Free You Are Here by Colin Ellard

daunting task even more difficult.
    Despite the finding that most victims are eventually discovered within a mile or two of their point of disappearance, the amount of ground that is covered by a circle of one or two miles’ radius, especially if the terrain is complex, is such that it may take hundreds of searchers many days to complete a comprehensive search.
    Elaborate mathematical formulas, based on the nature of the person who has become lost (age, background, reason for being in wilderness) and the type of terrain (changes in altitude, bodies of water), are used to constrain an intensive search to the areas most likely to yield success. Nevertheless, the best chance for survival of a lost person comes at the initial “hasty search,” in which a few fit, experienced searchers are dispatched in the area immediately surrounding the point of last contact. If the hasty search fails, the odds against survival steepen dramatically. Unless conditions are very mild, those lost in the wilderness for more than 24 hours are in real peril of losing everything.
WHY ANTS DON’T GET LOST
    Rüdiger Wehner has spent most of his professional life wandering the Sahara Desert in search of ants. One ant in particular, the
Cataglyphis fortis
, a bit less than a centimeter in length and weighing about 10 milligrams, has occupied most of Wehner’s scientific curiosity for a career spanning many decades. 4 It isn’t unusual for scientists to devote staggering amounts of time and attention to seemingly arcane subjects, but there are few cases where this attention has been as richly rewarded as it has been in Wehner’s case.
    Desert ants are scavengers searching for insects that have succumbed to the rigors of life in a harsh environment. When such victims are found, the ants collect the carcasses and then return to the nest. Though this pattern of behavior sounds simple enough, Wehner noticed something remarkable about the movements of the ant. Ants that are looking for food meander in seemingly random and circuitous paths that can carry them far from their nests (up to about 200 meters). Wehner’s surprising discovery was that, on their return to the nest with the food, the ants strike out on a direct, straight-line path for the nest.
    Unlike wandering human bush travelers, these ants maintain a seemingly iron grip on their location. How do they do it? One possibility is that the nest emits some kind of signal, such as a smell, that the ants can easily pinpoint. It is well known that ants sometimes follow each other’s paths using odor trails, so this seems like an obvious possibility. But using a simple but clever technique, Wehner proved that the ants were not following a scent. When foraging ants reached food sources in the desert, he picked up the ants and moved them to a new location. The ants responded to this displacement by running immediately in a direct course to where the nest
would
have been located if they had not been displaced. This proved that the ants were keeping track of the location of the nest by means of a continually updated estimate of the location and distance to it. The ability to keep such a careful record of one’s movements, and to extract an estimate of one’s current position from this record, is referred to as path integration. Path integration is one of the chief navigational tools possessed by many different types of animals, such as Wehner’s ants, which so excel at it that they can be considered to possess a biological version of Ariadne’s thread.
    Having shown that ants were making use of path integration rather than a signal that was continuously emitted by the nest, Wehner set out to determine how their knowledge of their own position was established and maintained. There are two separate requirements for the ant: to keep track of the direction of the nest, and to keep track of its own distance from the nest.
    We saw earlier that the vestibular system, at least theoretically, can be used to