Koalas can learn to live the city life if we give them the trees and safe spaces they need


Edward Narayan, Western Sydney University

Australia is one of the world’s most highly urbanised nations – 90% of Australians live in cities and towns, with development concentrated along the coast. This poses a major threat to native wildlife such as the koala, which can easily fall victim to urban development as our cities grow. Huge infrastructure projects are planned for Australian cities in the coming few years.

The need to house more people – the Australian population is projected to increase to as much as 49.2 million by 2066 – is driving ever more urban development, much of it concentrated in our biggest cities on the east coast. This is bad news for the koala population, unless the species’ needs are considered as part of planning approvals and the creation of urban green spaces. The good news is that koalas can learn to live the “green city life” as long as they are provided with enough suitable gum trees in urban green spaces.




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Indeed, our newly published research, which analysed stress levels in wild koalas according to their habitat, reveals that koalas are the most stressed in rural and rural-urban fringe zones. This appears to be due to factors such as large bushfires, heatwave events, dog attacks, vehicle collision and human-led reduction of prime eucalyptus habitats. Koalas living in urban landscapes are less stressed as long as the city includes suitable green habitats.

If there are suitable trees, koalas can learn to live among us – this one is next to a school in South Australia.
Vince Brophy/Shutterstock

In other words, wild animals including the koala can adapt to co-exist with human populations. Their ability to do so depends on us giving them the space, time and freedom to make that adaptation. This means ensuring they can carry out, without undue pressures, the biological and physiological functions on which their survival depends.

Wildlife species that lack access to suitable green habitats in cities are at higher risk of death and local extinction. Having to move between fragmented patches of habitat increases the risks. Land clearing and habitat destruction for infrastructure projects and other urban development are compounding the major threats to koalas, such as being hit by vehicles or attacked by dogs.




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Koalas are feeling the heat, and we need to make some tough choices to save our furry friends


How does human pressure cause stress in wildlife?

Animals cope with stressful situations in their lives through very basic life-history adjustments and ecological mechanisms. These include changes in physiology and behaviour in response to stresses in their environment.

We can help make the environment more suitable for wildlife species by ensuring their basic needs for food, water and shelter are met. If animals are deprived of any of these necessities, they will show signs of stress.

So by subjecting wildlife to extrinsic stressors such as habitat clearance, climate change and pollution we are making it even more difficult for these animals to manage stress in their daily lives.

Basically any unwanted change to an animal’s environment that prevents it from performing its basic life-history functions, such as foraging and social behaviour, will cause stress.

So what can be done?

The koalas are telling us it’s a major problem when urban design is not green enough. Innovative solutions are needed!

Cities can do much more for wildlife conservation. Creating safe green spaces for wildlife is critical. Not just koalas but other wildlife such as birds, small mammals, reptiles and frogs can benefit immensely from urban green spaces.

Even in suburbs with plenty of green space, problems still arise because urban planning typically designs this space around access for human recreation and not for the wildlife that was living there before the housing development moved in.

Urban planning should always incorporate the planning of green spaces that are safe for wildlife. Providing wildlife crossings is part of the solution. Another important element is educational programs to alert drivers to the need to look out for koalas.




Read more:
Safe passage: we can help save koalas through urban design


Measures like this can minimise impacts on wildlife that faces the many challenges of adjusting to city life.The Conversation

Edward Narayan, Senior Lecturer in Animal Science, Western Sydney University

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

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Koalas sniff out juicy leaves and break down eucalypt toxins – it’s in their genome


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Koalas spend a large part of the day sleeping – while their digestive enzymes get to work.
emmanueleragne/flickr , CC BY

Jenny Graves, La Trobe University

News is out today that the entire genome of the koala has been sequenced. This means we now have a complete read-out of the genes and other DNA sequences of this iconic marsupial mammal.

Knowing the full set of koala genes deepens our knowledge of koalas (and other Australian mammals) in many ways. Now we can understand how koalas manage to survive on such a toxic diet of gum leaves. Now we can follow the fortunes of historic koala populations and make good decisions about how to keep remaining koala populations healthy. Now we have a new point of comparison that we can use to understand how the mammal genome evolved.

This is important for science – but also economically. Koalas are incredibly well loved, with their baby-faces, shiny noses and big fluffy ears. Millions of visitors line up each year to spot them snoozing in gum trees – indeed, they are worth A$3.2 billion in tourist dollars.

