Dogs can sense Earth's magnetic field and use it to go to the toilet.

Dogs have an internal compass that makes them poop on the magnetic north-south axis, researchers have found.

Experts analysed the body orientation of 70 unleashed dogs of different breeds while doing their business in the open country.

The researchers, of the Czech University of Life Sciences in Prague, were looking to find out if dogs had a preference for body alignment when going to the toilet.

Unlike grazing cows, hunting foxed and landing waterfowls, dogs had no clear preference of body alignment.

However, after looking at their 7,000 observations, they noticed one striking similarity – all the dogs preferred a body-alignment along the magnetic north-south axis, but only during periods of calm magnetic field conditions.

They came to this conclusion by collecting data and looking at the small variations of geomagnetic field during that period. Tiny and irregular changes in the intensity and declination of the filed were found through freely accessible websites that record magnetic observations.

Vlastimil Hart and Hynek Burda said after taking into account all other environmental factors, such as location, time of day and familiarity of the terrain, the dogs showed a clear indication of magnetic sense.

While they have now established dogs have a sense of the planet's magnetic field, the researchers do not know what its purpose is.

The authors note that the reason for this sense could be of huge value as it is an area of research that is not well understood; a wealth of evidence shows migratory birds and other animals have an internal sensor.