Benjamin Mayne, CSIROIdentifying the age of animals is fundamental to wildlife management. It helps scientists know if a species is at risk of extinction and the rate at which it reproduces, as well as determining what level of fishing is sustainable.
Determining the age of fish has been difficult in the past — primarily involving extracting the inner ear bone, also known as the “otolith”. Layers of growth in the otolith are counted like rings on a tree to reveal an individual’s age. Unless a dead specimen is available, this method requires killing a fish, making it unsuitable for use on endangered populations.
However a non-lethal DNA test developed by the CSIRO enables researchers to determine fish age for three iconic and threatened Australian freshwater species: the Australian lungfish, the Murray cod and the Mary River cod. We outline the technological breakthrough in our research just published.
Our fast, accurate and cost-effective test can be adapted for other fish species. We now hope to share this method to improve the protection of wild fish populations and help promote sustainable fisheries around the world.
Iconic species at risk
Human activity has led to the population declines of the three Australian fish species at the centre of our research.
The threatened Australian lungfish is found in rivers and lakes in southeast Queensland. It’s often referred to as a “living fossil” because its extraordinary evolutionary history stretches back more than 100 million years, before all land animals including dinosaurs.
Man-made barriers in rivers reduce the movement of water, which lowers lungfish breeding rates.
Older lungfish do not have hard otolith structures, which makes determining their age difficult. Bomb radiocarbon, which analyses carbon levels in organic matter, has been used to age Australian lungfish, but this method is too expensive to be widely used.
The threatened Murray cod is Australia’s largest freshwater fish. The Mary River cod is one of Australia’s most endangered fish, found in less than 30% of its former range in Queensland’s Mary River.
Habitat destruction and overfishing are major threats to Murray cod and Mary River cod populations.
Otoliths can be used to determine age for both these cod species, however this has only been done on a population-wide scale for the more prevalent Murray cod.
When cells divide to make new cells, DNA is replicated. This can lead to DNA methylation, which involves the addition or the loss of a “methyl group” molecule at places along the DNA strand.
Research has found the level of DNA methylation is a reliable predictor of age, particularly in mammals, including humans.
To develop our test, we first worked with zebrafish. This species is useful when studying fish biology because it has a short lifespan and high reproductive rates. We took zebrafish whose ages were known, then removed a tiny clip of their fin. We then examined DNA methylation levels in the fin sample to identify the fish’s age.
Following this successful step, we transferred the method to Australian lungfish, Murray cod and Mary River cod. Again, we used fish of known ages, as well as bomb radiocarbon dating of scales and ages determined from otoliths.
We found despite the zebrafish and the study fish species being separated by millions of years of evolution, our method worked in all four species. This suggests the test can be used to predict age in many other fish species.
In the same way human population demographers use census data to understand and model human populations, we now have the tools to do this with animals.
We are looking to expand this DNA-based method to determine the age of the endangered eastern freshwater cod and trout cod. We will also continue to test the method across other species including reptiles and crustaceans.
This work is part of CSIRO’s ongoing efforts to use DNA to measure and monitor the environment. This includes estimating the lifespan of vertebrate species such as long-lived fish and surveying biodiversity in seawater using DNA extracted from the environment.
We envisage that in the not too distant future, these methods may be used by other researchers to better understand and manage wild animal populations.
But global biodiversity loss means many animal populations are becoming small and sparsely distributed. This jeopardises the ability of young animals to learn important behaviours.
Nowhere is this more true than in the case of regent honeyeaters. In a paper published today, we describe how a population crash to fewer than 300 has caused the species’ song culture to break down.
In healthy populations, the song of adult male honeyeaters is complex and long. But where the population is very small, the song is diminished and, in many cases, the birds have adopted the song of other species. Sadly, this makes the males less attractive to females, which may increase the chance the regent honeyeater will become extinct.
A soft, warbling song
Since 2015, we have monitored the regent honeyeater – a critically endangered, nectar-feeding songbird. The birds once roamed in huge flocks between Adelaide and Queensland’s central coast, tracking eucalyptus blossom.
Extensive postwar land clearing has destroyed regent honeyeater habitat and caused the population to plummet. Most breeding activity is now restricted to the Blue Mountains and Northern Tablelands in New South Wales.
