Torpor: a neat survival trick once thought rare in Australian animals is actually widespread



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Chris Wacker, University of New England

Life is hard for small animals in the wild, but they have many solutions to the challenges of their environment. One of the most fascinating of these strategies is torpor. Not, to be confused with sleep or Sunday afternoon lethargy, torpor is a complex response to the costs of living.

To enter torpor, an animal decreases its metabolism, reducing its energy requirements. A torpid animal will often be curled in a tight ball in its nest and look like it’s sleeping.

Once thought to occur only in birds and mammals in the Northern Hemisphere where winters are more pronounced, we now know torpor is widespread in small Australian mammals, and has also been observed in many small Australian bird species.

An echidna in the bush.
Echidnas use torpor to save energy.
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Read more:
Animal response to a bushfire is astounding. These are the tricks they use to survive


Masters of metabolism

Birds and mammals are endotherms and can maintain a high and constant body temperature independent of the environmental temperature, thanks to their high metabolic rate. This allows them to be active across a wide range of environments.

The downside? This high metabolic rate requires a lot of food to fuel it. By reducing the metabolism in a very controlled manner and entering torpor, an animal can live on less energy.

With a lower metabolic rate, the animal’s body temperature decreases — sometimes by as much as 30°C. How low it goes can depend on the extent of the metabolic reduction and the temperature of animal’s immediate environment. The reduced body temperature further lowers the metabolic rate.

Slowing down to survive

Torpor is an extremely effective survival strategy for small endotherms. For example, small mammals have been observed using torpor after bushfires.

Take the brown antechinus, for example. When other animals have fled, this 30g marsupial hides in refuges, waits out the fire, then uses torpor to cope with reduced food availability until local vegetation and invertebrate populations recover.

A brown antechinus on a tree.
The brown antechinus uses torpor to cope with reduced food availability after bushfire.
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Many pregnant and lactating bats and marsupials, and even the echidna, synchronise torpor with reproduction to cope with the energetic costs of mating, pregnancy or lactation.

There are two main types of torpor: daily torpor and hibernation.

Daily torpor

Animals that use daily torpor can do so for approximately 3-6 hours a day as needed.

Daily torpor is common in, but not exclusive to, endotherms living in arid areas, such as the fat-tailed dunnart. This species is a carnivorous marsupial and has a diet of insects and other invertebrates, which may be in short supply in winter.

A fat-tailed dunnart.
When finding enough food is difficult, the fat-tailed dunnart uses torpor.
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Weighing approximately 12 grams as adults, the fat-tailed dunnart may need to eat its body weight in food each day. When finding enough food is difficult, it uses torpor; foraging in the early part of the night then entering torpor in the early morning. Fat-tailed dunnarts reduce their metabolic rate, and subsequently their body temperature, from 35 °C to approximately 15°C, or the temperature of their underground nest.

Hibernation

Animals that hibernate lower their metabolic rate further and have longer torpor bouts than those that use daily torpor. An example of an Australian hibernator is the eastern pygmy possum, a 40g marsupial found in south eastern Australia that hibernates regularly, decreasing its body temperature from approximately 35 °C to as low as 5°C.

When active, this species can survive for less than half a day on 1g of fat, but when hibernating, it can survive for two weeks.

A torpid eastern pygmy possum. Note the curled posture.
Photo credit: Chris Wacker, Author provided

If it weren’t for the periodic increases in metabolic rate and body temperature, a hibernating pygmy possum could live for well over three months on 1g of fat. However, the exact purpose of these periodic arousals is unknown.

The metabolic rate during pygmy possum hibernation is just 2% of the minimum metabolic rate endotherms at a normal body temperature need to live. This baseline metabolism is called basal metabolic rate.

An American black bear
Black bears can’t hibernate with a lower body temperature.
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Compare this with a well-known hibernator, the American black bear.

At approximately 120kg, its metabolic rate during hibernation decreases to 25% of the basal metabolic rate, and the body temperature decreases from approximately 37°C to 30 °C. Black bears can’t hibernate with a lower body temperature, perhaps because it would take them a very long time to reduce it, and then cost them too much energy to rewarm at the end of hibernation.

Can humans do it?

The question people often ask about torpor, is “can humans do it?” Interestingly, some small primates have been observed using torpor. While it is technically possible to induce torpor in humans chemically, torpor is a very complex physiological process, and there are many aspects of it scientists still don’t fully understand.

A gray mouse lemur in Madagascar.
The grey mouse lemur in Madagascar is among the primates that uses torpor.
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Coping with climate change

Australia’s wildlife have evolved strategies to cope with life in an often-harsh environment affected by multiple year-long droughts, landscape-altering floods, and widespread bushfires.

Climate change is predicted to increase the duration, frequency and severity of these events, and in conjunction with landscape clearing, animals are facing new environmental and resource challenges.

