Can a species populated solely by males be saved from extinction?

Can a species populated solely by males be saved from extinction?

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How, if possible, can a species be saved from extinction if the only surviving population are males that cannot reproduce with each other?

The following answer only deals with theorical feasability

Can a species populated solely by males be saved from extinction?

Short answer : No, not with certainty

Nuanced : yes, in some species, it could be possible

It varies in function of how you determinate the sex of your species. Sex determination is a wide topic, see the appropriate wikipedia page

Some reptilian species are not sexually determined by chromosomes but by temperature. An example is the painted turtle, of which thermal sex determination has been studied by Carrie Lynne Morjan in an article titled Temperature-dependent sex determination and the evolutionary potential for sex ratio in the painted turtle, Chrysemys picta

Thermal sex determination allows you to get 2 different sexes from the "same" genome, as temperature will be the driver of the hormonal differentiation.

Cross-species cloning: influence of cytoplasmic factors on development, by Sun and Zhu states that cross species cloning has been successfully made with fishes and mammals.

Nevertheless, cross-species NT has succeeded in cloning some endangered mammals, such as the gaur

In fish, a type of relatively primitive vertebrate, cross-species NT [nuclear transfer] could be achieved in quite a few genetically distant species

It means we are able to use as a mother and egg-layer a different, albeit related, species.

We can, with a massive grain of salt, hypothesize that we could, in a specie solely constituted of sperm producing male, use the oocyte of another specie to clone it, then use the thermal differentiation to make a female out of our clone.

However, I am not aware of any information about how much genome and spermatozoids genetic payload is modified by the sex differentiation. Therefore, it is possible that sex-determined genes cannot produce a sexually naive clone. For more information, and if you want to research more about it, I recommend you to see the current state-of the art in de-differenciation technics and DNA-demethylation for cloning.

I hope I provided a sufficient answer for you.

Can Genetic Engineering Save Our Planet’s Biodiversity?

A U.N. report published last month painted a stark picture of global biodiversity loss, estimating that more than 1 million species are at risk of extinction — many of them within decades — due to farming, logging and other human activities.

While conservationists have been successful in restoring some species, such as the southern white rhino and American bison, the average risk of extinction for birds, mammals, amphibians and corals shows no sign of decreasing.

But what if it were possible to protect our planet’s biodiversity by rewriting the genetic code of plants and animals? It might sound like science fiction, but researchers at NC State’s College of Natural Resources — and around the world — are considering ways to employ genetic engineering for conservation purposes, from eradicating invasive rodents on islands to increasing the resilience of American chestnut trees to an invasive fungus.

“New tools for gene editing and strategies such as synthetic gene drives open up novel opportunities for imagining ways that we might ‘engineer’ biology beyond laboratories and agricultural fields,” said Jason Delborne, an associate professor in the Department of Forestry and Environmental Resources. “The conservation community, in particular, has begun to wrestle with whether, and how, genetic technologies might be applied to complex and challenging environmental problems.”

Delborne, who is also a research leader in the Genetic Engineering and Society Center at NC State, studies the interactions between policymakers, scientists and the public, particularly in the context of emerging biotechnologies.

Genetic engineering has potential. But every intervention has risks, so we have to consider — and anticipate — the potential impacts of these technologies and how they compare to other tools we might use.

He is also a member of the IUCN Task Force on Synthetic Biology and Biodiversity Conservation. The international group of scientists recently published an in-depth assessment of genetic engineering and its potential impacts on conservation.

We sat down with Delborne, who co-authored several of the report’s chapters, to find out all there is to know about genetic engineering, from the basics of how it works to whether or not it can actually help solve our planet’s biodiversity crisis.

New mathematical model can help save endangered species

What does the blue whale have in common with the Bengal tiger and the green turtle? They share the risk of extinction and are classified as endangered species. There are multiple reasons for species to die out, and climate changes is among the main reasons.

The risk of extinction varies from species to species depending on how individuals in its populations reproduce and how long each animal survives. Understanding the dynamics of survival and reproduction can support management actions to improve a specie's chances of surviving.

Mathematical and statistical models have become powerful tools to help explain these dynamics. However, the quality of the information we use to construct such models is crucial to improve our chances of accurately predicting the fate of populations in nature.

"A model that over-simplifies survival and reproduction can give the illusion that a population is thriving when in reality it will go extinct.," says associate professor Fernando Colchero, author of new paper published in Ecology Letters.

