Some animals pause their own pregnancies, but how they do it is still a mystery



Tammar wallabies are one of many species that can pause their pregnancies until the time is right.
LCAT Productions / Shutterstock

Jane Fenelon, University of Melbourne

Putting your pregnancy on pause until the time is right to give birth sounds like something out of a sci-fi novel, but for many mammals what’s known as “embryonic diapause” is an essential part of raising their young.

Although scientists have known since the 1850s that some animals have this ability, it is only now becoming clear how it could teach us valuable lessons about human pregnancy, stem cells, and cancer.

Which animals can do this?

More than 130 species of mammal can pause their pregnancies. The pause can last anywhere between a couple of days and 11 months. In most species (except some bats, who do it a little later) this happens when the embryo is a tiny ball of about 80 cells, before it attaches to the uterus.

It’s not just a single group of mammals, either. Various species seem to have developed the ability as needed to reproduce more successfully. Most carnivores can pause their pregnancies, including all bears and most seals, but so can many rodents, deer, armadillos, and anteaters.




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More than a third of the species that take a breather during gestation are from Australia, including some possums and all but three species of kangaroo and wallaby.

The record-holder for pregnancy pause time is the tammar wallaby, which has been studied extensively for its ability to put embryos on hold for up to 11 months.

Why pause pregnancy?

The main advantage to pausing pregnancy is that it separates mating and birth. There are two main ways in which animals do this.

The first way is to mate soon after giving birth, to have a backup pregnancy in case something happens to the newborn young. The stress of lactating triggers a pause that lasts during suckling, and the pregnancy restarts once the young leave.

The second way is to pause every pregnancy until the time is right (usually depending on the season). For example, minks mate around the start of March but put the embryos on pause until after the spring equinox (March 21), when the days are growing longer in their northern hemisphere homes. This ensures that the young are born in spring when conditions improve, and not in winter.

The tammar wallaby combines these two methods (suckling in the first half of the year, short days in the second) to pause for almost a year and give birth in January. This ensures the young leave the pouch the following spring instead of in the middle of a hot Australian summer.

What can we learn from diapause?

Diapause was first identified in 1854 after hunters in Europe noticed that pregnancy in roe deer seemed to last a lot longer than normal. Since then scientists have been fascinated by this process and it has helped us understand more about basic reproductive processes in all mammals.

But it took until 1950 before our knowledge of pregnancy had increased enough so that we could confirm what the hunters had observed 100 years earlier.

But how the process worked at the molecular level is still a mystery. Until recently, there seemed to be no connection between which species used it and which didn’t and there didn’t seem to be a unifying mechanism for how pregnancy was paused. Even the hormones controlling diapause are different between mammal groups.

However, research now suggests that regardless of what hormones affect the uterus, the molecular signalling between the uterus and the embryo is conserved, at least between the mouse, mink and tammar wallaby.

Furthermore, researchers in Poland paused embryos from sheep (a non-diapause species) by transferring them into a mouse uterus and then back into the sheep with no ill effects.

This indicates the potential for diapause could lie in all mammals, including humans.

So when can I pause my pregnancy?

It’s unlikely that pausing pregnancy will become the norm in humans. For starters, you’d have to know you were pregnant within five days of conceiving to match the time when most species start diapause.

Understanding how mammals pause their pregnancies does have significant implications for our understanding of how to make healthy embryos. The time when the embryo enters into diapause is the same time in IVF when an embryo is transferred into the uterus. Diapause could help us improve how we grow embryos in culture or how to recognise which is the “best” embryo to transfer.




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Diapause could also help create better stem cells and find new cancer treatments. The first stem cells ever isolated by scientists came from a mouse embryo in diapause, when the cell cycle of the embryo is arrested. Stem cells are also remarkably similar to a diapaused embryo.

So understanding how diapause works at the molecular level could lead to new therapies to halt cell division or to identify markers for tumour stem cells, which are thought to be responsible for metastasis in cancer.The Conversation

Jane Fenelon, Research fellow in monotreme and marsupial reproduction and development, University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Animals are disappearing from forests, with grave consequences for the fight against climate breakdown – new research



A toucan eating a fruit in the tropical wetlands of the Pantanal, Brazil.
Uwe Bergwitz/Shutterstock

Charlie Gardner, University of Kent; Jake Bicknell, University of Kent; Matthew Struebig, University of Kent, and Zoe Davies, University of Kent

It’s tempting to think that our forests would be fine if we could simply stop trees being felled or burnt. But forests – particularly tropical ones – are more than just trees. They’re also the animals that skulk and swoop among them.