While animals that use flexible, daily torpor may be well-suited to cope during these times, at least in the short term, hibernators that depend on long winters are most at risk.




Read more:
Summer bushfires: how are the plant and animal survivors 6 months on? We mapped their recovery


The Conversation


Chris Wacker, Postdoctoral Research Fellow – School of Environmental and Rural Science, University of New England

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

The small patch of bush over your back fence might be key to a species’ survival


File 20181212 76965 x1w7xf.jpg?ixlib=rb 1.1
A kangaroo finds refuge in a small patch of vegetation surrounded by a new housing estate.
Georgia Garrard, Author provided

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

It may not look like a pristine expanse of Amazon rainforest or an African savannah, but the patch of bush at the end of the street could be one of the only places on the planet that harbour a particular species of endangered animal or plant.

Our newly published global study of the conservation value of landscapes in 27 countries across four continents has found these small patches of habitat are critical to the long-term survival of many rare and endangered species.

In Australia, our cities are home to, on average, three times as many threatened species per unit area as rural environments. This means urbanisation is one of the most destructive processes for biodiversity.

It tends to be the smaller patches of vegetation that go first, making way for a housing development, a freeway extension, or power lines. Despite government commitments to enhance the vegetation cover of urban areas and halt species extinctions, the loss of vegetation in Australian cities continues.




Read more:
We’re investing heavily in urban greening, so how are our cities doing?


This story plays out all over the world day after day. Of course, it’s not just an urban story. Patches of rural vegetation are continually making way for, say, a new pivot irrigation system or a new mine to provide local jobs.

Remnant salmon gum woodland surrounded by cropland near Bencubbin in Western Australia’s northeast wheatbelt.
Mike Griffiths, Author provided

Mostly, policymakers and scientists do not consider these losses to be, on their own, a fatal blow to the biodiversity of a region or country. Small, often isolated patches of vegetation are considered expendable, tradeable, of limited ecological value due to their small size and relatively large amount of “edgy” habitat. Wrong.

Research forces a rethink

Our study analysed the relationship between conservation value of vegetation patches and their size and isolation in landscapes across Europe, Australia, North America and Africa. The findings prompt a rethink of long-held views about the relative importance of small, isolated habitat patches for biodiversity conservation. We show that these patches often have unique ecological and environmental characteristics.

The critically endangered Western Ringtail Possum lives mainly in small habitat patches in or around urban areas near Perth and is under intense pressure from housing development, foxes, cats and dogs.
Yokochi K., Bencini R./Wikimedia Commons, CC BY

That’s because they are the last patches left over from extensive clearing of flat, fertile land for agriculture or urban growth close to rivers and bays. They often contain habitats for rare or endangered species that have disappeared from the rest of the landscape. This makes these small, isolated patches of habitat disproportionately important for the survival of many species.

Our study calls for a rethink of urban planning and vegetation management regulations and policies that allow small patches of vegetation to be destroyed with lower (and often zero) scrutiny. We argue that the environment is suffering a death by a thousand cuts. The existence of large conservation reserves doesn’t compensate for the small patches of habitat being destroyed or degraded because those reserves tend to contain different species to the ones being lost.

The combined impact of the loss of many small patches is massive. It’s a significant contributor to our current extinction crisis.




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


Why are small patches seen as dispensable?

A key variable used in decisions on vegetation-clearing applications is the size of patch being destroyed. Authorities that regulate vegetation management and approve applications are more permissive of destruction of small patches of vegetation.

This is partly due to a large body of ecological theory known as island biogeography theory and subordinate theories from metapopulation ecology and landscape ecology. These theories suggest that species richness and individual species’ population sizes depend on the degree of isolation of the patch, its size and the quality of the habitat it contains.

While it is crucial that we conserve large, intact landscapes and wilderness, the problem with conserving only large and well-connected patches of high-quality vegetation is that not all species will be conserved. This is because some species exist only in small, isolated and partially degraded habitats, such as those characteristic of urban bushlands or remnant bush in agricultural areas.

A remnant wetland is still valuable habitat for species like the Pacific Heron.
Wayne Butterworth/Wikimedia Commons, CC BY

For this reason, we highlight the importance of protecting and restoring habitats in these small isolated patches. And these areas do tend to be more vulnerable to invasion by weeds or feral animals. If the impacts of invasive species are not managed, they will eventually lead to the destruction of the habitat values and the loss of the species those habitats support.

Small and isolated patches of vegetation on the urban fringe are under enormous pressure from human use, pets, escaped seed of Agapanthus and the many other invasive species we plant in our gardens. These plants spread into local bushland, where they outcompete the native plants.

Communities can make a difference

As well as these perils, being on the urban fringe also brings opportunity. If a remnant patch of vegetation at the end of the street is seen to be of national environmental importance, that presents a great opportunity to channel the energies of community groups into conserving and restoring these patches.

