Dig this: a tiny echidna moves 8 trailer-loads of soil a year, helping tackle climate change


David John Eldridge, UNSW

After 200 years of European farming practices, Australian soils are in poor shape – depleted of nutrients and organic matter, including carbon. This is bad news for both soil health and efforts to address global warming.

The native Australian echidna may hold part of the solution. Echidnas dig pits, furrows and depressions in the soil while foraging for ants. Our research has revealed the significant extent to which this soil “engineering” could benefit the environment.

Echidnas’ digging traps leaves and seeds in soil. This helps improve soil health, promotes plant growth and keeps carbon in the soil, rather than the atmosphere.

The importance of this process cannot be underestimated. By improving echidna habitat, we can significantly improve soil health and boost climate action efforts.

An echidna
Echidnas can help improve soil health.

Nature’s excavators

Many animals improve soil health through extensive digging. These “ecosystem engineers” provide a service that benefits not only soils, but plants and other organisms.

In Australia, most of our digging animals are either extinct, restricted or threatened. But not so the echidna, which is still relatively common in most habitats across large areas of the continent.

Echidnas are prolific diggers. Our long-term monitoring at Australian Wildlife Conservancy’s Scotia Sanctuary, in southwest New South Wales, suggests one echidna moves about seven tonnes – about eight trailer loads – of soil every year.

Soil depressions left by echidnas can be up to 50cm wide and 15cm deep. When ants are scarce, such as at highly degraded sites, echidnas dig deeper to find termites, making even larger pits.

This earth-moving capacity unwittingly provides another critically important function: matchmaking between seeds and water.

Echidna digging in soil
Echidnas’ huge digging capacity brings many environmental benefits.

Playing cupid

For seeds to germinate they must come together with water and soil nutrients. Our experiment showed how echidna digging helps make that happen.

We tested whether seeds would be trapped in echidna pits after rain. We carefully marked various seeds with different coloured dyes, and placed them on the soil surface in a semi-arid woodland near Cobar, NSW, where we’d dug pits similar to those echidnas create. We then simulated a rain event.

Most seeds washed into the pits, and those that started in the pits stayed there. The experiment showed how echidna pits encourage seeds, water and nutrients to meet, giving seeds a better chance to germinate and survive in Australia’s poor soils.

The recovering pits then become plant and soil “hotspots” from which plants can spread across the landscape.

Our research has also found pits also harbour unique microbial communities and soil invertebrates. These probably play an important role in breaking down organic matter to produce soil carbon.

It’s no wonder many human efforts to restore soil imitate the natural structures constructed by animals such as echidnas.

Read more:
Curious Kids: How does an echidna breathe when digging through solid earth?

Plant growth in artificial pits used to regenerate degraded semi-arid soils – a method that imitates echidna pits.

Echidnas as carbon farmers

Our recent research also shows how echidna digging helps boost carbon in depleted soils.

When organic matter lies on the soil surface, it’s broken down by intense ultraviolet light which releases carbon and nitrogen into the atmosphere. But when echidnas forage, the material is buried in the soil. There it is exposed to microbes, which break down the material and release carbon and nitrogen to the soil.

This does not happen immediately. Our research suggests it takes 16-18 months for carbon levels in the pits to exceed that in bare soils.

This entire process of echidna digging, capture and buildup creates a patchwork of litter, carbon, nutrients, and plant hotspots. These fertile islands drive healthy, functional ecosystems – and will become more important as the world becomes hotter and drier.

Read more:
The secret life of echidnas reveals a world-class digger vital to our ecosystems

An echidna foraging pit with litter, seed and soil.

Harness the power of echidnas

Soil restoration can be expensive, and impractical across vast areas of land. Soil disturbance by echidnas offers a cost-effective restoration option, and this potential should be harnessed.

Australia’s echidna populations are currently not threatened. But landscape management is needed to ensure healthy echidna populations into the future.

Echidnas often shelter in hollow logs, so removing fallen timber reduces their habitat and feeding sites. Restrictions on practices such as firewood removal are needed to prevent habitat loss.

And being slow-moving, echidnas are often killed on our roads. To address this, shrubs and ground plants should be planted between patches of native bush, creating vegetation corridors so echidnas can move safely from one spot to the next.

Echidna crossing a road
Why did the echidna cross the road? Because there were no vegetation corridors.

And while an echidna’s sharp spines give it some protection from natural predators, they’re less effective against introduced predators such as foxes and cats. So strategies to control these threats are also needed.

The health of Australia’s fragile environment is in serious decline. Echidnas are already providing a valuable ecosystem service – and they should be protected and nurtured to ensure this continues.

