Animals Are Overengineered for Navigation
Animals outshine us in many ways, but one capability that should humble us is animal navigation. From spiders to mice, from birds to bees, the ability of animals to find their way around is truly astonishing, and James L. Gould of Princeton has raised our awareness of just how astonishing in a short article in Current Biology (March 23, 2004).1
He starts by explaining that navigation is more than just knowing which way you are pointed: “Nearly all animals move in an oriented way,” he says, “but navigation is something more: the directed movement toward a goal, as opposed to steering toward or away from, say, light or gravity. Navigation involves the neural processing of sensory inputs to determine a direction and perhaps distance.” As an example, he mentions how honeybees have to correct for the angle of the sun from morning to afternoon. This involves much more than orienting at a fixed angle. The bee has to use changing sensory information to maintain its internal map.
Gould mentions four stumbling blocks that prevented early investigators from appreciating the navigational abilities of animals. Researchers apparently assumed natural selection was sufficient to explain it all. He writes, “Several trends reflecting favorably on natural selection and poorly on human imagination characterized early studies of navigation.” The stumbling blocks investigators have had to get over include:
- Spectral Breadth: Early researchers assumed that animals were limited to our own human senses, but found out they can utilize a shopping list of cues invisible to us: ultraviolet light, infrared light, magnetic fields, electric fields, chemical pheromones, ultrasonic sounds and infrasonic sounds. We were “blind to our own blindness,” he says, “and there is no reason to assume the list is complete.”
- Complexity: Another “crippling tendency” of early investigators was “what navigation pioneer Donald Griffin called our innate ‘simplicity filter’: the desire to believe that animals do things in the least complex way possible.” Perhaps it was from our own pride of place, but according to Gould, we should be humbled:
Experience, however, tells us that animals whose lives depend on accurate navigation are uniformly overengineered. Not only do they frequently wring more information out of the cues that surround them than we can, or use more exotic or weaker cues than we find conceivable, they usually come equipped with alternative strategies – a series of backups between which they switch depending on which is providing the most reliable information.
- Recalibration: Early studies assumed animals just needed to learn a trick once (a phenomenon called imprinting, true in some short-lived animals.) Then they found out that some animals are able to recalibrate their instruments.
- Cognition: The school of psychology known as behaviorism, which denies instinct, “puts a ceiling on the maximum level of mental activity subject to legitimate investigation,” Gould chides. As a result of this bias, “most researchers deliberately ignored or denigrated the evidence for cognitive processing in navigating animals.” Not all animals exhibit cognitive intervention, Gould admits. But he then makes a very unDarwinian countercharge: “However, the obvious abilities of hunting spiders and honey bees to plan novel routes make it equally clear that phylogenetic distance to humans is no sure guide to the sophistication of a species’ orientation strategies.”
He gives an example: “One of the problems we inherited from behaviorism was the assumption that exploratory behavior must be rewarded. However, many species examine their surroundings voluntarily and, in fact, do so in detail.” (See example on mice below.)
Let’s look at just a few of the “believe it or not” examples Gould showcases in the article:
- Honeybees: Here is an example of switching inputs to get the most reliable information. “A honey bee, for instance, may set off for a goal using its time-compensated sun compass. When a cloud covers the sun, it may change to inferring the sun’s position from UV patterns in the sky and opt a minute later for a map-like strategy when it encounters a distinctive landmark. Lastly, it may ignore all of these cues as it gets close enough to its goal to detect the odors or visual cues provided by the flowers.”
- Mice: Here is an example of the “overengineering” Gould spoke of. Many field animals, like mice, have a strong drive to acquire information about their home range in advance of need, whether or not (as behaviorism would expect) they get an immediate reward. “Consider mice,” he says,
which not only gallop endlessly in running wheels, but actually prefer difficulty, such as square ‘wheels’, or wheels with barriers that must be jumped. Given a 430 meter long opaque three-dimensional maze of pipes, mice will work out the shortest path within three days, and without reward.
Navigation requires determining direction:
This can be achieved in two ways, and mice use both: they can use another landmark from their mental map and triangulate the direction of the goal, or they can use a landmark-independent compass like the earth’s magnetic field.
–and they never joined the boy scouts. What’s more, mice “can also navigate perfectly well, even if the habitat fails to provide useful landmarks. They will remember the direction and length of each leg of their outward journey and integrate the result when they are ready to return and set off home,” even without a trail of bread crumbs.
