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Oh, Deer: Mammals Use Magnetic Navigation, Too


You’re in a herd of deer when a mountain lion is seen approaching. What’s your safest retreat? Is it to run directly away? Is it to scatter in all directions? Or is it to run according to a predetermined orientation?

Scientists in Europe were intrigued that roe deer seem to orient in a north-south direction when grazing and when startled, so they decided to investigate. What they uncovered was a novel case of magnetic navigation in the animal kingdom. A Springer news item says:

Why do deer in a group, when startled, suddenly bolt away together and never collide with each other? It’s because these deer have an inner compass that allows them to follow a certain direction in order to make their escape. Their getaway is almost always along a north-south axis, thanks to their ability to sense the magnetic field, says Petr Obleser of the Czech University of Life Sciences in the Czech Republic. He and Hynek Burda of the University Duisburg-Essen, Germany, are lead authors of a study in Springer’s journal Behavioral Ecology and Sociobiology. [Emphasis added.]

This is a first for large mammals. Illustra Media has shown in Metamorphosis how butterflies use the magnetic field to get to Mexico. They showed in Flight how Arctic Terns navigate from pole to pole, and in Living Waters how salmon and sea turtles use magnetosensing in their long-distance migrations. Suggestions of magnetosensing had been reported for bats and mole rats, but large mammals like deer — who would have thought they use an inner compass for everyday safety?

One of the authors of the new paper, Dr. Hynek Burda of University of Duisburg-Essen, had contributed to a 2008 study published in PNAS that used Google Earth to find cattle and deer preferentially orienting on a north-south axis. BBC News commented on this finding, saying that this phenomenon “has apparently gone unnoticed by herdsmen and hunters for thousands of years.” At the time, the function of this orientation was unknown. One biologist remarked, “We need to think about some really fundamental things that this sensory ability provides in animals.”

Since then, Obleser and Burda monitored roe deer from April to August 2014. This species of deer tends to congregate in flat areas on agricultural land, making them easy to observe with binoculars. From 60 locations, they recorded data on the deer’s orientation at rest and when startled, monitoring 188 escape behaviors under a variety of conditions.

It was found that roe deer tend to align their bodies along the north-south axis when grazing. When startled, the animals generally fled away from observers. They did not merely make their getaway in the direction directly opposite to the approaching threat, but consistently did so north- or southwards. In fact, they seemed to actively avoid escaping westwards and eastwards, says Obleser. Wind direction or the position of the sun had no influence on the direction of their escape route.

The authors took note of the time of day, odor, wind and other factors; the magnetic orientation still prevailed. If a forest shelter was nearby, however, the herd could override the magnetic tendency and escape directly toward the shelter.

Is there a reason for this behavior? The north-south escape strategy was especially pronounced when the deer were congregated in groups. The authors feel the strategy helps the deer avoid collisions that would be more likely to occur if each animal took off in a random direction. Other possible functions include keeping group cohesion, guiding the deer get back to the previous grazing spot after the danger has subsided, and helping a mother find its fawn it left hiding in the grass.

For the strategy to work, an animal needs hardware and software programmed into its body and brain.

The researchers believe that the tendency of deer to align their bodies with respect to a north-south magnetic field line confirm that they are magnetosensitive and magnetoreceptive. This assists the animals to “read” and comprehend the mental maps they hold of the landscapes they occupy.

The authors did not speculate about the predator. What if it has a compass, too? What if it knows the strategy? Just speculating, it would seem the deer still have an advantage. The lion can’t run north and south at the same time, and would have no way of knowing in advance which direction the deer will choose to run. If they split directions, the deer in both groups would still have some safety in numbers. Most of the advantages would appear to accrue to the prey; the wide angle of 180 degrees “would maximize the distance between the animal and the danger,” the authors say.

The authors feel this pioneering study points to magnetosensing being common in mammals. It might even reside in us humans!

This is the first study of escape behavior in animals which considers also the role of absolute compass direction. Our findings confirm existence of magnetic alignment and thus magnetosensitivity in the roe deer and provide first evidence for its role as the so-called direction indicator in control of escape behavior in roe deer in particular and in mammals in general. Our results make the speculations more plausible that the magnetic alignment helps to organize and read the mental (cognitive) map of space. (In analogy, humans are more efficient in reading and commenting the map, if it is held in an accustomed direction: with north pointing upwards and if the person aligns with the map and with the visible landmarks.)

Many of us can probably relate to that: facing north and holding a map to try to find our way around when vacationing in an unfamiliar city. It’s just by “analogy” the authors say we might also have directional sensing. That deserves further study. Could a latent human ability for magnetosensing be trained? Could it augment orienteering by the sun and the stars? Fascinating thought. Maybe it will put compass makers out of business.

In the new open-access paper, the authors make no use of evolutionary theory to explain the coordinated escape strategy of roe deer with its requirements for magnetosensing equipment. There’s no mention of natural selection, fitness or phylogeny. Why would that be, if nothing in biology makes sense except in the light of evolution?

As design theorists, we can identify prerequisites for magnetically-based escape strategy in roe deer and other mammals:

  1. Construction of crystals of iron or protein that respond to the earth’s magnetic field.

  2. Neurons that can sense the response of the crystals.

  3. Brain receptors that can process the neural inputs and interpret them.

  4. Mental maps to place the interpretations in a regional context.

  5. Brain regions that can coordinate the magnetic data with other sensory data.

  6. Stored instincts to activate body systems to respond appropriately.

  7. Genes to encode the construction of all the above.

  8. Epigenetic systems to guide the development of the genetic information.

That’s a bigger parts list than in the classic mousetrap model of irreducible complexity. In fact, each item on the list could itself be called irreducibly complex.

Needless to say, magnetosensation presupposes a planet with a strong magnetic field. Of the rocky planets in our solar system, the Earth is unique in that regard; Mercury’s magnetic field is too weak, Venus has none, and Mars has only patches of magnetism. Many regard a strong magnetic field as a requirement for habitability, to act as a shield from stellar and cosmic radiation. It’s one of at least twenty improbable factors listed in The Privileged Planet that point to fine-tuning for habitability.

Intelligence is the only cause we know that is capable of arranging multiple independent factors for a function. The design inference strengthens with the improbability or specified complexity of each factor. With Darwinian evolution apparently of no use in explaining why roe deer know how to escape along a north-south axis, an inference to intelligent design beckons.

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