A mammal that evolved and persisted in such a small space, with such scarce resources
On two rocky islands off the coast of Santa Catarina, a creature found nowhere else on Earth clings to existence in a population of fewer than fifty individuals. The preá-de-moleques-do-sul, a small rodent shaped by generations of isolation, now faces the quiet peril of its own evolutionary success — a genetic narrowing so severe that any disruption could extinguish it entirely. The Serra do Tabuleiro State Park, one of Brazil's most ecologically significant reserves, has sealed these islands from human entry, placing the fate of an irreplaceable species in the hands of remoteness, law, and vigilance.
- With fewer than fifty individuals left, the preá-de-moleques-do-sul sits at the very edge of biological viability — one disease outbreak or climate shock away from disappearing forever.
- Generations of inbreeding have hollowed out the species' genetic resilience, leaving it with almost no capacity to adapt to external threats.
- The state responded by declaring the Ilhas Moleques do Sul an Intangible Zone, prohibiting all unauthorized landings and deploying the Navy, Environmental Military Police, and state agencies to enforce the isolation.
- Even as the preá survives under strict protection, the park continues to yield surprises — a newly described golden frog, the Brachycephalus tabuleiro, signals that significant undiscovered life still waits within these boundaries.
- The reserve also safeguards drinking water for over a million people and holds UNESCO recognition, making its stewardship one of the most consequential conservation efforts in southern Brazil.
Em um arquipélago de ilhas rochosas ao largo de Santa Catarina, vive um dos mamíferos mais raros do planeta. O preá-de-moleques-do-sul — um pequeno roedor do tamanho de um porquinho-da-índia — existe exclusivamente nas Ilhas Moleques do Sul, dentro do Parque Estadual da Serra do Tabuleiro, a maior unidade de conservação do estado. Menos de cinquenta indivíduos restam, todos confinados a esse fragmento de terra no Atlântico.
A história do preá é a de um isolamento que se tornou armadilha. Uma população fundadora chegou às ilhas há gerações e, separada do continente, foi se diferenciando até se tornar uma espécie única. Mas a reprodução entre aparentados, ao longo do tempo, reduziu drasticamente a variabilidade genética do grupo. A bióloga Luthiana Carbonell dos Santos alerta que essa fragilidade deixa os animais sem defesa diante de qualquer perturbação externa — uma doença, uma mudança climática, uma alteração na disponibilidade de alimento poderia ser suficiente para extinguir a espécie inteira.
Diante dessa vulnerabilidade, o órgão ambiental estadual designou as ilhas como Zona Intangível, proibindo o acesso sem autorização expressa. A Marinha do Brasil, a Polícia Militar Ambiental e o instituto estadual realizam patrulhas regulares nas águas ao redor. As ilhas estão fechadas — e essa clausura é, por ora, a principal garantia de sobrevivência do preá.
O parque, no entanto, guarda mais do que essa espécie singular. Recentemente, pesquisadores descreveram uma nova espécie de minúsculo sapo dourado, o Brachycephalus tabuleiro, encontrado exclusivamente dentro dos limites da unidade. Para o biólogo Daniel de Araújo Costa, coordenador do parque, a descoberta confirma que o lugar ainda reserva muito a ser revelado pela ciência. Reconhecido pela UNESCO como zona núcleo da Reserva da Biosfera da Mata Atlântica, o parque também protege as bacias hidrográficas que abastecem mais de um milhão de pessoas na região de Florianópolis.
O preá-de-moleques-do-sul persiste, por enquanto, nesse refúgio vigiado. Mas a margem é estreita: a população é pequena demais, a diversidade genética limitada demais para que qualquer gestão, por mais cuidadosa, possa garantir o futuro. As ilhas permanecem fechadas. As patrulhas continuam. E naquelas pedras cobertas de vegetação rasteira, algumas dezenas de animais vivem como testemunho silencioso de quanto a evolução pode criar — e de quão perto podemos chegar de perder para sempre o que ela construiu.
In the southern reaches of Santa Catarina, on a cluster of small islands that few people will ever see, lives one of the world's rarest mammals. The preá-de-moleques-do-sul—a small rodent no larger than a guinea pig—exists nowhere else on Earth. Fewer than fifty of them remain, all confined to the Ilhas Moleques do Sul, a pair of rocky outcrops in the Atlantic that have become so precious, so fragile, that the state has declared them off-limits to visitors.
