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.

Echidnas use torpor to save energy.
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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.

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.

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.

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.

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.

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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.

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The 2016 Great Barrier Reef heatwave caused widespread changes to fish populations

Some fish fared better than others amid the extreme temperatures of the 2016 heatwave.
Rick Stuart-Smith/Reef Life Survey

Rick Stuart-Smith, University of Tasmania; Christopher Brown, Griffith University; Daniela Ceccarelli, James Cook University, and Graham Edgar, University of Tasmania

The 2016 marine heatwave that killed vast amounts of coral on the Great Barrier Reef also caused significant changes to fishes and other animals that live on these reefs.

Coral habitats in the Great Barrier Reef (GBR) and in the Coral Sea support more than 1,000 fish species and a multitude of other animals. Our research, published in Nature today, documents the broader impact across the ecosystem of the widespread coral losses during the 2016 mass coral bleaching event.

While a number of fish species were clearly impacted by the loss of corals, we also found that many fish species responded to the increased temperatures, even on reefs where coral cover remained intact. The fish communities in the GBR’s southern regions became more like those in warmer waters to the north, while some species, including parrotfishes, were negatively affected by the extreme sea temperatures at the northern reefs.

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How the 2016 bleaching altered the shape of the northern Great Barrier Reef

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The loss of coral robs many fish species of their preferred food and shelter. But the warming that kills coral can also independently cause fish to move elsewhere, so as to stay within their preferred temperature range. Rising temperatures can also have different effects on the success, and therefore abundance, of different fish populations.

One way to tease apart these various effects is to look at changes in neighbouring reefs, and across entire regions that have been affected by bleaching, including reefs that have largely escaped coral loss.

We were able to do just this, with the help of highly trained volunteer divers participating in the Reef Life Survey citizen science program. We systematically surveyed 186 reefs across the entire GBR and western Coral Sea, both before and after the 2016 bleaching event. We counted numbers of corals, fishes, and mobile invertebrates such as sea urchins, lobsters and giant clams.

Sea temperatures and coral losses varied greatly between sites, which allowed us to separate the effects of warming from coral loss. In general, coral losses were much more substantial in areas that were most affected by the prolonged warmer waters in the 2016 heatwave. But these effects were highly patchy, with the amount of live hard coral lost differing significantly from reef to reef.

For instance, occasional large losses occurred in the southern GBR, where the marine heatwave was less extreme than at northern reefs. Similarly, some reefs in the north apparently escaped unscathed, despite the fact that many reefs in this region lost most of their live corals.

Sea temperatures the culprit

Our survey results show that coral loss is just one way in which ocean warming can affect fishes and other animals that depend on coral reefs. Within the first year after the bleaching, the coral loss mostly affected fish species that feed directly on corals, such as the butterflyfishes. But we also documented many other changes that we could not clearly link to local coral loss.

Much more widespread than the impacts of the loss of hard corals was a generalised response by the fish to warm sea temperatures. The 2016 heatwave caused a mass reshuffling of fish communities across the GBR and Coral Sea, in ways that reflect the preferences of different species for particular temperatures.

In particular, most reef-dwelling animals on southern (cooler) reefs responded positively to the heatwave. The number of individuals and species on transect counts generally increased across this region.

By contrast, some reefs in the north exceeded 32℃ during the 2016 heatwave – the typical sea temperature on the Equator, the hottest region inhabited by any of the GBR or Coral Sea species.

Some species responded negatively to these excessive temperatures, and the number of observations across surveys in their northernmost populations declined as a consequence.

Parrotfishes were more affected than other groups on northern reefs, regardless of whether their local reefs suffered significant coral loss. This was presumably because the heatwave pushed sea temperatures beyond the level at which their populations perform best.

Nothing to smile about: some parrotfishes don’t do well in extreme heat.
Rick Stuart-Smith/Reef Life Survey

Local populations of parrotfishes will probably bounce back after the return of cooler temperatures. But if similar heatwaves become more frequent in the future, they could cause substantial and lasting declines among members of this ecologically important group in the warmest seas.