Koalas are listed as a vulnerable species in some parts of Australia, affected by habitat destruction, disease and other stresses.




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Drop, bears: chronic stress and habitat loss are flooring koalas


We now have a high quality read-out of the koala genome. Video thanks to the Australian Academy of Science.

The koala genome

Koala DNA was sequenced with new “long-read” technology that delivers a complete and well-assembled genome. As far as quality of the read-out goes, it’s as good as the human genome, with continuous sequences now known over huge (almost chromosome-scale) spans. New technology enabled us to achieve this at a tiny fraction of the $2.7 billion it cost to sequence the first human.

The obtained koala genome sequence is much better quality than that for other sequenced marsupials – opossum, tammar wallaby and Tasmanian devil – and will really help us to assemble and compare genomes from all marsupials.

The koala has a genome a bit bigger than that of humans, with 3.5 billion DNA base-pairs. This amounts to about a metre of DNA, which is divided and packaged into eight large bits that we recognise as chromosomes.




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An animal has a set of chromosomes from mother and a set from father, so koalas have 16 large chromosomes in each cell. This is similar to other marsupials; as a group they seem to have a low chromosome number and a very stable genome arrangement. In placental mammals the number and arrangement of chromosomes is much more varied: for example, humans have 46, and rhinos 82 chromosomes.

The source of junk DNA

New findings from the koala genome help us to understand how mammal genomes evolved and how they work.

A lot (sometimes more than 50%) of animal genomes seem to be “junk DNA” – these are repeated sequences, many deriving from ancient viral infections. The koala, uniquely, seems to be in the middle of one such invasion. A DNA sequence derived from a retrovirus is present in different numbers and sites in different koala populations, testifying to its recent movement and amplification. This helps us learn how the genomes of humans and other mammals got so puffed up with junk DNA.

Like the human genome, the koala genome contains about 26,000 genes. These are stretches of DNA that code for or control proteins. Indeed, most koala genes are present in humans and other mammals – these are the same genes doing the same basic jobs in different animals.

So why is it important to sequence different species if their genomes are so similar? Well, it’s the special genes that have evolved to adapt the koala to its unique lifestyle that give us new and valuable information.




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How to survive on gum leaves

How koalas exist on an exclusive low-calorie and toxin-laced diet of eucalyptus leaves has been somewhat of a science mystery.

The genome provides answers. The koala has multiplied a family of genes that code for enzymes (members of the cytochrome P450 family) that break down the toxins of gum leaves. Evolution of these additional gene copies has enabled the koala to outstrip its competition, even at the cost of sleeping most of the day.

The genome also gives us clues to the koala’s picky eating habits. The koala genome contains many additional copies of genes that enable them to taste and avoid bitter flavours and even to “smell” water and choose juicy leaves (they don’t drink water).

Koalas have 16 chromosomes per cell.
chrisfithall/flickr, CC BY

The genome also gives us new information about how koalas develop. Like other marsupials, they are born about the size of a pea, and complete most of their growth and differentiation in the pouch. Developing koalas are nurtured by milk with a complex composition that changes with the stage of development.




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Saving an iconic Australian

Managing koala populations is very fraught, and there has long been a need for a holistic, scientifically-grounded approach to koala conservation.

Today’s koalas are the “last stand” of the marsupial family Phascolarctidae – and the koala genome contains new information about this evolutionary history. It also tells us that koala populations peaked about 100,000 years ago, then plunged to about 10% of their numbers 30-40,000 years ago, at the same time that the megafauna became extinct. This population was fairly stable until European settlement, when it plunged again to its present numbers (about 300,000).

Koalas once occupied a swathe of timbered habitat from Queensland to South Australia; now, only fragmented populations survive in the south. These are intensively managed, and small numbers of koalas are translocated to other sites, producing dangerously inbred populations. Bizarrely, one of the greatest problems is overbreeding in isolated populations – for example, on South Australia’s Kangaroo Island – which leads to animals eating themselves out of house and home.

The enemies of koalas in the north are habitat destruction and fragmentation by urbanisation and climate change.




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The koala genome paper reports sequence comparisons of different populations and identifies barriers to gene flow. With the information from the koala genome, we can now monitor genetic diversity in the surviving populations, and maximise gene flow between connected populations.

Koalas are the sole surviving member of the Phascolarctidae marsupial family group.
Photo by Holger Link on Unsplash, CC BY

Maintaining genetic diversity is important because different animals can mount different responses to environmental threats and diseases such as chlamydia, a bacteria that affects koala reproduction and eye health.

