21 January 2014 Last updated at 00:06

Urban fox's record-breaking country walk

By Ella Davies Reporter, BBC Nature

A fox has been tracked more than 40 miles (70km) away from its home range, breaking the previous British record.

The fox was named Fleet by University of Brighton researchers and fitted with a satellite tagged collar.

Scientists were surprised to record Fleet walking a total of 195 miles (315km) as he headed into the Sussex countryside from his home in the city.

Naturalist Chris Packham joined the team to retrace the animal's path for BBC Two series Winterwatch.

"Foxes will disperse for lots of different reasons, mainly to find some space to form their own territories," explained Dr Dawn Scott who led the study.

"The movement away from an area where they're born to another area is usually due to competition within the group."

A team of researchers has been studying the movements of urban foxes living in Brighton to understand more about how their population dynamics and movements.

Through their records and observations by members of the public, Dr Scott's team learned that Fleet was pushed out of the group as the dominant male by his son, causing him to look for territory elsewhere.

"The previous furthest distance recorded, which was in Wales, was 52km [32 miles]," said Dr Scott.

A straight line measurement from Fleet's home to his furthest distance was 40 miles (70km) as he took a roundabout route through the Sussex countryside.

The tag in his collar provided the researchers with a GPS location every 30 minutes. Analysis of this data provided the team with a detailed picture of Fleet's movements.

Between 9 December 2013 and 2 January 2014, Fleet walked a total of 195 miles (315km) around Sussex.

He headed north from Brighton through the South Downs National Park to commuter town Hassocks and then took a rambling route east to Rye.

Dr Scott explained that he followed roads, train lines and rivers but where the wet weather had flooded land he was cautious to skirt around the water.

During the day, he rested in gardens or on railway sidings before journeying through the countryside at night.

"We know from other studies in Europe and in the [United] States that foxes can travel very far... this is the furthest record in this country," said Dr Scott.

The team expected Fleet to stop but he carried on in what Dr Scott described as "very unusual behaviour".

According to their records, Fleet was born in Brighton and his home range was a few neighbouring streets. He was fed by a member of the public in their garden and raised cubs in the area.

"We know they move between urban and rural [environments] but that transition from this very urbanised fox to then going across country for a long distance is not what we would expect," said Dr Scott.

"We think that his son has pushed him out and that pressure has caused him to leave and try to find somewhere else."

His early movements were across Brighton but with about 20 foxes per kilometre squared in the city, Dr Scott explained that finding a new territory would have been difficult.

Fleet's whereabouts now are unknown after researchers lost his collar's signal early in the New Year.

However, the data they were able to collect will help scientists to understand how foxes move around their environment and what factors affect this, such as the availability of food and mates and any obstacles including flood waters and human developments.

"It helps us understand the divide that people perceive between urban and rural foxes - that actually the populations are connected and they do move between the two," Dr Scott said.

She added that the results confirm the animals will move out to colonise other areas when populations in urban areas reach their maximum densities.

The fortunes of Fleet and other foxes tagged in the study feature in Winterwatch which continues on BBC Two at 2000 GMT, Tuesday 22 January.