Regent honeyeaters are most vocal during the early stages of their breeding season. Before the population decline, the birds were known for their soft, warbling song produced with characteristic head-bobbing. But with few birds left in the wild, their song is changing – with potentially tragic consequences.
Song-learning is often completed in first year of life, after which a birds’ song is “fixed”.
Despite the increasing number of endangered bird species, there is surprisingly little research into how declines in population size and density might damage song culture in wild birds. We sought to explore whether this link existed in regent honeyeater populations.
Male regent honeyeaters sing to secure breeding territories and attract mates. We classified the songs of 146 male regent honeyeaters between 2015 and 2019. We made or obtained high-quality recordings of 47 of these in the wild, and more in captivity. This included wild birds found by the general public and reported to BirdLife Australia. We quickly chased up these public sightings to record the birds’ songs before they moved on.
Our research showed the songs of remaining wild males vary remarkably across regions. For example, listen to the “proper” song of regent honeyeaters occurring in the Blue Mountains west of Sydney, where most of the remaining population occur:
Regent honeyeater singing a ‘proper’ song. Author provided121 KB(download)
You’ll notice they sound noticeably different to the small number of males hanging on 400km to the north, near Glen Innes. Although these males still sound like a regent honeyeater, their songs are slower and have a different melody:
Regent honeyeater singing a slower song.
Across the species’ entire range, we found 18 males whose songs sounded nothing like a regent honeyeater. Instead, they closely resembled those of other bird species. Five male regent honeyeaters had learned the song of the little wattlebird:
Regent honeyeater singing the song of the little wattlebird.
Four males had learned songs of the noisy friarbird. Others sounded like pied currawongs, eastern rosellas or little friarbirds:
Regent honeyeater singing the song of a little friarbird.
There are isolated cases of individual songbirds mistakenly learning the song of a different species. But to find 12% of males singing only other species’ songs is unprecedented in wild animal populations.
We believe regent honeyeaters are now so rare in the landscape, some young males are unable to locate adult males from which to learn their song. Instead, the young males mistakenly learn the songs of different bird species they’ve associated with when developing their repertoires.
Evidence suggests this song behaviour is distinct from the mimicry common in some Australian birds. Mimicry involves a bird adding the songs of other birds to its own repertoire – and so, not losing its original song. But the regent honeyeaters we recorded never sang songs that resembled that of their species.
Also, mimicry in other species has typically evolved because it increases breeding success. However in regent honeyeaters, we found the opposite. Even among males that sounded like a regent honeyeater, those whose songs were unusual for the local area were less likely to impress, and be paired with, a female. Females that did couple up to males with unusual songs were less likely to lay eggs.
These data suggest the loss of song culture is associated with lower breeding success, which could be exacerbating regent honeyeater population decline.
A captive-breeding program is a key component of the regent honeyeater recovery plan. However our research showed the songs of captive-bred regent honeyeaters were shorter and less complex than their wild counterparts:
The song of a captive-bred regent honeyeater.
This may affect the breeding success of captive-bred males once they’re released to the wild. Consequently, we’re teaching captive juveniles to sing correctly by playing them our recordings of “proper” songs from wild birds in the Blue Mountains.
The honeyeaters’ final song?
Maintaining animal cultures in both wild and captive populations is increasingly recognised as crucial to preventing extinctions. These cultures include not just song, but also other important behaviours such as migration routes and feeding strategies.
The loss of the regent honeyeater song culture may be a final warning the species is headed for extinction. This is an aspect of species conservation we can’t ignore.
We must urgently restore and protect breeding habitats, protect nests from predators and teach captive-bred birds to sing. We must also address climate change, which threatens the species’ habitat. Otherwise, future generations may never hear the regent honeyeater’s dulcet tones in the wild.
Tigers are one of the world’s most iconic wild species, but today they are endangered throughout Asia. They once roamed across much of this region, but widespread habitat loss, prey depletion and poaching have reduced their numbers to only about 4,000 individuals. They live in small pockets of habitat across South and Southeast Asia, as well as the Russian Far East – an area spanning 13 countries and 450,000 square miles (1,160,000 square kilometers).
