Leopard Barbel, Mussau Triller & Co.: Rediscovered Animals in 2024

From time to time, animals are rediscovered that were thought to have gone extinct for decades or longer—whether by chance or through targeted searches. These so-called Lazarus species not only highlight nature’s resilience, but also attract a great deal of public interest. They inspire people around the world to get involved in conservation. Among tetrapods—amphibians, birds, mammals, and reptiles—424 species have been rediscovered so far. These rediscoveries usually receive the most attention, while finds of insects, spiders, or mussels often attract less notice.

A study at the beginning of the year examined the factors that make a rediscovery more likely. The size of an animal, its habitat, and human impacts play a central role. Island species are often truly extinct, while inconspicuous species in remote or hard-to-access habitats often remain undetected for a long time. Tropical regions, with their high biodiversity, in particular offer great potential for rediscoveries and new discoveries. This article takes a closer look at some of the animals rediscovered in 2024 that were reported on during the year.

Mussau triller rediscovered after 44 years

The Mussau triller (Lalage conjuncta) from the island of Mussau in Papua New Guinea had been missing since 1979. In June 2024, the songbird species from the cuckooshrike family was rediscovered during a birdwatching tour by Australian bird photographer Joshua Bergmark. Nine individuals in three flocks were documented. The birds live in the densely forested highlands of the island, which made their detection difficult for decades.

The forests of Mussau—the only known habitat of the species—are severely threatened by logging. Since the 1980s, intensive timber harvesting has destroyed large parts of the primary forest and drastically reduced the Mussau triller’s habitat. While newly built logging roads made the rediscovery easier, they could endanger the population in the long term. This rediscovery underscores the urgent need to protect the forests of Mussau and to carry out further studies on the species’ distribution and population size.

Two long-lost bird species found on Bougainville

Joshua Bergmark also played a key role in the rediscovery of two other long-lost bird species. On the mountainous, little-studied island of Bougainville, which belongs to Papua New Guinea, he and other birdwatchers rediscovered the Bougainville thicketbird (Cincloramphus llaneae), missing since 2002, and the moustached kingfisher (Actenoides bougainvillei) in September 2024. The latter, a relative of the kingfisher, was described in 1904, but until this expedition there had been no confirmed record. The Bougainville thicketbird was photographed alive for the first time after the group recorded its distinctive song and lured it in.

The Bougainville thrush (Zoothera atrigena), not documented since 2002, was also a target of the expedition. Although there was no direct sighting, the observers recorded the melodious song of a bird that can very likely be attributed to this species.

A rediscovery in a museum archive

Sometimes major discoveries are not made in dense forests or remote mountains, but in museum archives. This was the case with the spiny-knee leaf frog (Phrynomedusa fimbriata), a small tree frog species from Brazil. With its pale blue back and reddish-yellow belly, this species was long a mystery, known from just a single specimen: a female collected in 1898 in the Atlantic rainforest of the state of São Paulo.

After more than a century of intensive but unsuccessful searching, the species was officially added to Brazil’s Red List of extinct species in 2004. But in October 2024, a study caused a stir: while reviewing the collection of the Museu de Zoologia da Universidade de São Paulo, researchers discovered another specimen—a male that had been mistakenly identified as a different species.

Investigations showed that this second specimen was collected between 1950 and 1960 in the state of Paraná, about 350 kilometers from the original locality. This temporally and geographically distant find raises questions: could the range of the spiny-knee leaf frog be larger than previously assumed? Is it possible that the species has survived in the remaining refuges of the Atlantic rainforest? The discovery raises new hope of one day finding this species alive.

Surprising return: Mesilau toad survives earthquake

The Mesilau toad (Ansonia guibei), which occurs only on Mount Kinabalu in Malaysia, had been missing since the devastating 2015 earthquake. Scientists have now been able to confirm tadpoles and a subadult specimen in the waters of the Mesilau River. This discovery shows that the species not only survived the natural disaster, but is also still reproducing—a testament to its resilience in an environment heavily impacted by the earthquake.

Despite its rediscovery, the Mesilau toad remains threatened with extinction. Its already extremely limited habitat in the highland regions around the Mesilau River continues to be threatened by landslides, pollution, and the effects of climate change. These factors worsen the water quality, which is essential for the species’ survival. Scientists are working on a conservation plan to protect the toad’s habitat and secure its population in the long term.

Frog species from Ecuador rediscovered after a century

The frog Pristimantis ruidus, found only in the Ecuadorian Andes, had been missing since its first description in 1922. The species went unobserved for a full century until it was rediscovered in the Molleturo Forest by a team led by biologist Juan Sánchez-Nivicela in 2022. Two tiny frogs, whose rough skin and distinctive W-shaped folds on the back matched the original description, were found. Final confirmation that they were P. ruidus came from comparing their genetic data with preserved specimens from 1922.