Colchero's research focuses on mathematically recreating the population dynamics by better understanding the species's demography. He works on constructing and exploring stochastic population models that predict how a certain population (for example an endangered species) will change over time.

These models include mathematical factors to describe how the species' environment, survival rates and reproduction determine to the population's size and growth. For practical reasons some assumptions are necessary.

Two commonly accepted assumptions are that survival and reproduction are constant with age, and that high survival in the species goes hand in hand with reproduction across all age groups within a species. Colchero challenged these assumptions by accounting for age-specific survival and reproduction, and for trade-offs between survival and reproduction. This is, that sometimes conditions that favor survival will be unfavorable for reproduction, and vice versa.

For his work Colchero used statistics, mathematical derivations, and computer simulations with data from wild populations of 24 species of vertebrates. The outcome was a significantly improved model that had more accurate predictions for a species' population growth.

Despite the technical nature of Fernando's work, this type of model can have very practical implications as they provide qualified explanations for the underlying reasons for the extinction. This can be used to take management actions and may help prevent extinction of endangered species.

2. Siberian tiger

The largest wild cat on Earth, the Siberian tiger is also the most endangered. Once, Siberian tigers roamed throughout the Russian Far East, parts of China, and the Korean peninsula. But systematic hunting and capturing of tigers for zoos reduced the wild population to as few as 40 individuals by the 1940s. The world came perilously close to losing one of its most magnificent wild cats.

Thankfully, in 1947 Russia afforded full legal protection to the Siberian tiger, and the population slowly began to recover. In 1992, the Siberian Tiger Project — a joint initiative between the Wildlife Conservation Society and Sikhote-Alin Reserve in Russia — was established to study the ecology and conservation biology of the Siberian tiger in the Russian Far East. To date, more than 60 tigers have been outfitted with radio collars, allowing the researchers to gather data on tigers’ social structure, habitat requirements, reproduction, and survival rates.

The data collected by the project team has been used to improve protection of tigers and their prey species. As a result, the population of the Siberian tiger in Russia increased to 502 individuals, according to the 2015 census. And while the Siberian tigers is not quite out of the weeds, its population is considered stable and slowly increasing.


There is no unique definition of what is a sufficient population for the continuation of a species, because whether a species survives will depend to some extent on random events. Thus any calculation of a minimum viable population (MVP) will depend on the population projection model used. [3] A set of random (stochastic) projections might be used to estimate the initial population size needed (based on the assumptions in the model) for there to be (say) a 95% or 99% probability of survival say 1,000 years into the future. [4] Some models use generations as a unit of time rather than years, in order to maintain consistency between taxa. [5] These projections (population viability analyses, or PVA) use computer simulations to model populations using demographic and environmental information to project future population dynamics. The probability assigned to a PVA is arrived at after repeating the environmental simulation thousands of times.

Small populations are at a greater risk of extinction than larger populations due to small populations having less capacity to recover from adverse stochastic (i.e. random) events. Such events may be divided into four sources: [3]

Demographic stochasticity Demographic stochasticity is often only a driving force toward extinction in populations with fewer than 50 individuals. Random events influence the fecundity and survival of individuals in a population, and in larger populations these events tend to be stabilized toward a steady growth rate. However, in small populations there is much more relative variance, which can in turn cause extinction. [3] Environmental stochasticity Small, random changes in the abiotic and biotic components of the ecosystem that a population inhabits fall under environmental stochasticity. Examples are changes in climate over time, and arrival of another species that competes for resources. Unlike demographic and genetic stochasticity, environmental stochasticity tends to affect populations of all sizes. [3] Natural catastrophes An extension of environmental stochasticity, natural disasters are random, large scale events such as blizzards, droughts, storms, or fires that reduce a population directly within a short period of time. Natural catastrophes are the hardest events to predict, and MVP models often have difficulty factoring these in. [3] Genetic stochasticity Small populations are vulnerable to genetic stochasticity, the random change in allele frequencies over time, also known as genetic drift. Genetic drift can cause alleles to disappear from a population, and this lowers genetic diversity. In small populations, low genetic diversity can increase rates of inbreeding, which can result in inbreeding depression, in which a population made up of genetically similar individuals loses fitness. Inbreeding in a population reduces fitness by causing deleterious recessive alleles to become more common in the population, and also by reducing adaptive potential. The so-called "50/500 rule", where a population needs 50 individuals to prevent inbreeding depression, and 500 individuals to guard against genetic drift at-large, is an oft-used benchmark for an MVP, but recent study suggests that this guideline is not applicable across a wide diversity of taxa. [4] [3]

MVP does not take external intervention into account. Thus, it is useful for conservation managers and environmentalists a population may be increased above the MVP using a captive breeding program, or by bringing other members of the species in from other reserves.

