Trailing giants: clues to how people and giraffes can thrive together


Masai giraffes in northern Tanzania.
Sonja Metzger

Monica Bond, University of ZürichThe giraffe (Giraffa camelopardalis) is an iconic megaherbivore whose populations are declining across Africa, the only continent where they are found. Giraffe numbers have plummeted from an estimated 150,000 in 1985 to fewer than 100,000 today.

Like many species of African wildlife, giraffes face numerous threats. The biggest threats are hunting for bushmeat markets and loss of habitat due to deforestation and the spread of farms.

Giraffes shape and sustain healthy ecosystems. For example, woody plant spines, such as thorn trees, are a response to giraffe browsing. Giraffes are also a big attraction for tourists.

The best way to reverse giraffe population declines is to monitor individual animals and learn why they do better in one place over another. This helps to pinpoint threats and evaluate conservation strategies, such as how the presence of people influences giraffes and whether community conservation areas work.

Fortunately, giraffes are a good study species for this type of research. Each animal has a unique and unchanging spot pattern for its entire life, like a human thumbprint. Giraffes can therefore be easily identified from photographs without any need for dangerous captures.

In 2011, my colleagues and I launched the Masai Giraffe Project to learn what helps and what harms giraffes, and how people and giraffes can thrive together. Although the giraffe is still considered a single species, genetic information suggests there may be three species with Masai giraffes a separate species.

The Masai Giraffe Project is a partnership between the Wild Nature Institute, the University of Zurich, Pennsylvania State University and the Tanzania Wildlife Research Institute. It has become one of the biggest studies of a large mammal, with nearly 3,000 individuals identified in a vast, 4,500-km2 area of the Tarangire ecosystem in Tanzania.

To date we’ve published more than 10 original studies about giraffe survival, movements and behaviour in relation to human disturbances – specifically human settlements.

The Tarangire ecosystem features two distinctive types of human settlements: towns – whose inhabitants include farmers and bushmeat poachers – and small, traditional homesteads, inhabited by members of the livestock-keeping Maasai community.

We revealed that survival of giraffes is influenced by how close they live to towns. Adult female survival was higher within national parks and community-based conservation areas, away from towns which brought them closer to farming and poaching. These results were not surprising, but we were encouraged to also discover that traditional homesteads are compatible with giraffe conservation. They were even a benefit to mothers with small calves.

Our findings help wildlife authorities understand where and why giraffe numbers are stable, increasing or declining.

Giraffes and people: a future in the balance

Our study area includes two national parks, a large cattle and ecotourism ranch, two community-managed wildlife areas as well as unprotected lands with towns and traditional homesteads. The entire area has no fences so giraffes can roam freely around their large home ranges, which average about 130 hectares.

The giraffe’s habitat outside the parks is affected by human activities which include farming, charcoal making and livestock. Giraffe habitat throughout Africa has become similarly fragmented. Thus, our study area is representative of the diversity of threats and conservation opportunities facing giraffes.

We found that the probability of adult female giraffe survival was higher in protected areas than less-protected areas where poaching for bushmeat markets was prevalent.

We also learned that community-based conservation is helping giraffes. For instance, the survival rates of giraffes in community conservation areas adjacent to national parks improved. These areas also had higher giraffe population densities than outside the protected zones.

Survival of breeding females in long-lived species like giraffes is absolutely critical to sustain populations. Lower survival rates of adult females outside protected areas resulted in population declines.

In contrast to adult giraffes, survival of calves was lower inside protected areas where predator densities are highest. However, the seasonal presence of migratory wildebeests and zebras attracted predation away from giraffe calves. This means that conservation of giraffes requires the safeguarding of all the other animals in the savanna.

Different lifestyles

One of the most promising results from our research is that some human lifestyles seem to be more compatible with giraffe conservation. Most giraffes tended to avoid human areas altogether, however giraffe mothers didn’t always. They stayed far from towns but actually preferred to be closer to traditional homesteads.

We discovered that female giraffes living near traditional homesteads had weaker social relationships, but this did not reduce their survival. Closer to towns, adult female giraffes had lower survival and their home ranges were larger in size. This indicated that they had to roam farther to evade poachers and obtain necessary resources, like food and water.

