normal. I watched one weevil crawl across the underside of a leaf quite happily with a tracker glued to its back.

In this case the tracking technology used on the weevils is passive. So the tiny trackers do not send out a constant signal, rather they allow a handheld scanner used by researchers to locate and more importantly identify the tiny weevils amongst the plants and so work out how far they are moving.

But that is just one way tracking can work.

The sooty terns being tracked by the University of Birmingham are tagged with technology that gathers the location of the birds for a prolonged period. All the researchers have to do then is recapture the individual birds and their trackers and download the data. (I say "all", as you can imagine it is not an easy task.)

At the top end of the scale you have trackers that send out a real time signal that can be followed by researchers. This sort of technology obviously needs a bit more battery power so the tracking devices turn out to be a bit larger too.

But the history and general technological drift is for tracking devices to become smaller, more powerful and cheaper and so help us learn much more about wildlife.

That said, snakes are still likely to hold onto some of their secrets since they will eventually shed their skin and any attached transmitter. Sneaky.