Black-and-white ruffed lemur (Varecia variegata) feeding on a tamarind. Photo by: Rhett A. Butler.
Many tropical plants depend on other species to carry their progeny far-and-wide. Scientists are just beginning to unravel this phenomenon, known as seed dispersal, which is instrumental in supporting the diversity and richness of tropical forests. Researchers have identified a number of animal seed dispersers including birds, rodents, monkeys, elephants, and even fish. Now a new study in the Journal of Tropical Ecology adds another seed disperser to that list: the Critically Endangered black-and-white ruffed lemur (Varecia variegata). Capable of dispersing big tree species, the black-and-white ruffed lemur may even play a big role in carbon sequestration.
“It’s difficult to say why the black-and-white ruffed lemur had received very little attention, despite being an ideal candidate for seed dispersal,” Kara Moses, lead author of the paper told mongabay.com. A Masters by Research in Primatology student at Roehampton University, Moses is the first researcher to examine the black-and-white lemurs’ potential as seed dispersers in-depth.
“It may be partly due to the difficulties involved in studying them—they are only found in the eastern rainforests of Madagascar, where the terrain and conditions are often pretty heavy going. They also spend most of their time in the high canopy, making fecal sample collection—a crucial part of seed dispersal studies—quite a challenge,” she says.
Focusing on two groups of black-and-white ruffed lemurs, Moses catalogued their seed dispersal abilities over three months. Collecting 3,252 seeds from fecal samples, as well as watching the primates feed, Moses found that the lemurs dispersed the seeds of 40 different species of plants with a special affinity for big seeds.
“Ruffed lemurs are the most fruit-reliant of all the lemurs and have a very diverse diet, meaning they can disperse a large number of seeds and wide diversity of species; they are the largest of the seed-dispersing lemurs, with the largest gape size, so they can swallow the big seeds that other animals can’t—tree species with the biggest seeds may then depend exclusively on ruffed lemurs to disseminate their seeds; they range relatively far during their daily travels, so can potentially carry seeds over long distances; and their droppings are very loosely held together, and broken up further by falling through the branches from the high canopy where they live. This means that seeds are highly scattered when they reach the ground, so they suffer less from competition and predation by seed eating animals,” Moses explains, adding that, “all of these things are good news for seed germination.”
Listed as Critically Endangered by the IUCN Red List, the black-and-white ruffed lemur’s population is thought to have fallen by 80 percent in less than three decades. Habitat loss due to slash-and-burn agriculture has been the primary driver of the lemur’s decline.
“But logging and mining are ever-increasing pressures on forests too,” Moses adds. Hunting is also a problem in some parts of their remaining habitat.
Yet, even as they are vanishing, Moses believes the lemurs’ seed dispersal ability may play an important role in the capacity of Madagascar’s forests to store carbon. This is directly linked to the lemurs as large seed-specialists.
“Trees that produce large seeds tend to be large, slow-growing, long-lived and have relatively dense wood, so they’re able to store more carbon over their lifetimes than small-seeded trees which, conversely, are generally smaller, faster-growing, shorter-lived, and have lighter wood,” Moses explains. “If the trees that produce large seeds don’t get their seeds dispersed—a likely scenario if large seed-dispersing animals like ruffed lemurs disappear—they begin to die out. Species with small seeds that can be dispersed by many animals, and species with wind-dispersed seeds, may then gain a competitive advantage and begin to dominate the forest. The forest becomes one composed mainly of trees with low carbon-storage potential, and the carbon-storage capacity of the whole forest is affected.”
Moses adds, however, that much work needs to be done on the possible connection between seed dispersers and carbon sequestration: “these links are only just starting to be tentatively made, and we don’t know the full story, but it’s a worrying prospect.”
Still, black-and-white ruffed lemurs “play a crucial role in maintaining forest diversity, structure and dynamics by dispersing large numbers of seeds and particularly by moving large seeds that may not be dispersed by anything else,” Moses concludes, adding that “it’s essential that these animals are protected to ensure the future of Madagascar’s rainforests.”
CITATION: Kara L. Moses and Stuart Semple. Primary seed dispersal by the black-and-white ruffed lemur
(Varecia variegata) in the Manombo forest, south-east Madagascar. Journal of Tropical Ecology (2011) 27:529–538. doi:10.1017/S0266467411000198.
Black-and-white ruffed lemurs spend most of their time in the trees. Photo by: Rhett A. Butler.
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