Updating the top 100 weirdest and most imperiled mammals

Jeremy Hance
January 24, 2011

A lot can change in three years. In January 2007, the Zoological Society of London (ZSL) jumpstarted a program unique in the conservation world: EDGE, which stands for Evolutionarily Distinct and Globally Endangered, selects the species it works with not based on popularity or fund-raising potential but on how endangered and evolutionary unique (in laymen's terms: weird) they are. When EDGE first arrived in 2007, it made news with its announcement of the world's top 100 most unique and endangered mammals. While this list included a number of well-known species—such as the blue whale and the Asian elephant—it also introduced the public to many little-recognized mammals that share our planet, such as the adorable long-eared jerboa, the ancient poisonous solenodon, and the ET-like aye-aye. However, after three years the EDGE program found that their top 100 mammals list already need updating.

Carly Waterman, the EDGE's Program Manager, told mongabay.com that two events particularly affected the list. The first was a Global Mammal Assessment by the IUCN in 2008 that reevaluated species threat levels.

The long-eared jerboa is no longer considered endangered and so has been removed from the Top 100 EDGE Mammals List. Photo courtesy of ZSL.
"Some species (e.g. long-beaked echidnas) are now regarded as more threatened than they were in 2007, while others (e.g. the bumblebee bat or long-eared jerboa) are now thought to be less so. […] This change in threat status for so many mammal species has had the greatest influence on the EDGE list," Waterman explains.

But it's not just the threat of extinction that EDGE measures in its top 100 list. EDGE combines this threat with the species 'uniqueness' or in scientific terms, evolutionary distinctness. Recent research has led to changes here too. In 2009 researchers re-evaluated the mammal's evolution supertree, adding new mammals and applying recent studies that change how scientists understand mammal evolution.

"Some recently discovered species that weren’t included in the previous supertree are new entries to the EDGE list, while others, such as the long-beaked echidnas, have recently been split into two or more separate species. In some cases, several different species have now been lumped together as one. All of this new information has resulted in a slightly different tree shape, which has had an influence on [the list]," explains Waterman.

The new top three: echidnas

As Waterman says changes in how evolutionary biologists view long-beaked echidnas have pushed these truly bizarre mammals—Attenborough's long-beaked echidna, the western long-beaked echidna, and the eastern long-beaked echidna—to the top 3 spots on the list.

The western long-beaked echidna is number tied for number one on the Top 100 EDGE Mammals List.
Echidnas belong to an ancient group of mammals, known as monotremes. These strange mammals, of which only 5 species survive, are the only ones in the world to lay eggs like a bird or reptile. But it's not just egg-laying that makes them notable.

"They have surprisingly large, complex brains and display unusually specialised ecological adaptations to their environment," Waterman explains, adding that, "long-beaked echidnas, for example, have a mosaic of electro-receptors on the skin of their snouts. These enable the animals to detect weak electrical fields and thus locate invertebrate prey in the dark."

Unlike most contemporary mammals, monotremes walked with dinosaurs. Monotremes go back an incredible 160 million years to the Jurassic Age.

"The fact that such a huge amount of unique evolutionary history is today represented by just five species, three of which are classified as Critically Endangered, is cause for concern," says Waterman.

Each of the long-beaked echidnas is listed as Critically Endangered on the IUCN Red List. Fortunately, though, the remaining two monotremes—the duck-billed platypus and the short-beaked echidna—are currently safe from extinction.

New species storm the list

In addition to taxonomic changes impacting the list, newly discovered species are also making noise. While finding a new species of mammal is far more difficult than discovering a new insect or bird, researchers continue to stumble on mammals unknown to science—some nearly as odd as the echidnas.

