How we rediscovered ‘extinct’ giant tortoises in the Galápagos Islands – and how to save them

Luciano Beheregaray, Flinders University and Adalgisa ‘Gisella’ Caccone, Yale University

The Galápagos Islands, 1,000 kilometres off the coast of South America, are probably most famous as the place that inspired Charles Darwin’s theory of evolution. They are home to an extraordinary array of wildlife, including giant Galápagos tortoises, the world’s largest land-living cold-blooded animals.

The tortoises once thrived in the archipelago. There were originally 15 species that evolved as the islands formed volcanically. However, since the arrival of people four species have become extinct.

A few weeks ago we returned from an expedition to the islands in search of two of these extinct species of tortoises. It may sound like a fool’s errand, but our expedition was a success.

Here’s how we did it.

Tortoises under threat

The Galápagos Islands were colonised in the late 1800s. A combination of poaching by whalers and pirates, and introduced pests competing for food and eating eggs and hatchlings, led to tortoises being exterminated on some islands, and dramatically reduced on others.

Lonesome George, photographed before his death at the age of about 100.
Flickr/putneymark, CC BY-SA

Darwin wrote about the harvesting of the species of tortoise found only on Floreana Island (Chelonoidis elephantopus), which was exterminated within 15 years of his visit to the Galápagos in 1835.

The tortoise found only on Pinta Island (Chelonoidis abingdoni) went formally extinct in 2012, when its last representative, a male held in captivity and nicknamed Lonesome George, died. He was a major conservation icon and at one point considered by Guinness World Records as the world’s rarest living creature.

Finding extinct tortoises

Ten years ago our genetic research program made a very surprising discovery. Some tortoises on Volcano Wolf, on Isabela Island, didn’t match others normally found on the volcano (Chelonoidis becki). Instead, their DNA matched that of the extinct species from Floreana and Pinta.

Volcano Wolf – the highest point of the Galápagos Islands.
Luciano Beheregaray

These exciting discoveries led to an expedition on Volcano Wolf in 2008, where we tagged and sampled over 1,600 tortoises. DNA analyses revealed an astonishingly large number of tortoises with mixed genetic ancestry in this sample: 89 with DNA from Floreana and 17 with DNA from Pinta.

How was this possible?

It is likely that people have been moving tortoises around the islands. Old logbooks from the whaling industry indicate that, in order to lighten the burden of their ships, whalers and pirates dropped large numbers of tortoises in Banks Bay, near Volcano Wolf.

These animals were collected from lower altitudes islands (Floreana and Pinta) during centuries of exploitation by whalers and pirates, who made the archipelago a regular stop-off for their crews to stock up on these handy living larders.

Many of these tortoises made it to shore and eventually mated with the native Volcano Wolf species, producing hybrids that still maintain the distinctive saddleback shell found in the species from Floreana and Pinta. These hybrids include animals whose parents represent purebred individuals of the two extinct species.

An arduous expedition

Our recent expedition was aimed at finding the animals with a high proportion of ancestors from Floreana or Pinta.

It was ambitious, logistically complex, and very strenuous.

Our team of park rangers, scientists, and veterinarians from 10 countries were divided in nine groups of three to four people each. The daily mission included patrolling large areas of unstable razor-sharp lava fields and of spiny thick vegetation across Volcano Wolf, the tallest of the Galápagos. Added to this ordeal were the frequent encounters with wasps, the equatorial heat, and an El Niño induced six-day period of non-stop rain.

When one of the target tortoises was found, we would contact our mother ship by radio and clear the vegetation of the volcano slopes to make room for the cargo net of our expedition’s helicopter. The precious tortoise would then be moved into the net and airlifted to the ship, which was anchored in Banks Bay.

Our teams discovered more than 1,300 tortoises, including nearly 200 that potentially have mixed ancestry from Floreana or Pinta. We airlifted 32 of them to the ship and then to the captive breeding facility of the Galápagos National Park on the island of Santa Cruz.

A giant Galápagos tortoise with ancestry of an extinct species being airlifted to our ship.
Elizabeth Hunter

Included in the 32 were four females with Floreana genes and one male and one female from Pinta that were tagged and analysed in 2008.

