Tag Archives: extinction

New study offers innovative model to reindeer conservation with global potential

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A groundbreaking study from the University of Calgary presents a novel method for identifying wildlife populations at risk—such as caribou and reindeer—based on their individual movement patterns. This approach could revolutionize future conservation strategies.

Published in Biological Conservation, the study utilizes a long-term dataset from GPS-collared caribou across Western Canada. Researchers identified six distinct behavioral groups, each requiring tailored conservation actions.

Spanning vast regions of the Rocky Mountains, particularly in British Columbia, the study area encompasses protected parklands as well as private and multi-use public lands. This diverse landscape, with its rugged topography and climate of long winters and short summers, has been increasingly impacted by habitat fragmentation due to roads, seismic exploration, railways, and logging.

The research analyzed key movement behaviors—such as migration patterns, range sizes, and elevation shifts—to gain deeper insights into caribou ecology. Lead author Margaret Hughes, a PhD candidate in the Department of Biological Sciences, explains that the study revealed subtle but significant differences from current caribou management practices in Western Canada.

“Our approach focuses on behavior to distinguish differences between individuals and groups, clustering them based on movement patterns,” Hughes says. “By understanding where they go and why, we can better inform conservation efforts.”

Behavioural Analysis

This behavioral analysis offers a more comprehensive framework for defining population boundaries, optimizing conservation resource allocation, and improving biodiversity management. While genetic studies have traditionally guided caribou conservation, Hughes emphasizes the added value of integrating movement behavior into conservation planning.

“It helps managers recognize ecologically meaningful variations within species, ultimately leading to more effective conservation strategies,” she explains.

Caribou, an iconic member of the deer family, face mounting threats from habitat loss, industrial development, and climate change. Professor Marco Musiani, a co-author from the University of Bologna and adjunct professor at UCalgary, underscores the species’ significance.

“Caribou are one of the most affected species in Canada due to oil and gas development, forestry, and climate change. Their sensitivity makes them a key indicator of ecosystem health,” Musiani says.

Beyond caribou, the study’s methodology holds promise for broader conservation efforts. Hughes notes that the findings could inform habitat protection, ecological corridor design, and even species translocation strategies—critical areas receiving increasing conservation investment.

By incorporating behavioral science into conservation, this research offers a powerful tool for safeguarding not only caribou populations but also broader biodiversity in a rapidly changing world beset with human activities which have driven species extinction rates to nearly 1,000 times from the natural background rate.

What IUCN says?

The International Union for Conservation of Nature (IUCN) reports that over 42,100 assessed species are at risk, including 25% of mammals, 14% of birds, and 40% of amphibians. However, the true numbers could be far higher, as not all species have been evaluated.

A 2019 UN biodiversity report estimated that up to one million species worldwide could face extinction, highlighting the urgent need for conservation. Yet, limited resources often force conservationists to prioritize species based on economic, ecological, or aesthetic value—leaving many vulnerable species without sufficient protection.

Ecosystems supporting endangered species are also disappearing at an alarming rate despite the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and the Convention on Biological Diversity (CBD) in vogue to protect vulnerable species and habitats across the planet. Beyond government efforts, conservation organizations such as the Nature Conservancy, World Wildlife Fund, and Conservation International are playing a crucial role in safeguarding biodiversity.

As global collaboration model remains essential to preserving the planet’s natural ecosystems for future generations, “This approach can be applied to other at-risk species, helping guide habitat restoration and protection on a much larger scale,” Hughes says.

A big step toward producing rhino gametes

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To save the northern white rhinoceros from extinction, the BioRescue team is racing to create lab-grown egg and sperm cells of the critically endangered subspecies. The team has now reported a milestone in Science Advances: they have generated primordial germ cells from stem cells – a world’s first.

Thirty-three-year-old Najin and her daughter Fatu are the last surviving northern white rhinos on the planet. They live together in a wildlife conservancy in Kenya. With just two females left, this white rhino subspecies is no longer capable of reproduction – at least not on its own. But all hope is not lost: according to a paper published in the journal Science Advances, an international team of researchers has successfully cultivated primordial germ cells (PGCs) – the precursors of rhino eggs and sperm – from embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs).