Giraffe mothers were more likely to be found near traditional homesteads where predators on calves – like lions and hyenas – were fewer. This was probably due to pastoralists eliminating predators and disrupting predator behaviour to protect their livestock.

Ways forward

Our 10 years of research on giraffes in a human-natural landscape revealed constructive ways forward for giraffe conservation. Livestock-keeping and farming people have different influences on giraffes, yet both have important roles to play in saving giraffes from extinction.

We can help the tallest of the megaherbivores by giving them enough living space in the savanna. By limiting habitat loss and expanding community-based conservation areas, and eating livestock rather than bushmeat, we can ensure a future where both humans and giraffes will thrive.The Conversation

Monica Bond, Research associate, University of Zürich

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

From baby blue-tongues to elephant doulas: motherhood across the animal kingdom


Diana Robinson, Author provided

Oliver Griffith, Macquarie University and Jessica Suzanne Dudley, Macquarie UniversityWith Mother’s Day around the corner, it’s a good opportunity to ask what being a mother looks like across the animal kingdom. Most of us have a solid concept of human motherhood, but in nature maternal care comes in many forms.

Let’s take a closer look at the diversity of ways animals provide care, to give young the best chance of success.

The power of the placenta

For many species, life begins in the womb. One of the most significant ways mothers support their young before birth is via a placenta, the temporary organ that grows inside the uterus to support a fetus. Placentas not only act as the interface between mother and baby, but can provide all fetal nutrition, allow for exchange of oxygen and carbon dioxide with the mother, and even remove the fetus’s waste.




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Using the placenta to understand how complex organs evolve


While our close relatives (eutherian or placental mammals) are known for having a placenta, we are not unique in having one. In fact, the placenta has evolved more than 100 times independently in the animal kingdom!

Blue-tongued lizard with her newborn young.
National Parks and Wildlife Service, South Australia

Other placental species include some reptiles such as the blue-tongued lizard, and many sharks including the Australian sharpnose. Even marsupials have a placenta, although it typically only supports young for a few days.

Marsupial mothers

Outside the womb, the queens of maternal care are marsupials such as kangaroos, koalas and Tasmanian devils. Marsupial mothers provide food and protection from predators through a prolonged period of lactation inside the pouch.

In marsupials, pregnancy is relatively short but young spend a long time in the pouch afterwards. For example, tammar wallabies’ pregnancy can be as short as four weeks, but mothers can provide milk to their young in the pouch for almost a year. During this time the babies increase in weight 2,000-fold. In comparison, human infants increase in weight threefold during their first year of life.

A kangaroo mother, looking after her joey in the pouch.
Ethan Brooke/www.pexels.com

Egg-layers

An African rock python, looking after her eggs. Python mothers will coil around their eggs while they incubate, and can even shiver to keep the eggs warm.
J. Lanki/wikimedia

In contrast to animals that develop a placenta, egg-laying animals typically lay nutrient-rich eggs to support development. Parents of some species consider their job done after the eggs are laid, but others continue to care for their young by protecting the eggs and providing food once the babies hatch.

A Port Jackson Shark egg. After laying eggs, mothers carry them in their mouth and screw them into a secure rock crevice, hoping they will be protected for their 10-12 months of development.
Kate Bunker/flickr

Some egg-laying sharks continue to provide care after birth. Port Jackson sharks carry their eggs in their mouths until they find a protected rock crevice to hide them in.

Hummingbird mothers look after their young without any paternal support.
Mike’s Birds

In birds, mothers provide warmth and protection while incubating their eggs. In some bird species such as hummingbirds, only the mother provides care after birth. However, in other cases, such as penguins, it’s a team effort with mothers and fathers providing food and protection to their offspring.

For some, it takes a village

For some animals, motherhood extends beyond looking after your own children. Like humans, orcas (killer whales) forgo the potential to reproduce later in life by going through menopause.

Menopause may prevent them from raising any more children, but it allows them to divert their efforts to raising the next generation by looking after their grandchildren.