There is naturally some debate on the accuracy of PVAs, since a wide variety of assumptions are generally required for forecasting however, the important consideration is not absolute accuracy, but promulgation of the concept that each species indeed has an MVP, which at least can be approximated for the sake of conservation biology and Biodiversity Action Plans. [3]

There is a marked trend for insularity, surviving genetic bottlenecks and r-strategy to allow far lower MVPs than average. Conversely, taxa easily affected by inbreeding depression – having high MVPs – are often decidedly K-strategists, with low population densities while occurring over a wide range. An MVP of 500 to 1,000 has often been given as an average for terrestrial vertebrates when inbreeding or genetic variability is ignored. [6] [7] When inbreeding effects are included, estimates of MVP for many species are in the thousands. Based on a meta-analysis of reported values in the literature for many species, Traill et al. reported concerning vertebrates "a cross-species frequency distribution of MVP with a median of 4169 individuals (95% CI = 3577–5129)." [8]

Threatened Species? Science to the (Genetic) Rescue!

Like the doomed passenger pigeon in 1914, the pink pigeon of Mauritius is standing on the edge of a precipice. After watching all of its other pigeon cousins on this remote island go extinct—including the dodo, its infamous island-mate last seen in 1662—this rosy-hued bird is now looking down the dark gullet of extinction itself.

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After yo-yo’ing down to a population of just around nine individuals in the 1990s, the studly birds are back up to a population of about 400 today. But that number is still small enough to leave them dangerously vulnerable. The pink pigeon’s lack of genetic diversity has left it increasingly susceptible to a parasite-causing disease called trichomonosis, which kills more than half of its chicks and limits population growth.

Fortunately, it isn't 1662 anymore. Today, an evolving conservation tool could help pull these birds back from the brink of extinction: genetic rescue. It works by adding genetic diversity to these kinds of precariously numbered populations — by introducing specific individuals or, potentially, by someday directly editing their genes. If it works, this pigeon’s future may once again be as rosy as its plumage.

“We want to try to give them the tools to fight this disease,” says Camilla Ryan, a graduate student who studies the Mauritius pigeon with genomics researcher Matt Clark at England’s Earlham University. “The birds don’t have the numbers or potentially the genetic diversity to deal with the disease themselves.”

Clark and Ryan are hoping to pull this population back on its feet by pinpointing the genes that make these birds so vulnerable to in the first place. Then, they’ll sample captive pink pigeons in zoos and parks around the world in search of genes better suited to fight the disease, with the ultimate goal of potentially mating these with the wild population. The team has already generated genetic data from 180 different pink pigeons.

Still, the pair remain cautious in implementing a technique that has brewed controversy ever since it started becoming more readily implemented in the 1990s, in hallmark cases of rescuing Florida panthers and Illinois prairie chickens. They aren’t alone: Many conservationists argue that the approach could create unforeseen problems for species at risk, and that it doesn't resolve the underlying problems that push so many species to the brink of extinction, including habitat loss due to human development.

But as humans continue to encroach on wild habitats and alter global climate patterns, the situation for many species has become more dire. Now, many researchers are turning to genetic rescue this as a viable tool to pull these most vulnerable species from the brink of extinction. In the more distant future, some scientists think we might be able to go further, genetically modifying animals to become better suited to their rapidly changing environments.

But let’s not get too ahead of ourselves. For now, scientists are focused on sharpening their genomics tools. 

Crossing captive bird with wild bird populations can have mixed effects on their genomes. These domestic rock pigeons soar above Hurlstone Park, a suburb of Sydney. (Toby Hudson)

When populations like the pink pigeon’s shrink down to the double or even single digits, they experience something called inbreeding depression. Essentially, that means they have less diversity in their gene pool, which makes it harder for them to beat challenges in their environment. Signs of this have been found in numerous species, including an isolated population of wolves in Michigan where individuals started to develop an unusual arched posture and stubby tails—possible indicators of poor health.