Parrotfishes are particularly important to the health of coral reef ecosystems, because their grazing helps to control algae that compete with corals for habitat space.

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Read more:
How the 2016 bleaching altered the shape of the northern Great Barrier Reef

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A key message from our study is not to overlook the overarching influence of temperature on coral reef ecosystems – and not to focus solely on the corals themselves.

Even if we can save some corals from climate change, such as with more stress-tolerant breeds of coral, we may not be able to stop the impacts of warming seas on fish.

Future ecological outcomes will depend on a complex mix of factors, including fish species’ temperature preferences, their changing habitats, and their predators and competitors. These impacts will not always necessarily be negative for particular species and locations.

One reason for hope is that positive responses of many fish species in cooler tropical regions may continue to support healthy coral reef ecosystems, albeit in a different form to those we know today.

Rick Stuart-Smith, Research Fellow, University of Tasmania; Christopher Brown, Research Fellow, Australian Rivers Institute, Griffith University; Daniela Ceccarelli, Adjunct Senior Research, ARC Centre of Excellence for Coral Reef Studies, James Cook University, and Graham Edgar, Senior Marine Ecologist, Institute for Marine and Antarctic Studies, University of Tasmania

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

Why aren’t Australia’s environment laws preventing widespread land clearing?

Samantha Hepburn, Deakin University

Australia has national environment laws – the Environment Protection Biodiversity Conservation Act (EPBC Act). Yet given the staggering rates of land clearing taking place, resulting in the extinction and endangerment of plants and animals in Australia, these laws are clearly not working.

About 395,000 hectares of regrowth and old growth vegetation were cleared during 2015-16 in Queensland. Australia is set to clear up to 3 million hectares of native forest by 2030, and more than 1,800 plant and animal species are currently listed as threatened nationally.

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When the EPBC Act was first implemented in 1999, the idea was for it to provide reinforced federal environmental protection to areas of national environmental significance. But in reality, many projects that come within the ambit of the Act are not rigorously evaluated for their environmental impact.

Why isn’t the EPBC Act working?

Land clearing was listed in the 2001 and 2006 State of the Environment Reports as one of the greatest threats to biodiversity.

Deforestation and excessive land clearing fundamentally impacts existing biodiversity, damages fragile ecosystems, destroys wildlife habitat, and increases greenhouse gas emissions. In Queensland, where much of the land clearing is taking place, the state law (Vegetation Management Act) is not strong enough to diminish incentives for land clearing. Yet the national environmental laws have not provided greater protection.

There are several reasons for this. While land clearing is indirectly regulated by the EPBC Act due to the significant impact it can have on the environment, land clearing is not directly addressed by the EPBC Act.

As it stands, land clearing will only attract EPBC Act application where it can be established that it impacts a directly protected entity such as a World Heritage area, Ramsar wetland, threatened species, ecological community, or migratory species. If this connection cannot be established, no environmental assessment under the EPBC Act will occur.

Even where projects do attract the application of the EPBC Act, its capacity to advance best practice environmental impact assessment is highly questionable. One of the biggest problems is that the process of assessment is insufficiently robust.

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Commonwealth should keep final say on environment protection

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This problem is evident in other environmental issues too. Where a bilateral state and federal assessment is approved, as was the case with the Adani coalmine, the federal department often relies on state counterparts to undertake a thorough environmental assessment. Many of the proposals evaluated by state departments are assessed with reference to the least onerous environmental impact assessment available.

This documentation is generally prepared by the project proponent. Unsurprisingly, as a consequence, many of the projects that are evaluated under the EPBC Act are approved, subject to the imposition of environmental conditions. This means the environmental conditions need to be carefully monitored if environmental protection is to be optimised.

