That they have something in common; dogs prefer to do their business while in a body-alignment along the magnetic north-south axis - but only during periods of calm magnetic field conditions.
At least they found something. Prior to the discovery, they had to have been frustrated that, in contrast to grazing cows, hunting foxes and landing waterfowl, dogs showed no clear preference for a particular body alignment while doing number one or number two.
Dr. Vlastimil Hart and Prof. Dr. Hynek Burda ran statistical analyses of the more than 7,000 observations, recorded together with the currently prevailing environmental conditions of the location, time of day and other important parameters such as the familiarity of the terrain for each dog. Only when they sorted the collected data according to the small variations of the geomagnetic field during the period of data collection did they strike brown gold.
The irregular, tiny changes in the intensity and declination of the magnetic field lines are recorded by magnetic observatories and freely accessible online and when they combined that with their categorized data the picture became more clear. After taking into account all other factors the researchers concluded they found clear indication of a magnetic sense in our four-legged friends.
To many dog owners who recognize the navigation abilities of their protégés, the findings might not come as a surprise – people often believe their pets have "supernatural" abilities, although it is not clear to science what the dogs might use their magnetic sense for.
Citation: Vlastimil Hart, Petra Nováková, Erich Pascal Malkemper, Sabine Begall, Vladimír Hanzal, et al, 'Dogs are sensitive to small variations of the Earth's magnetic field', Frontiers in Zoology, 2013, 10:80 doi:10.1186/1742-9994-10-80, 27 December 2013