What happens to an animal's Red List status when scientists split a species?

Published September 25, 2026

When one species is split into several, the new species starts with no Red List category at all: it is Not Evaluated until IUCN assessors judge it on its own range and numbers. The old assessment keeps covering the name it was written for, and the change of status that follows a split is recorded as a taxonomic change, not a real decline. September 2026 brought two live cases, the tilcayo cat of Bolivia and the four gentoo penguins.

A split sounds like a naming exercise, a matter for museum drawers. For an animal on the edge, it can decide whether anyone is counting it at all. A widespread species with a healthy total can hide a small, isolated population that is falling fast, and as long as both sit under one name, the Red List category describes the average, not the animal in trouble. This page explains what happens between the paper that announces a split and the day the new species appears in a catalog like this one, using the two splits in the news this month and one that has already run its full course.

What does it mean when a species is split?

A split is a taxonomic revision: researchers argue, with evidence, that what has been treated as one species is really two or more that have evolved separately for a long time. The evidence is usually a mix of genetics, body measurements, coat or plumage, calls and geography. If one of the resulting groups has never had a scientific name, it is described as a new species ("sp. nov."). If an old name that had been demoted to a subspecies or synonym is brought back, it is revived ("stat. rev.").

Nobody votes a split into force. It is published, then accepted or disputed by other specialists and by the checklists that conservation bodies follow. That lag matters. The IUCN Red List guidelines (version 16, March 2024) say the inclusion of newly described species "is addressed on a case-by-case basis," with the Red List Authority consulting experts "to ascertain how widely accepted these are." A split can be sound science for years before it changes a single entry.

What did scientists split in September 2026?

Two papers reached the news within days of each other.

The first is the tilcayo. On September 17, 2026, Current Biology published a study by Jonas Lescroart, Paola Nogales-Ascarrunz, Eduardo Eizirik and colleagues that sequenced the complete genomes of 38 cats in the genus Leopardus, 26 of them from the tiger cat complex, a group of small spotted cats that has resisted tidy classification since the 18th century. Eight genomes came from museum specimens, including the first genetic look at tiger cats from the Guiana Shield, where the original Leopardus tigrinus was named. The authors conclude that the complex holds five species: the southern tiger cat (L. guttulus), the northern tiger cat (L. tigrinus), the eastern tiger cat (L. emiliae), the clouded tiger cat (L. pardinoides), and a new one from the Bolivian Yungas, Leopardus tilcayo. They also describe a new subspecies from the Peruvian Yungas, L. tigrinus antisuyo.

By the paper's estimate, the tilcayo's lineage split from the other tiger cats about 1.4 million years ago, in the Early Pleistocene, when shifting climate broke up the montane forests of the Andes. The type specimen is an adult male caught alive in September 2021 near the village of Arapata, in the Nor Yungas of La Paz, at 1,570 meters. The name comes from the local word for the cat, which the authors propose as its English common name too.

The second is the gentoo penguin. A study in Communications Biology, led by Daly Noll with Juliana Vianna and colleagues in Chile, the US and elsewhere, proposes four gentoo species where the Red List has one. The paper went online on April 23, 2026; a University of California, Berkeley release brought it to wide attention on September 21. The four are the northern gentoo (Pygoscelis papua) of the Falkland Islands (Malvinas), the southern gentoo (P. ellsworthi) of the Antarctic Peninsula and South Georgia, the eastern gentoo (P. taeniata) of Crozet, Marion and Macquarie, and a newly named southeastern gentoo (P. kerguelensis) of the Kerguelen and Heard islands.

Does a newly split species get a Red List category straight away?

No. A species that has never been assessed is Not Evaluated, which the guidelines define simply: a taxon "has not yet been evaluated against the criteria." Not Evaluated is not a verdict of safety. It means the question has not been asked.

The tilcayo paper spells this out in its own table. Next to each tiger cat unit it gives the IUCN category, and for the tilcayo, the clouded tiger cat, the eastern tiger cat and the two northern subspecies it gives Vulnerable, with a footnote: these populations "were evaluated as a single species, Leopardus tigrinus," and, taken separately, "each population can be considered NE (not evaluated)." The authors point out that the Red List "commonly treats species complexes under a single species name," so a single Vulnerable listing currently stands in for several animals with very different histories.