Worryingly, these furry and feathered companions are rapidly disappearing – and our new research indicates that this will have grave repercussions for the role forests play in combating climate breakdown.

Healthy tropical forests swarm with life. Beyond myriad invertebrates there are seed-eating rodents, a range of leaf eaters, birds of all kinds, and often primates. However, many forests have already lost most of their largest animals, mainly as a result of hunting to supply a growing bushmeat trade.

Hunting isn’t the only reason. Thanks to deforestation for farmland and logging, many forests today are highly fragmented. The small, unconnected patches that remain aren’t big enough to support populations of the largest species, which tend to need more space.

The disappearance of animals from otherwise intact habitats is known as defaunation, and it is leading to a growing number of empty forests not just in tropical countries, but around the world. The UK has already lost most of its largest species (think lynx, wolf, and wisent), while woodland bird numbers have declined by a quarter since 1970.




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The impacts of this defaunation have attracted the attention of the world’s conservation scientists, but studies to date have usually been carried out at single locations. Consequently, we lack a worldwide picture that takes into account different types of forest and the diversity of animals that are disappearing.

To fill this gap, we worked with William Baldwin-Cantello, chief adviser on forests at the World Wide Fund for Nature UK, to gather together all the existing research and perform a meta-analysis – an analysis of analyses – on the available data.

Forest flora need flourishing fauna

Our findings reveal a worrying trend. The loss of animals compromises the ability of forests to reproduce. This effect is particularly severe when primates and birds disappear, because of the key role they play in seed dispersal. Trees make fruit to entice animals to transport their seeds, because they are more likely to germinate and grow successfully if they fall further from their parent tree. So when fruit-eating animals disappear, fewer seeds are dispersed and the trees struggle to reproduce.

A black howler monkey eating a juicy cashew fruit.
akramer/Shutterstock

This animal absence will slowly change how forests look. Most tropical forests today are dominated by trees whose seeds are dispersed by animals. Over time, they are likely to be gradually replaced by trees that use the wind to reproduce. Naturally, these usually have small seeds, and therefore produce smaller trees that store less carbon for the same area of forest. As a result, forests will store less and less carbon, even if we completely halt deforestation.

This is particularly concerning because roughly 20% of the carbon dioxide we emit is absorbed by the world’s vegetation and soils, and half of this is due to tropical forests alone.

Rethinking forest health

Conserving forests is essential for the fight against climate breakdown – and, we do have a global tool at our disposal to help. Known as Reducing Emissions from Deforestation and forest Degradation, or REDD+ for short, it allows wealthy countries with large carbon footprints to pay poorer, tropical countries to protect their forests.

Of course, REDD+ is only an effective tool if the forests countries pay to protect continue to store the same amount of carbon. We usually monitor this by taking satellite images of the quantity of forest canopy remaining. But what satellite imagery can’t do is measure aspects of forest quality beneath the canopy.

Our research strongly suggests that one aspect of forest quality – defaunation – is a vital early warning sign of future losses in the carbon storing capacity of forests. In light of this, policies for managing forest carbon around the world may need a rethink.

We need to pay more attention to what’s going on beneath global forest canopies through research on the ground, though this will be difficult in remote areas. More importantly, we must make sure we’re doing all we can to conserve the full complement of animal species that live in our forests. For example, we need to heavily invest in conservation actions that help communities accustomed to hunting bushmeat to meet their dietary protein needs without harming wildlife. We must also enforce existing rules better, such as those that outlaw hunting within parks and reserves.

Preventing defaunation in forests won’t be easy. But given what we know about the critical role forest animals play, doing so will be essential if we hope to retain diverse and carbon-rich forests in the tropics and around the world. If the beauty and wonder of the forest’s animals wasn’t enough reason to protect them, we now have another: by conserving wildlife, we will be helping to save ourselves from the catastrophic effects of climate breakdown.


