It’s an evolutionary arms-race out there!

There’s always been a natural appeal to understanding the battle between two enemies.  As one adapts, so must the other.

Police officers use radar guns to capture their unsuspecting prey.  Photo courtesy of rcgov.org.

Police officers use radar guns to capture their unsuspecting prey.  Photo courtesy of rcgov.org.

Consider the sit-and-wait predator in his shiny patrol car waiting behind a freeway overpass to catch speeders on the highway.  As drivers became more aware of police, they had to employ radar guns to catch their prey.  Soon drivers started purchasing radar detectors, until the discovery of X, K, and then Ka band radars.  The radar detectors were soon modified to handle each new frequency, but in response some jurisdictions passed laws banning the detectors.  To catch those using radar detectors, police started using VG-2 detector hunters (radar detector detectors) to identify motorists with illegal detectors.  Consequently radar detectors soon started being sold that could jam the detector hunters.  Lidar detectors, a form of radar relying on remote sensing with lasers, were soon employed by police.  This gave little time for drivers to react and reduce their speed.  In response, the newest detectors not only detect Lidar, but jam the frequency providing several precious seconds to slow down and avoid capture. 

Arms-races, like the one described above, are happening throughout the natural world through an evolution of biological traits.  These races normally involve a highly specialized predator and an equally specialized prey, both of which have been locked in a battle of survival for millennia responding to one another’s adaptations as they arise.

For example, bats evolved the ability to detect their prey through echo location.  Insectivorous bats eat a wide array of insects, but many species prefer the high-nutrition of moths.  Without the ability to detect this echo location, moths were blind to approaching bats, but over time some species of moths have developed the ability to detect this sonar hunter before it’s too late.  As bats get closer, moths become more erratic in their flying behavior, diving out of the sky when bats get too close.  Some species have even evolved the capability to advertise their toxicity to bats, similarly to how brightly-colored poison dart frogs advertise their unpalatability through audible clicking noises.  One species of moth (Bertholdia trigona), has developed the ability to emit a signal that jams the bat’s biological sonar, which results in the moth becoming nearly undetectable to the bat.  Check out the video below for a more in depth look at the bat-moth arms race.  And this video to see the echo location jamming organ of B. trigona.

Most plant-herbivorous insect relationships involve an arms race on a chemical level.  Plants are constantly developing highly adaptive toxins to stop herbivorous insects in their tracks.  Those plants within a species that were most toxic, and hence more likely to survive herbivory to reproduce, replaced those that were less toxic.  In response, individuals of an insect species that could handle a higher dosage of the toxin became more successful than those who couldn’t.   Hence, the race rages on; plants became more and more toxic as insects became better and better adapted at handling the toxins.

Chemical warfare is also not limited to plants; one extreme example involves newts and snakes.  The rough-skinned newt Taricha granulosa (like all species belonging to this genus) exudes one of the most potent neurotoxin known: tetradotoxin.  Some species of Taricha produce enough neurotoxin to wipe out thousands of mice.  Why would the rough-skinned newt produce enough poison to kill a potential predator several times over?  To discourage their one predator: the common garter snake Thamnophis sirtalis.  The common garter snake is resistant enough to the poison that they make a living out of eating toxic newts.  Normally, tetradotoxin binds to sodium channels in nerve and muscle membranes, blocking electrical signals that are necessary for proper communication between cells.  This eventually leads to paralysis of muscles including the diaphragm and heart and in turn, death.  The snakes have evolved specialized modifications to their sodium channels, inhibiting the poison from binding.  The resistance of the snake places selective pressure on the newt to increase the toxicity of its toxin, which in turn drives increasing resistance in the snake.

The rough-skinned newt Taricha granulosa.  Photo courtesy of wikipedia.org.

The rough-skinned newt Taricha granulosa.  Photo courtesy of wikipedia.org.

The common garter snake Thamnophis sirtalis.  Photo courtesy of wikipedia.org.

The common garter snake Thamnophis sirtalis.  Photo courtesy of wikipedia.org.

One way organisms escape these arms races is by being transported to a new locations where there aren’t any predators or prey that are adapted to their “skill set”.  You do not need to upgrade your radar detector if the local police do not use radar. This is one of the reasons introduced species do so well.  Without their well-adapted predators and prey, the species is free to do as it pleases (reproduce and take over!).

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