The last two surviving females live in the Ol Pejeta Conservancy in Kenya./CREDIT:Jan Stejskal, Safari Park Dvůr Králové

This represents a major milestone in an ambitious plan. The BioRescue project, which is coordinated by the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) and has been funded by the German Federal Ministry of Education and Research (BMBF) since 2019, wants to save the northern white rhino from extinction. To this end, the scientists are pursuing two strategies – one of them trying to generate viable sperm and eggs from the skin cells of deceased rhinos. The idea is to implant the resulting embryos into closely related southern white rhino females, who will then carry the surrogate offspring to term. And so the northern white rhino subspecies, which humans have already effectively wiped out through poaching, may yet be saved thanks to state-of-the-art stem cell and reproductive technologies.

First success with an endangered species

To get from a piece of skin to a living rhinoceros may be a true feat of cellular engineering, but the process itself is not unprecedented: the study’s co-last author Professor Katsuhiko Hayashi leads research labs at the Japanese universities of Osaka and Kyushu in Fukuoka, where his teams have already accomplished this feat using mice. But for each new species, the individual steps are uncharted territory. In the case of the northern white rhinoceros, Hayashi is working in close cooperation with Dr. Sebastian Diecke’s Pluripotent Stem Cells Technology Platform at the Max Delbrück Center and with reproduction expert Professor Thomas Hildebrandt from Leibniz-IZW. The two Berlin-based scientists are also co-last authors of the current study.

“This is the first time that primordial germ cells of a large, endangered mammalian species have been successfully generated from stem cells,” explains the study’s first author, Masafumi Hayashi of Osaka University. Previously, it has only been achieved in rodents and primates. Unlike in rodents, the researchers have identified the SOX17 gene as a key player in rhinoceros PGC induction. SOX17 also plays an essential role in the development of human germ cells – and thus possibly in those of many mammalian species.

The southern white rhino embryonic stem cells being used in Japan come from the Avantea laboratory in Cremona, Italy, where they were grown by Professor Cesare Galli’s team. The newly derived northern white rhino PGCs, meanwhile, originated from the skin cells of Fatu’s aunt, Nabire, who died in 2015 at Safari Park Dvůr Králové in the Czech Republic. Diecke’s team at the Max Delbrück Center was responsible for converting them into induced pluripotent stem cells.

Next step: cell maturation

Masafumi Hayashi says that they are hoping to use the cutting-edge stem cell technology from Katsuhiko Hayashi’s lab to save other endangered rhino species: “There are five species of rhino, and almost all of them are classified as threatened on the IUCN Red List.” The international team also used stem cells to grow PGCs of the southern white rhino, which has a global population of around 20,000 individuals. In addition, the researchers were able to identify two specific markers, CD9 and ITGA6, that were expressed on the surface of the progenitor cells of both white rhino subspecies. “Going forward, these markers will help us detect and isolate PGCs that have already emerged in a group of pluripotent stem cells,” Hayashi explains.

The BioRescue scientists must now move on to the next difficult task: maturing the PGCs in the laboratory to turn them into functional egg and sperm cells. “The primordial cells are relatively small compared to matured germ cells and, most importantly, still have a double set of chromosomes,” explains Dr. Vera Zywitza from Diecke’s research group, who was also involved in the study. “We therefore have to find suitable conditions under which the cells will grow and divide their chromosome set in half.”

Genetic variation is key for conservation

Leibniz-IZW researcher Hildebrandt is also pursuing a complementary strategy. He wants to obtain egg cells from 22-year-old Fatu and fertilize them in Galli’s lab in Italy using frozen sperm collected from four now deceased northern white rhino bulls. This sperm is thawed and injected into the egg in a process known as intracytoplasmic sperm injection (ICSI). However, Hildebrandt explains that Fatu is not able to bear her own offspring, as she has problems with her Achilles tendons and cannot carry any additional weight. Her mother Najin, meanwhile, is past child-bearing age and also suffers from ovarian tumors. “And in any case, since we only have one donor of natural eggs left, the genetic variation of any resulting offspring would be too small to create a viable population,” he adds.

The team’s top priority, therefore, is turning the PGCs they now have at their disposal into egg cells. “In mice, we found that the presence of ovarian tissue was important in this crucial step,” Zywitza explains. “Since we cannot simply extract this tissue from the two female rhinos, we will probably have to grow this from stem cells as well.” The scientist is hopeful, however, that ovarian tissue from horses could come in useful, as horses are among the rhinos’ closest living relatives from an evolutionary standpoint. If only humans had taken as good care of the wild rhino as they had of the domesticated horse, the immense challenge now facing the BioRescue scientists could perhaps have been avoided altogether.