Click here to subscribe to our climate action newsletter. Climate change is inevitable. Our response to it isn’t.The Conversation

Charlie Gardner, Lecturer in Conservation Biology, University of Kent; Jake Bicknell, Lecturer in Conservation Biology, University of Kent; Matthew Struebig, Senior Lecturer in Biological Conservation, University of Kent, and Zoe Davies, Professor of Biodiversity Conservation, University of Kent

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Rewild 25% of the UK for less climate change, more wildlife and a life lived closer to nature



Eduard Militaru/Unsplash, CC BY-SA

Simon Lewis, UCL

The UK’s Labour Party has pledged to offer voters a Green New Deal at the next election. This is a radical programme for decarbonising society and the economy by 2030, through phasing out fossil fuels, investing in renewable energy and creating a public works programme to build the zero-carbon infrastructure of the future.

In my recent report, A Green New Deal for Nature, I argued that giving land back to nature could be another part of this vision. Restoring forests and other natural habitats to 25% of the UK’s land surface could sequester 14% of the UK’s annual greenhouse gas emissions each year. As emissions are scaled down and these ecosystems expand, they could continue to remove much greater quantities of carbon dioxide (CO₂) in future.

Often called “natural climate solutions”, restoring forests and wetlands draws carbon down from the atmosphere and stores it in the tissue of new vegetation and soil. On a large scale, and alongside leaving fossil fuels in the ground, this could help to limit global heating to well below 2°C.

The Domesday Book of 1086 indicated forest cover of 15%, ‘but significant loss of woodland started over 4,000 years ago in prehistory’. By the beginning of the 20th century, this had dropped to 5%.
Defra

These habitats can be restored through rewilding, which means giving natural processes a helping hand by stopping the draining of peatland for example, or letting a woodland regrow. Reintroducing species that were once extinct in a region can also help ecosystems regenerate. While letting nature take care of itself isn’t appropriate in all cases, rewilding is one of the most powerful and cost-effective ways to resist climate breakdown and wildlife loss at the same time.

But what might that look like in practice?




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The “green” in the Green New Deal

For wildlife, it’s important that restored habitats are connected. Linked habitats allow plants and animals to move more easily as temperatures rise and rainfall patterns change. If species can migrate through green corridors to cooler areas, they could avoid local extinctions. This could mean a network of expanded hedgerows and woodland that criss-crosses the land, connecting wild habitats and ensuring species can migrate safely between them.

Other changes include reintroducing European beavers to flood plains to help manage flood risks. In remote places like the Scottish Highlands, wolves could return to keep herbivores in check and help woodlands rebound, increasing their long-term potential to store carbon. Rewilding instead of burning or draining carbon-rich peatlands would allow their vegetation and carbon stocks to recover. Wildlife, from insects to birds and large mammals, would have space to flourish. The UK would switch from being one of the world’s most nature-depleted countries to a green and vibrant land.

Beavers have returned to the UK’s rivers after an absence of 500 years.
Abi Warner/Shutterstock

This may sound utopian, but it’s not. The UK is a densely populated country, and with 72% of the land area used for agriculture, it might seem that there’s little room for anything else. But less than 20% of the UK is occupied by crops or dense urban communities, so 80% of it could be better managed for nature and storing carbon.

Some 45% of the UK’s land surface is given to grazing livestock. The poorest land for agricultural productivity is only farmed because of taxpayer subsidies. Meanwhile, about 13% of the UK is allocated to grouse-shooting and deer-stalking, often on degraded peatlands that are managed at huge environmental cost for the benefit of a tiny number of hunters. This land is currently of little value for food production, but it could store plenty of carbon if rewilded.




Read more:
Rewilding is essential to the UK’s commitment to zero carbon emissions


The exact locations should be the subject of local knowledge and consultation, but reducing grazing land from 45% of the UK to 33% and returning that 12% to wild habitat could provide half of the carbon storage needed. Restoring half of the UK’s peatlands could add 6% more land, alongside protecting the 7% of the UK that is already broadleaf woodlands and wildflower meadows. Together, this would make 25% of the UK’s land a refuge for wildlife and a vast reservoir of CO₂.

The Lady Fen wetland in Norfolk was recently restored to 300 acres.
Tony Mills/Shutterstock

How can it be done?

Farm subsidies currently give £3 billion to UK farmers ever year. By some estimates, subsidies are half the income of many farmers. After Brexit, this money could be given to farmers to reward them for storing carbon and rewilding, making this more financially viable than grazing on agriculturally poor land.

Economy-wide carbon taxes could also pay for rewilding schemes, while the government could also issue green bonds to raise funds to lend to landowners, helping cover the early costs of restoring land to wild habitat.

