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


File 20171023 13961 13qa7bq.jpg?ixlib=rb 1.1
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.

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Let’s get this straight, habitat loss is the number-one threat to Australia’s species


Brendan Wintle, University of Melbourne and Sarah Bekessy, RMIT University

Earlier this month, Australia’s outgoing Threatened Species Commissioner Gregory Andrews told ABC radio that land clearing is not the biggest threat to Australia’s wildlife. His claim caused a stir among Australia’s biodiversity scientists and conservation professionals, who have plenty of evidence to the contrary.

The ecologist Jared Diamond has described an “evil quartet” of threatening processes that drive species to extinction: habitat destruction; overhunting (or overexploitation); the presence of introduced species; and chains of linked ecological changes, including co-extinctions.


Read more: Australia’s species need an independent champion


In modern times we can add two more to this list. The first is catastrophic disease outbreaks, such as the chytrid fungus that has been instrumental in the catastrophic decline or extinction of almost 200 frog species, or the facial tumour disease that still threatens to
wipe out Tasmanian devils in the wild.

The second is human-induced climate change, which appears to have caused one extinction in Australian Territories and is predicted to result in many more.

So the evil quartet has now become an evil sextet. It sounds ugly because it is. But does habitat loss through land clearing still top the list? The answer, in short, is yes.

Land clearing threat

According to an analysis of data from the International Union for the Conservation of Nature (IUCN), habitat loss is the number-one threat to biodiversity worldwide. Many more species are affected by processes such as logging and land clearing for agriculture and housing than by invasive species, disease or other threats.

Number of amphibians impacted by key threats.
IUCN, Author provided
Number of mammals impacted by key threats.
IUCN, Author provided

Habitat loss is the top threat here in Australia too, an assessment that is backed up by the federal government’s State of the Environment Reports in 2011 and 2016.

Pressures affecting species on Australia’s list of nationally threatened species.
State of the Environment Report 2011, Author provided

Compared with the rest of the world, Australia’s introduction of feral predators such as cats and foxes has had a devastating impact on iconic small mammals such as bilbies, and birds such as night parrots. Nationally, we invest a large amount of resources (relative to other threats) in creating predator-proof havens for threatened animals to keep feral predators out of key areas.

But despite this, habitat loss and land clearing pose an even bigger threat to animals and plants alike. It is the single biggest factor adding to Australia’s list of threatened species list, especially given the recent return to record-breaking land clearing rates.

Interacting threats

Of course, the evil sextet do not operate independently; they gang up, often with devastating results. The joint impact of two threats is often larger than the sum of its parts. Habitat destruction is the gang leader that joins forces with other threats to accelerate the slide to extinction.

When habitats are intact, large and in good condition, the species that depend on them are much better equipped to withstand other threats such as bushfires or invasive species. But as habitat is destroyed and chopped into smaller fragments, species’ populations become smaller, more isolated, and more vulnerable to predation or competition.

Larger populations of animals and plants also generally have larger gene pools, making them more able to adapt to new threats before it’s too late. Small populations, on the other hand, are sitting ducks.

You can see where this is heading. It’s all about habitat loss, because habitat loss makes all other threats more acute.

Classic depiction of habitat fragmentation in Warwickshire between 400 AD and 1960.
Wilcove et al. Cons. Biol. (1986), Author provided

The political landscape

Habitat loss is a polarising political issue, which makes it hard to legislate against. Most habitat is lost through land clearing for agriculture and urban development.

The quality and effectiveness of land clearing policy and legislation in Australia has risen and fallen like the tide over the past four decades. After being the world’s largest land clearing jurisdiction behind Brazil in the post-war era, the Beattie government in Queensland introduced hugely improved land-clearing laws in the mid-1990s.

But under the Newman government, Queensland resumed its world leadership in habitat destruction. While Queensland may be the most extreme example, every Australian state and territory has witnessed similar policy uncertainty over the decades. Meanwhile, no federal environment minister has made significant inroads into the problem since the establishment of the 1999 Environment Protection and Biodiversity Conservation Act.


Read more: More sightings of an endangered species don’t always mean it’s recovering


Reducing the impact of land clearing is not a job for a fainthearted politician, given the likely objections from the powerful agriculture and development lobbies.

The federal government’s Threatened Species Strategy and Action Plan provided some excellent initiatives to shield our species from some threats, but action to reduce habitat loss is notably absent. The number-one cause of extinctions has simply not been addressed.

The ConversationOf course, the outgoing Threatened Species Commissioner is right to acknowledge the impact that feral cats and foxes. But I hope that whoever next takes on the role will be prepared to deliver an unambiguous message about the biggest threat to our plants and animals, and to outline a strong vision for how we can address it.

Brendan Wintle, Professor of Conservation Ecology, University of Melbourne, University of Melbourne and Sarah Bekessy, Professor, RMIT University

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

Indonesia: Sumatran Elephant Facing Extinction


In Indonesia, the Sumatran Elephant is facing extinction, due to habitat loss. It would seem that is largely due to Palm plantations.

For more visit:
http://wwf.panda.org/wwf_news/?203227