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Giraffes, parrots, oak trees, cacti among many species facing extinction

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It may be surprising to learn that even giraffes, parrots, and oak trees are included in the list of threatened species, as well as cacti and seaweed.

Seaweed is one of the planet’s great survivors, and relatives of some modern-day seaweed can be traced back some 1.6 billion years. Seaweed plays a vital role in marine ecosystems, providing habitats and food for marine lifeforms, while large varieties – such as kelp – act as underwater nurseries for fish.

However, mechanical dredging, rising sea temperatures and the building of coastal infrastructure are contributing to the decline of the species.

The world’s trees are threatened by various sources, including logging, deforestation for industry and agriculture, firewood for heating and cooking, and climate-related threats such as wildfires.

Unsplash/Shane Stagner.
Kelp, a type of seaweed, can be fed to animals and could help to reduce greenhouse gas emissions.

It has been estimated that 31 per cent of the world’s 430 types of oak are threatened with extinction, according to the International Union for Conservation of Nature (IUCN) Red List of threatened species. And 41 per cent are of “conservation concern”, mainly due to deforestation for agriculture and fuel for cooking.

Giraffes are targeted for their meat, and suffer from the degradation of their habitat due to unsustainable wood harvesting, and increased demand for agricultural land; it’s estimated there are only around 600 West African giraffes left in the wild.

Rare Tapanuli Orangutan to be extinct soon, thanks to China’s mega dam

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A Tapanuli orangutan (Pongo tapanuliensis) in northern Sumatra, Indonesia. Credit: Maxime Aliaga

The rare Tapanuli Orangutan, discovered last year in Sumatra, Indonesia, and one of the rarest animals on the planet could become an extinct species soon unless urgent action is invoked to reign in on a mega dam in China, said a team of global scientists.

Besides the usual deforestation, the researchers have pointed out that the Batang Toru project being constructed by Chinese state-owned corporation Sinohydro as the major threat to the survival of the rare orangutan.

“This is just the seventh species of Great Ape ever discovered, and it could go extinct right before our eyes,” said Prof. Jatna Supriatna from the University of Indonesia. Echoing similar view, William Laurance from James Cook University in Australia, co-author of the study said, “In 40 years of research, I don’t think I’ve ever seen anything this dramatic.”

A baby Tapanuli orangutan (Pongo tapanuliensis) in northern Sumatra, Indonesia. Credit: Maxime Aliaga

Currently, fewer than 800 of the apes are surviving facing assault from mega-projects, deforestation, road building, and poaching, explained Sean Sloan, lead author of the article in Current Biology. “Their entire remaining habitat is unbelievably small, less than a tenth the size of Sydney, Australia,” said Sloan.

The authors are vehemently zeroing in on the culprit — the planned $1.6 billion Batang Toru mega dam that would go into construction phase soon, relegating the available forest cover for the Tapanuli orangutan, driving them to extinction.

“If it proceeds, the dam will flood crucial parts of the ape’s habitat, while chopping up its remaining habitat with new roads and powerlines,” said Supriatna.

Since the rare ape survives only in areas with virtually no roads, the project will stifle their livelihood, said researchers. “This is a critical test for China and Indonesia. They say they want sustainable development–but words are cheap,” said Laurance. “This could be ecological Armageddon for one of our closest living relatives,” he quickly added.

A Tapanuli orangutan (Pongo tapanuliensis) in northern Sumatra, Indonesia. Credit: Maxime Aliaga

What IUCN says?

The newly described Tapanuli orangutan (Pongo tapanuliensis) exists in an isolated area in around 1100 km2 of forests in the Central, North and South districts of Tapanuli, in the province of North Sumatra.

Until recently, it was thought that only two species of orangutan existed; the Bornean (Pongo pygmaeus) and Sumatran (Pongo abelii). Orangutans are found only in Indonesia and Malaysia and are listed as Critically Endangered on The IUCN Red List of Threatened Species.

