Identifying the elusive lost species of South-East Asia
- info729479
- Jul 20
- 5 min read
A lost species is defined as any plant, animal or fungi that has not had a scientifically documented sighting in 10 years or longer. The RIDGES Foundation’s mission is to fund and execute biological exploration in some of the most remote and understudied corners of the world. We have a longstanding partnership with Re:wild’s Search for Lost Species and are compiling the most complete list of lost species in South-East Asia to guide our exploration strategy for the next five years.
The Malay Archipelago, consisting of the countries of Malaysia, Brunei, Papua New Guinea and Indonesia is home to one of the largest expanses of tropical rainforest in the world, blanketing the over 17,500 islands. The archipelago is filled with key biodiversity areas and is an endemism hotspot. It has also been crucial to Western science’s understanding of evolution and ecology. Early expeditions pioneered by Alfred Wallace, Ernst Mayr, and Albert Meek to this vast Archipelago respectively have revolutionized the fields of ecology, evolutionary biology and zoology.
However, this vast region suffers from some of the highest rates of habitat destruction anywhere on the planet. Between 1972 and 2014, around 9 million hectares—an area the size of Portugal—of forest was felled in Papua New Guinea alone. The destruction of forest and microhabitats for things such as mining, logging and growing oil palm, is threatening species across the 17,500 islands, and can cause them to become lost to science.
Creating a list of lost species involves working with a combination of historical and modern data, which can pose an interesting but rewarding challenge. Identifying possible lost species from a list of all native species, is a task made more complex by the extraordinary diversity in the Malay archipelago. This project has led to the most complete list of lost species from the archipelago and identified lost species hotspots, using range data of those species. Lost species hotspots are strong indicators of biodiversity “darkspots”, which are understudied areas of high diversity. By overlaying lost species ranges onto open-source satellite imagery, we can identify priority landscapes for exploration using a data-driven conservation strategy.
Ultimately, the RIDGES Foundation assessed 20,280 known species across 6 months, from the Malay archipelago. Of those more than 20,000 plant, animal and fungi species, we identified 1,050 meeting the criteria to be defined as 'lost to science'. More than half of these lost species have not had a documented sighting since before 1980. Almost thirty percent of those lost species meet the criteria of “long lost” and have not had a documented sighting since 1945. 4% have not been recorded since the start of the 20th century.
Case Study: The Papuan Treesnake
Around ten percent of lost animal species in the Malay archipelago are reptiles, and one of those is the Papuan tree snake (Dendrelaphis papuensis). It was likely last scientifically documented in 2014 and is endemic to New Guinea and surrounding islands. There are various preserved samples, one of which is at the Louisiana State University Museum of Natural Science. Its known range is shown below (left) with a related species (D. punctatus) depicted (right).
Case Study: Fly River Bandicoot
The Fly River Bandicoot (Echymipera echinista) is a marsupial first described in 1838, but has not had a documented sighting since 1993. It has only ever been collected 2 (verified) times, hence there is very little known about this enigmatic creature aside from where it was found, in gallery forest in the Fly-Strickland drainage area around the Fly River (below left). It is possible it is restricted to this area, which is still suffering severe ecological damage from the Ok Tedi mine, which discharged 90 million tons of waste per year for more than a decade into the Ok Tedi river, a tributary of the Fly River. The long-lasting effects of the pollution, along with deforestation pose a severe threat to the the Fly River Bandicoot. Bandicoots are typically omnivorous, and mainly eat insects, grasses and fungi (representative species below right).
Marine lost species
As for the aquatic world, there are around 130 species of fish that are lost to science in the Malay Archipelago and fish make up 21% of all lost animal species in the archipelago. One of these is the curious Kai stingaree (Urulophus kaianus), last scientifically documented in 1870 in the Pacific Ocean, just west of Kai Island. This bathydemersal ray resides in the murky oceanic depths of 256 metres, and is harmless to humans. The reasons for its singular recorded observation could be the high proportion of fish aggregating devices (FADs) used in the Kai Island area for deep-sea fishing. FADs can cause marine pollution, high bycatch rates and potentially disrupt fish migrations.
The duck-billed buntingi (Adrianichthys kruyti) was first described by Western science in 1913 by Dr Albert Christian Krueger, a Dutch Christian missionary, but has not had a scientifically documented sighting since 1983. It is a rice fish endemic to Lake Poso in Sulawesi and has a peculiar duckbill, overhanging upper jaw and protruding eyes that are visible from underneath. One of the main reasons for this species’ disappearance could be due unsustainable fishing practices in Lake Poso, where fishers catch rice fish of all ages and sizes in nets. Additionally, non-native species are out-competing endemic fish species, which has led to population declines. Thankfully, local organisations such as PROGRES Sulawesi, have been working on surveying critically endangered fish populations such as Adrianichthys kruyti, providing hope for endemic fish conservation.
Other victims of the pollution from the Ok Tedi mine were freshwater fish, such as Paska’s blue eye (Pseudomugil paskai). P. paskai was last scientifically documented in Papua New Guinea in 2010. The beautiful teleost is known to small creeks in the upper Fly River system, which were especially susceptible to the pollution stretching for hundreds of miles. Fish populations decreased drastically due to the heavy metal toxicity and acid rock drainage, causing colossal reductions in biodiversity; just another example of the threats facing the biodiversity of the Indonesian archipelago.
These species represent just a handful of the hundreds that may still be rediscovered in this region - each with its own unique story. Some have been lost to science for over a century, while others vanished from records as recently as the 2010s. Yet they all share one critical truth: the only way to protect lost species - and the ecosystems they support - is to find them, and fast. By using lost species as indicators of biodiversity "darkspots" - areas where ecological data is scarce and threats are mounting - we can spotlight urgent priorities for exploration and conservation before it’s too late.
Species range data accessed through IUCN. 2025. The IUCN Red List of Threatened Species. Version 2025-1. https://www.iucnredlist.org
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