I walked 1,200km in the outback to track huge lizards. Here’s why



Sophie Cross, Author provided

Sophie Cross, Curtin University

In 2017 and 2018 I walked the equivalent of 28 marathons in the scorching Western Australian outback. Why, you ask? To assess how some of Australia’s largest lizard species interact with restored mines.

As part of my PhD research, I hiked in often extreme heat on a mine site in WA’s sparsely populated Mid West region. My fieldwork was both physically and mentally demanding, as I spent many hours each day walking through the bush looking for signs of monitor lizards.

Being in a remote location and mostly alone, I had plenty of time to ponder the wisdom of my career choice, particularly on days when temperatures exceeded 40℃ and not even the lizards ventured from their homes.

Pushing through these mental challenges was difficult at times, but my work has provided me with some of my most rewarding experiences. And what I discovered may be crucial for restoring habitats destroyed by mining.

Restoring abandoned mines

Habitat loss is a leading cause of biodiversity loss worldwide. Although mining typically has a smaller environmental footprint than other major industries such as agriculture or urbanisation, roughly 75% of active mines are on land with high conservation value.




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There are around 60,000 abandoned mines in Australia, but very few of them have been officially closed. How to restore them is a growing public policy problem.

Sophie Cross walked more than 1,200km and tracked a young-adult perentie to find out whether they were using a restored mining area.
Author provided

Recovering biodiversity can be an exceptionally challenging task. Animals are vital to healthy ecosystems, yet little is understood about how animals respond to restored landscapes.

In particular, reptiles are often overlooked in assessments of restoration progress, despite playing key roles in Australian ecosystems.




Read more:
What should we do with Australia’s 50,000 abandoned mines?


Do animals return to restored habitats?

I wanted to know whether restored habitats properly support the return of animals, or whether animals are only using these areas opportunistically or, worse still, avoiding them completely.

To study how reptiles behave in restored mining areas, I hand-caught and tracked a young adult perentie. The perentie is Australia’s largest lizard species, growing to around 2.5m in length, and is an apex predator in arid parts of the country.

I tracked the lizard for three weeks to determine whether it was using the restored area, before the tracker fell off during mating.

The tracking device revealed how the perentie navigated a restored mine, before it fell off during mating.
Author provided

Previous methods of tracking assume the animal used all locations equally. But I used a new method that measures both the frequency with which animals visit particular places, and the amount of time they spend there. This provided a valuable opportunity to assess how effective restoration efforts have been in getting animals to return.

Restoration needs more work

My research, published this week in the Australian Journal of Zoology, shows that while the perentie did visit the restored mine, it was very selective about which areas it visited, and avoided some places entirely. The lizard went on short foraging trips in the restored mine area, but regularly returned to refuge areas such as hollow logs.

The method used GPS and a VHF tracking antenna to follow the perentie.
Author provided

This is because hot, open landscapes with minimal refuges present high risks for reptiles, which rely on an abundance of coverage to regulate their body temperature and to avoid predators. Such costs may make these areas unfavourable to reptiles and limit their return to restored landscapes.

In comparison, undisturbed vegetation supported longer foraging trips and slower movement, without the need to return to a refuge area. Unfortunately, areas undergoing restoration often require exceptionally long time-periods for vegetation to resemble the pre-disturbed landscape.




Read more:
Why we’re not giving up the search for mainland Australia’s ‘first extinct lizard’


How can we help reptiles move back into restored areas?

Restored landscapes often lack key resources necessary for the survival of reptiles. As vegetation can require a long time to reestablish, returning fauna refuges like hollow logs and fauna refuge piles (composed of mounds of sand, logs, and branches) could be crucial to aiding in the return of animal populations.

My research team and I have called for animals to be considered to a greater extent in assessments of restoration success. In the face of increasing rates of habitat destruction, we need to understand how animals respond to habitat change and restoration.

Failing to do so risks leaving a legacy of unsustainable ecosystems and a lack of biodiversity.The Conversation

Sophie Cross, PhD candidate, Curtin University

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

Why we’re not giving up the search for mainland Australia’s ‘first extinct lizard’



A grassland earless dragon at Jerrabomberra, NSW, November 1991. The search is now on for this species’ Victorian cousin.
CSIRO/Wikimedia Commons, CC BY

Jane Melville, Museums Victoria

You may have seen news in recent days of the suspected demise of the Victorian grassland earless dragon – now thought to be the first lizard species to be driven to extinction by humans in mainland Australia.