What happens next follows a pattern. The relevant specialist group, here the IUCN SSC Cat Specialist Group, decides whether to accept the new taxonomy. If it does, assessors write a fresh assessment for each new species, and the old one is revised to cover only what is left under the original name. Until then, the old category is the only one on the books.

There is a second rule that matters for anyone tracking trends. When a category changes because the taxonomy changed, the guidelines require the reason to be recorded as a non-genuine change: the taxon was "newly split," "newly lumped" or is no longer recognized. Genuine change is reserved for real shifts in population, range or threats. That keeps the Red List Index, which measures how the world's species are faring over time, from showing a crash that is really a change of names. Our guide to reading an IUCN assessment shows where that reason appears on an assessment page.

Why can a split make an animal look more endangered?

Because the Red List criteria are thresholds on range size, population size and rate of decline, and a split redraws all three. A population that is a small corner of a common species can be, on its own, a rare species with a tiny range. Nothing about the animals changes on the day of the split. What changes is whether their numbers are pooled with someone else's.

The gentoo paper puts figures on this. The IUCN lists the gentoo as a single Least Concern species. According to the authors, the southern gentoo makes up about 65% of all gentoos, the northern about 24%, the southeastern about 9% and the eastern about 2%. The total has grown by about 11% since 2013, but that growth is driven mainly by southern colonies on the Antarctic Peninsula, where warming has opened up new ground. The eastern gentoo is heading the other way: on Macquarie Island breeding pairs have fallen by 50% over the last three generations, and the monitored colony on Possession Island in the Crozet archipelago fell by 32.6% between 1992 and 2018.

Read against the Red List criteria, a 50% fall over three generations is the kind of decline that criterion A was written for. Pooled with a growing Antarctic population many times its size, it disappears. The authors write that the global Least Concern status "is largely influenced by the southern gentoo penguin," and they "urge that future conservation assessments, including IUCN Red List evaluations, recognize each gentoo penguin species separately." They also note how old the counts are: the most recent full censuses they cite date from 1981 for Crozet, 1985 for Kerguelen and 1987 for Heard and South Georgia. A new assessment will need new counts.

The same arithmetic runs through the tiger cats. The Current Biology team estimated how each unit's effective population size, a genetic measure of breeding numbers, changed between the Pleistocene and the recent past. For the tilcayo it fell by an estimated 63%. That is a long-term genetic signal, not a census, and it cannot by itself set a Red List category, but it is the kind of evidence assessors will weigh alongside field data.

How fast can a new species be assessed? The Tapanuli orangutan

It can happen within weeks when the animal is obviously in trouble and the experts are ready. The Tapanuli orangutan is the clearest case. For decades, the orangutans living south of Lake Toba in Sumatra were counted as Sumatran orangutans. In November 2017, Current Biology published Nater and colleagues' morphometric, behavioral and genomic evidence that they are a separate species, Pongo tapanuliensis, the third orangutan species after the Sumatran and the Bornean orangutan.

The IUCN assessment for the new species was dated October 11, 2017 and came out in the Red List's 2017-3 update, the same year as the description, with the category Critically Endangered. The catalog's dossier records it as the rarest great ape, with fewer than 800 individuals in about 1,000 square kilometers of forest. Under the old name, those animals were a slice of a species that was already Critically Endangered; under their own name, they became one of the most threatened primates on Earth, with a range small enough for a single development project to matter.

Orangutans are unusual: great apes attract researchers, funders and assessors in a way that a cryptic cloud forest cat or a sub-Antarctic penguin colony rarely does. For less studied animals, the wait between the description and the first assessment can run for years, and the new species can enter as Data Deficient when there is too little information to place it.

Why do conservationists care so much about the name?

Because protection, money and monitoring are mostly organized by species. The tilcayo paper notes that national and regional versions of the Red List feed into threatened species laws in tiger cat range countries, and that the species rank is what counts when a cat is considered for the strictest international trade listing. "Given the relevance of species-level assessments for legal protection," the authors write, the revisions "will have important impacts on conservation assessments targeting these species."

