Early naturalists had seen Hawaiian Crows breaking these open. The hoawa tree, for example, hides its oily, black seeds inside hard pods. ![]() The birds showed a special affinity for some plants. For three species, seeds that the crows had eaten (stripping away the fruit and partially digesting the seed coat) showed a better chance of sprouting than untouched seeds. (The answer: 7,144.) They planted seeds from six tree species and found even more evidence for a crow-plant link. The researchers then collected the birds’ droppings and pellets, painstakingly washing through them to count how many seeds were eaten. The birds ate fruits from all 16 species and, in classic crow fashion, carried many of them around their enclosures to store for later. They gave hundreds of the fruits, containing more than a million seeds, to 57 captive Hawaiian Crows. To investigate, the researchers collected the fruits of 16 native tree species. “Maybe the Alala are the missing seed dispersers for these large-fruited plants.” “There are so many that lack any known seed disperser, and many of them are endangered,” said Susan Culliney, lead author of the study. A group of researchers recently looked into the bird’s disappearance to see what broken relationships lay in its wake. None of these crows are moving seeds around the Big Island anymore, though fewer than 100 remain, all in captive-breeding facilities. Weighing in at just over a pound, the Hawaiian Crow is not exactly a giant sloth-but it was one of Hawaii’s largest remaining native fruit eaters. His idea has since been widely applied, including recently in Hawaii. After an extinction, an animal’s absence can be seen in what remains: piles of fruit rotting under branches trees unable to spread across the landscape. Janzen’s insight was that ecosystems can be full of broken relationships. The original dispersers must also have been big beasts with heavy jaws: ground sloths, giant armadillos, and elephantlike animals that had roamed Costa Rica until about 10,000 years ago. The answer was on the ground in front of him: a horse had easily cracked the fruit, eaten the seeds, and moved on. Why evolve such an inaccessible package for the seeds? The whole point of a fruit is to tempt an animal into moving seeds around. In Costa Rica, all the fruit-eaters are small. ![]() The scientist, Daniel Janzen of the University of Pennsylvania, had never been able to figure out why the jicaro, and many other tropical trees, produce such big, hard fruits. One day around 1980, a scientist in Costa Rica found a pile of horse dung that changed the course of tropical ecology-a chance encounter that, 30 years later, is helping the case for saving the Hawaiian crow, or Alala.īuried in that pile was the seed of a jicaro, a tree with a fruit like a small cannonball.
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