Reintroducing ‘extinct’ tortoises

The DNA of these tortoises will be analysed to inform the best breeding strategy. We want to restore as much as possible the genes originally found on Floreana and Pinta.

The captive-born offspring of the two extinct species are expected to be released in their native islands within the next five to ten years.

Giant tortoises relocated by our expedition from the Volcano Wolf, Isabela Island, to the captive breeding program of the Galápagos National Park, Santa Cruz Island.
Joe Flanagan

Reintroduction of these tortoises to the islands where they evolved, together with large-scale habitat restoration efforts, is essential for the restoration of the island ecosystems. These long-lived large herbivores act as “ecosystem engineers”, altering the habitat they live in to the benefit of other species.

Wouldn’t low genetic diversity hinder the long-term persistence of reintroduced populations?

This is a logical concern for reintroduction programs that rely on a small number of captive breeders. However, giant Galápagos tortoises can bounce back from major demographic crashes and respond well to reintroduction programs.

For instance, the Volcano Alcedo tortoise population, arguably the largest in the Galápagos, is derived from a single female lineage thought to have survived a catastrophic volcano eruption in pre-historical times.

The reintroduction of over 1,500 captive-born offspring of the species once found on Española Island is another success story. The repatriated Española population, all derived from 15 captive breeders, now seems well-established.

Bringing back the Floreana and Pinta species from extinction, something inconceivable not long ago, is now a possibility. Its appeal is further increased by the fact that our expedition found that many more tortoises with genes from Floreana and Pinta still wander on the slopes of the Volcano Wolf. Adding them to breeding programs will boost the genetic diversity in the released individuals and calls for a new expedition soon to come.

We anticipate arduous but rewarding times ahead for giant tortoise conservation biologists.

The Conversation

Luciano Beheregaray, Professor in Biodiversity Genetics and ARC Future Fellow, Flinders University and Adalgisa ‘Gisella’ Caccone, Senior Research Scientist and Lecturer, Department of Ecology & Evolutionary Biology, Yale University

This article was originally published on The Conversation. Read the original article.


Unique Australian wildlife risks vanishing as ecosystems suffer death by a thousand cuts

Ayesha Tulloch, Australian National University; James Watson, The University of Queensland; Jeremy Ringma, The University of Queensland; Megan Barnes, The University of Queensland, and Richard Fuller, The University of Queensland

Australia is renowned globally for its vast expanses of untouched wilderness. But for anyone who has travelled across its breadth, the myth of Australia’s pristine wilderness is quickly debunked as evidence of human impact spreads before the eye.

Most ecosystems have suffered huge losses. In a recent study, we looked at the magnitude of land clearing since European settlement. Some ecosystems have been devastated.

There are 75 major terrestrial ecosystems or vegetation communities in Australia, each of which are composed of hundreds of smaller communities of plants and animals. As you can see from the map below, many have been cleared extensively.

Much of Australia’s vegetation communities have been extensively cleared – the worst hit ecosystems occur in the south-west and east.
Ayesha Tulloch

Six of these 75 terrestrial ecosystems have lost 50% or more of their original extent which, combined, originally added to almost a million square kilometres. The worst hit are some of the mallee ecosystems in southern Australia, suffering up to 97% loss.

The temperate eucalypt woodlands of south-east Australia previously covered more than a million square kilometres. Now there are less than half that, having been cleared for agriculture and urban development.

Among these areas are some of the most biodiverse woodland communities on Earth, including the critically endangered Box-Gum Grassy Woodland, which has been reduced to less than 10% of its pre-1750 extent.

The critically endangered Box-gum Grassy Woodlands near Young in south-eastern Australia are now largely made up of small patches.
Ayesha Tulloch

The loss hasn’t been confined to trees. Temperate grasslands have lost 80%. Even the open woodland habitats across the north – which have a fraction of the people of the east and are considered the last great savannah wilderness on Earth – have lost 20-30% of their extent largely as a result of pastoral activities.

First cleared, then cut to pieces

But that’s not the worst of it.

As well as the declines in the extent of almost every vegetated ecosystem in Australia, most ecosystems are increasingly fragmented. That is, the ecosystem occurs in smaller and smaller patches surrounded by agriculture, urbanisation, and corridors such as roads and railways.