Tadeu Gomes de Oliveira, a co-chair of the IUCN Cat Specialist Group, put it more bluntly in a Mongabay interview published September 24. Talking about the tiger cats, he said, "It went from two to three and could go from three to six or even seven." About the munoai, a pampas cat population he estimates at no more than about 200 animals, he said: "If the pampas cat is not split, munoai is doomed." His case is that "formal species recognition is the key to unlocking focused conservation efforts and funding." He also described the other side of the process, the evidence an assessment needs. "For IUCN, you need to prove everything," he said, which is why he is setting up long-term monitoring of small wild cat populations.

That is the honest tension in splitting. Too few names, and small, declining populations vanish into healthy averages. Too many, based on thin evidence, and scarce conservation money is spread across units that may not be real. The guidelines' insistence on waiting until a new taxonomy is "widely accepted" is how the Red List tries to steer between the two.

What happens to legal and trade protection after a split?

Legal lists move on their own timetables, and they often lag behind the Red List. CITES, the treaty that governs international wildlife trade, uses its own standard naming references, updated by its Conference of the Parties. Its Species+ database still lists the tiger cats under two names, Leopardus tigrinus and Leopardus guttulus, both on Appendix I since January 18, 1990. The new names from this month's paper do not appear yet. The practical protection does not depend on the label, though: the paper notes that every wild cat species is on at least Appendix II, and trade in wild tiger cats already falls under the Appendix I listing of the names CITES uses.

US law has its own lists too, and a split does not change them automatically. That is the same pattern this site keeps finding with pets: an animal's wild status, its trade status and the rules in your state are separate layers, set by different bodies for different reasons, as what "in crisis" means explains. A new name does not loosen any of them, and for how US states treat small wild cats kept as pets, see our page on servals and savannah cats.

Why is the tilcayo not in this catalog?

The catalog lists animals whose IUCN category, as recorded on Wikidata, is Critically Endangered, Endangered or Extinct in the Wild. The tilcayo has no IUCN category yet, and neither do the four gentoo penguins as separate species, so none of them qualifies. If assessors place any of them in one of those three categories, they will become eligible when the catalog is next rebuilt from Wikidata. The count on the catalog stats page changes that way: through assessments, not through headlines.

A close relative shows what a threatened small cat in the catalog looks like. The Andean mountain cat, another Leopardus species of the high Andes, is listed as Endangered, and the tilcayo paper's genomic table places it at the low end of genetic diversity in the genus.

Key facts and dates

• January 18, 1990: Leopardus tigrinus and L. guttulus go on CITES Appendix I (Species+).
• November 2017: the Tapanuli orangutan is described in Current Biology; its IUCN assessment, dated October 11, 2017, appears in the 2017-3 update as Critically Endangered.
• March 2024: version 16 of the IUCN Red List guidelines, which handle newly described species case by case and record category changes from splits as non-genuine.
• April 23, 2026: the gentoo penguin split is published online in Communications Biology, naming Pygoscelis kerguelensis.
• September 17, 2026: Leopardus tilcayo is described in Current Biology, one of five tiger cat species.
• September 21, 2026: UC Berkeley publicizes the gentoo split.
• September 25, 2026: neither split has a separate IUCN assessment yet.

What should you watch for next?

Three things will show whether these splits change anything on the ground. The first is acceptance: whether the Cat Specialist Group and the bird checklists the Red List follows adopt the new species. The second is assessment: the first Red List entries for the tilcayo and the four gentoos, and whether the eastern gentoo, with its steep declines, lands in a threatened category. The third is counting: new censuses on Kerguelen, Crozet and Macquarie, and camera trap work in the Bolivian Yungas, because an assessment is only as good as its numbers.

If you want to follow a species through that process, the assessment page on iucnredlist.org shows the category, the criteria, the year and the reason for any change. This page is not affiliated with the IUCN, and status on our species pages is the category stored on Wikidata, not a copy of the Red List.