The saola is listed as 46 in the Top 100 EDGE Mammals List. This photo is of the only live adult saola ever seen by the outside world. This female was captured in 1996 in Laos by local villagers, and transferred to a nearby menagerie (in the town of Lak Xao, Bolikhamxay Province), but survived only a few weeks. Copyright 1996 by W. Robichaud/WCS.
For example, discovered in a market in Laos in 2005, the kha-nyou "was subsequently shown to be a living fossil—the sole surviving member of an ancient group of rodents that was previously considered to have gone extinct some 11 million years ago," says Waterman. "The kha-nyou is extremely distinct from all other mammal species, having separated from its closest living relatives, the gundis of Africa, 44 million years ago. It resembles a cross between a squirrel and a large rat, with its elongated head, small, rounded ears and bushy tail."

But the kha-nyou isn't the only new mammal on the list. In 2001 researchers announced a new species of sloth in 2001 surviving on a single island off the coast of Panama.

Known as the pygmy three-toed, Waterman says that the species is "found exclusively in red mangrove forests surrounding the island where the land meets the sea. These mangroves are thought to cover an area of just 1.3-1.5 square kilometres on the island. The pygmy three-toed sloth is ideally suited to life in the mangroves and is surprisingly good at swimming."

However, it's not only small mammals that scientists have discovered over the past few decades. In 1992 researchers found a large forest-dwelling animal in Vietnam. Dubbed the saola, this bizarre mammal continues to beguile scientists and conservationists.

"Known as the Asian unicorn because of its rarity, the saola remains one of the most mysterious and poorly-known large mammals on the planet. Its long, straight horns and striking white facial markings give it the appearance of a North African antelope. However, research shows that it is in fact more closely related to wild cattle," says Waterman.

Unfortunately as with many recently discovered species of mammal, the kha-nyou, the pygmy three-toed sloth, and the saola are on the precipice of extinction. The kha-nyou is threatened with hunting and habitat degradation due to logging and firewood collecting; the pygmy three-toed sloth lives on a protected island, but its habitat is still being destroyed by locals; and, the saola, according to Waterman, "has come to be regarded as one of the most threatened mammals in Southeast Asia."

She explains that "fewer than 250 mature [saola] are thought to survive, restricted to remaining forest in the Annamite Mountains between Vietnam and Laos. The forests they inhabit are littered with snares set for other species. With the population at such a critically low level, conservationists fear that hunting could spell the end for this incredible animal unless urgent conservation action is taken."

Gone for good?

For some species it is already too late. Although the EDGE program is young (four years old last week) it has already witnessed the likely extinction of one of its top mammals: the baiji. A dolphin once endemic to China's Yangtze River, surveys have shown that the baiji has succumbed to pollution, collisions with ships, illegal electrocution fishing, and other hazards on one of the world's most degraded waterways.

Very likely extinct the baiji is listed as number 5 in the Top 100 EDGE Mammals List. Photo by: Wang Ding.
Currently, the baiji remains on the EDGE list at number 5 (down from number 1), because, as Waterman explains, "it is still listed as Critically Endangered on the IUCN Red List—officially it is not extinct."

Despite the fact that the dolphin is not officially considered extinct yet, Waterman explains that the outlook isn't positive.

"[The baiji] was declared functionally extinct by scientists that were involved in a range-wide survey for the species in 2006. For some time after this declaration I remained hopeful that some baiji survived; perhaps a pocket of animals could be found in some of the smaller tributaries of the Yangtze that hadn’t been surveyed," she says. "However, extensive fishermen interviews carried out along the entire historical range of the baiji in 2007 indicate that few, if any, individuals survive. Most of the older fishermen interviewed reported massive declines in baiji populations over the past three decades, and the majority of younger fishermen had never even heard of the baiji, let alone seen one."

Waterman explains that while a few individual baiji may survive even today, the Goddess of the Yangtze—as it was sometimes known—will likely never recover enough to survive the on-going degradation of the Yangtze River.

"I’d love to be proved wrong though," she adds.

Now, she says, the focus should be on saving other Yangtze species that appear to be following the same path as the baiji, such as the Yangtze finless porpoise.