“It is rather amazing that this population of orangutans differs so much from the orangutans in the north of Sumatra and that even today, after many decades of intensive research on Great Apes, a new species of this primate family can still be discovered” stated Dr. Ian Singleton, Director of the Sumatran Orangutan Conservation Programme (SOCP), who has worked on improving protection of the Tapanuli orangutans and their habitat since 2005.

The Tapanuli orangutan was initially found by scientists in 1997, but was not confirmed as a separate species until 2017. To reach that conclusion, researchers needed to closely examine the genetic, morphological and behavioural traits which differed from the other two known orangutan species.

“Despite only just now being described, with less than 800 left, the Tapanuli orangutan is already the most endangered great ape species in the world” stated Matthew Nowak, co-author of the recently published ‘Population Habitat Viability Analysis for Orangutans’ and Director of Research at the Sumatran Orangutan Conservation Programme. ”

The Red List status of this new orangutan is currently being assessed, but conservation concerns for the species are high. This is due to a small population, slow reproduction levels, concerns over local habitat destruction, and killing.

Researchers involved in the definition of this new species included experts from the IUCN Species Survival Commission (SSC) Primate Specialist Group (including Ian Singleton, Matthew Nowak and Serge Wich).

Trichomonosis disease discovered among myna birds in Pakistan: Report

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A strain of the disease responsible for killing off nearly two thirds of the UK’s greenfinches has been discovered in myna bird populations in Pakistan.

Mynas are native to the Indian subcontinent and are one of the world’s most invasive species. Although the disease is not generally fatal to them, experts from the University of East Anglia studying the birds say there is a risk they might pass it on to other species.

Avian trichomonosis, more commonly called canker or frounce, is carried by a parasite that primarily infects pigeons in the UK and the larger birds of prey which feed on them.

But in 2005 scientists found the disease had jumped into Britain’s garden songbird populations, predominantly affecting greenfinches and chaffinches.

Since then, the greenfinch population in the UK has fallen from around 4.3 million breeding pairs to fewer than 1.5 million in 2016.

In 2011, the disease was discovered to have reached European finch populations. Now researchers at the University of East Anglia (UEA) have found it in an entirely separate songbird species – the common myna.

Working in partnership with the University of Agriculture in Pakistan, researchers captured and screened 167 myna birds from eight different sites around the Faisalabad region of Pakistan. They discovered that around 20 per cent of the birds were infected with the disease and that there were infected birds at all of the sites surveyed.

The study, published in the journal Parasitology, also identified that the disease affecting the mynas was a different strain from the one found in the UK songbirds. Few of the infected birds had signs of poor health, suggesting that they can carry the disease without it being fatal.

Because myna birds are so invasive, however, there is a significant risk that they can spread the disease to other species that might not otherwise come into contact with it.

Dr Kevin Tyler, from UEA and a senior author of the study, said: “Mynas are able to roost almost anywhere in warm climates, which is one reason they are so successful, but it could also mean they are likely to spread the disease further.

“Mynas have already been implicated in the spread of bird flu through contact with poultry, so this could be of concern to poultry farmers. However, further research and testing is needed to see whether the disease has yet spread from mynas to other species.”

He added: “In the UK, pigeons carry this disease without serious symptoms and it looks like myna birds are able to do the same. This could be due to a natural resilience to the disease, or it could be that this is a less virulent strain – again, we need to carry out further research to investigate.”

Although mynas are thought to be native to the Indian subcontinent, populations of the birds have spread around the world, so the team is also keen to test for the disease in other countries.

Burma’s Star Tortoise Makes a Comeback

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The Burmese star tortoise (Geochelone platynota), a medium-sized tortoise found only in Myanmar’s central dry zone, has been brought back from the brink of extinction thanks to an aggressive captive-breeding effort spearheaded by a team of conservationists and government partners.

Efforts to restore the tortoise are described in the latest issue of the peer-reviewed journal Herpetological Review.

The tortoises now number over 14,000 individuals, up from an estimated population of just a few hundred animals in the early 2000s. Burgeoning demand from wildlife markets in southern China beginning in the mid-1990s virtually wiped out the tortoise in a matter of years until viable populations could no longer be found, and the species was considered ecologically extinct.

