~Seismic Feelers!~

Do you reckon that animals have a sixth sense? Well some zoologists certainly seem to think so. They believe that certain animal species have an innate ability to sense subsonic waves from an earthquake or tsunami.

There are claims about animals displaying erratic behaviour and moving to higher ground in the face of impending danger. For instance in Sri Lanka, up to an hour before the tsunami bore down on the coast land (following the infamous December 2004 Sumatra quake) elephants ‘trumpeted hysterically’ and ran for higher ground, flamingos abandoned their low-lying breeding areas and dogs refused to go outdoors.

But by the same token, many other animals in the same area were caught unsuspecting and drowned when the tsunami hit. In such scenarios, sometimes animals display abnormal behaviour; sometimes they don’t. That is why the evidence in support for animals having a sixth sense is debatable and not widely accepted.

However, it is possible that some animals may have heard the quake before the tsunami made landfall. Underwater quakes can generate sound waves known as infrasound, which are below 20 Hertz—beyond the hearing range of humans (which is limited from 20 Hertz to 20,000 Hertz) but within the range of many animals like dogs, elephants, tigers and pigeons.

Besides their hearing abilities, another remarkable way that animals can sense that something is amiss when a quake has struck, is through detecting ground vibration. A number of them are quite adept at detecting vibrations that are imperceptible to humans.

Rayleigh waves (vibrations from earthquakes) can move through the ground at 10 times the speed of sound. These vibrations can reach coastal areas hours before the water hits. The low frequency Rayleigh waves can be detected on the ground and through the air by mammals, birds, spiders and insects.

To get a closer look at how they sense vibrations and for what purposes they create their own vibrations, here’s a snapshot of a few critters that are naturally endowed with ‘state-of-the-art’ seismic communication systems!

Jumping Spiders (Salticidae)

Source: Lukas Jonaitis

These spiders are right up there among the world’s most fascinating arachnids. And do they know how to razzle dazzle us with their colourful mating displays! Male spiders approach the females and start to oscillate their abdomens and rap-a-tap-tap and fling their legs in an almost flamenco-like manoeuvre!

The low frequency drumming vibrations are detected by females using exoskeletal sensory structures (through their legs in this case). However, one shouldn’t underestimate the cannibalistic voracity of female spiders. If the dance is not well received by the female, they will reject the male as a mate and will likely eat it! (Crikey!)

Kangaroo Rats (Dipodomys spp)

Source: National Park Service

These critters are likely the fastest tap dancers on the planet. While they hop about on two legs, they also drum out some incredibly fast ‘footrolls’ in the dirt to communicate with other rodents. Apparently, the footroll or series of thumps is done both on top of and inside their burrows.

By keeping their tap dances near-constant, the rats can easily distinguish between neighbours and foreign intruders. Their fleet footwork is also used to signal their awareness of predators like snakes, as well as to compete for mates!

Elephants (Elephantidae)

An elephant at Paignton Zoo. Source: Paul Dickson

It just wouldn’t be right to leave a mammal of this size out of the whole seismic shebang. So here we have it! For years, we know their trumpet calls contain low rumbling frequencies.  But did you know that elephant vocalisations also shake the ground? Also, they are able to detect vibrations through their nose and their toes, honing in on the shaking source using their unique sensory structures.

Sometimes they will deftly place the tips of their toes on the ground, or lift up a foot. Ground sound vibrates the toe bone and travels up through the leg, before jangling the middle ear. Other times, they may lean forward dramatically or put their trunk on the ground.

Well that about sums up my snapshot of critters! To say ‘animals are psychic or intuitive’ might be overplaying it, but we can certainly agree that they have heightened, refined senses, that easily top that of humans’ sensory abilities. In fact, we’re probably ‘vibrationally challenged’ in comparison!

As for natural disasters, if nothing else, perhaps we are better off watching animals for cues since they are always vigilant. It is after all what helps to keep them alive in the wild. Cheers!

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