Today Asia is experiencing a road-building boom. To maintain economic growth, development experts estimate that the region will need to invest about US$8.4 trillion in transportation infrastructure between 2016 and 2030.
Major investment projects, such as China’s Belt and Road Initiative – one of the largest infrastructure projects of all time – are fueling this growth. While roads can reduce poverty, especially in rural areas, many of Asia’s new roads also are likely to traverse regions that are home to diverse plants and animals.
To protect tigers from this surge of road building, conservation scientists like me need to know where the greatest risks are. That information, in turn, can improve road planning in the future.
In a newly published study, I worked with researchers at the University of Michigan, Boise State University and the University of British Columbia to examine how existing and planned Asian roads encroach on tiger habitats. We forecast that nearly 15,000 miles (24,000 kilometers) of new roads will be built in tiger habitats by 2050, and call for bold new planning strategies that prioritize biodiversity conservation and sustainable road development across large landscapes.
Letting humans in
Road construction worsens existing threats to tigers, such as poaching and development, by paving the way for human intrusion into the heart of the tiger’s range. For example, in the Russian Far East, roads have led to higher tiger mortality due to increased collisions with vehicles and more encounters with poachers.
To assess this threat across Asia, we focused on areas called Tiger Conservation Landscapes – 76 zones, scattered across the tiger’s range, which conservationists see as crucial for the species’ recovery. For each zone we calculated road density, distance to the nearest road and relative mean species abundance, which estimates the numbers of mammals in areas near roads compared to areas far from roads. Mean species abundance is our best proxy for estimating how roads affect numbers of mammals, like tigers and their prey, across broad scales.
We estimated that more than 83,300 miles (134,000 kilometers) of roads already exist within tiger habitats. This is likely an underestimate, since many logging or local roads are missing from the global data set that we used.
Road densities in tiger habitat are one-third greater outside of protected areas, such as national parks and tiger reserves, than inside of protected areas. Non-protected areas averaged 1,300 feet of road per square mile (154 meters per square kilometer), while protected areas averaged 980 feet per square mile (115 meters per square kilometer). For tiger populations to grow, they will need to use the forests outside protected areas. However, the high density of roads in those forests will jeopardize tiger recovery.
Road networks are expansive. Over 40% of areas where tiger breeding has recently been detected – crucial to tiger population growth – is within just 3 miles (5 kilometers) of a nearby road. This is problematic because mammals often are less abundant this close to roads.
In fact, we estimate that current road networks within tiger habitats may be reducing local populations of tigers and their prey by about 20%. That’s a major decrease for a species on the brink of extinction. And the threats from roads are likely to become more severe.
Making infrastructure tiger-friendly
Our findings underscore the need for planning development in ways that interfere as minimally as possible with tiger habitat. Multilateral development banks and massive ventures like the Belt and Road Initiative can be important partners in this endeavor. For example, they could help establish an international network of protected areas and habitat corridors to safeguard tigers and many other wild species from road impacts.
National laws can also do more to promote tiger-friendly infrastructure planning. This includes keeping road development away from priority tiger populations and other “no go” zones, such as tiger reserves or habitat corridors.
Zoning can be used around infrastructure to prevent settlement growth and forest loss. Environmental impact assessments for road projects can do a better job of assessing how new roads might exacerbate hunting and poaching pressure on tigers and their prey.
Funding agencies need to screen proposed road developments using these tiger-friendly criteria before planners finalize decisions on road design, siting and construction. Otherwise, it might be too late to influence road planning.
There are also opportunities to reduce the negative effects of existing roads on tigers. They include closing roads to vehicular traffic at night, decommissioning existing roads in areas with important tiger populations, adding road signs announcing the presence of tigers and constructing wildlife crossings to allow tigers and other wildlife to move freely through the landscape.
Roads will become more pervasive features in Asian ecosystems as these nations develop. In my view, now is the time to tackle this mounting challenge to Asian biodiversity, including tigers, through research, national and international collaborations and strong political leadership.
Yet, the federal environment minister approved the dispersal last month under the Environment Protection and Biodiversity Conservation Act (EPBC Act) – Australia’s key environment legislation for protecting threatened species, and currently under a ten-year review.
Today, the camp is not only home to a big portion of the species, but also around 2,000 pups each year. Flying-foxes are extremely mobile in the region, so the camp provides a roosting habitat for more than what’s present at any one time.