That suspicion arose on the basis of a newly published study in Royal Society Open Science by our research team, in which we discovered that the grassland earless dragons of southeastern Australia are not a single species, but four distinct ones: one that lives around Canberra, two in New South Wales, and one restricted to the Melbourne region.

The most recent confident sighting of the Melbourne species was 50 years ago, in 1969 – hence the fears that the Victorian species has already succumbed.

But despite this worrying news, we’re not leaving this lizard for dead just yet. Conservationists are now combing remaining grassland around Melbourne in a search for survivors.




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Although no lizard species have previously been declared extinct on the Australian mainland, the grassland earless dragons (Tympanocryptis) of southeastern Australia have long been the subject of conservation concern. Even before being split into four separate species, they were already officially listed as endangered.

The Victorian grassland earless dragon (Tympanocryptis pinguicolla) is known only to occur in the native grasslands around Melbourne. A review of historical collections at Museums Victoria show that it was found at several locations including Sunbury, Maribyrnong River (then called “Saltwater River”), and as far west as the Geelong area until the late 1960s.

Although there is little information available about the ecology of this species, it was described by Lucas and Frost in 1894 as:

Inhabiting stony plains and retreating into small holes, like those of the ‘Trap-door Spider,’ in the ground when alarmed […] Often met with under loose basalt boulders.

The last confirmed sighting was near Geelong in July 1969.

First mainland extinction?

Globally, 31 reptiles have been listed as extinct or extinct in the wild, according to the IUCN Red List, the global authority on the status of species. Two skinks and one gecko species have been declared extinct in the wild on Christmas Island, a remote Australian territory in the Indian Ocean. But until now there have been no recorded reptile extinctions on the Australian mainland.

Yet it is too early to give up on the Australian grassland earless dragon. Zoos Victoria researchers have completed a mapping analysis of potential grassland habitats. But this doesn’t give us enough information to say whether or not any grassland earless dragons remain.

There are several factors that leave open the possibility that the Victorian grassland earless dragon is still clinging to survival. There are some remaining habitat areas that have not yet been surveyed, and this species is small, secretive and hard to find. We urgently need more surveys to try and find any remaining populations.




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If these lizards are not yet extinct, their protection will clearly become an urgent conservation priority. But it is hard to develop a conservation program without knowing where the target species actually lives, or indeed whether it is still alive at all.

Zoos Victoria is now leading a campaign, alongside expert ecologists and local communities, to try and confirm the presence or absence of the Victorian grassland earless dragon. This involves various methods, including habitat mapping, camera trapping, and active searching. The team is also working to identify unsurveyed areas that might potentially be home to these elusive lizards.

Last year the team deployed a series of small pitfall traps at two locations in Little River. Unfortunately, no earless dragons were detected during the survey and few lizards of any species were caught, despite the fact that these locations seemed to offer appropriate food and habitat.

The team is not giving up yet and is committed to continuing the search, with Zoos Victoria researchers having identified sites with suitable habitat both within and outside of the historical distribution, which they aim to survey intensively over the coming years. Meanwhile, reptile keepers at Zoos Victoria are developing husbandry techniques to help look after the grassland earless dragon species from Canberra and NSW.

The conservation challenge has got harder, because where previously we were tasked with looking after one species, we now have to safeguard at least three – and hopefully four!


This article is based on a blog post that originally appeared here. It was coauthored by Adam Lee and Deon Gilbert of Zoos Victoria.The Conversation

Jane Melville, Senior Curator, Terrestrial Vertebrates, Museums Victoria

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

The first known case of eggs plus live birth from one pregnancy in a tiny lizard


Melanie Laird, University of Otago and Camilla Whittington, University of Sydney

For most animals, reproduction is straightforward: some species lay eggs, while others give birth to live babies.

But our recent research uncovered a fascinating mix between the two modes of reproduction. In an Australian skink, we observed the first example of both egg-laying and live-bearing within a single litter for any backboned animal.

This suggests some lizards can “hedge their bets” reproductively, taking a punt on both eggs and live-born babies to improve overall survival chances for offspring.




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Making reproductive leaps

Most vertebrate species (animals with a backbone) fall neatly into one of two distinctly different reproductive categories.