Now, Ryan and Clark are scouring historic tissue samples from five museums across Europe to look for genes that older pink pigeons may have once had to fight off disease before inbreeding depression took hold. The team will then look for captive birds that may have maintained these historic helpful genes to mate them with the wild population.

Sounds fairly straightforward, right? Unfortunately, playing a genetic deity isn’t that simple.

Each genotype you introduce into the existing population comes with its own pros and cons. So the team must be careful not to introduce new problems into the wild birds’ immune systems, says Clark. “You could end up breeding a population that is very successful at fighting off Trichomonas, but what you have done is accidentally decreased the amount of diversity in the immune system,” says Clark.

If that’s the case, he adds, a new disease that they weren’t prepared for could theoretically hit and wipe out the entire population.

Mating captive birds with wild birds also runs the risk of introducing genes that the captive birds had evolved to survive in captivity, weakening the wild bird’s ability to survive in the wild. “By trying to help them out, you’ve made it worse,” Clark says. This threat, called outbreeding depression, raises hackles amongst conservation biologists and is a primary argument against using genetic rescue more widely.

The Florida panther is a hallmark of how genetic rescue can help pull species from the brink of extinction. (U.S. Fish and Wildlife Service)

Yet despite these risks, several success stories have shown that genetic rescue can work. One of the major success stories conservationists point to is the Florida panther.

This large, iconic cat once lurked through the southeastern U.S in large numbers, enjoying its status as top predator and vital member of the ecosystem. But by the 1970s, habitat loss and hunting had shrunk the population to between 12 and 20 adults. Not only were their numbers dismal, but almost all of the male panthers showed signs of inbreeding depression, including undescended testicles, kinked tails and low sperm counts.

 Conservationists didn’t want to see this cat—which helped keep populations of white-tailed deer, wild hog, and other prey animals in check—go extinct. So in 1995, the U.S. Fish and Wildlife Service worked with a team of researchers to transfer eight female mountain lions from Texas to mate with the Florida panthers. They hoped the mountain lions, which are a subspecies of the panther, would revitalize the gene pool and boost the population size.

Stuart Pimm, a conservation ecologist at Duke University, says he had his doubts at first. If you were trying to rescue a species that had become so rare that it showed genetic damage, he believed, then it was already too late to save them. Many of his colleagues agreed. “You were treating the symptom rather than the cause,” Pimm says, citing habitat loss as the major cause in this case.

But the researchers went ahead, and mated the panthers and the mountain lions. Amazingly, their efforts seemed to work. The panther population grew and the next generation appeared free of kinked tails, undescended tentacles, and other signs of inbreeding. “All of those things disappeared,” says Pimm. Ten years later, Pimm ran a follow-up study showing they had sustained a growing population free of these signs of inbreeding depression.

“It was fast, it was a very effective process,” he says now.

Other success stories popped up in the 1990s. Great prairie chicken populations grew for the first time in decades (though more recent studies question the role of genetic rescue in this success), along with the Swedish adder, a venomous snake that had suffered from inbreeding. Today, Pimm has changed his tune: He now believes genetic rescue can be an excellent tool in a conservationist’s toolbox, and is considering using it to protect other top predators, including lions in Africa.

Florida panthers have become an icon of genetic rescue success. (Michaelstone428 )

As researchers around the world consider implementing genetic rescue, they must better understand how the risk of outbreeding depression could differ from species to species. Unfortunately, because genetic rescue has been so controversial, few cases exist that could offer this information.

Even the success stories of the panthers, chickens and adders hold limited information regarding how the mechanism might transfer from one species to another, says Andrew Whiteley, a conservation genomics researcher at the University of Montana. That’s partly because these cases weren’t done systematically—they were more of a last-ditch effort to save a critically endangered species.

“Those were done in response to a pressing management concern, they weren’t really done to test the concept of genetic rescue in an experimentally rigorous way,” says Whiteley. “So those uncertainties are going to remain.”

Working to fill those knowledge gaps, Whitely has been conducting experiments with brook trout—a species easier to experimentally study than large predators—in which his team has moved fish into four different isolated populations and introduced fish from elsewhere to mate with them. Preliminary results suggest that the first round of matings were successful, but the real measure of success will come with the second generation’s ability to survive and reproduce—this is where symptoms of outbreeding depression tend to arise.

