After centuries of research and documentation, scientists continue to uncover new mammal species at a pace that surpasses common expectations. A recent study published in the Journal of Mammalogy and led by researchers from Arizona State University (ASU), working with the American Society of Mammalogists, demonstrates that global mammal diversity is still being charted and understood.
The study provides an updated overview of known mammal species, their distribution, and recommendations for future conservation efforts. It draws on the latest data from the Mammal Diversity Database, which now lists 6,759 living and recently extinct mammal species—a nearly 25% increase compared to figures reported in 2005.
Researchers have added 1,579 new distinct species since the previous major reference taxonomy, including both newly described species and those split from previously recognized ones. In contrast, 226 species were merged or removed from records during this period. This results in a net gain of 1,353 species, averaging about 65 new mammal species recognized each year.
Nathan Upham, assistant professor in ASU’s School of Life Sciences and a leader on the database project, emphasized the ongoing nature of this work: “Every week, new papers come out that change what we know about mammal diversity,” he said. “Sometimes it’s a brand-new species to science, and sometimes it’s realizing that what we thought was one species is actually two, or five.”
The database tracks taxonomic changes across all major groups of mammals. Over the past two decades, new species have been documented in most orders and families—highlighting rodents (595 new species), bats (410), shrews and moles (166), and primates (161) as areas with significant growth.
“Rodents and bats together make up almost two-thirds of mammal diversity,” Upham noted. “They’re everywhere, but they’re also some of the least understood animals, partly because they’re small, nocturnal and elusive. There’s still an incredible amount left to discover about small mammals.”
Prior to this centralized resource, updates in mammalian taxonomy relied heavily on infrequently published print volumes. “Before this database existed, mammal taxonomy was kind of stuck in books,” Upham explained. “If you were studying a species, you might not realize that its name or classification had already changed years earlier. Now, all the literature, citations and updates are centralized, and we even track the differences between versions so researchers can more directly see how our understanding is evolving through time.”
A key feature of the database is its record-keeping for synonyms—previous scientific names used for currently recognized species—which helps ensure continuity across historical literature: “It’s like a translation table,” Upham said. “If you’re reading a paper from the 1800s or looking at a museum specimen with a name no one uses anymore, the database tells you what that species is called today. It keeps the language of biodiversity consistent across time.”
He continued: “Species names are how we communicate about life on Earth,” adding that accurate naming supports clear communication among scientists over generations.
Geographically, many recent discoveries originate from mountainous tropical regions such as Madagascar; South America’s Andes; Indonesia; and the Philippines—areas known for their rich biodiversity and complex landscapes fostering isolated evolution. However, regions like West and Central Africa; parts of India; Central Asia; Amazon Basin; and certain Indonesian islands remain under-researched due to limited access to advanced genetic tools or funding.
“A lot of what’s driving new discoveries now is technology,” Upham said. He pointed out advances such as genomic methods and CT scanning along with increased global collaboration: “In South America… most of the new taxonomic work is being led by scientists in Brazil, Argentina and Peru rather than from Global North countries… which is also starting to happen in Africa as well.”
The current edition of the Mammal Diversity Database reflects over two centuries’ worth of scientific progress—including shifts between periods when taxonomists created numerous categories based on physical traits (“splitters”) versus later consolidation (“lumpers”). Today’s approaches combine multiple lines of evidence such as genomics alongside morphology.
“In the early 1900s there was this explosion of species names based on fur color… Then in the 1960s scientists realized they needed to clean up that mess,” Upham recalled. “Today we’re in another wave of discovery… integrating genomics [and other fields].”
Projections suggest more than 8,000 living mammal species could be recognized by mid-century if trends persist—reflecting better scientific tools as well as broader participation globally.
Despite these advances in cataloging diversity, challenges remain for conservation assessments: The International Union for Conservation of Nature currently classifies about one-quarter of mammal species as Data Deficient or Not Evaluated regarding threats—a gap highlighting needs for improved integration between databases like ASU’s resource with organizations such as IUCN.
For Upham—and his team—the focus remains on increasing collective knowledge rather than achieving finality: “It’s easy to think we’ve already found everything,” he said. “But we’re still learning about the animals that share this planet with us. Every new name is a reminder that the story of life on Earth is still being written…”
Arizona State University has been repeatedly recognized for innovation efforts across disciplines including being named number one in innovation by U.S News & World Report eight years running.