Given that the EDGE works with such imperilled species, the organization has to confront the fact that some of the animals on its lists may already be gone. In these cases, on-the-ground research is necessary to uncover a species' status.

The newly discovered kha-nyou is listed as number 16 in the Top 100 EDGE Mammals List. Photo by: Nonn Panitvong.
"We’re currently supporting a Bolivian conservation biologist, María Copa Alvaro, to locate any remaining populations of short-tailed chinchillas in Bolivia. There have been no records of this species in Bolivia since 1938. […] We also hope to support conservation biologists in Papua New Guinea to determine the status of the possibly extinct Telefomin cuscus," Waterman says.

She adds that the EDGE program is "keen to support and/or encourage others to carry out surveys to determine the status of these species. These actions are urgently needed, for if the animals survive they are likely to be extremely threatened and in need of conservation attention".

Among the top 100 EDGE mammals, 10% are considered possibly extinct .

Good news for a few

The news isn't always bad for EDGE species. Over the past three years a number of mammals have been removed from the EDGE list—but not due to extinction. For example, the long-eared jerboa is no longer in the top 100, because it is no longer considered immediately threatened with extinction. In fact with more research this Mongolian mammal went from 81st on the list to 1,160th. Still, conservation work begun by EDGE continues for this charismatic rodent.

The Asian tapir is number 18 on the Top 100 EDGE Mammals List. Photo by Fletcher and Baylis.
"The long-eared jerboa is still listed as Vulnerable in Mongolia and Mongolian conservation biologist, Uuganbadraakh Oyunkhishig, is continuing his EDGE fellowship research into its ecology, status and threats," says Waterman.

Other species that have been removed from the list include the bumblebee bat and the aye-aye, both of which are not as endangered as previously thought.

"In most cases [these changes are] because new information about the species has come to light, usually as a result of research. For example, new populations may have been discovered, increasing the known population size and distribution of the species," Watermen explains.

She adds that while "many species are undoubtedly benefitting from current conservation actions", EDGE hasn't been around long enough yet to know for certain how well its conservation programs are working.

"It can take decades for monitoring to reveal a marked increase in the population size of the target species. The efforts of our EDGE conservation biologists over the past few years are hopefully paving the way for the recovery of our Focal Species," she says.

Focal species

Focal species are those that the EDGE program works with directly. Since its start in 2007, the EDGE's focal mammals have been recently updated much like the top 100 mammals list.

The hairy eared dwarf lemur was taken off the Top 100 EDGE Mammals List, since it was classified as Data Deficient by the IUCN Red List, which means researchers lack the information needed to determine threat status. Photo by: Nick Garbutt.
The EDGE will be starting new conservation programs on the saola, the three echidna species, the rondo dwarf galago, and the South Asian river dolphin, while continuing to work with the red slender loris, the hirola, the pygmy hippo, the Bactrian camel, and the Hispaniolan solenodon.

At EDGE, focal species are as carefully chosen as those among the top 100. Researchers first consider how high a species ranks then they examine how much conservation attention is already being spent on the mammal. For example, while the panda comes in at number 19 on the list, it's unlikely to become a 'focal species' since a number of conservation programs are already working extensively on this popular mammal. The EDGE prefers to focus on species that have been left behind by traditional conservation programs.

Finally, the EDGE considers how feasible conservation action is on a species, including what types of conservation actions and the likelihood of making a positive impact. After the focal species are selected then the conservation work begins!

With the saola as an example, Waterman says, "we aim to support saola conservation through raising awareness about this species and assisting with research into its current distribution. The area of potential saola habitat is huge compared to the estimated surviving saola population, so determining exactly where saola occur will help target conservation measures such as patrolling and snare removal."

Hopefully with the EDGE's help, the saola and many other little-known mammals will survive the current extinction crisis.

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Jeremy Hance
mongabay.com (January 24, 2011).

Updating the top 100 weirdest and most imperiled mammals.