He plans to conduct a comprehensive assessment of the second generation’s ability to survive and reproduce, building a so-called pedigree to see how genes flow through the system. “And ultimately dig in with genomics to understand at the genome level what happened when this pulse of gene flow entered this small population,” says Whiteley. “Those are the types of data we need to be able to make solid recommendations.”

Crossing captive bird with wild bird populations can have mixed effects on their genomes. Here, a wild rock dove in flight. (Alan D. Wilson)

If the traditional form of genetic rescue is considered controversial, a newly developing iteration will like start a far louder hullabaloo. Today, biologists are considering literal tinkering with animal genomes, by genetically engineering them to have certain traits.

Robert Fleischer, head of the Center for Conservation Genomics at Smithsonian’s National Zoo & Conservation Biology Institute, is considering this option to make birds in Hawaii resistant to or tolerant of avian malaria, a human-introduced pathogen devastating many Hawaiian bird populations today. But researchers in his group and elsewhere say they are just in the preliminary stages of investigating this technique.

“We are not at the stage of doing any rescuing yet, we are just setting the stage for doing that in the future if it will work out,” says Fleischer.

Oliver Ryder, director of Conservation Genetics at San Diego Zoo Global, says these techniques could someday prove invaluable, but that broader discussions about the ethics and logistics would need to come first. Within those discussions, researchers would need to weigh the risks associated with each case—including the risk that the efforts simply wouldn’t work.

“In spite of the efforts, the pathogen would find a way around the solution or the engineering,” says Ryder, “so all of the effort would not be sufficient to keep the species from going extinct.”

Ryder is involved in a broader effort to develop yet another genetic rescue approach, and is interested in using it to save the Northern White Rhino. The technique, which is still years away, would use stem cell technology to produce eggs and sperm from frozen Northern White Rhinos cells stored at the San Diego Zoo Global. His team is also looking into using frozen sperm to create embryos from eggs obtained either from the last living females or through stem cell techniques. They would then theoretically transfer embryos into closely related rhinos, who would serve as surrogates. 

This rhino is the perfect candidate for such an approach, in part because there are only three of these individuals left that are all unable to breed naturally, Ryder says. “The Northern White Rhino is functionally extinct,” says Ryder. “The only way to keep it from going extinct would be to genetically rescue it using advanced genetic and reproductive technologies.”

For now, researchers generally agree that traditional genetic rescue without genetic modification offers the most immediate conservation solution. However, it will never be the end-all solution to saving degrading populations. Instead, it offers a stop-gap opportunity to deal other overlying issues like reducing isolation and improving habitat, says Chris Funk, a researcher at Colorado State University who has conducted studies on Trinidadian guppies to track when and how outbreeding depression may arise.

Funk, like Pimm, at first called himself a skeptic—not because he didn’t believe genetic rescue could work, but because he considered himself a purist when it came to conservation. But as more and more populations become isolated and threatened by increasing human pressures and development, he says he has come to realize that some compromises may be necessary. “There is accumulating evidence that it can work in a lot of circumstances,” says Funk.

“We are not going to have the luxury to have this purist attitude,” he continues. “If we want these populations on the landscape, we are going to have to use genetic rescue to keep them from going extinct.”

About Laura Poppick

Laura is a freelance writer based in Portland, Maine and a regular contributor to the Science section.

Can a bounty of females save reptile species from climate change?

A new paper published in BMC Ecology today asks whether climate change could bias the sex ratio of certain reptiles, leading to potential extinction risk. In this guest blog, Lisa Schwanz, one of the authors, describes what they found.

As humans, we take for granted that roughly equal numbers of sons and daughters will be born into our populations every year. But, have you ever considered what problems would arise if we started producing 75% sons? Or 90% daughters?

While this is just a thought experiment for humans, it’s a reality for many reptile species around the world whose sex ratios are linked to climate. For most turtles and many lizards, the sex of an individual is determined during embryonic development by egg incubation temperature – a trait known as temperature-dependent sex determination. The contrasting system in mammals, birds, and other reptiles involves sex chromosomes (e.g. female XX and male XY), and is relatively insensitive to temperature.

The strong tie between temperature and individual sex in reptile species has led to concern that climate, and climate change, could bias the sex ratio of the entire offspring cohort and increase extinction risk.

