Scientists confirm discovery of a new otter species

For decades, wildlife guides said a single Neotropical river otter species occurred from northern Mexico to northern Argentina. Fresh genomic work now shows that to be unlikely.

Researchers have confirmed that what looked like one kind of otter is actually two distinct species across Latin America. The change reshapes maps, field manuals, and conservation plans.

What changed in the otter map

Lead author Vera de Ferran from the Pontifical Catholic University of Rio Grande do Sul (PUCRS), along with colleagues, analyzed DNA from river otters. Samples came from Mexico, Central America, and South America.

Their analyses separated the trans-Andes populations from those east of the mountain chain.

Researchers looked at DNA from 29 otters and discovered that they fall into two very different groups.

They suggest giving the western populations a new name and keeping the eastern ones under the older name, which covers otters living in the Amazon, Orinoco, and Paraná River regions.

The authors made it clear: their results show that otters living west of the Andes should be treated as a separate species, now called Lontra annectens.

Why this otter classification matters

Species boundaries guide how scientists count wildlife and how agencies protect it. When one widespread species turns out to be two, each part can face different pressures and need its own specific management.

Splitting a species also changes how we track recovery. If two smaller species replace one big one, national laws and local plans often need updates to match the new picture.

How the team figured it out

The researchers used phylogenomics, a field that traces family trees using large sets of DNA and statistical models.

A maximum likelihood tree from their data showed strong support for the view that the trans-Andes group sits apart from the cis-Andes populations.

They also used statistical tests to check the DNA patterns across otter species.

One test showed that 35.5 percent of the genetic differences clearly separated the otters west of the Andes from the rest. Another test split the Amazon otters from other eastern groups.

To build that picture, the team captured thousands of ultraconserved genetic elements – short regions of the genome that change very slowly and anchor comparisons across species.

Those elements let researchers gather many comparable markers from the samples.

This method provides a reliable way to tell apart species that look almost the same. It works especially well for uncovering hidden diversity, where different species cannot be identified just by appearance.

Where the new otter species lives

The Andes are not just scenic mountains. For small to medium carnivores that depend on rivers and coasts, the range works like a wall that can block movement and restrict gene flow.

The study’s tree and clustering results track that barrier. West of the Andes, the Mexican and Colombian animals form one cluster, while east of the Andes, Amazonian and southern groups sort differently.

The newly named species, Lontra annectens, lives in rivers and wetlands across Mexico and Central America, and continues down the Pacific side of Colombia and Ecuador to the base of the Andes.

On the other side of the mountains, the other species is found in the Amazon, Orinoco, and Paraná River systems.

These ranges match river histories and watershed divides. They also line up with hints from skull shape and nose pad variation that earlier workers noticed but could not confirm at a species level.

How names shape protection

Today, the Neotropical river otter is listed as near threatened on the Red List, reflecting ongoing habitat loss and pressure from pollution and overfishing in many places.

A formal species split will require new assessments and possibly separate management plans for the two lineages.

Any change of this kind needs a formal review by the IUCN. That process weighs data on range, trends, and threats before assigning categories like “Vulnerable” or “Endangered.”

Taxonomy moves first, and red lists follow. The Mammal Diversity database now lists Lontra annectens and marks its Red List status as “Not Evaluated.”

That Not Evaluated tag is normal in the early stages. It signals that conservation bodies should begin separate monitoring and, where needed, targeted protections.

What the numbers tell us

Sampling included 29 individuals spread across the full range. That spread matters because patchy sampling can produce misleading clusters, while broad coverage tests whether divisions hold across landscapes.

The analysis used 30,205 variable genomic sites and reported high support for the branching pattern that isolates the trans-Andes clade. In plain terms, the math behind the tree is solid and consistent across methods.

Cutting through technical terms

The paper labels the old single species concept as paraphyletic, meaning that the group, as defined, left out some descendants that belong together.

In conservation genetics, that is a red flag that the name does not match the evolutionary story.

The authors also report principal component analysis, a technique that reduces complex DNA variation to a few axes that explain most of the differences. This helps visualize clusters without getting lost in thousands of markers.

Window into American otter migrations

The split between trans-Andes and cis-Andes otters fits a broader pattern for New World otters.

Earlier whole genome phylogenomics placed Nearctic and Neotropical otters in a sequence that likely reflects movements across the Isthmus of Panama and subsequent southward diversification. 

Seeing the same signal in a focused river otter analysis and in a global otter tree builds confidence in the story. It also helps biologists ask better questions about how rivers, coasts, and mountains shaped these carnivores.

The team points to potential structure within the eastern group, including an Amazonian cluster that may deserve special management attention. That question needs denser sampling in areas that connect the Amazon to Atlantic drainages.

Field teams will also need to refine identification keys for camera traps and track surveys. Clearer names can then flow into national action plans, fisheries policies, and river corridor protections.

The study is published in the Journal of Mammalogy.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–