Tag Archives: navigation

How dogs sense the Earth’s magnetic field

The perception of the Earth’s magnetic field is used by many animal species for orientation and navigation. A magnetic sense is found in some insects, fish, reptiles, birds and mammals, whereas humans do not appear to be able to perceive the Earth’s magnetic field.

The magnetic sense in migratory birds has been studied in considerable detail: unlike a boy scout’s compass, which shows the compass direction, a bird’s compass recognizes the inclination of the magnetic field lines relative to the Earth’s surface. Surprisingly, this inclination compass in birds is linked to the visual system as the magnetic field activates the light-sensitive molecule cryptochrome 1a in the retina of the bird’s eye. Cryptochrome 1a is located in the blue- to UV-sensitive cone photoreceptors and only reacts to the magnetic field if it is simultaneously excited by light.

dogs and magnetic field

Dogs and some primates can sense the earth magnetic field with the help of molecules in their eyes. © L. Peichl

Cryptochrome-distribution among mammals

Together with colleagues from the Ludwig-Maximilians-University Munich, the Goethe University Frankfurt, and the Universities of Duisburg-Essen and Göttingen, Christine Nießner and Leo Peichl from the Max Planck Institute for Brain Research in Frankfurt investigated the presence of cryptochrome 1 in the retinas of 90 species of mammal. Mammalian cryptochrome 1 is the equivalent of bird cryptochrome 1a. With the help of antibodies against the light-activated form of the molecule, the scientists found cryptochrome 1 only in a few species from the carnivore and primate groups.

As is the case in birds, it is found in the blue-sensitive cones in these animals. The molecule is present in dog-like carnivores such as dogs, wolves, bears, foxes and badgers, but is not found in cat-like carnivores such as cats, lions and tigers.

The active cryptochrome 1 is found in the light-sensitive outer segments of the cone cells. It is therefore unlikely that it controls the animals’ circadian rhythms from there, as this control occurs in the cell nucleus which is located a considerable distance away. It is also unlikely that cryptochrome 1 acts as an additional visual pigment for colour perception. The researchers thus suspect that some mammals may use the cryptochrome 1 to perceive the Earth’s magnetic field. In evolutionary terms, the blue cones in mammals correspond to the blue- to UV-sensitive cones in birds. It is therefore entirely possible that the cryptochrome 1 in mammals has a comparable function.

Observations of foxes, dogs and even humans actually indicate that they can perceive the Earth’s magnetic field. For example, foxes are more successful at catching mice when they pounce on them in a north-east direction. “Nevertheless, we were very surprised to find active cryptochrome 1 in the cone cells of only two mammalian groups, as species whose cones do not contain active cryptochrome 1, for example some rodents and bats, also react to the magnetic field,” says Christine Nießner.

Many fundamental questions remain open in the research on the magnetic sense. Future studies will have to reveal whether the cryptochrome 1 in the blue cones is also part of a magnetic sense in mammals or whether it fulfils other tasks in the retina.

Source:  Max-Planck Institute for Brain Research media release

Female dogs are better navigators

New data from Dognition shows that female dogs tend to be more flexible navigators than males. This is the opposite of trends in humans, and gives us important insight into how dogs see the world.

Map reading dog

In the navigation game, part of the monthly Dognition subscription, owners hid food inside two bowls, and taught their dog that the treat was always on one side, for example always on the left. Then the owner brought their dog around to the opposite side and recorded which bowl their dog chose.

Brain

Female dogs were more likely to use an allocentric, or a landmark based strategy. They used objects in the room to figure out which bowl to choose. For instance, in the beginning, perhaps the bowl with the treats was near a door, or a lamp. When the females were brought around to the opposite side, they still looked for those landmarks, which means no matter which way they were oriented, they would always go back to the bowl they learned was ‘correct’ in the beginning.

In people, this is called forming a mental map, or using a ‘bird’s eye’ view. Using allocentric navigation means the dogs were mostly relying on their hippocampus, a part of the brain that mediates spatial awareness and memory. This strategy is particularly effective in large and unfamiliar environments, and is the more flexible of the two strategies. Not surprisingly, humans who rely on environmental navigation are good at reading maps.

Male dogs were more likely to be egocentric navigators. They learned the association by thinking ‘the treat is on my right’. When owners brought the dogs around to the opposite side, these dogs chose the bowl on their right, which was the opposite bowl that they had chosen before. By using this strategy, the dogs were mostly relying on their basal ganglia, a part of the brain that mediates motor skills.

Before there were maps or navigational instruments, Pacific islanders used egocentric navigation for long sea voyages. They used the position of the stars in relation to themselves, (e.g. to get to this island, the Milky Way should be on my right). People who rely on egocentric navigation tend to make good cinematographers – they have a special talent for allowing others to see the world as they do.

The results are exactly the opposite as in humans, where men are usually allocentric navigators and women are egocentric navigators. Perhaps male dogs just need to get better at asking for directions.

Source:  Dognition news