Orcas and a few of their close relatives (including beluga whales and narwhals) are one of the few non-human mammals that forgo reproduction later in life and enter menopause. This allows mothers to continue to support the next generation by looking after their grandchildren.
Gregory ‘Slobirdr’ Smith/flickr

Many animals need even more support, so some species form societies where the whole community will care for the young, rather than just the parents. Meerkats live in groups of up to 30 individuals where parental duties are shared.

Meerkat mother keeping an eye out for predators with one of her pups.
Theo Stikkelman

Younger females will “babysit” the pups while the rest of the mob forage for food, sometimes having to put their own lives in danger to protect the younger members of the group.

Within elephant herds, the mothers provide milk for their babies but other members of the herd (known as doulas, they can be either male or female) provide encouragement and physical support to both the mother and the growing calves. This same behaviour is seen in dolphins, as well as in several primates including chimpanzees and gorillas.

Pregnant male Hippocampus whitei. Seahorse fathers experience male pregnancy, providing nutrition, gas exchange and protection to developing embryos within his pouch.
Marine Explorer

In a few species, it is the father that provides the most care for offspring. For example, seahorses exhibit male pregnancy, providing nutrition and protection from predators while inside his pouch. For a seahorse mother, her care responsibilities end once she has deposited her eggs into the male’s pouch.

If we can learn anything from the animal kingdom, it’s that motherhood comes in many forms.The Conversation

Oliver Griffith, Lecturer, Macquarie University and Jessica Suzanne Dudley, Postdoctoral Fellow, Macquarie University

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

Feral desert donkeys are digging wells, giving water to parched wildlife


Erick Lundgren, University of Technology Sydney; Arian Wallach, University of Technology Sydney, and Daniel Ramp, University of Technology SydneyIn the heart of the world’s deserts – some of the most expansive wild places left on Earth – roam herds of feral donkeys and horses. These are the descendants of a once-essential but now-obsolete labour force.

These wild animals are generally considered a threat to the natural environment, and have been the target of mass eradication and lethal control programs in Australia. However, as we show in a new research paper in Science, these animals do something amazing that has long been overlooked: they dig wells — or “ass holes”.

In fact, we found that ass holes in North America — where feral donkeys and horses are widespread — dramatically increased water availability in desert streams, particularly during the height of summer when temperatures reached near 50℃. At some sites, the wells were the only sources of water.

Feral donkeys and horses dig wells to desert groundwater.
Erick Lundgren

The wells didn’t just provide water for the donkeys and horses, but were also used by more than 57 other species, including numerous birds, other herbivores such as mule deer, and even mountain lions. (The lions are also predators of feral donkeys and horses.)

Incredibly, once the wells dried up some became nurseries for the germination and establishment of wetland trees.

Numerous species use equid wells. This includes mule deer (top left), scrub jays (middle left), javelina (bottom left), cottonwood trees (top right), and bobcats (bottom right).
Erick Lundgren

Ass holes in Australia

Our research didn’t evaluate the impact of donkey-dug wells in arid Australia. But Australia is home to most of the world’s feral donkeys, and it’s likely their wells support wildlife in similar ways.

Across the Kimberley in Western Australia, helicopter pilots regularly saw strings of wells in dry streambeds. However, these all but disappeared as mass shootings since the late 1970s have driven donkeys near local extinction. Only on Kachana Station, where the last of the Kimberley’s feral donkeys are protected, are these wells still to be found.

In Queensland, brumbies (feral horses) have been observed digging wells deeper than their own height to reach groundwater.

https://www.kachana-station.com/projects/wild-donkey-project/
Some of the last feral donkeys of the Kimberley.
Arian Wallach

Feral horses and donkeys are not alone in this ability to maintain water availability through well digging.

Other equids — including mountain zebras, Grevy’s zebras and the kulan — dig wells. African and Asian elephants dig wells, too. These wells provide resources for other animal species, including the near-threatened argali and the mysterious Gobi desert grizzly bear in Mongolia.

These animals, like most of the world’s remaining megafauna, are threatened by human hunting and habitat loss.

Other megafauna dig wells, too, including kulans in central Asia, and African elephants.
Petra Kaczensky, Richard Ruggiero

Digging wells has ancient origins

These declines are the modern continuation of an ancient pattern visible since humans left Africa during the late Pleistocene, beginning around 100,000 years ago. As our ancestors stepped foot on new lands, the largest animals disappeared, most likely from human hunting, with contributions from climate change.