For turtles, 100% females can hatch in warm years and 100% males in cold years. There is an unusual reptile in New Zealand, called the tuatara, that shows the opposite pattern, where males are produced at warm temperatures and females at cold temperatures. A large number of lizard species will only develop as a male at intermediate temperatures, and as a female at either extreme.

Due to a dearth of empirical data in the literature, we performed computer simulations to address this question, with the aim of gaining insight into fundamental processes that might operate in any species, rather than placing the focus on a single species.

Importantly, we knew that the impact of climate on population persistence would depend crucially on two factors – how biased the sex ratios are and what proportion of males is necessary for females in a population to reproduce. The number of females in a population is crucial for persistence since it puts a limit on how many offspring can be produced. Intuitively, a female-biased sex ratio can aid in population persistence as long as the mating system is polygamous and there are ‘just enough’ males to fertilize all of the females.

For the sake of comparison, we contrasted our results for temperature-sensitive species to those for species without temperature-driven sex ratios (i.e. with sex chromosomes). For species without temperature-driven sex ratios, we found that the geographic range is limited purely by the effects of climate on the ability of an embryo (i.e. egg) to survive and hatch. Where enough juveniles recruit into the population to replace dying adults, populations will persist.

In contrast, the range limits for a species whose sex ratios are driven by temperature were greatly reduced by the effect of climate. At the range edges, eggs can hatch sufficiently well, but too few males or too few females are produced to sustain future generations.

Populations don’t exist in isolation, however. They are connected to other populations through dispersal. And dispersal can bring an immigrant of the ‘rare’ sex.

As soon as we add dispersal, the predictions of our model change in a dramatic fashion. Importantly, species with temperature-driven sex ratios push their range boundaries to greater climatic extremes than species without biased sex ratios, as long as the rare sex immigrates to the biased populations at the range boundary.

To understand why this happens, consider a very warm population of a reptile without temperature-driven sex ratios. Most of the eggs die from overheating, and those eggs that do hatch are 50% males and 50% female. Not enough females hatch to become adults and sustain the population. Immigration can help support a few populations, but not many.

Now consider a population with temperature-driven sex ratios at the same warm climate. Similarly, only a small number of eggs hatch, but now all of the offspring are females. This means twice as many females hatch in a warm population if sex ratios are driven by climate compared to if they are not. This is a problem if there are no males to mate with. But add in the possibility of males dispersing from the colder part of the range, and you have enough reproductively-competent females to sustain the population.

Overall, when males disperse from their population or origin, the geographic range of species with temperature-driven sex ratios shifts into relatively warm (female-producing) climates. In contrast, when females disperse, the range shifts to relatively cold (male-producing) climates.

This might be good news for the majority of reptile species facing climatic warming. Most species with temperature-driven sex ratios overproduce females at warm temperatures and have male-biased dispersal. As long as some populations produce sufficient sons to disperse across the range, some populations may thrive under a warming climate.

Our next step in this research is to address this very question – how do climate-driven sex ratios influence the rate at which populations grow or decline under warming climates? The result will tell us whether reptiles with temperature-driven sex ratios are more vulnerable to climatic warming, or whether they have an advantage over their cousins with 50:50 sex ratios.

Lisa Schwanz is a Senior Lecturer and holds an ARC Discovery Early Career Researcher Award in the School of Biological, Earth and Environmental Sciences and Evolution & Ecology Research Centre at the University of New South Wales.

Critically endangered species successfully reproduced using frozen sperm from ferret dead for 20 years

Black-footed ferrets, a critically endangered species native to North America, have renewed hope for future survival thanks to successful efforts by a coalition of conservationists, including scientists at Lincoln Park Zoo, to reproduce genetically important offspring using frozen semen from a ferret who has been dead for approximately 20 years. The sire, "Scarface," as he is affectionately called by the team, was one of the last 18 black-footed ferrets to exist in the world in the 1980s. Eight kits, including offspring of Scarface, were born recently, significantly increasing the gene diversity of this endangered population that a dedicated team is working to recover in the wild.

Their work published Aug. 13 in the journal Animal Conservation "Recovery of Gene Diversity Using Long-Term Cryopreserved Spermatozoa and Artificial Insemination in the Endangered Black-Footed Ferret."