Ecuador’s Andean forests, the only known habitat of P. ruidus, are heavily threatened by logging and conversion to pastureland, pushing many endemic species in the region to the brink of extinction. This frog species stands as a symbol of the urgent need to comprehensively protect the southern Andes—one of Ecuador’s most endangered ecosystems.

Rediscovery of Berezowski’s reed snake solves an old mystery

The rediscovery of Berezowski’s reed snake has solved a long-standing mystery in herpetology. The species was scientifically described in 1896, but since then had been considered potentially invalid because no further specimens were found. Many experts suspected it might simply be a variant of the collared reed snake (C. pavimentata). Between 2017 and 2022, researchers carried out several expeditions to the mountain regions of China’s Sichuan Province and discovered three snakes that matched the original description exactly, based on their yellow collar markings and other physical characteristics. Morphological studies and DNA analyses ultimately confirmed that C. berezowskii is a distinct species.

This rediscovery is not only taxonomically significant, but also contributes substantially to our understanding of the genus Calamaria, one of the most species-rich groups of Asian snakes. The dwarf snake, which lives in mountain forests and is active underground, illustrates how little is known about such cryptic species. The results underscore the need for further research and conservation measures in China’s biodiversity hotspots to ensure the survival of other threatened species.

Abrau sprat: missing since 2008

In September 2024, the rediscovery of the Abrau sprat (Clupeonella abrau) was announced, an endemic fish of Lake Abrau in the Krasnodar region of Russia. The small herring species had been missing since 2008. Only DNA analyses of samples collected as early as 2019 have now clearly confirmed the species’ existence.

The Abrau sprat population has been severely reduced in recent decades by the introduction of invasive fish species such as pikeperch and by water withdrawals. Nevertheless, its rediscovery offers hope: targeted conservation measures could enable the species to recover. Because of its extremely limited range, the Abrau sprat is a stark example of how important targeted protection is for maintaining biodiversity in isolated and threatened ecosystems.

Leopard barbel thought extinct resurfaces

Once widespread in the Tigris and Euphrates river system, from eastern Anatolia to Iraq, the population of the leopard barbel (Luciobarbus subquincunciatus) has declined dramatically in recent decades. The causes included overfishing, pollution, habitat destruction, and the construction of dams. In light of these developments, the species was considered possibly extinct.

But in early 2024, an expert team succeeded in the rediscovery of the leopard barbel in the Turkish part of the Tigris River. With support from local fishers, two specimens were caught and unambiguously identified, including a fish 50 centimeters long. The IUCN lists the leopard barbel as “Endangered”, as the population is said to have declined by more than 80 percent over the past three decades. The find offers hope for possible conservation measures to ensure the survival of this species.

Rediscovered after 140 years: Chilean angelshark

The rediscovery of the Chilean angelshark (Squatina armata) off the coast of Chile after almost 140 years marks a significant moment for marine research. This ray-like shark, known for its flat body shape and characteristic hook-shaped spines, largely disappeared from science’s view after its first description in 1887. It was not until 2024 that fishers managed to retrieve several specimens from the depths. Two of them were examined in more detail at the National Museum of Natural History in Santiago. A study published in April designated a neotype for the species for the first time and refined its description. This made it possible to clearly distinguish the Chilean angelshark from similar species such as the Pacific angelshark (S. californicus).

The rediscovery highlights the challenges of protecting and studying rare deep-sea species. Because of their nocturnal hunting methods and their life in the sand and mud of the seafloor, angelsharks often evade scientific documentation. At the same time, they are particularly threatened due to bycatch and slow reproduction.

The return of the shortnose cisco after 40 years

The shortnose cisco (Coregonus reighardi), a freshwater fish species in the salmon family, was considered extirpated since 1985. Its rediscovery in the Upper Lake (Lake Superior), the largest of North America’s five Great Lakes, was made public recently. Surprisingly, the species was found in a body of water where it had never been documented before.

Once widespread in the Great Lakes, the shortnose cisco disappeared due to overfishing, invasive species such as the sea lamprey, and declining water quality. During a fish stock assessment in 2022, scientists from the United States Geological Survey (USGS) discovered three young individuals of this long-lost species near the Keweenaw Peninsula in the Upper Lake. Later investigations confirmed the presence of adult individuals, indicating a small, stable population. The rediscovery of the shortnose cisco offers an opportunity to reassess the biodiversity of the Great Lakes and to intensify measures to protect threatened species and their habitats.