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Giant marsupials once migrated across an Australian Ice Age landscape


If their modern relatives dig wells, we presume many of these extinct megafauna may have also dug wells. In Australia, for example, a pair of common wombats were recently documented digging a 4m-deep well, which was used by numerous species, such as wallabies, emus, goannas and various birds, during a severe drought. This means ancient giant wombats (Phascolonus gigas) may have dug wells across the arid interior, too.

Likewise, a diversity of equids and elephant-like proboscideans that once roamed other parts of world, may have dug wells like their surviving relatives.

Indeed, these animals have left riddles in the soils of the Earth, such as the preserved remnants of a 13,500-year-old, 2m-deep well in western North America, perhaps dug by a mammoth during an ancient drought, as a 2012 research paper proposes.




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From feral camels to ‘cocaine hippos’, large animals are rewilding the world


Acting like long-lost megafauna

Feral equids are resurrecting this ancient way of life. While donkeys and horses were introduced to places like Australia, it’s clear they hold some curious resemblances to some of its great lost beasts.

Our previous research published in PNAS showed introduced megafauna actually make Australia overall more functionally similar to the ancient past, prior to widespread human-caused extinctions.

Donkeys share many similar traits with extinct giant wombats, who once may have dug wells in Australian drylands.
Illustration by Oscar Sanisidro

For example, donkeys and feral horses have trait combinations (including diet, body mass, and digestive systems) that mirror those of the giant wombat. This suggests — in addition to potentially restoring well-digging capacities to arid Australia — they may also influence vegetation in similar ways.

Water is a limited resource, made even scarcer by farming, mining, climate change, and other human activities. With deserts predicted to spread, feral animals may provide unexpected gifts of life in drying lands.

Feral donkeys, horses (mapped in blue), and other existing megafauna (mapped in red) may restore digging capacities to many drylands. Non-dryland areas are mapped in grey, and the projected expansion of drylands from climate change in yellow.
Erick Lundgren/Science, Author provided

Despite these ecological benefits in desert environments, feral animals have long been denied the care, curiosity and respect native species deservedly receive. Instead, these animals are targeted by culling programs for conservation and the meat industry.

However, there are signs of change. New fields such as compassionate conservation and multispecies justice are expanding conservation’s moral world, and challenging the idea that only native species matter.The Conversation

Erick Lundgren, PhD Student, Centre for Compassionate Conservation, University of Technology Sydney; Arian Wallach, Lecturer, Centre for Compassionate Conservation, University of Technology Sydney, and Daniel Ramp, Associate Professor and Director, Centre for Compassionate Conservation, University of Technology Sydney

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

Next time you see a butterfly, treasure the memory: scientists raise alarm on these 26 species


The bulloak jewel (Hypochrysops piceatus)
Michael Braby, Author provided

Michael F. Braby, Australian National University; Hayley Geyle, Charles Darwin University; Jaana Dielenberg, Charles Darwin University; Phillip John Bell, University of Tasmania; Richard V Glatz; Roger Kitching, Griffith University, and Tim R New, La Trobe UniversityIt might sound like an 18th century fashion statement, but the “pale imperial hairstreak” is, actually, an extravagant butterfly. This pale blue (male) or white (female) butterfly was once widespread, found in old growth brigalow woodlands that covered 14 million hectares across Queensland and News South Wales.

But since the 1950s, over 90% of brigalow woodlands have been cleared, and much of the remainder is in small degraded and weed infested patches. And with it, the butterfly numbers have dropped dramatically.

In fact, our new study has found it has a 42% chance of extinction within 20 years.

It isn’t alone. Our team of 28 scientists identified the top 26 Australian butterfly species and subspecies at greatest risk of extinction. We also estimated the probability that they will be lost within 20-years.


Author provided, Author provided

Without concerted new conservation effort, we’ll not only lose unique elements of Australia’s nature, but also the important ecosystem services these butterflies provide, such as pollination.