Partners working to save black-footed ferrets from extinction, and recover a healthy population back to the wild include Lincoln Park Zoo, The Smithsonian Conservation Biology Institute (SCBI), U.S. Fish and Wildlife Service, Louisville Zoological Garden, Cheyenne Mountain Zoo, Phoenix Zoo and Toronto Zoo.

"Our study is the first to provide empirical evidence that artificial insemination with long-stored spermatozoa is not only possible but also beneficial to the genetic diversity of an endangered species," said David Wildt, lead author, senior scientist and head of the Center for Species Survival at SCBI. "What we've done here with the black-footed ferret is an excellent example of how sperm preservation can benefit species recovery programs."

The U.S. Fish and Wildlife Service developed and oversee the Black-Footed Ferret Recovery Program. The Association of Zoos and Aquariums' Species Survival Plan manages the black-footed ferret breeding program at ex situ facilities, the breeding population in which is comprised of approximately 300 animals.

"The entire species survival depends on successful captive management to ensure healthy genetics over the next 100 years and to produce individuals for the reintroduction program," explained Black-Footed Ferret Reproduction Advisor Rachel Santymire, PhD, director of the Davee Center for Endocrinology and Epidemiology at Lincoln Park Zoo. "To balance out these demands on the breeding program, we have to ensure that each individual ferret passes its genes on to the next generation."

Over the past several years, the team has been developing assisted reproductive technology like artificial insemination and semen cryopreservation. For this study, all of the males were managed either at SCBI or at the USFWS National Black-Footed Ferret Conservation Center. Scientists collected semen samples from adult black-footed ferrets that ranged in age from one to six years old. All females were managed at SCBI.

Initially, scientists used fresh semen to artificially inseminate females who failed to naturally mate with males, resulting in 135 kits. With just a few founders to rebuild an entire species, early managers of the black-footed ferret recovery program knew that genetic diversity would be lost. Loss of genetic variation can lead to increased sperm malformation and lower success of pregnancy over time. Researchers, led by Santymire, routinely collected and preserved black-footed ferret semen for later use as part of standard operating procedures.

SCBI developed a successful laparoscopic artificial insemination technique for black-footed ferrets. Females are induced ovulators, which mean that mating itself causes the ovary to release its eggs. SCBI researchers developed a hormone treatment that artificially causes ovulation to occur. Scientists then deposited the male's fresh or frozen-thawed sperm directly into the female's uterus. Animal care staff closely monitored potentially pregnant females by taking weight measurements and remote monitoring of the nest boxes via closed-circuit cameras.

During the 2008 breeding season, SCBI scientists used semen samples from four male black-footed ferrets donors that had been frozen for 10 years. Black-footed ferret Population Advisor Colleen Lynch of Riverbanks Zoo and Garden conducted population genetic analysis to select pairings of deceased sperm donors with living females based on several genetic metrics including mean kinship of the parents and inbreeding coefficients of potential offspring to maximize the genetic benefit of successful pairings. In the years that followed, subsequent AIs incorporated semen that had been cryopreserved up to 20 years, also resulting in successful pregnancies.

"Our findings show how important it is to bank sperm and other biomaterials from rare and endangered animal species over time," said Paul Marinari, senior curator at the Smithsonian Conservation Biology Institute. "These 'snapshots' of biodiversity could be invaluable to future animal conservation efforts, which is why we must make every effort to collect, store and study these materials now."

The science of ‘de-extinction’: Can cloning bring extinct animals back to life?

Which theme park would you rather visit – the one with roaming dinosaurs or the one with a bunch of pigeons? At least the pigeons wouldn’t eat you.

While Jurassic Park remains a fantasy – the latest research indicates the DNA techniques used to recreate dinosaurs in Michael Crichton’s novel and Steven Spielberg’s subsequent movie are not possible – scientists are confident they can bring back an extinct bird.

For its first project in ‘de-extinction’, the Revive & Restore initiative in the US aims to resurrect the North American passenger pigeon, which became extinct in 1914.

While separate attempts to revive the Tasmanian tiger, the California condor and the woolly mammoth may seem more attention-grabbing, the pigeon project could prove to be a milestone in de-extinction.

Its population fell from billions to nothing in the space of a century, but there are hundreds of preserved specimens with extractable DNA to work from. The first step on the road to re-introducing the passenger pigeon will be to sequence the DNA of its nearest living relative, the band-tailed pigeon.

