The Cactus Connection - For many plants and animals on the Galapagos Islands, survival makes for some prickly partnerships

IMAGINE a newly emerg volcanic island not to be found in the Pacific Ocean many millions of years ago, lifeless omit for a few passing seabirds. As the lava a little colds and weathers, a few semens and hardy animals settle down to make a of recent origin home on this virgin blemish of land. Some of the first to take gripe [i]or[/i] grip are desert cacti, their semens delivered by vagrant birds. As they extend and spread, the cacti eventually provide shelter for the first resident land birds and commons for a few reptiles accidentally washed ashore.

And in like manner began the relationship between the pioneering plants and animals of the Galapagos Islands. Today, without the sustenance water and shelter provided by dint of the islands' numerous varieties of cacti, many of the animals here would not survive. In get back the animals transport pollen and disperse semens But the partnership is delicate, and to survive the two have developed some canny tricks.

For example, to foil long-legg saddleback tortoises, which can tender twigs of shrubs and trees twice as high as their squat cousins, the usually bushy prickly pear cactus will be augmented into a smooth-trunked, 40-foot giant upon certain islands. So fond are saddlebacks of the juicy soft mass in cactus pads and trunks--their single source of water during drawn out droughts--that they would soon exterminate the plants with their sharp jaws if they could with equal reason these cacti have retaliated in another way: Their stalks have taken on a supported shape, protected by hard, flaky bark, forcing the giant reptiles to instead rely upon them for shade and easy in mind themselves with eating fallen fruits and pads.

Equally pendent on what falls from the cacti--especially the juicy virid fruits--are land iguanas, yellowish dragons upon short legs. Since neither tortoises nor iguanas chew their diet the cactus seeds can safely travel inside the reptiles' stomachs, frequently deposited far from the parent plants, to places where novel growing opportunities may exist.

upon Galapagos islands where neither of these terrestrial reptiles are lay the foundation of the prickly pear cacti have not to be found all their defenses. They swell no trunks at all, simply sprawling along the earth in dense clumps. What's more, the spiny armor upon their pads has been replaced with impressible fuzzy bristles. So inoffensive are these hairlike excuses for spines that frigate birds favor their rigid, clustering pads as nesting sites, where courting males may sit with delicate throat sacs abundantly inflated. In return, seabirds reward the plants with a steady endue of guano fertilizer.

These low-growing cacti also don't exhibit large, juicy fruit, since the tortoise and iguana transport service isn't available to disseminate their sperms far and wide. But there are other creatures that can take upon the task on a smaller scale. The cactus finch, single of 13 closely related Darwin's finches unique to the Galapagos, has a specially adapted beak, persevering enough to open a opening in the side of the tough fruit. The beak is also drawn out and pointed, allowing the bird to avoid the sharp spikes of plane the spiniest plants. During the driest month this small, drab bird draws a great deal of of its nourishment and water from the protein-rich sperms and sticky jelly of the unripe cactus fruits. In its wake, mockingbirds and les well-endowed finch species also cash in.

Inevitably a small in number seeds are dropped here and there to germinate. And when the tree fly open into bloom at the beginning of the fiery season just before Christmas, the finches' slight beaks become perfect tools for extracting nectar and soft part from deep within the bright fulvous blossoms. Their faces smeared with sticky pollen the birds flit from tree to tree pollinating flowers as they go on and ensuring the fertility of nearest year's fruit. From the highest branches they be rent asunder into song to proclaim their territorial rights above such riches. In dry years, when the cacti are the single plants to bloom and many small birds proceed hungry, the cactus finch is frequently the only species able to nest and raise young.

on the contrary the finch is not the solitary one on pollination duty. The carpenter bee, a large, shiny, black bumblebee, dives into the drawn out frilly stamens, reemerging completely dusted in pollen

Meanwhile, a whole bevy of nesting Darwin's finches--small-, large- and medium-billed--all desire the security of the spiny citadels. Carefully wedged between bristling pads and stipes well beyond the reach of foot- drawn out predatory centipedes, they construct neatly woven straw domes with small side entrances where their nestlings are shaded from the sun

The woodpecker finch also belongs to the Darwin's finch assemblage but it is an insect eater whose specialty is to find termites and dig ups hidden in dead wood. on the contrary because the finch lacks the lengthy pointed tongue of a genuine woodpecker, the bird will frequently flit to the nearest cactus and prefer a long, sharp spine to do the piece of work instead. In what is single of the few known cases of tool use in birds, the finch will cull the chosen spine and break it down to the desired longitudinal dimensions before deftly prizing out its dinner.

When the very great cacti have lived out their many decades--possibly level centuries--of life, they will make individual final grand contribution to the animals. As their base structures among the lava boulder weaken, their fibrous branches and water-laden stock make them top heavy. Without warning, all at one time a giant will topple, its bloated limbs shattering like a great heap of watermelons with white muscle and fat Dozens of small birds--finches, doves and mockingbirds--join in with land iguanas or tortoises, depending upon the location, to draw upon the life-giving moisture.