21 species rediscovered in Madagascar

Another significant event reported in 2024 was the rediscovery of 21 missing species in the Makira Forest, Madagascar’s largest contiguous forest area. The expedition, which took place in September 2023, was part of Re:wild’s Search for Lost Species initiative and marked the first multi-taxa expedition of its kind. Rediscovered species include three almost transparent, iridescent fish species: the Makira rainbowfish (Bedotia alveyi), an as-yet undescribed Rheocles species, and the cichlid Ptychochromis makira. These fish species, which are severely threatened by overfishing and habitat loss, were confirmed thanks to the support of local fishers and guides.

A highlight of the expedition was the rediscovery of the millipede Spirostreptus sculptus, which since 1897 had been known only from a single type specimen. Reaching lengths of up to 27.5 centimeters, the species appears to be more common in the Makira Forest than previously assumed. Other notable finds include the snail Kaliella crandalli, missing since 2010, and five spider species, including the jumping spider Tomocyrba decollata, last documented in 1900. The team also discovered 17 previously unknown spider species, including a striking zebra spider whose unique egg sacs were found in a cave.

The results of this expedition show that, despite threats from logging and agricultural activities, the Makira Forest remains an important refuge for species thought to be lost and for still undescribed species. All the more reason to better protect Madagascar’s unique biodiversity.

Colorful weevil back after almost 100 years

After almost 100 years, the strikingly colored weevil Metapocyrtus bifoveatus was rediscovered in the rainforests of the Philippine island of Negros. Known for its metallic green, blue, and rusty-brown coloration, the species had previously been known only from a type specimen from 1925. It was not until 2016 and 2017 that new samples were collected in Northern Negros Natural Park and conclusively identified by biologist Tom Terzin.

This discovery is a glimmer of hope for Negros’ forests, heavily damaged by logging. While large-scale deforestation in the 20th century destroyed the weevil’s original lowland habitat, forests on the mountain peaks appear to be gradually recovering. Interestingly, M. bifoveatus was discovered at around 1,400 meters above sea level—well above its presumed historical habitat. This find suggests that the species may have adapted to higher elevations, or that it once had a wider range before its habitat was destroyed.

Micromoth rediscovered after 87 years thanks to a museum specimen

The rediscovery of the micromoth Pachyrhabda citrinacma was made possible by a specimen accidentally found in the insect collection of National Taiwan University. While reorganizing the archive, researchers came across the tiny moth, which had been collected in 1935 and had since been forgotten in a box. The species was originally described in 1936 by the British entomologist Edward Meyrick, but the two original specimens were lost shortly after his brief initial description. This made P. citrinacma a scarcely studied and enigmatic species for decades—until its rediscovery.

The rediscovered museum specimen helped researchers to search for the species in the wild more specifically. They eventually found larvae of P. citrinacma in oval shelters and reared them under controlled conditions to adulthood. The adult moths, with their pink, feathery wings and striking hind legs, made it possible for the first time to document the entire life cycle of this species. This discovery underscores the immense importance of museum collections for species conservation. They not only provide insights into past biodiversity, but can also serve as a basis for locating and better understanding species thought to be lost.

Cicada rediscovered after more than 100 years thanks to citizen science

Thanks to the citizen-science platform iNaturalist, the western red cicada (Okanagana arctostaphylae) was rediscovered after more than a century. In July 2020, nature observer Lucinda Collings Parker photographed a striking red cicada in her garden in the foothills of the Sierra Nevada in California and uploaded the image to the platform. Scientists identified the cicada as the species missing since 1915 and then began targeted follow-up searches. Specimens were found the very next day on manzanita shrubs, the species’ typical host plant. In 2023, the western red cicada was spotted again in the region.

This rediscovery shows how important citizen science is for the study of cicadas, whose life cycles are often difficult to unravel. Spending most of their lives underground—sometimes up to 17 years—and appearing only occasionally, cicadas pose a particular challenge for entomologists. The collaboration between science and nature observers has not only redefined the range of the western red cicada, but also expanded our understanding of these insects.

Why are rediscoveries so important?

Rediscoveries of species believed to be extinct are far more than scientific sensations—they form the basis for targeted conservation action. Only the certainty that a species still exists makes it possible to protect its habitat and implement focused recovery projects.

In addition, rediscoveries provide invaluable scientific insights. They reveal how species survive under extreme conditions, which threats endanger them, and which ecosystems are particularly resilient. This knowledge is not only valuable for the rediscovered species themselves, but also helps to protect other threatened species and habitats more effectively.

Rediscovered species often draw attention to endangered ecosystems, whose protection has far-reaching positive effects. Conservation measures do not only safeguard a single species, but support many other organisms that live in the same habitat.

Every saved species is a gain for biodiversity—and thus for the stability of ecosystems that secure our livelihoods: food, clean water, and protection from natural disasters. At the same time, such discoveries carry strong symbolic power. They highlight nature’s fragility, spark enthusiasm, and motivate action. They show that conservation can succeed—and give us hope.