Why dispersals don’t work
The council is permitted to disperse the flying-foxes with deterrent measures, including pyrotechnics, intense lighting, acoustic devices and other non-lethal means.
The Conversation sought a response to this article from Cairns Regional Council. A spokesperson said:
Relocation measures will only occur between May and September – outside of the spectacled flying fox pup rearing season to avoid a disruption to the species’ breeding cycle.
The relocation activity will be undertaken by appropriately qualified and experienced individuals and non-lethal methods will be used.
The program is tailored to minimise any stress on the animals and causes no injury of any type.
Dispersals risk stressing the already disturbed animals, and causing injuries and even abortions and other fatalities. They also risk shifting the issues to other parts of our human communities, as the bats tend to end up settling in an unanticipated location after having been shuffled around town like a game of musical chairs.
Cairns Regional Council argues their decision to attempt to move the bats to the Cairns Central Swamp is in the long-term interest of their survival. A council spokesperson says:
Heat stress events, urban development and increased construction in close proximity to the Cairns City Library roost will continue to stress and adversely affect the spectacled flying fox population.
Also, the health of roost trees at the library site, and therefore the viability of the site as a spectacled flying fox roost, is diminishing.
Council believes relocation will mitigate human/flying fox conflict, enable the trees at the library to recover, and will likely reduce the high rates of pup mortality that have been recorded at the library colony.
But these animal welfare concerns arose from the accumulated impacts of the council’s poor management actions, or actions the council supported.
In 2014, the council was found guilty, under the Queensland Nature Conservation Act, of driving away spectacled flying-foxes and illegally pruning the habitat trees.
The Cairns camp was then subjected to a series of EPBC-approved roost tree removals in 2014, 2015, 2016 and 2017. Collectively these destroyed more than two-thirds of the available roosting habitat at the site.
This directly contradicts the specific EPBC Act referral guideline, which states actions to manage the flying-fox camps should not significantly impact the species.
And in 2015, Cairns Aquarium developers had to destroy trees home to hundreds of spectacled flying-foxes before they could start construction. That’s because under the EPBC Act, no building near or around the flying-foxes is permitted. In this case, the act’s well-intentioned protection measures caused far more harm than good.
Warnings fall on deaf ears
In the meantime, the national conservation status of the spectacled flying-fox moved too slowly from “vulnerable” to “endangered” in the listing process.
What’s more, the state government’s recovery plan for the spectacled flying-fox – in place since 2010 – has never been implemented.
Are there any solutions?
There are no solutions under the EPBC Act as it’s currently framed.
The tragic end to the story is that a dangerous precedent is being set for flying-fox management in Australia. Bat carers in Cairns are readying themselves for an influx of casualties from the dispersal.
Some bat carers have sadly reached the conclusion the dispersal is now the least-bad option for the bats after their stronghold suffered a death by a thousand cuts, leaving their home unviable.
Maree Kerr contributed to this article. She is a co-convenor of the Australasian Bat Society’s Flying-Fox Expert Group; an invited expert on the Cairns Regional Council’s Flying-fox Advisory Committee; President of Bats and Trees Society of Cairns; and is studying the role of education in public perceptions of flying-foxes at Griffith University
Evan Quartermain contributed to this article. He is Head of Programs at Humane Society International and a member of the IUCN World Commission on Protected Areas.
In box gum grassy woodlands, widely spaced eucalypts tower over carpets of wildflowers, lush native grasses and groves of flowering wattles. It’s no wonder some early landscape paintings depicting Australian farm life are inspired by this ecosystem.
But box gum grassy woodlands are critically endangered. These woodlands grow on highly productive agricultural country, from southern Queensland, along inland slopes and tablelands, into Victoria.
Many are degraded or cleared for farming. As a result, less than 5% of the woodlands remain in good condition. What remains often grows on private land such as farms, and public lands such as cemeteries or travelling stock routes.
Very little is protected in public conservation reserves. And the recent drought and record breaking heat caused these woodlands to stop growing and flowering.
But after Queensland’s recent drought-breaking rain earlier this year, we surveyed private farmland and found many dried-out woodlands in the northernmost areas transformed into flower-filled, park-like landscapes.
