Most people assume that birds and monkeys are the champions of seed spreading. But scientists are now discovering that some of the hardest workers in the plant world have no wings at all.
A major review from the University of Hong Kong has found that tiny ground-dwelling creatures like slugs, beetles, earthworms, crickets and crabs are major seed spreaders — a role scientists have largely overlooked until now. The research, published in the journal Trends in Plant Science, challenges the traditional focus on birds and mammals and offers new hope for forest recovery.
Professor Si-Chong Chen led the study in collaboration with researchers from the Chinese Academy of Sciences, Durham University in the United Kingdom, and Kobe University in Japan. The team reviewed 43 previously published studies and found evidence that at least 51 species of invertebrates can eat seeds and later pass them out still able to grow. Those seeds came from 186 different types of plants, with records from Oceania, Asia, Europe and North America.
"If you walk through a forest, you might think only birds or monkeys are spreading seeds. But beneath our feet, a hidden group of gardeners is also at work," said Professor Kenji Suetsugu, a collaborator on the study from Kobe University.
One of the most striking examples involves the freshwater crab in Japan. A single crab can eat over a thousand tiny seeds in one night and deposit them inside underground burrows. Those burrows are humid and protected from rodents and dryness, giving the seeds a better chance to survive and sprout.
Plants that rely on these small creatures have evolved special traits to attract them. They tend to produce tiny, tough seeds inside dull-colored fruits that grow close to the ground. These fruits are less appealing to birds and mammals but easy for crawly creatures to reach. The digestive process of the invertebrates can also scratch the seed coating in a way that actually helps the seed germinate, similar to how scarping sandpaper can help a sprouting seed break through its shell.
Professor Chen said that scientists have often treated these interactions as isolated curiosities rather than part of a larger pattern. Because invertebrates are small, researchers assumed they mattered less than bigger animals. But their sheer numbers and frequent contact with seeds means their overall impact could be significant.
The research does not suggest that birds and mammals are unimportant. They still carry seeds much farther across the landscape. But recognizing the role of invertebrates expands our understanding of how plants find partners to survive. In forests where larger animals are declining due to habitat loss, these tiny creatures may become even more vital for helping trees and plants regenerate.
"We need to broaden our perspective," Professor Chen said. "Plant-animal partnerships are more diverse and interwoven than we previously assumed."