Dogs do some weird and amazing things, but one habit researchers have discovered is that dogs, who can sense the Earth's magnetic field, prefer to poop while aligned with the north-south axis of the Earth's magnetic field.
That's the conclusion of an exhaustive study conducted by a team of German and Czech researchers led by a zoologist from Germany’s University of Duisburg-Essen. The team spent two years watching 70 dogs while they defecated and urinated thousands of times then compared the dogs' behavior and orientation with the geomagnetic conditions prevailing at the time.
But they do it only when the magnetic field is calm. Magnetoreception (also Magnetoception) is a sense which allows an organism to detect a magnetic field to perceive direction, altitude or location. A lot of animals have it and use it for navigation. It is present in bacteria, arthropods, molluscs and members of some vertebrates, but not humans although there is a chemical in the eye which could serve this function.
It is believed that red foxes use magnetoreception when hunting small rodents. When foxes perform their high-jumps onto small prey like mice and voles, they tend to jump in a north-eastern direction with successful attacks most generally facing north.
Resting and grazing cattle, as well as some deer, tend to align their body axes in the geomagnetic north-south direction. Body orientation on observed animals was random on pastures under or near power lines which apparently disturbs their inner compass.
That's why the scientists conducted their dog poop study; they were investigating magnetoreception in mammals. It's not clear what else dogs might use their magnetic sense for.
They studied 70 dogs from different breeds as they (they dogs) relieved themselves. At first there was no clear pattern of dogs preferring any particular orientation, but when they (the researchers) took into account the natural variations of Earth’s magnetic field and factors like the time of the day, the position of the sun, and wind direction, the secret was revealed. Dogs prefer alignment along the magnetic north-south axis, but only in periods of calm magnetic field conditions.
I guess this information could be of practical value to people lost in the woods with their dog. Instead of finding north by looking for moss on the north side of a tree, just watch your dog.
The idea that moss grows on the north side of trees is an old one and makes some sense. The north side gets less sunlight so it tends to be cooler, damper and have more shade which are good conditions for moss.
But, as for it growing on the north side of trees, it depends on where you live. If you live in the southern hemisphere, it tends to grow on the south side. Even then, it's not always so simple because lots of things can create the shady conditions that moss prefers.
The most reliable method of knowing which way is north is to use a compass. But then which north? Magnetic or true? What if you're using a compass in the Southern Hemisphere?