1In the desert world, water thieves can come in many forms
2to exploit even the smallest chink in a plant's defense.
3One of the strangers travels within the gut of a fruit-eating mockingbird.
4These are the seeds - the tristerix -
5a kind of mistletoe.
6Their goal is the water inside this hedgehog cactus.
7Using the spines as anchors, the seeds start to germinate.
8Each produces a long probe with which to try and locate the cactus's skin.
9For most, that's a stretch too far and they perish.
10But for this one, the cactus's surface is within reach.
11It clamped onto it with a special sucker
12and then waits for darkness.
13At night, the cactus opens its pores in order to respire.
14Oxygen goes out, carbon dioxide goes in
15and so does tristerix.
16Once within, its tissues spread throughout the body of the cactus,
17sustained by the precious store of water that they find there.
18Then a year later, it breaks through the cactus's skin
19and bursts into flower.
20Hummingbirds come to drink their nectar
21and pollinate them as they do so.
22And then, to complete the cycle,
23tristerix produces hundreds of white eye-catching seeds,
24ready to be carried away by a bird to invade another cactus.