These islands sit within the Serra do Tabuleiro State Park, Santa Catarina's largest protected area, a sprawling reserve of more than 84,000 hectares that guards not just this singular creature but an entire ecosystem of endemic species found nowhere else. The preá-de-moleques-do-sul arrived here through evolutionary accident—a founding population that somehow made the crossing generations ago and then, isolated on this small patch of land, began the long process of becoming something unique. But isolation, over time, becomes a trap. The animals have interbred for so long that their genetic diversity has collapsed. According to biologist Luthiana Carbonell dos Santos, this genetic poverty leaves them defenseless. Any external shock—disease, climate disruption, a change in food availability—could unravel the entire population. "The species is threatened with extinction and has an extremely restricted distribution," she explained. "Over the course of evolution, individuals have been breeding with one another, which reduces genetic variability and gives them little resilience in the face of external impacts that could reach the island."
The fragility of what lives on those islands is so acute that the state environmental agency designated the Moleques do Sul as an Intangible Zone—a designation that sounds almost poetic until you understand what it means in practice: no one lands there without explicit permission. The islands are closed. The waters around them are watched. The Brazilian Navy, the Environmental Military Police, and the state environmental institute conduct regular patrols. Anyone attempting an unauthorized landing faces legal consequences. Carbonell noted the paradox of the place: "The island is a true biological extreme; it is remarkable how a mammal managed to evolve and persist for so long in such a small space, with such scarce resources."
Yet the preá-de-moleques-do-sul is not alone in its rarity. The park has become a kind of living archive of endemic life. Recently, researchers described a new species of tiny golden frog, the Brachycephalus tabuleiro, found nowhere but within the park's boundaries. The frog was named in honor of the reserve itself—a small gesture of recognition for what the place contains. Daniel de Araújo Costa, the biologist who coordinates the park for the environmental institute, sees these discoveries as evidence of something larger. "We do not have only exclusive species, but also species with extremely restricted distribution," he said. "The discovery of this new amphibian reinforces that the unit is a space of constant scientific revelation and indicates that there is still much to be discovered within the park."
The park's significance extends far beyond its role as a refuge for rare animals. The Serra do Tabuleiro protects the watersheds of three major rivers—the Cubatão, D'Una, and Vale do Braço—that supply drinking water to more than a million people across the greater Florianópolis region and the southern coast. The park is recognized by UNESCO as a core zone of the Atlantic Forest Biosphere Reserve, a designation that places it among the world's most important protected landscapes. It is managed by the state environmental institute in partnership with universities and research organizations, a collaborative effort that reflects the complexity of stewarding a place this valuable.
For now, the preá-de-moleques-do-sul persists in its island refuge, protected by law and by the simple fact of its remoteness. But the species remains on a knife's edge. The population is so small, the genetic variation so limited, that even careful management cannot guarantee survival. The islands stay closed. The patrols continue. And somewhere on those rocky outcrops, in the scrub and grass, the last few dozen of these creatures live out their lives, a reminder of how quickly evolution can create something irreplaceable, and how easily we can come close to losing it forever.
Citações Notáveis
The species is threatened with extinction and has an extremely restricted distribution. Over the course of evolution, individuals have been breeding with one another, which reduces genetic variability and gives them little resilience in the face of external impacts.— Biologist Luthiana Carbonell dos Santos
The discovery of this new amphibian reinforces that the unit is a space of constant scientific revelation and indicates that there is still much to be discovered within the park.— Biologist Daniel de Araújo Costa, park coordinator
A Conversa do Hearth Outra perspectiva sobre a história
Why is a population of fewer than fifty animals considered the threshold for critical danger? Is there a scientific number where a species simply cannot recover?
There's no magic number, but the principle is real. With fifty individuals, you're looking at what geneticists call a bottleneck. The animals are breeding with close relatives—siblings, cousins—generation after generation. That inbreeding purges genetic diversity, which is like removing tools from a toolbox. When disease arrives, or climate shifts, the population has fewer ways to adapt. It's not impossible to recover from fifty, but the margin for error vanishes.
The islands are closed to visitors. But how do you actually enforce that on water? Who's watching?
The Brazilian Navy patrols the waters. The Environmental Military Police monitor the area. The state environmental institute coordinates. It's not a perfect system—you can't have a guard boat there every hour—but it's taken seriously. People who land illegally face prosecution. The real enforcement is that the islands are genuinely remote and genuinely small. There's nowhere to hide, nowhere to anchor easily. It's not glamorous protection, but it works.
You mentioned the park supplies water to a million people. Does that create pressure to develop the park, or does it actually protect it?
It protects it. A park that supplies drinking water to a million people becomes politically untouchable. You can't dam it, can't log it, can't turn it into a resort. The water dependency makes the conservation argument self-evident. It's one of the few cases where human need and ecological need align perfectly.
They just discovered a new frog species there. What does that tell you about what else might be hiding in that park?
It tells you the park is still largely unknown. We've probably catalogued maybe half of what lives there. Every time researchers spend serious time in the forest, they find something new. That's not unusual in tropical reserves, but it's a reminder that we're protecting places we don't fully understand yet. The preá-de-moleques-do-sul gets the headlines because it's so rare, but it might be just one thread in a much larger tapestry.