MAMMALS can be difficult things to survey for and trying to establish the size of the population is even harder.

This topic has been in the news recently, unfortunately for all the wrong reasons as it relates to the badger cull currently underway in south west England. I heard a recent radio interview with someone who was heavily involved in the field trial held several years ago that established that culling did not work as a method of reducing Tb in cattle.

He questioned why, if he knew the numbers of badgers per square kilometre in that region of the country, the present Government does not.

Who knows the answer, but it highlights the uncertainty around mammal populations.

Durham Wildlife Trust faces the same problem in trying to get information on population size.

We are particularly interested in otters as we have done a considerable amount of conservation work for that species. We know that 20 years ago the great majority of watercourses in the county had no signs of otters and that now they do have otter signs – droppings are easy to find.

But, if you don’t know how many otters there are and and have a way of regularly recounting, it is difficult to establish how the species is doing.

Is there a problem, a disease or pollutant that is killing otters perhaps, that needs to be addressed?

The Trust is pinning its hopes on DNA. Collecting droppings and recording where otters have been, then doing DNA analysis to identify individuals and the overall population.

It’s early days, but we’re hopeful it can work.