20 July 2011 Last updated at 09:18

Female urban foxes are top dogs, study shows

By Mark Kinver Environment reporter, BBC News

Dominant females force male cubs to leave the family group in order to reduce the risk of inbreeding

• BBC Nature - Red fox fact file

Mothers in urban fox populations decide which cubs get to stay and which ones must leave the group and find a new territory, a study has found.

Based on a 33-year study of foxes and DNA data, UK researchers said dominant mothers played a key role in shaping the group dynamics of the mammals.

They added that it was the first study to identify the importance of juvenile dispersal among social mammals.

The findings have been published in the journal Plos One.

Co-author Helen Whiteside from the University of Bristol said that the findings came from a project that had been tracking radio-collared urban foxes in the city for more than three decades.

"I have been working on my PhD for the past three years and I have got to know these foxes very well," she told BBC News.

"As I was studying dispersal, I noticed this pattern emerging, so when we got the genetic data it was quite exciting to actually see it."

Miss Whiteside explained that establishing foxes' family trees was difficult, but combining data collected in the field with DNA paternity testing allowed the team to work out the canids' family trees.

Family matters

From this data, the team was able to identify a dispersal strategy based on the male cubs' genetic relationship with the dominant female.

This strategy appears to be an important factor in terms of the long-term well-being of the family unit, Miss Whiteside explained.

"Certainly for the males and their mother, it seems to be an out-breeding mechanism, which stops them breeding with their mothers - which is a good thing," she said.

"It does seem to be very important for mothers and sons, but from a female point of view, for daughters and fathers, it does not seem to be that important.

"Dominant males (on average) tend to move up to 2.7 territories away in the search for mates, so even if his daughter moves away there is always that risk of inbreeding.

"There is something else going on there but we do not know what at this stage."

She said that it was not yet possible to say whether the behaviour was unique to urban foxes, or whether the same thing happened within rural populations.

"Unfortunately, there is not such a good database on rural foxes. It is likely that the rural population is mimicking what the urban fox is doing but we do not have any data on this."

Miss Whiteside added that the control of cub dispersal appeared to be much more important for female foxes than males.

"These findings have important implications for the evolution of dispersal and group living in social mammals, and provide a unique opportunity to advance our understanding of the key biological process of dispersal."