In 2004, The Nature and Wildlife Conservation Division of the Myanmar Ministry of Natural Resources and Environmental Conservation in collaboration with the Wildlife Conservation Society (WCS)/Turtle Survival Alliance (TSA) Myanmar Program established three “assurance colonies” to hedge against the extinction of wild populations. The three colonies began with an estimated 175 individuals, mostly confiscated from illegal wildlife traffickers.

The colonies were sited at facilities within existing wildlife sanctuaries. After the colonies were established, conservationists had to determine the species’ husbandry requirements including diet, feeding, reproduction, and hatchling care. Herpetologists from WCS’s Bronx Zoo helped design the breeding centers as well as provide husbandry expertise. In addition, veterinarians and molecular scientists from the Bronx Zoo conducted health screenings of the captive population to determine what diseases might be present (no major diseases of concern were discovered). Bronx Zoo vets continue to consult with WCS Myanmar vets on various health cases, confirming diagnoses and recommending treatment options.

Approximately 750 animals have been released into wild areas of the sanctuaries, and the long term objective of restoring viable populations in every protected area in the central dry zone is now biologically attainable. However, political and social challenges need to be resolved before large-scale reintroduction takes place to ensure the tortoises are not taken by poachers.

Said lead author Steven Platt, a herpetologist with WCS’s Myanmar Program: “This is the modern day equivalent of saving the bison from extinction. A team of conservationists spearheaded an aggressive captive breeding effort, and have brought an animal back from the brink to where it now has the potential to be reintroduced into the wild in large numbers.”

Said Andrew Walde, Chief Operating Officer of Turtle Survival Alliance: “The Myanmar WCS/TSA partnership is a model chelonian conservation success story. If you had told me more than 10 years ago when the project started that we would have more than 10,000 Burmese Star tortoises, and that we would have returned nearly a thousand to the wild, I wouldn’t have believed it. It is success stories like this that make all the hard work worth it.”

WCS works to save turtles and tortoises around the world. In 2012, WCS launched an organization-wide program to revive some of the most endangered turtle and tortoise species. Efforts include breeding programs at the Bronx Zoo in New York, head-start programs abroad, and working with governments and communities to save species on the brink of extinction.

WCS tortoise conservation in Myanmar is supported by The Leona M. and Harry B. Helmsley Charitable Trust, the Andrew Sabin Family Foundation, the Panaphil and Uphill Foundations, and the Turtle Conservation Fund.

Fossil Site Shows Impact of Early Jurassic Period’s Low Oxygen Oceans

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Using a combination of fossils and chemical markers, scientists have tracked low ocean-oxygen in early Jurassic marine ecosystem that could have led to survival of only a few species.

The research, led by Rowan Martindale of the University of Texas at Austin Jackson School of Geosciences, zeroes in on a recently discovered fossil site in Canada located at Ya Ha Tinda Ranch near Banff National Park in southwest Alberta. The site records fossils of organisms that lived about 183 million years ago during the Early Jurassic in a shallow sea that once covered the region.

 

The oxygen level of the surrounding environment during the Early Jurassic influences the type and amount of carbon preserved in rocks, making the geochemical record an important method for tracking an anoxic event.

“We have this beautiful geochemical record that gives us a backbone for the timing of the Oceanic Anoxic Event,” said Martindale. “So with that framework we can look at the benthic community, the organisms that are living on the bottom of the ocean, and ask ‘how did this community respond to the anoxic event?”

The fossils show that before the anoxic event, the Ya Ha Tinda marine community was diverse, and included fish, ichthyosaurs (extinct marine reptiles that looked like dolphins), sea lilies, lobsters, clams and oysters, ammonites, and coleoids (squid-like octopods). During the anoxic event the community collapsed, restructured, and the organisms living in it shrunk. The clams that were most abundant in the community before the anoxic event were completely wiped out and replaced by different species.

Crispin Little, a senior lecturer in paleontology at the University of Leeds who was not involved with the research, said that the similarity between the sites underscores the widespread nature of the anoxic event. “This confirms previous work suggesting that the T-OAE (anoxic event) was genuinely a global event,” Little said.

However, while other sites were recovering from the anoxic event, the environment at Ya Ha Tinda continued to face stress. Even for small, hardy bivalves, life was tough. “One of the interesting things about the recovery is that we actually see fewer individuals at a time when we’re supposed to be seeing community recovery,” Martindale said.