Read more:
10 million animals are hit on our roads each year. Here’s how you can help them (and steer clear of them) these holidays

The Conversation

David John Eldridge, Professor of Dryland Ecology, UNSW

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

The secret life of echidnas reveals a world-class digger vital to our ecosystems

Christine Cooper, Curtin University and Christofer Clemente, University of the Sunshine Coast

Echidnas may not seem the most active of animals. Waddling around, they spend much of their time dozing and hiding. But in research published today in the Journal of Experimental Biology, we show that echidnas dig huge amounts of soil, and play a crucial role in Australia’s ecosystems.

By attaching miniature GPSs and accelerometers to echidnas in Western Australia, we found that these mammals move on average 200 cubic metres of soil each year. For the 12 echidnas we studied, this is the equivalent of an Olympic-sized swimming pool.

Attaching tiny tracking devices to echidnas is harder than it sounds.

Zoology gets small

Short-beaked echidnas are one of few surviving species of monotreme; unique mammals that reproduce by laying eggs. As well as a strange anatomy, they have an unusually low body temperature and metabolism.

We were interested in how the echidna’s unusual limbs influenced their walking and digging, and how this in turn was related to patterns of activity and their potential ecosystem impact.

So we attached tiny custom-made accelerometers to the spines of wild echidnas at Dryandra Woodland, in Western Australia. We also attached GPS units to monitor their location, and radio-transmitters so we could find them again.

The miniaturisation of electronic devices has changed the way we study wildlife. We can get details about wild animals’ behaviour in their natural habitat that we couldn’t previously. This is now revealing more information not only about the biology of these species, but the roles they play in ecosystems.

Echidna fitted with an accelerometer and GPS unit, and a radio-tracking transmitter
Christine Cooper

The accelerometers were about the size of a wrist-watch, hand-soldered with a microscope and tiny soldering iron. These let us determine exactly when and for how long echidnas were resting, walking and digging.

Our biggest challenge was getting to the echidnas again so we could remove their tracking devices. Echidnas spend much of their time sheltering in inaccessible caves, rocky crevices and hollow logs and are mostly active at night, especially during summer. We studied echidnas during the hot West Australian summer, when temperatures rose to 45℃, and during spring when it was 25℃ cooler.

Tracking an echidna to a rock cave at Dryandra Woodland
William Parkinson

Walk like an echidna

Our data revealed that echidnas take shorter and slower strides compared with similar-sized mammals. Unlike most other mammals, they take more strides rather than increasing the length of their strides to walk faster. This reflects the anatomy of the limbs, which are adapted to digging rather than rapid movement and as a consequence, echidnas cannot walk very fast, with a maximum speed of 2.3 kilometres per hour, and have a characteristic waddling gait.

But their covering of sharp spines offers good protection from predators. Indeed you don’t need to be able to run quickly if nothing can eat you. This armour of spines and the echidna’s ability to dig rapidly into the ground or roll into a tight, spikey ball is one reason that echidnas have not suffered the same dramatic decrease of many other Australian mammals.

Echidnas are also not as vulnerable to the ravages of introduced predators that are often the final straw for native mammals already threatened by increasing aridity, land clearing, altered fire regimes and competition with introduced herbivores.

Removing the accelerometer and GPS from an echidna to download the data and re-charge the batteries.
Kellie McMaster

When echidnas were active, they spent most of the time digging and looking for food. Compared to many other animals, echidnas have longer activity times, presumably due to the time required to find their food of ants and termites; echidnas eat about 40,000 individual ants and termites a day.

Echidnas spend a similar amount of time foraging in both spring and summer, but during spring they move more slowly and are more likely to ramble, at a leisurely 1 kilometre per hour, from their rest sites to foraging areas. But in summer, they sprint at their top speed directly to and from feeding sites, presumably to minimise activity during hot weather.

The importance of digging

The considerable time that echidnas spend digging and the area over which they dig means that they act as important “bioturbators”. They turn over the soil which reduces compaction, improves soil mixing and water penetration, incorporates leaf litter and other organic matter into the soil, and reduces run-off and erosion.

Therefore, bioturbators such as echidnas are “ecosystem engineers”. They play a crucial role in the environment as their digging can make for better soils, and in turn influence plant growth and species diversity.

Echidna digging for termites, Dryandra Woodland
Christine Cooper

Echidnas are particularly important ecosystem engineers in Australian landscapes, as many of the other native mammals that once performed this function are rare or have become extinct, and so are no longer doing this essential role. Echidnas have one of the widest distributions of any native Australian mammal.

Their persistence in almost all Australian habitats means that their extensive digging is a critical component of maintaining ecosystem function throughout the Australian continent.

The Conversation

Christine Cooper, Senior Lecturer, Department of Environment and Agriculture, Curtin University and Christofer Clemente, Lecturer in Animal Ecophysiology, University of the Sunshine Coast

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

Australia: Western Australia – Western Long-Beaked Echidna May Still Exist in the Kimberley

The link below is to an article reporting on the possible existence of what was thought to be an extinct Echidna in Western Australia.

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