A patch that is actively cared for by the community will provide better habitat for species. It’s also less likely to fall foul of development aspirations or infrastructure projects. The vicious cycle of degradation and neglect of small patches of habitat can be converted into a virtuous cycle when their value is communicated and local communities get behind preserving and managing them.

Volunteer community groups can play a vital role in preserving and enhancing small habitat patches.
Robin Clarey, Friends of Edithvale Seaford Wetlands, Author provided

Urban planners and developers can get on board too. Rather than policies that enable the loss of vegetation in urban areas, we should be looking at restoring habitats in places that have lost or are losing them. This is key to designing healthy, liveable cities as well as protecting threatened species.

Biodiversity-sensitive urban design makes more of local vegetation by complementing the natural remnant patches with similar habitat features in the built environment, while delivering health and well-being benefits to residents. Urban development should be seen as an opportunity to enhance biodiversity through restoration, instead of an inevitable driver of species loss.




Read more:
Here’s how to design cities where people and nature can both flourish


The Conversation


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

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

Eco-Tourism and the Lemur


The link below is to an article that looks at the future of Lemurs in Madagascar and the hopes of eco-tourism in their survival.

For more visit:
http://www.escapistmagazine.com/news/view/132435-Eco-Tourism-May-Be-Best-Hope-for-Endangered-Lemurs

Greater Bilby’s Battle with Cats


The link below is to an article that reports on the Greater Bilby’s battle with cats for survival.

For more visit:
http://grist.org/list/australia-had-to-kill-a-lot-of-cats-to-save-these-tiny-marsupials/

Australia: NSW – Warrumbungle National Park


The link below is to a media release concerning the survival of Brush-Tailed Rock Wallabies at Warrumbungle National Park following the devastating bushfire that swept through the park recently.

For more visit:
http://www.environment.nsw.gov.au/media/OEHMedia13020601.htm

Australia: Snowy River Westringia Rediscovered


Until very recently, the Snowy River Westringia was thought to be close to extinction. However, it still literally clung to survival on the steep banks of the Snowy River in Victoria’s east.

Cuttings have been taken to Melbourne’s Royal Botanic Gardens for propagation and cultivation there.

Read more at:
http://www.smh.com.au/victoria/daring-government-expedition-runs-rare-plant-to-ground-after-years-of-living-on-the-edge-20111223-1p8oy.html
http://www.heraldsun.com.au/news/breaking-news/rare-plants-found-on-cliff-walls-of-snowy-river/story-e6frf7jx-1226231756607

Birds: Feeding Birds not a Good Thing?


Many people love to have native birds visit their gardens. To achieve this we feed birds in a variety of ways. Feeding wild birds does have consequences for the long term survival of the birds being fed. The following link is to an article with more on this subject.

For more visit:
http://www.nwf.org/News-and-Magazines/National-Wildlife/Birds/Archives/2011/Effects-of-Bird-Feeding.aspx

 

BUSH HERITAGE AUSTRALIA – Update September 2008


One of the groups I have a lot of time for in Australia and one which I am planning to support in a more active way in the New Year (once I get back on my feet so to speak) is Bush Heritage Australia.

Bush Heritage Australia is actively seeking to protect 1% of Australia by 2025, ensuring the protection of our unique flora, fauna and wild places. This is done through purchasing land by money donated to it by those wanting to protect the Australian environment and natural heritage. Bush Heritage currently owns some 1 million hectares, meaning it needs to acquire a further 6 million hectares to obtain its 2025 goal.

In September 2008, Bush Heritage Australia purchased the 8 100 hectare Edgbaston Station, 140km north-east of Longreach in Queensland for 3.5 million dollars. In doing so, Bush Heritage has ensured the survival of Australia’s most endangered and smallest freshwater fish species, the Redfin Blue-Eye Fish. This region is the only location in which this fish species now lives.

But it is not only the Redfin Blue-Eye Fish that will be protected by the purchase of this property as this region and the springs found on the property is the only known habitat for several other species of fish, snails, plants and a crustacean.

The springs on Edgbaston Station are located in the upper catchment of Pelican Creek which flows into the Thompson River and Lake Eyre. There are some 50 artesian springs on the property, supporting a large diversity of life.

The 3.5 million dollars required for the purchase of Edgbaston Station included 1.324 Million dollars from the Australian government’s Maintaining Australia’s Biodiversity Hotspots program and donations from the Queensland Department of Natural Resources and Water and the Queensland Department for Sustainability, Climate Change and Innovation.

Bush Heritage will be working alongside of the Iningai people, who are the traditional owners of the land on which Edgbaston Station is located, to manage the property.

For information on what you can do to assist Bush heritage Australia or to get more information on any of the reserves managed by Bush heritage Australia visit the web site below.

http://www.bushheritage.org.au/