The durian is a large, spiky fruit, native to the tropical rainforests of South-East Asia - where is is known as "the king of the fruits".
It is known to those who hate it for its penetrating, powerful smell - and to those who love it for its wonderful taste.
Seeds
The durian - for whatever reason - has very large seeds - too large to pass through the guts of many creatures - and this rules out many potential seed distribution vectors.
The durian seed relies upon being discarded after its fruit is eaten (much like a mango pit) - and the raw seeds contain toxins that are effective at discouraging most of those who would try eating them.
Barrier
Many fruit "prefer" to be eaten by birds (or fruit bats) - since these represent some of the best long- distance transportation vectors.
Some fruit actively discourage being eaten by creatures such as large mammals - using toxins. However some fruit also do not seem to mind being eaten by large mammals.
Among these are a number of tropical fruit - bananas, rambutan, mangoes, papaya, pomegranates, organges and guava.
However many of these fruit face a difficult problem - how to make themselves attractive to animals without also becoming the prey of all manner of insects (who do not represent a very attractive vector for their seeds).
Some take to poisons - strong enough to deter insects, but easily dealt with by the liver of a large animal.
Others have taken to using a protective barrier - thick enough to discourage insects - but removed easily enough removed by a sufficiently large creature.
Bananas, oranges, rambutan, mangoes, pomegranates, jackfruit and breadfruit have adopted the "barrier" solution - with some success.
However none of them have taken the approach of using a physical barrier to the same heights that the durian has.
The durian doesn't just have a skin: its flesh and seeds are secured inside a well-defended fortress. Durian rind is not just impenetrable to insects - the innumerable sharp spikes also represent a defense against the beaks of birds, rodents - and all manner of small creatures.
However the durian's rind is also self-opening - when the durian is ripe it cracks along internal fault lines, and starts to open all by itself.
The practiced eye can sometimes make out these "lines of structural weakness" by the effect they have on the spines on the outer shell - though they can sometimes be difficult to identify.
