Move over, Kardashians. Keeping up with the world’s smallest monkey is considerably more engaging than any reality TV show, says behavioral ecologist Stella de la Torre, who has been studying Pygmy Marmosets in South America since 1994. Different groups of Pygmy Marmosets have different dialects, gum-feeding preferences and insect-hunting techniques, each population has its own dynamics, and they may even be able to teach their young new skills—a remarkably human-like trait.
“I fell in love with these marvelous little animals,” says de la Torre, who was originally interested in studying Pygmy Marmosets to understand how environmental factors affect the evolution of vocal communication in primates. “Local people usually think scientists are crazy when we stay in the forest all day looking at the trees. But when we bring the locals in as volunteers to help observe the monkeys, they get hooked like they’re watching a TV series. The interactions among individual monkeys and their behaviors are just so similar to our own. Each day with them is fascinating.”
Although Pygmy Marmosets are small—they fit within the palm of an adult human’s hand—they are found across an immense area of the western Amazon in Bolivia, Brazil, Colombia, Ecuador and Peru. This has made them the subject of debate among primatologists, many of whom believed that with a range that size, there must be more than the one species currently recognized. Primatologists recently answered, at least in part, the seemingly simple—but, in reality, complex—question: How many Pygmy Marmoset species are there?
The answer, according to a study published in November that used genetics in an in-depth analysis: at least two. One has tawny brown to dirty yellowish fur on its underside and the other an off-white or even bright white belly. The study was restricted to Pygmy Marmosets in the Brazilian Amazon, but there are indications that researchers may discover more species with further research in the forests of the other countries where they live.
“We need to get a full understanding of the diversity of what we’re trying to save,” says Anthony Rylands, Global Wildlife Conservation’s primate conservation director and a co-author of the study published in Molecular Phylogenetics & Evolution. “If you don’t know what you’re trying to save—if you don’t know the geographic ranges and the differences in ecology, and natural history of the different species—your conservation efforts probably aren’t going to work. Protecting our wild world requires knowing as much as we can about the species we share this home with.”
The study, led by Professor Jean Boubli at Salford University, UK, is the first ever to use genomics to investigate the evolutionary history of a group of New World primates. The researchers found one of the distinct Pygmy Marmoset species is found in Brazil’s Japurá basin, extending west into Colombia, northern Peru and Ecuador, while the other, with the whiter chest and belly, is found south of the Amazon River, east to the Madeira River in Brazil, and possibly extending south and west to central and southern Amazonian Peru and Bolivia. The paper’s authors examined and compared the fur of numerous newly collected specimens from Brazil’s Japurá, Jutaí, Juruá, Madeira and Purus river basins with specimens preserved in the Smithsonian Natural History Museum, and also some kept in Stockholm’s Natural History Museum that were collected in 1936 and 1940, and provided crucial evidence for the existence of the second species.
Primatologists are now collecting Pygmy Marmoset feces in Bolivia, Peru and Ecuador to extract and analyze DNA to get a better sense of the full range for both species, and to determine whether the Pygmy Marmoset family is even more diverse than this paper reveals.
“The species is the most important biological unit we have to catalogue biological diversity,” Rylands says. “And it isn’t easy. Biology isn’t simple. It doesn’t obey laws and rules. But I love the challenge of improving our understanding of these primates.”
According to the IUCN Red List of Threatened Species, Pygmy Marmosets are species of “Least Concern.” But de la Torre–who has seen Pygmy Marmosets suddenly vanish from 13 of her 15 study areas in Ecuador–and the IUCN Species Survival Commission’s Primate Specialist Group are recommending updating that status to Vulnerable. Habitat loss, human encroachment and the pet trade have been among the biggest threats to the animals, but de la Torre says she suspects the recent population crashes she has witnessed are the result of a disease epidemic that researchers need to study to protect the animals from future declines.
de la Torre is also working on local reforestation campaigns and advocating for the protection of the still-intact forests where the monkeys live, while she continues her research on the animals’ behavior. And she’s part of the team collecting Pygmy Marmoset feces from different localities to contribute to the ongoing work to clarify the taxonomy of Pygmy Marmosets and the geographic ranges of the two species already identified—and possibly even that of new ones.
“It’s a really, really terrible thing to see these tiny monkeys die-off,” de la Torre says. “Even in pristine environments, they just aren’t abundant. Considering these population declines, it’s even more important now to know if we’re looking at the local extinction of a population or the extinction of a completely separate, distinct species. If we’re losing a species instead of a population of a species, that’s a much more drastic loss.”
Top photo: Sub-adult Pygmy Marmoset (Photo by P. Yépez)