- Pigeons: Daytime provides celestial cues. “…once the relationship between azimuth and time of day is memorized,” Gould says, “the animal has a highly accurate compass.” We’ve all heard about the navigational feats of homing pigeons. They can discern ultraviolet (UV) light, which accentuates polarization patterns of scattered sunlight, for drawing their mental map, and add to it individual data points like “the average of a night’s attempts to escape from a cage, or some other directional measure.” The cues help them derive a mean vector, with direction pointing to the goal, and length representing scatter. When all the cues line up, they’ve got their bearing.
- Migratory birds: Birds who migrate between nesting grounds and wintering grounds can use sun cues, star cues, magnetic fields and landmarks to find their way. Not only that, they can recalibrate the cues for seasonal changes, latitude, and longitude. This requires recalibration:
To infer the pole point through broken clouds, the animal’s map of the sky must be updated. And as the migrants move south in the fall, new sets of stars in the southern sky appear, while northern stars slip below the horizon. Clearly, changes in both season and latitude make relearning the stars essential. Only fairly recently has this constant updating been demonstrated.”
In fact, for unknown reasons, “nocturnal migrants calibrate their star pole to the magnetic pole. Instead of simply taking the pole point as the true guide, the birds constantly recalibrate the magnetic pole to the geographic pole, and then the geographic pole to the magnetic pole.”
- Latitude: Fish, turtles, lobsters, and birds all determine their latitude by the angle of the magnetic field. “In theory,” Gould says, “animals could obtain the same information from the sun’s noon elevation, but I know of no case in which this traditional human solution is used.” The critters must know something we don’t.
- Longitude: house wrens, pigeons, sharks, salmon, sea turtles and spiny lobsters have all conquered a navigational problem that “bedeviled human navigators until very recently,” the problem of determining longitude. How do they know distance east from west? How can house wrens find their way back, unerringly, to the same nest box after a long flight at a different time of year from when they left? “The apparent answer to this conundrum is provided by a map sense,” Gould answers. The earth’s magnetic field provides both a map and a compass – just the tools you would need if released in an unfamiliar area.
- Pigeons again: When homing pigeons circle around before heading home, they are reading the local map of magnetic gradients and extrapolating it from the one they learned at home. How do pigeons detect the earth’s magnetic field? They actually have magnetite grains in their heads, in the ethymoid sinus. Experiments have shown that magnetic anomalies make the birds disoriented. A sharp pulse of magnetism can severely impair their compass. But remagnetize the organ by putting it into a magnetic field, and the bird is back to normal
Gould ends by pointing out two of the biggest challenges to researchers studying animal navigation: (1) the nature of the map sense, and (2) the issue of recalibration, which is still puzzling. “The interaction of these specific learning programs,” he promises, “doubtlessly holds many magnificent secrets.”
1James L. Gould, “Magazine: Animal Navigation,” Current BiologyVol 14, R221-R224, 23 March 2004.
Wow. Thank you, Dr. Gould. This article contains absolutely no hints about how such abilities could have evolved; in fact, it contains a couple of off-handed swipes at the notion that natural selection could explain them, or that skill correlates with “phylogenetic distance.” This is surprising, considering that James L. Gould is a member of the Department of Ecology and Evolutionary Biology at Princeton. It could just as well have been written by Dr. Gary Parker at the Institute for Creation Research. It’s a wonder the editors of Current Biology let this one get by without the required pinch of incense to Emperor Charlie.
Notice that these highly refined and accurate navigational skills are possessed by a wide variety of animals: mammals (e.g., mice), insects (e.g., Monarch butterflies — see 05/23/2003 and 07/09/2002 headlines), birds (e.g., Pacific golden plovers, which can navigate over open sea to the Hawaiian islands without having ever seen them), reptiles (e.g., sea turtles), crustaceans (e.g., lobsters), and fish (e.g., salmon). Skill does not scale with presumed evolutionary advancement: for instance, the spiny lobster wins the prize for magnetic mapping (see 01/06/2003 headline). Even bacteria and plants can orient themselves with respect to environmental cues. Humans were given ability to build tools that can navigate a spacecraft to Saturn, but we must surely stand in awe of a God who could put technology that outperforms NASA into a bird brain. This article goes to show that the film “Incredible Creatures That Defy Evolution” could become an infinite series. Click your way back through the “Amazing” chain links for many more examples.