In theory, nothing new, the size of the territory of most animals would be linked to its cognitive abilities, if only to remember its limits.

But this remains difficult to prove "because they may have other reasons for limiting themselves to a small territory", for example if they find enough resources there, explains evolutionary biologist Robert Heathcote, of the University of Bristol.

To find out for sure, a team from the British University of Exeter, and Dutch and Israeli universities, conducted a life-size experiment in a forest in Devon, in the south-west of England.

Before being released there, 126 captive-bred pheasants underwent three tests over a few weeks to gauge their cognitive abilities, and in particular two types of spatial memory.

So-called working memory, which is short-term, allows an individual to remember that if he has found an earthworm in one place, there is no point in going back there five minutes later.

The second, called spatial reference memory, of longer term, allows the pheasant to remember a route even after several days.

The study published in Nature Ecology & Evolution establishes that it is this spatial reference memory that dictates the size of a pheasant's territory.

This territory, "which is the area where he spends most of his time, is also the one he knows best", according to Mr. Heathcote.

Its extent is less than one hundred meters long and up to one square kilometer.

A red fox sitting under a tree, in Greenwich Park, London, May 14, 2020 © Glyn KIRK / AFP/Archives

Territories of death

In the space of six months, the researchers recorded the predation of 45 pheasants, all under the fangs of red foxes.

Each bird was equipped with a tiny beacon of about ten grams, designed by Israeli researchers, allowing its location almost in real time.

"This made it possible to know when the trajectory of the beacon was no longer that of the pheasant, but had become that of the fox", explains with a smile Mr. Heathcote to AFP.

The cautious ambulation of the bird changed, once seized in the jaws of its predator, into a rectilinear, rapid and distant trajectory of the fox, towards a place where it could quietly devour its prey.

The pheasants most likely to end their lives this way were those with poor spatial reference memory.

Their end was also much more likely at the borders of their territory.

"Knowing an area helps the pheasant stay alive," and vice versa, according to Dr Joah Madden, from the University of Exeter, quoted in a statement.

Even in fox-favorite hunting grounds, which Mr Heathcote has dubbed 'territories of the dead', a pheasant's chances of survival depend primarily on its experience of the terrain.

The most skilled do not avoid the death zone, but "in time they can learn what are the quickest and safest ways to evade an attack".

A pheasant flaps its wings in a field of buttercups, near Goring, England, May 9, 2020 © Adrian DENNIS / AFP

For the pheasants that escape the fangs, there remains the risk of ending up riddled with lead by man.

© 2023 AFP