 

The paper was published in Palaeogeography, Palaeoclimatology, Palaeoeconology. The co-authors include Martin Aberhan, a curator at the Institute for Evolution and Biodiversity Science at the Natural History Museum in Berlin, Germany.

Wiped out Dinosaurs Gave New Life to Frogs: Study

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The dinosaurs wiped out from Earth gave rise to most of the frogs alive today.

A new study by Chinese and American biologists shows that if the calamity had not wiped the planet clean of most terrestrial life 66 million years ago, 88 percent of today’s frog species wouldn’t be here. Nearly nine out of 10 species of frog today have descended from just three lineages that survived the mass extinction.

The findings to be published in the journal Proceedings of the National Academy of Sciences, show that frog evolution pinpointed the blossoming of the main frog lineages to about 35 million years earlier, in the middle of the Mesozoic era.

The new analysis of 95 genes from frogs within 44 of 55 living families shows that these three lineages started to take off precisely at the boundary between the Cretaceous and Paleogene periods — the K-Pg boundary, formerly called the KT boundary — when the last mass extinction occurred, and not 100 million years ago.

According to herpetologist and co-author David Wake, a University of California, Berkeley professor of the graduate school and a curator of the Museum of Vertebrate Zoology, new frog species likely radiated rapidly throughout the world because so many environmental niches were available after the animals occupying them disappeared.

“We think the world was quite impoverished as a result of the KT event, and when the vegetation came back, angiosperms dominated. That’s when trees evolved to their full flowering,” Wake said. “Frogs started becoming arboreal. It was the arboreality that led to the great radiation in South America in particular.”

Trees are an ideal habitat for frogs not only because they allow them to escape from terrestrial predators, but also because their fallen leaves provide protection while the frogs are on the ground, breeding habitat and plenty of food, such as insects. Trees and other flowering plants took off in the late Cretaceous, and were ready for exploitation by frogs after they recovered from the extinction.

Another adaptation that became popular was direct development, that is, producing young without a tadpole stage, which is standard for about half of all frog species today.

“The majority of the frogs that thrive now are thriving because of direct development of eggs in terrestrial situations,” he said. “It is a combination of direct development and use of arboreal habitat that accounts for a great deal of the radiation.”

Two of the three surviving lineages came out of Africa, which remained intact as the continents shifted around over the ensuing eons, with the breakup of Pangea and then Gondwana to form the continents.

Today’s frogs, comprising more than 6,700 known species are, however, under severe stress around the world because of habitat destruction, human population explosion and climate change, possibly heralding a new period of mass extinction, says the new study.

Crocodiles Set to Face Extinction, Says Australian Researcher

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An estuarine crocodile, also known as a “saltie”.

Many of the world’s 27 species of crocodylians will soon be either totally or locally extinct due to human population expansion and intensive land-use for agriculture depleting the water bodies, which provide succour to crocs, said a University of Queensland researcher.

Emeritus Professor Gordon Grigg of UQ says the fact that these reptiles had survived millions of years was no good owing to current rate of human expansion and encroachment of natural resources. “The current human population level and its magnitude and rate of resource consumption are unprecedented,” Professor Grigg said.

Only those crocs living in remote wetland habitats in which humans see no benefit may survive into the future, he said. Some crocodylians might have already become extinct if not for active conservation management undertaken in the second half of the 20th Century.

“For some species, the incentive for conserving them has been the commercial value of their hides, but that is dependent upon its use in high fashion garments and accessories, and that is a somewhat fragile foundation,” he said.

On flip side, the rising temperatures and sea levels may turn a more positive note for crocodylians, as it may create more habitat that will be suitable for any species to survive the human onslaught, he said wryly.

The largest living crocodiles, the estuarine or saltwater crocodile (Crocodylus porosus), are found in Northern Australia and can grow to six metres and weigh more than 900 kilograms.

Professor Grigg said estuarine crocodiles, also known as Indo-Pacific crocodiles or “salties”, were one of the luckier species because human populations across Australia’s north were unlikely to increase significantly in the next few decades.  They might be among the survivors.

Professor Grigg and illustrator and biologist David Kirshner, in their recent book, Biology and Evolution of Crocodylians, reviewed the biology of the crocodiles, alligators, caimans and gharials, and also discusses the great diversity of their gigantic extinct ancestors, some of which were probably warm-blooded.