The koala genome provides us with information about the immune genes of the koala, and the changes in activity of these genes in infected animals. This will help us understand the different responses of animals, vital for developing vaccines and treatments.

The koala genome also identifies powerful anti-bacterials in milk that protect the baby koala from disease – and may provide humans with the next generation of antibiotics.

So sequencing the koala genome is good for science and good for koalas, an iconic species at the top of the tree for conservation efforts.


The Conversation


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Jenny Graves, Distinguished Professor of Genetics, La Trobe University

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

Drop, bears: chronic stress and habitat loss are flooring koalas


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Koalas are stressed out by a range of pressures, from habitat loss to dog attacks.
Edward Narayan, Author provided

Edward Narayan, Western Sydney University

Koalas are under a lot of stress. Heatwaves, land clearing and even noise pollution are all taking a toll.

Each year, hundreds of koalas are taken to veterinary clinics after being rescued from roadsides or beneath trees, and the incidences increase during the summer months.

Chronic and ongoing pressures such as habitat destruction are overwhelming koalas’ ability to cope with stress. Koalas are nationally listed as vulnerable, so it’s important to understand how they are affected by threats that can reduce life expectancy and their ability to cope with problems.

What is stress?

The term “stress” was coined in 1936 by Hans Sayle after experiments on rats. Sayle demonstrated that the adrenal glands, which sit on top of the kidney and produce the stress hormones adrenaline and cortisol, can swell in response to any noxious stimulus or due to pathological state. In addition, there are changes in the tissues and glands involved in the basic functioning of the immune system, reproduction and growth.


Read more: What happens to your body when you’re stressed


The short-term stress response is not necessarily bad, because it prepares the body to cope with external challenges. For example, tadpoles that are exposed to dragonfly nymphs grow larger and have bigger tail fins than other tadpoles.

However, chronic stress over a long time can seriously affect an animal’s health (humans included) and survival rates.

How do koalas respond to stress?

Koalas release the stress hormone cortisol in response to any unpleasant stimulus like being handled by humans (oddly, males are much more stressed by handling than females, unless the females are lactating).

Koalas have biological feedback mechanisms that can regulate the amount of cortisol they produce, so they can carry on with their day-to-day routine. However, if koalas are continuously stressed by something large and permanent, such as land clearing of their territory, it’s difficult for them to relax from a stressed state.

When this happens, the body undergoes a barrage of sub-lethal chemical changes. The resulting chronic stress can negatively affect the animals’ reproductive hormones and immune system function.

Koalas, like all animals that call Australia home, have basic physiological and behavioural adaptations needed for life in Australia’s often extreme environment. But human-induced threats such as land clearing continue to create ecological imbalances, and chronic stress makes it very difficult for koalas to cope with environmental change.

How much stress can a koala bear?

As my review of the research shows, the most common sources of stress for koalas are heat stress, car impacts and dog attacks. Foetal development of koalas could also be impacted by maternal stress due to lack of adequate food from gum trees in drought periods.

Urban and fringe zones (areas between rural and urban zones) are particularly stressful for koalas, with added pressures like noise pollution and a higher chance of land clearing.

All of these factors create a continual strain on koala physiology. The sight of a koala dead by the road is the distressing culmination of multiple, complex and dynamic environmental influences.

Clinical research has shown that wild koalas are suffering from chronic stress. Koalas are often rescued with signs of trauma, caused by car accidents, burns or dog attacks, which is very difficult to handle in veterinary clinics.

Koalas are a living treasure, the only extant representative of the family Phascolarctidae. They live exclusively on Australia’s east coast, but are considered rare in New South Wales and South Australia.

There are now numerous local dedicated koala conservation centres aimed at safeguarding their habitat and educating the public. Koalas also help increase public awareness of conservation among both young people and adults.

But more research is needed in studying how they respond to the stresses of life in a human-dominated landscape. Techniques such as non-invasive hormone monitoring technology can be used to provide a rapid and reliable index of how our koalas are being affected by stress.

The ConversationSimply put, if land clearing is not reduced now we will continue to add invisible stress on koalas. Our children may one day be more likely to see a koala dead on the road than one happily cuddling their gum tree.

Edward Narayan, Senior Lecturer in Animal Science; Stress and Animal Welfare Biologist, Western Sydney University

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