Oviparous species are egg-layers. These eggs may undergo external fertilisation – such as in spawning fish – or are fertilised and shelled internally, like those of reptiles and birds. Oviparous embryos rely on egg yolk as a source of nutrition to continue development until hatching.

In contrast, viviparous species are live bearers that carry their young to term. Some live-bearing species, including humans, support embryonic development internally via a placenta. Egg-laying is ancestral, meaning that modern live-bearers have descended from egg-laying ancestors.

Physiologically, the evolution of live birth from egg-laying is no mean feat. This transition requires a whole suite of changes, sometimes including the evolution of a placenta – an entirely new specialist organ – as well as loss of the hard outer eggshell, and keeping the embryo inside the body for a longer time.

The placenta is a highly complex organ. One of its jobs is to transfer nutrition to the developing baby.
from www.shutterstock.com

Despite these complex steps, reptiles, particularly snakes and lizards, appear to be unusually predisposed to making the leap to live birth. This capacity has evolved in at least 115 groups of reptiles independently.




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Having it both ways

It’s easy to see why reptiles, as a group, are fascinating models for studying how live birth evolves from egg-laying.

Of particular interest are two Australian skinks that have both live-bearing and egg-laying individuals (known as being bimodally reproductive). These lizards are incredibly valuable to evolutionary biologists as they offer a snapshot into evolutionary processes in action.

The three-toed skink Saiphos equalis is one such species. Reproduction in S. equalis varies geographically: populations around Sydney lay eggs, while those further north give birth to live young.

Whether individuals are live-bearing or egg-laying seems to be genetically determined: when researchers swap their environmental conditions (by moving them from one site to another), the females retain their original reproductive strategy.




Read more:
Lizards help us find out which came first: the baby or the egg?


Mothers know best

Our latest research shows this lizard is intriguing in another completely unexpected way.

We observed a live-bearing female that laid three eggs, and then gave birth to a living baby from the same litter weeks later. We incubated two of the eggs, one of which hatched to produce a healthy baby.

A live-bearing female S. equalis in our laboratory colony laid three eggs, one of which hatched to produce a healthy baby.
Camilla Whittington

This finding is remarkable for two reasons. First, as far as we are aware, this is the first example of both egg-laying and live birth within a single litter for any vertebrate.

Second, in some cases, individuals may be capable of “switching” between reproductive modes. In other words, as laying eggs and giving birth each come with their own advantages and disadvantages, individuals may be able to “choose” which option best suits the current situation.

Closer look at eggshells

To better understand this reproductive phenomenon, we investigated the structure of the egg coverings of these unusual embryos in minute detail (using an advanced technology called scanning electron microscopy).

We found that in this litter, the egg-coverings were thinner than those of normal egg-laying skinks and had structural characteristics that overlapped with those of both egg-layers and live-bearers (which have thinner coverings that are greatly reduced).

Egg coverings of S. equalis consist of an outer crust (C) and an inner shell membrane (SM). We compared the structure and thicknesses of these layers of both egg-laying (A) and live-bearing (B) S. equalis to identify similarities with our ‘unusual’ embryos (C).
Melanie Laird

How evolution works

We still don’t know the trigger that caused this female to lay eggs and give birth to a live baby from the same pregnancy.

However, our findings suggest that species “in transition” between egg-laying and live bearing may hedge their bets reproductively before a true transition to live birth evolves.

Being able to switch between reproductive modes may be advantageous, particularly in changing or uncertain environments.

The three-toed skink lives in eastern Australia.
Doug Beckers / flickr, CC BY

For example, extreme cold, drought or the presence of predators can be risky for vulnerable eggs exposed to the environment, meaning that mothers that can carry offspring to term may have the upper hand.

In contrast, lengthy pregnancies can be taxing on the mother, so depositing offspring earlier as an egg may be beneficial in some situations.

We suggest that other species in which live birth has evolved from egg-laying relatively recently may also use flexible reproductive tactics.

Further research into this small Australian lizard, which seems to occupy the grey area between live birth and egg-laying, will help us determine how and why species make major reproductive leaps.




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Curious Kids: why do hens still lay eggs when they don’t have a mate?


The Conversation


Melanie Laird, Postdoctoral Fellow, University of Otago and Camilla Whittington, Senior lecturer, University of Sydney

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