Reducing the demand for farm produce from land will also be key to making space for nature. This means cutting down on the most inefficient use of land – farming for meat and dairy, which uses between four and 100 times the land area to produce a single gram of protein compared to beans, nuts and other plant sources. Policies which make it easier for everyone to eat food that’s healthy and sustainable – including less meat and dairy – are the final pieces of the puzzle.

Less climate change, more wildlife, and a longer life lived closer to nature. That’s a lot to gain from modest investments in how land is used in the UK.


Click here to subscribe to our climate action newsletter. Climate change is inevitable. Our response to it isn’t.The Conversation

Simon Lewis, Professor of Global Change Science at University of Leeds and, UCL

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Here’s how your holiday photos could help save endangered species



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Kasim Rafiq, Liverpool John Moores University

Animal populations have declined on average by 60% since 1970, and it’s predicted that around a million species are at risk of extinction. As more of the Earth’s biodiversity disappears and the human population grows, protected landscapes that are set aside to conserve biodiversity are increasingly important. Sadly, many are underfunded – some of Africa’s most treasured wildlife reserves operate in funding deficits of hundreds of millions of dollars.

In unfenced wilderness, scientists rarely have an inventory on the exact numbers of species in an area at a particular time. Instead they make inferences using one of many different survey approaches, including camera traps, track surveys, and drones. These methods can estimate how much and what kind of wildlife is present, but often require large amounts of effort, time and money.

Camera traps are placed in remote locations and activated by movement. They can collect vast quantities of data by taking photographs and videos of passing animals. But this can cost tens of thousands of dollars to run and once in the wild, cameras are at the mercy of curious wildlife.

Track surveys rely on specialist trackers, who aren’t always available and drones, while promising, have restricted access to many tourism areas in Africa. All of this makes wildlife monitoring difficult to carry out and repeat over large areas. Without knowing what’s out there, making conservation decisions based on evidence becomes almost impossible.

Citizen science on Safari

Tourism is one of the fastest growing industries in the world – 42m people visited sub-Saharan Africa in 2018 alone. Many come for the unique wildlife and unknowingly collect valuable conservation data with their phones and cameras. Photographs on social media are already being used to help track the illegal wildlife trade and how often areas of wilderness are visited by tourists.

Despite this, tourists and their guides are still an overlooked source of information. Could your holidays snaps help monitor endangered wildlife? In a recent study, we tested exactly this.

Partnering with a tour operator in Botswana, we approached all guests passing through a safari lodge over three months in the Okavango Delta and asked them if they were interested in contributing their photographs to help with conservation. We provided those interested with a small GPS logger – the type commonly used for tracking pet cats – so that we could see where the images were being taken.

We then collected, processed, and passed the images through computer models to estimate the densities of five large African carnivore species – lions, spotted hyaenas, leopards, African wild dogs and cheetahs. We compared these densities to those from three of the most popular carnivore survey approaches in Africa – camera trapping, track surveys, and call-in stations, which play sounds through a loudspeaker to attract wildlife so they can be counted.

The tourist photographs provided similar estimates to the other approaches and were, in total, cheaper to collect and process. Relying on tourists to help survey wildlife saved up to US$840 per survey season. Even better, it was the only method to detect cheetahs in the area – though so few were sighted that their total density couldn’t be confirmed.

Thousands of wildlife photographs are taken every day, and the study showed that we can use statistical models to cut through the noise and get valuable data for conservation. Still, relying on researchers to visit tourist groups and coordinate their photograph collection would be difficult to replicate across many areas. Luckily, that’s where wildlife tour operators could come in.

Tour operators could help collect tourist images to share with researchers. If the efforts of tourists were paired with AI that could process millions of images quickly, conservationists could have a simple and low-cost method for monitoring wildlife.

Tourist photographs are best suited for monitoring large species that live in areas often visited by tourists – species that tend to have high economic and ecological value. While this method perhaps isn’t as well suited to smaller species, it can still indirectly support their conservation by helping protect the landscapes they live in.

The line between true wilderness and landscapes modified by humans is becoming increasingly blurred, and more people are visiting wildlife in their natural habitats. This isn’t always a good thing, but maybe conservationists can use these travels to their advantage and help conserve some of the most iconic species on our planet.The Conversation

Kasim Rafiq, Postdoctoral Researcher in Wildlife Ecology and Conservation, Liverpool John Moores University

This article is republished from The Conversation under a Creative Commons license. Read the original article.