And landholders even came across rarely seen marsupials, such as the southern spotted-tail quoll.
Huge increase in plant diversity
These surveys were part of the Australian government’s Environmental Stewardship Program, a long-term cooperative conservation model with private landholders. It started in 2007 and will run for 19 years.
We found huge increases in previously declining native wildflowers and grasses on the private farmland. Many trees assumed to be dying began resprouting, such as McKie’s stringybark (Eucalyptus mckieana), which is listed as a vulnerable species.
This newfound plant diversity is the result of seeds and tubers (underground storage organs providing energy and nutrients for regrowth) lying dormant in the soil after wildflowers bloomed in earlier seasons. The dormant seeds and tubers were ready to spring into life with the right seasonal conditions.
For example, Queensland Herbarium surveys early last year, during the drought, looked at a 20 metre by 20 metre plot and found only six native grass and wildflower species on one property. After this year’s rain, we found 59 species in the same plot, including many species of perennial grass (three species jumped to 20 species post rain), native bluebells and many species of native daisies.
On another property with only 11 recorded species, more than 60 species sprouted after the extensive rains.
In areas where grazing and farming continued as normal (the paired “control” sites), the plots had only around half the number of plant species as areas managed for conservation.
Spotting rare marsupials
Landowners also reported several unusual sightings of animals on their farms after the rains. Stewardship program surveyors later identified them as two species of rare and endangered native carnivorous marsupials: the southern spotted-tailed quoll (mainland Australia’s largest carnivorous marsupial) and the brush-tailed phascogale.
The population status of both these species in southern Queensland is unknown. The brush-tailed phascogale is elusive and rarely detected, while the southern spotted-tailed quolls are listed as endangered under federal legislation.
Until those sightings, there were no recent records of southern spotted-tailed quolls in the local area.
These unusual wildlife sightings are valuable for monitoring and evaluation. They tell us what’s thriving, declining or surviving, compared to the first surveys for the stewardship program ten years ago.
Sightings are also a promising signal for the improving condition of the property and its surrounding landscape.
Changing farm habits
More than 200 farmers signed up to the stewardship program for the conservation and management of nationally threatened ecological communities on private lands. Most have said they’re keen to continue the partnership.
The landholders are funded to manage their farms as part of the stewardship program in ways that will help the woodlands recover, and help reverse declines in biodiversity.
For example, by changing the number of livestock grazing at any one time, and shortening their grazing time, many of the grazing-sensitive wildflowers have a better chance to germinate, grow, flower and produce seeds in the right seasonal conditions.
They can also manage weeds, and not remove fallen timber or loose rocks (bushrock). Fallen timber and rocks protect grazing-sensitive plants and provide habitat for birds, reptiles and invertebrates foraging on the ground.
So can we be optimistic for the future of wildlife and wildflowers of the box gum grassy woodlands? Yes, cautiously so.
Landholders are learning more about how best to manage biodiversity on their farms, but ecological recovery can take time. In any case, we’ve discovered how resilient our flora and fauna can be in the face of severe drought when given the opportunity to grow and flourish.
Climate change is bringing more extreme weather events. Last year was the warmest on record and the nation has been gripped by severe, protracted drought. There’s only so much pressure our iconic wildlife and wildflowers can take before they cross ecological thresholds that are difficult to bounce back from.
More government programs like this, and greater understanding and collaboration between scientists and farmers, create a tremendous opportunity to keep changing that trajectory for the better.
Western Australia boasts seemingly endless fields of pink, white and yellow everlasting daisies. But while there might seem to be an infinite number, one species in particular is actually endangered. The showy everlasting (or Schoenia filifolia subsp. subulifolia) once grew in the Mid West of WA. Now it is found in just a few spots around the tiny inland town of Mingenew.
But a WA primary school is helping my colleagues and me save the beautiful showy everlasting. With new seed banks, a genetic project and a whole lot of digging, we’re hopeful we can keep this gorgeous native daisy around for the next generation.
The first European to collect the showy everlasting was eminent botanist James Drummond, most likely in the mid-1800s. Initially the species was placed in the Helichrysum family (a group of plants also known as everlastings), but in 1992 botanist Paul Wilson formally described the species based on a specimen collected from Geraldton.
