Exposing the badger's social life By Mark Ward

Technology correspondent, BBC News Published duration 15 June 2011

image caption Badgers live in large social groups but not much is known about their lives underground

The social life of the badger is gradually being exposed thanks to some smart technology.

Many animals are tracked above ground but until recently what goes on inside their setts and burrows has been largely hidden.

Now a project to track them using magnetic fields and sensor collars is giving scientists a unique look at these elusive creatures.

"Detailed information about badger locations underground is currently impossible to obtain with existing technology," said Dr Andrew Markham, a computer scientist at the University of Oxford who along with Principal Investigators Dr Niki Trigoni and Professor David Macdonald and zoologist Dr Stephen Ellwood designed the underground badger tracking system.

The limits of direct observation techniques, such as putting cameras inside setts, lairs and warrens, meant a novel approach was needed.

Hidden lives

"With a camera you can only monitor a small area, typically one chamber at a time," explained Dr Markham. "To monitor a whole sett would be very difficult.

"And it is quite challenging to identify badgers when they are underground."

The research team was keen to see if the process could be automated, thereby minimising human-badger interaction.

The underground tracking system was designed as part of the EPSRC funded WildSensing project, a collaboration between Dr Cecilia Mascolo at the University of Cambridge, and Professor David Macdonald and Dr Trigoni at the University of Oxford. It employs low frequency magnetic fields of different strengths to localize animals underground.

These were chosen because, unlike radio waves, they can easily penetrate the soil and reach the chambers, even in complex, well established setts.

Antennas emitting magnetic fields with different patterns are placed on the forest floor above the sett being studied. Special collars have been prepared for the badgers which contain sensors that log the orientations of the different fields along three axis.

"We know where we have placed the antenna above the surface," said Dr Markham, "the collar picks up signal strength from the intensity."

Data about the orientation of the separate fields is recorded about 250,000 times a day on a memory chip on the collar.

When a badger emerges above ground, the data is downloaded to a micro-SD card sitting on a local base station, ready for the researchers to pick up and take for analysis.

"It's like back-to-front, underground GPS," said Dr Markham.

Badger net

image caption The badgers in Wytham Woods have been under scrutiny for years

Limited trials with the system, monitoring four badgers for a month, gathered 7 million readings.

The trials recorded how active the animals were when underground and started the process of mapping their sett.

A longer project is planned to start later in 2011. This will see collars put on more badgers, with an expansion of the area being monitored.

One of the team's main objectives is to learn more about the animal's social lives.

"A lot of work has been done on badger society and they seem to have a strong social system where they live in a central burrow but forage individually," said Dr Markham.

Up to 20 badgers can live in the same sett which can be spread across an area 30m by 20m, he said.

The badgers being studied are in Wytham Woods near Oxford. They have been monitored one way or another since 1987 by members of the Wildlife Conservation Research Unit in Oxford University's department of zoology.

"We want to see how different they are above and below ground and how they interact with each other," said Dr Markham. "Do they always sleep in the same burrow or do they move from sleeping chamber to sleeping chamber?"

The longer trial will also refine the technology to make it more accurate, ensure it survives being attached to a badger for long periods and establish if it can be quickly deployed in new places.