Revive & Restore wants to help scientists attempting to bring extinct species back to life. It also wants to establish an ethical framework for such practices.

On Friday, it will host a day-long TEDx conference in Washington on the subject. Speakers will include experts from the fields of genetics, conservation and biology.

Proponents of de-extinction insist it is viable and point to a recent Spanish experiment in which a Pyrenean ibex, or mountain goat, which went extinct more than ten years ago, was cloned and brought to life, albeit only for a few minutes before it died because of breathing difficulties.

The big question, of course, is one of ethics – why should we play God to bring back extinct animals?

‘We are bringing back extinct species in order to preserve biodiversity, to undo harm that humans have caused in the past and restore ecosystems, and because it’s just the right thing to do,’ said Ryan Phelan, executive director at Revive & Restore.

‘Did we play God when we drove most of these species to extinction? Humans have actually been “meddling” with nature for thousands of years— look at the breeding of horses or dogs, for instance.

‘Through rapidly advancing genomic technology and techniques, it is becoming possible to reconstitute the genomes of extinct species using preserved specimens and archaeological artefacts.

‘Revive & Restore is working with de-extinction scientists worldwide to build a roster of potentially revivable species and establish criteria for which are the most practical and desirable species for conservation and molecular biologists to attempt to bring back.’

Extinction is big news. An exhibition at the Natural History Museum in London, ‘Extinction: Not the End of the World?’, even goes so far as to ask if humankind will destroy itself.

It points out that extinction is a ‘natural part of life on Earth’ and that the animals and plants alive today would not have survived without it.

Ms Phelan said that de-extinction has the same aim as conservation.

‘The highest priority of conservation is to first protect living, endangered species, but de-extinction methodologies can be used to help reduce the threat to some of these species,’ she said.

‘For the species that are revivable, de-extinction project will take decades, if not centuries to complete, so it is extremely important that de-extinction is not seen as a replacement for conservation. In most cases, once a species is extinct, it is truly gone forever.’

Despite these assertions, the World Wide Fund for Nature (WWF) believes we need to concentrate on the species currently under threat, rather than ploughing resources into bringing back those which are extinct.

Glyn Davies, director of global programmes at WWF-UK, said: ‘Although this is exciting technology, it’s important to remember that we are only looking at the possibility because we have failed to look after our natural world.

‘It’s much more important to safeguard species now for a healthy and varied planet and it’s much less expensive to keep thriving populations of plants and animals alive in the wild.’

Revive & Restore insists that transparency and ethics are key to its goals.

‘De-extinction projects are also not going to be hasty or ill-conceived projects,’ said Ms Phelan.

‘First, extensive research about a candidate species is conducted before moving into a lab setting for genomic work to revive the species.

‘Then, once the initial revival is completed, the species will be bred in captivity. The growing population will be studied and then eventually moved to quarantine areas for further observation and analysis.

‘Getting the okay from regulatory agencies will be required before the creatures are ultimately re-introduced to the wild.’

While it might take years before we are petting a woolly mammoth in a zoo for cloned animals, Ms Phelan believes that breakthroughs are on the horizon.

‘There is no doubt that we will see significant de-extinction milestones within the next decade,’ she said.

‘Further de-extinction work is currently underway and species revival projects will rapidly advance. As a field of study and research, we project that de-extinction is poised to rapidly grow into its own discipline.’

The Last Resort for Northern White Rhinos

Northern white rhinos, a subspecies with only three left in its population, would require nothing short of a miracle to be saved from extinction.

The trio, two females and a male, are watched 24/7 by armed guards, who make sure they don't succumb to poachers at their home in the Ol Pejeta Conservancy in Kenya.

Last November, a tweet went viral that showed Sudan, the male, lying on the ground. The tweet came from biologist Daniel Schneider, who underscored that Sudan was the last male of his species.

It wasn't the first time Sudan stirred public sympathy. In May of last year, Ol Pejeta partnered with Tinder to launch a campaign to raise awareness about the rhino, "the most eligible bachelor in the world."

The campaign's goal was to raise money to fund new assisted reproductive techniques.

The price to make that happen? A whopping $9 million. But scientists say they aren't ready to give up quite yet.

Watch the video: Kann ich nur mit Mauzi Pokémon Schild durchspielen? (May 2022).


  1. Drystan

    remarkably, very much the pretty thing

  2. Dall

    Have you been writing this article for a long time?

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