The genus name Schoenia is in honour of the 19th-century eye specialist and botanical illustrator Johannes Schoen, and the species name filifolia refers to its long, slender leaves.
Everlastings get their name from the fact that that the flowers hold their colour long after they have been picked and dried. The species is known as the showy everlasting because its large, brightly coloured flowers put on a spectacular show when in bloom.
The showy everlasting is an annual plant, growing around 30cm high, with long narrow leaves. Its bright yellow flowers bloom from August to October. The showy everlasting has two closely related sister species: the more common Schoenia filifolia subsp. filifolia, found throughout the WA Wheatbelt, and Schoenia filifolia subsp. arenicola, which grows around Carnarvon but hasn’t been collected for decades. The main differences between the showy everlasting and its sister species are the much larger flowers and the shape of the base of the flower, which is hemispherical rather than vase-shaped.
Collections of the showy everlasting housed in the Western Australian Herbarium indicate the species was once more widespread. It’s likely land clearing for farms and infrastructure led to the disappearance of the species from much of its known range.
It was listed as endangered in 2003. At that time the species was found in just three locations. At each of these sites, threats such as chemical drift from nearby agricultural land, grazing by animals, competition from weeds, and increasing soil salinity were all jeopardising the survival of the species.
Unfortunately, by the late 2000s two of these three populations had succumbed to these threats and were lost. However, continued search efforts since then have uncovered two new populations. The showy everlasting is hanging on, but a concerted conservation effort is needed to ensure its survival in the wild.
New populations needed
To ensure the long-term survival of the showy everlasting, we need to establish new populations – a process called translocation.
As an insurance policy, in 2007 seeds were collected and frozen in the Threatened Flora Seed Vault at the Western Australia Seed Centre. In 2015 my colleagues and I used some of these seeds in small-scale translocation trials, successfully getting new plants to grow, flower and seed in three small populations.
Despite this success, we knew the populations would need to be much, much larger and we would need many more populations to ensure persistence of the species. And for that we needed more information about the showy everlasting’s biology, and larger amounts of seed.
Currently a genetic study is underway to look at the difference between the showy everlasting in different locations and its sister species. As part of my PhD study with Murdoch University, I am running a glasshouse experiment to see whether different populations of the showy everlasting can cross and produce viable seed, and whether there are benefits or risks to such crosses.
The initial translocation trials have proved we can successfully establish new populations, but we’re currently limited by the amount of available seed. This is because our trials showed the most efficient way to establish the showy everlasting is by planting seeds directly into the ground. However, this process uses a lot of seeds – more than we have stored in the Seed Vault. Rather than denude the wild populations, we needed a new source.
Fortunately, at this time Andrew Crawford, manager of the Threatened Flora Seed Vault at the Western Australian Seed Centre, was approached by the principal of the Woodlupine Primary School, Trevor Phoebe. He was looking for a meaningful way to involve his students with plant conservation. This led to the establishment of a seed production area at the school which aims to grow and harvest seed of the showy everlasting. The students at the school are involved with planting, monitoring and taking care of the plants, and will help collect the seed when they ripen.
It is still early days for this project, however early signs are promising. Seedlings have established well and have begun flowering. Seed collection is planned for later in the year.
The seed harvested will be used in the future to boost plant numbers in the existing populations, and to establish new sites, hopefully securing this beautiful species in the wild so that everyone can enjoy the showy everlasting for decades to come.
In unfenced wilderness, scientists rarely have an inventory on the exact numbers of species in an area at a particular time. Instead they make inferences using one of many different survey approaches, including camera traps, track surveys, and drones. These methods can estimate how much and what kind of wildlife is present, but often require large amounts of effort, time and money.
Camera traps are placed in remote locations and activated by movement. They can collect vast quantities of data by taking photographs and videos of passing animals. But this can cost tens of thousands of dollars to run and once in the wild, cameras are at the mercy of curious wildlife.
Track surveys rely on specialist trackers, who aren’t always available and drones, while promising, have restricted access to many tourism areas in Africa. All of this makes wildlife monitoring difficult to carry out and repeat over large areas. Without knowing what’s out there, making conservation decisions based on evidence becomes almost impossible.