Many Australian vegetation communities now occur in small patches. Startlingly, one in five Australian vegetation communities have more than half of their remaining extent in patches smaller than 10 square kilometres. This has serious consequences for the species inhabiting these systems.

Most ecosystems in Australia (such as this temperate eucalypt woodland near Gundagai) have been fragmented through clearing from large, adjoining patches of vegetation into thousands more smaller patches.
Ayesha Tulloch

The brigalow forests and woodlands of Queensland contain the only remaining populations of a number of unique species, including the endemic Retro Slider, Brigalow Scaly-foot and Golden-tailed Gecko. Brigalow previously covered almost 100,000 square kilometres of inland Queensland – bigger than Tasmania.

Brigalow has been affected by the double jeopardy of high loss (87%) and high fragmentation. Two-thirds of its remaining extent is in patches smaller than 50 square kilometres.

The Golden-tailed Gecko is a habitat specialist dependent on Brigalow that has been extensively cleared and fragmented.
Jeremy Ringma

In the far north, the Mahogany Glider, one of Australia’s most threatened tree-dwelling mammals, is dependent on lowland tropical rainforest for its survival.

Lowland rainforest is highly vulnerable to loss of small patches – half of its remaining extent consists of patches smaller than 15 square kilometres. The continuous erosion of small patches of rainforest will certainly lead to the extinction of the Mahogany Glider, as well as declines in and extinctions of many other species surviving in small patches around Australia.

Time for new way of thinking

Current environmental policy means we continue to degrade nature at a rapid pace. Clearing of remnant vegetation in Queensland alone nearly doubled from 520 square kilometres in 2012-13 to 950 square kilometres in 2013-14, and nearly quadrupled since 2009-10. The Queensland Labor government has vowed to reform land clearing laws that contributed to this increase.

Patches smaller than five hectares can be routinely cleared without permits. Small patches such as these are mostly ignored by conservation activities, and instead, policies in fragmented landscapes largely focus on keeping remaining large patches intact. This will not be enough to save some ecosystems.

Well over 1,100 square kilometres of remnant vegetation patches have been approved for clearing for High Value Agriculture in Queensland. On a single property in the north, almost 580 square kilometres was recently cleared to make way for high-value agriculture such as sorghum and soy beans.

Patches smaller than 50 square kilometres comprise up to half of the remaining extent of many of the vegetation communities around Australia and are still being cleared. White areas represent no remaining vegetation
Ayesha Tulloch

These cleared ecosystems contained vulnerable and endangered birds such as the Red Goshawk. Satellite analysis has detected unexplained, possibly illegal, broadscale clearing of small vegetation patches in many parts of Queensland that are still mapped as regulated remnant. Much of this clearing is occurring in places where we identified high vulnerability to loss of small patches, such as the tropical rainforests in the far northeast of Australia.

The Red Goshawk is a habitat specialist and Australia’s rarest bird of prey. Land clearing in northern and eastern Australia is a major threat to the species.
James Watson

Policies urgently need to change at state and federal levels. We need to stop the clearing of vegetation communities and fragments. For example, the arbitrary five hectare threshold for land clearing in Queensland needs to be re-evaluated. These thresholds should instead be tailored to each ecosystem.

Globally we need to stop thinking only about the total amount of vegetation loss and consider size and number of remaining fragments. This will be crucial for assessing the health of ecosystems and protecting remnants.

Since most remaining vegetation is on private land, landholders will need incentives to retain small patches, and developers will need a way of choosing between two patches to ensure economic growth and resource consumption needs can still be met.

The long-term consequences of policy inaction is the slow, inevitable decline of remaining vegetation communities, and further loss of the species dependent on them: a death by a thousand cuts.

The Conversation

Ayesha Tulloch, Research Fellow, Australian National University; James Watson, Associate professor, The University of Queensland; Jeremy Ringma, PhD Candidate, Conservation Biology, The University of Queensland; Megan Barnes, PhD Student in Conservation Science, The University of Queensland, and Richard Fuller, Associate professor, The University of Queensland

This article was originally published on The Conversation. Read the original article.