This creates a new set of problems. Where a breach is alleged, it must be proved and appropriate sanctions enforced. In reality, this rarely happens, and the sanctions that are imposed can be woefully inadequate. For example, Adani was fined A$12,000 for breaching an environmental condition relating to the release of coalwater in Abbott Point coal terminal, which flowed into the fragile Caley Valley Wetlands.

The substantive problem with the EPBC Act is that its implementation is subject to departmental discretion and therefore the vagaries of government administration. This is particularly problematic given the political nature of many of these decision-making processes.

Lack of rigorous scrutiny

In circumstances where, for example, there is a need to challenge the approval of a resource title in light of its environmental consequences, the EPBC Act relies heavily on environmental groups or other third parties to scrutinise the federal decision-making process.

For example, the Australian Conservation Foundation took strong action in challenging the issuance of the mining licence for Adani’s proposed Carmichael coal mine. It argued the endangered species and climate change impacts were insufficiently taken into account by the then Environment Minister Greg Hunt in exercising discretion under the EPBC Act.

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The case was dismissed because the Federal Court found that this decision was authorised by the discretions included within the EPBC Act. The minister was therefore within his power to decide not to take account of the climate change impacts of such a vast new coalmine. This is concerning given the profound impact that climate change can have upon fragile ecologies in areas of national environmental significance.

These findings indicate a lack of preparedness by the federal minister to accept a causal connection between climate change and domestic coal production, and to focus on narrow jurisdictional boundaries and strict domestic obligations. It also strongly highlights the deficiencies of our national environment act because the existing triggers do not address some of the most important environmental concerns of the modern world.

New environment laws urgently needed

Climate change is almost universally accepted as one the most serious environmental threats. Yet the EPBC Act does not include a climate change trigger (or a land clearing trigger, as discussed above).

This means these key threats to Australia’s environment will not be protected by EPBC Act. They may attract the EPBC Act indirectly, but only if it can be established that they raise a different trigger that is listed under the Act. This calls into question the capacity of our national environment laws to truly protect areas of national environmental significance.

In order to reverse unacceptable rates of land clearing, preserve ecosystems and habitats and diminish greenhouse gas emissions, a new framework for our national environment act is urgently needed.

Samantha Hepburn, Director of the Centre for Energy and Natural Resources Law, Deakin Law School, Deakin University

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

Greenland: Widespread Ice Melt

The links below are to two articles reporting on the incredible ice melt occurring in Greenland at the moment. It would seem to be clear evidence of climate change on a dramatic scale.

For more visit:
– http://grist.org/news/nasa-unprecedented-extraordinary-ice-melt-in-greenland/
– http://www.nasa.gov/topics/earth/features/greenland-melt.html

Holiday Planning: NSW Road Trip 2010

The planning for my holiday is now well and truly underway, with the holiday now being referred to as my ‘NSW Road Trip 2010.’ There is also a website address for viewing my itinerary and for following my progress. It has been a rushed process in the end, organising this road trip, so there will yet be some changes to the itinerary.

I am expecting changes in far western NSW due to road conditions, especially given recent weather conditions out that way, including the widespread rain and flooding that has taken place. Given I have only got a small rental for this trip, I am not really prepared to take the car onto certain roads (which I believe will be part of the rental agreement anyway).

At this stage I am expecting to miss Ivanhoe and head for Mildura instead. I also expect to miss Tibooburra in the far northwest corner of the state, as the Silver City Highway is largely dirt. With these probable changes to the itinerary, I will also miss driving through the Menindee Lakes area, which really was something I was hoping to see – another time perhaps.

On another ‘track,’ I found our that the hottest February temperature experienced in Ivanhoe was around 48 degrees Celsius. No, not the reason I am thinking of bypassing Ivanhoe – most centres out west have similar temperatures in February anyway.

The website:

http://www.kevinswilderness.com/NSW/nswRoadTrip2010.html 

Is the Drought in New South Wales Finally Over: More Follow Up Rain Needed Despite Widespread Flooding