Despite this, tourists and their guides are still an overlooked source of information. Could your holidays snaps help monitor endangered wildlife? In a recent study, we tested exactly this.
Partnering with a tour operator in Botswana, we approached all guests passing through a safari lodge over three months in the Okavango Delta and asked them if they were interested in contributing their photographs to help with conservation. We provided those interested with a small GPS logger – the type commonly used for tracking pet cats – so that we could see where the images were being taken.
We then collected, processed, and passed the images through computer models to estimate the densities of five large African carnivore species – lions, spotted hyaenas, leopards, African wild dogs and cheetahs. We compared these densities to those from three of the most popular carnivore survey approaches in Africa – camera trapping, track surveys, and call-in stations, which play sounds through a loudspeaker to attract wildlife so they can be counted.
The tourist photographs provided similar estimates to the other approaches and were, in total, cheaper to collect and process. Relying on tourists to help survey wildlife saved up to US$840 per survey season. Even better, it was the only method to detect cheetahs in the area – though so few were sighted that their total density couldn’t be confirmed.
Thousands of wildlife photographs are taken every day, and the study showed that we can use statistical models to cut through the noise and get valuable data for conservation. Still, relying on researchers to visit tourist groups and coordinate their photograph collection would be difficult to replicate across many areas. Luckily, that’s where wildlife tour operators could come in.
Tour operators could help collect tourist images to share with researchers. If the efforts of tourists were paired with AI that could process millions of images quickly, conservationists could have a simple and low-cost method for monitoring wildlife.
Tourist photographs are best suited for monitoring large species that live in areas often visited by tourists – species that tend to have high economic and ecological value. While this method perhaps isn’t as well suited to smaller species, it can still indirectly support their conservation by helping protect the landscapes they live in.
The line between true wilderness and landscapes modified by humans is becoming increasingly blurred, and more people are visiting wildlife in their natural habitats. This isn’t always a good thing, but maybe conservationists can use these travels to their advantage and help conserve some of the most iconic species on our planet.
The debate around the Murray-Darling Basin is often sharply polarised: irrigation is destroying the environment, or water reforms are ruining farming communities.
But there is another story. In the Riverina region of southern New South Wales, a strange waterbird is using rice fields to live in and breed.
The endangered Bunyip Bird, also called the Australasian Bittern, is famous for its deep booming call – for thousands of years thought to be the sound made by the mythical Bunyip.
It’s a sound now familiar to most rice growers. In 2012, Birdlife Australia and the Ricegrowers’ Association teamed up to learn more about bitterns in rice. The total bittern population, including New Zealand and New Caledonia, is estimated at no more than 2,500 adults.
The first question was how many bitterns are using rice crops. After surveying the birds on randomly selected farms, we crunched the numbers. Our results, just published, are staggering.
Across the Riverina, we conservatively estimate these rice crops attract 500-1,000 bitterns during the breeding season, about 40% of global population. It turns out the way rice is grown provides ideal water depths and vegetation heights for bitterns. It’s also favourable for their prey: frogs and tadpoles, fish and yabbies.
There is a growing body of global research investigating how human-made habitats can help fill the gap left by our vanishing wetlands, from ditches for rare turtles to constructed ponds for threatened amphibians. Rice fields around the world show great promise as well, with various “wildlife-friendly” farming initiatives. In California, farmers re-flood harvested fields to support thousands of migratory shorebirds and waterfowl, while in Japan consumers pay a premium for “Stork Rice” to help endangered species.
However, rice fields are no substitute for natural wetlands, and it’s now clear both play a crucial role in sustaining the bittern population.
Satellite tracking has shown us that at harvest time bitterns disperse to some of southeastern Australia’s most important wetlands, including the Barmah-Millewa system along the Murray River, Coomonderry Swamp near Shoalhaven Heads in New South Wales, Pick Swamp in South Australia, and Tootgarook Swamp on the Mornington Peninsula near Melbourne.
Water efficiency might be bad news for the bittern
Rice farming in Australia’s Riverina has a century-long history. The amount grown varies greatly from year to year, depending on water allocations, and ranged from 5,000-113,000 hectares over the past decade. Around 80% is exported and it provides food for up to 20 million people each year.
