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organise themselves into communities.

Scientists have proved that trees communicate danger by using chemical signals. For example,

some acacia species on the African savannah defend themselves against giraffes by pumping

toxins into the leaves. The giraffes get the message and move on. 5.1. _____ The giraffes have

learned that when one tree tastes bad, others in the vicinity will, too. This is because when the

acacias come under attack, they give off a warning gas that signals a crisis situation to the

immediately adjacent trees. That triggers other acacias to dump toxins into their own leaves as

a defensive measure.

Pines use a different tactic. When an insect bites on a leaf, electrical signals travel from the

damaged area to the roots, which produce a bitter substance that begins to flow back to the leaf.

5.2. _____ For example, pines attract wasps that lay their eggs on the back of caterpillars which

are eating their leaves, in this way condemning the caterpillars to death.

Another fascinating discovery is that trees seem to help their neighbours in times of need.

5.3. _____ Sometimes they can even pick out their close relatives. Some become so tightly

connected at the roots that they die together, like a devoted married couple. Other individuals,

diseased or hungry, can be identified and nourished until they recover. When thick silver-grey

beeches behave like this, they bring to mind elephants. 5.4. _____ Many rot and disappear

within a couple of hundred years — which is not very long for a tree. It appears to be the

closeness of connection, or even affection, that determines how helpful the other trees will be.

adapted from www.dailymail.co.uk

A. Like the herd, trees look after their own, helping the sick and the weak back to health. Of

course, this does not work for every tree whose life is threatened.

B. Interestingly, this support is not random. They distinguish members of their own species

from among others surrounding them.

C. If the roots find themselves in trouble, this information is broadcast throughout the tree and

the leaves start to release off-putting compounds.

D. But in addition to this, something even more amazing happens: the tree identifies the

attacker by its saliva. After that, it releases pheromones which encourage specific predators

to prey on the attacker.

E. However, instead of going right to the next tree, they wander at least 100 yards before trying

their luck again. Why do they go that far?

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