Armed with some amazing senses and skills, animals can communicate in many different conditions, some of them extreme and challenging. On this page we have picked out some fascinating examples from the environment featured in the programme Open Worlds.
Sound can travel well over open spaces. Deep, low
frequency sound travels furthest and is least deflected by
obstacles. Elephants can travel over 20km whilst feeding every
day, but still need to keep in touch with their families. They
do this using infra-sonic calls, which are broadcast at high
volume. A calling elephant is as noisy as a diesel train
going past! As a result elephants can hear each other at
an amazing 4km away, but at this distance, they cannot
tell which individual is calling.
Elephants tell identity from
contact calls. These are individually distinct and have a low
fundamental frequency. The harmonics of the call combine
to create a very high energy harmonic at 115Hz, which,
although it is higher pitched, travels particularly well.
Elephant hearing is also very good at these
frequencies, so elephants can probably tell individual
identity at 1-1.5km.
Humans rely heavily on vision to communicate, using words, signs and body language, but over long distances, visual signals can be lost. Movement can be a great way to
increase the chances of being seen, as eyes are drawn to moving objects. One bird that
capitalises on this is the Jackson's widowbird. Males clear dancing ground for themselves,
leaping high into the air in order to attract females.
Other animals use scent to communicate over long distances,
but in hot, dry environments like the Californian desert, small,
volatile molecules, can easily be 'baked' away. Desert
iguanas have developed a way to overcome this problem.
They excrete their scent in a waxy base, which is smeared
on the ground allowing the scent to disperse slowly over
time. However, this decreases the distance over which animals
can detect the scent marks so iguanas have another cunning
way to ensure their scent makes an impact.
The iguanas can see ultra-violet light. The desert reflects
UV and the scent marks absorb it, so they
appear as dark patches against a light background.
Parrots have another way of using UV light. Their
plumage absorbs UV rays and re-emits it at longer
wavelengths, such as yellow, orange or red, so they appear
to ‘fluoresce’. The fluorescent feathers are often those used
in courtship and are difficult to make, so healthy birds
have more of them. Budgerigars coated with sunscreen no
longer absorb UV, so stop fluorescing and become
unattractive to their mates.