Driven by water efficiency, many rice growers in the Riverina are switching their methods to intermittent flooding and not “ponding” the water – maintaining inundated fields – until later in the season.
A shorter ponding period will likely reduce opportunities for the bitterns to breed successfully before harvest. Another threat to bitterns is farmers switching to alternative crops and horticulture, none of which provides them habitat.
During the 2017-18 irrigation season, there was more cotton grown than rice for the first time in the Riverina. It’s usually simple economics: irrigators will generally grow whatever gives them the best return per megalitre of water, with their choice having no net effect on the overall amount of irrigation water used in the system.
Water management in the Murray-Darling Basin is complicated, with fluctuating temporary water prices and trading between catchments. Water is allocated to either agriculture or the environment, setting up a dichotomy. But we think allocations to serve a single purpose may be overly simplistic, and the way bitterns use rice offers a case study for considering multi-purpose water use.
Working closely with growers, we are identifying ways to develop cost-effective incentive programs for bittern-friendly rice growing, where a sufficient ponding period is provided, with complementary habitat on banks, in crop edges and adjacent constructed wetland refuges. The aim is to boost the bittern population with the help of rice farmers.
We are also surveying consumers about their attitudes towards bittern-friendly rice. Would you pay a premium for rice products that offset additional costs to growers for bittern conservation? How do you feel about adjusting water and conservation policies?
Bitterns are not the only threatened species that use the Riverina’s rice fields. The endangered Southern Bell Frog and Australian Painted Snipe have also adapted to rice crops, and it’s likely there are significant populations of other species too.
With 61% of Australia managed by farmers, the need to incorporate wildlife conservation on farms has never been greater. We hope our work will help address the divisive, sometimes toxic debate around water use in the Murray-Darling Basin, uniting irrigators and environmentalists.
This knowledge changes how we think pregnancy evolved in mammals. It may also help in breeding programs for threatened or endangered marsupials by contributing to new technologies such as a marsupial pregnancy test.
Marsupials do things differently
When people think of marsupials – animals that mostly rear their young in a pouch (although not all marsupials have a pouch) – kangaroos and koalas tend to spring to mind. But marsupials come in a range of shapes and sizes.
In addition to Australia’s marsupial diversity, there are also 120 marsupial species in South America – most of which are opossums – and just one species in North America, the Virginia opossum.
One thing all marsupials have in common is they give birth to very small, almost embryonic, young.
Because marsupial pregnancy passes so quickly (12-40 days, depending on the species), and marsupial young are so small and underdeveloped at birth, biologists had thought the biological changes required to support the fetus through a pregnancy happened as a follow on from releasing an egg (ovulation), rather than a response to the presence of a fetus.
Marsupial pregnancy is quick
One way to explore the question of whether it is an egg or a fetus that tells the marsupial female to be ready for pregnancy is to look at the uterus and the placenta.
We looked at two groups of opossums: females that were exposed to male pheromones to induce ovulation, and females that were put with males so they could mate and become pregnant.
We then used microscopy and molecular techniques to compare females from the two groups. Contrary to the current dogma, we found that the uterus in pregnancy looked very different to those females that did not mate.
In particular, we found the blood vessels that bring blood from the mother to the placenta interface were only present in pregnancy. We also noticed that the machinery responsible for nutrient transport (nutrient transporting molecules) from the mother to the fetus was only produced in pregnancy.
While hormones may be regulating some aspects of maternal physiology, the mother is certainly detecting the presence of embryos and responding in a way that shows she is recognising pregnancy.
How this knowledge can help others
Given that recognition of pregnancy has now been found in both eutherian (formerly known as placental) mammals like ourselves and marsupials with the more ancestral reproductive characters, it appears likely that recognition of pregnancy is a common feature of all live bearing mammals.
But this knowledge does more than satisfy our curiosity. It could lead to new technologies to better manage marsupial conservation. Several marsupials face threats in the wild, and captive breeding programs are an important way to secure the future of several species.
But management can be made more difficult when we don’t know which animals are pregnant. Our research shows that maternal signals are produced in response to the presence of developing embryos. With a bit more research, it may be possible to test for these signals directly.
New reproductive technologies are likely crucial for improving outcomes of conservation programs, and this work shows, that to do this we first need a better understanding of the biology of the animals we are trying to save.