Only six are protected under law

We are now sounding the alarm as most species identified as at risk have little or no management underway to conserve them, and only six of the 26 butterflies identified are currently listed for protection under Australian law.

The Ptunarra Xenica is one of three at risk butterflies identified in Tasmania.
Simon Grove/Tasmanian Museum and Art Gallery

The good news is there’s still a very good chance of recovery for most of these species, but only with new targeted conservation effort, such as protecting habitat from clearing and weeds, better fire management and establishing more of the right caterpillar food plants.

Let’s meet a few at-risk butterflies

The butterflies identified are delightful and fascinating creatures, with intriguing lifecycles, including fussy food preferences, subterranean accommodation and intimate relationships with “servant” ants.

The Australian fritillary

Our most imperilled butterfly is the Australian fritillary, with a 94% chance of extinction within 20 years. Like many of our butterfly species, a major threat facing the fritillary is habitat loss and habitat change.

The swamps where the fritillary occur have been drained for farming and urbanisation. At remaining swamps, weeds smother the native violets the larvae depend on for food.

This is one of the last known photos of the Australian fritillary. If you see a fritillary, immediately contact the NSW Department of Planning Industry and Environment.
Garry Sankowsky

No one has managed to collect or take a photo of a fritillary in two decades, although a butterfly expert observed a single individual flying near Port Macquarie in 2015.

It might already be extinct, but as it was once quite widespread at swampy areas along 700 kilometres of coastal Queensland and NSW, we have hope there are still some out there.

The fritillary has impressive jet black caterpillars with a vibrant orange racing stripe and large spikes along their back, which transform into stunning orange and black butterflies.

Black caterpillar
Australian fritillary caterpillars are black with a distinctive orange stripe and spikes.
Garry Sankowsky

Anyone who thinks they have seen a fritillary should record the location, try to photograph it and the site and immediately contact the NSW Department of Planning Industry and Environment.

The fritillary is among many butterflies with specific diets. And these preferences can make species vulnerable to environmental changes such as vegetation clearing, weed invasions and fires.




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The small bronze azure

Caterpillars of the small bronze azure — found on Kangaroo Island (and a few other patches in South Australia and Victoria) — only eat common sourbush.

Following the extensive 2020 fires, the butterfly hasn’t been found in areas where the sourbush burnt. Luckily, it’s been found in small patches of unburnt vegetation, so for now it’s hanging in there.

The small bronze azure has not been re-found in parts of Kangaroo Island where common sourbush burnt in the January 2020 fires.
Richard Glatz

Like many butterflies, the lifecycle of the small bronze azure is enmeshed with a specific species of ant.

By day the butterfly larvae shelter underground in sugar ant (Camponotus terebrans) nests, then at night they’re escorted up by the ants to feed on the sourbush. For their care the ants are rewarded by a sugary secretion the caterpillars produce.

The eastern bronze azure

Some relationships with ants are even more unusual. Kangaroo Island’s other imperilled species — the eastern bronze azure — stays underground in sugar ant nests for 11 straight months. We don’t yet know what they eat.

Grey butterfly on a rock
An eastern bronze azure (Ogyris halmaturia) on Kangaroo Island. Their colouring is excellent camouflage on branches.
Michael Braby

In a macabre twist, they may be eating their hosts — the ants or the ant larvae. So why the ants carry them down and look after them is also a mystery.

It might be for sugary secretions, like with the small bronze azure, but the caterpillars could also be using chemical trickery, mimicking the scent of ant larvae to fool the ants.

Adults of the eastern bronze azure emerge only to flutter about for a few weeks in November, so at the time of the Kangaroo Island fires in January the entire population was safely underground in ant nests. And as the larvae don’t come up to feed on plants, they weren’t impacted by the loss of vegetation.

Orange and black butterfly on a green leaf
This is the black grass-dart, found near Coffs Harbour. The caterpillars eat Floyd’s grass (Alexfloydia repens) which is listed as endangered in NSW.
Mick Andren

It’s not too late to save them

By raising awareness of these butterflies and the risks they face, we aim to give governments, conservation groups and the community time to act to prevent their extinctions.

Local landowners and Landcare groups have already been playing a valuable role in recovery actions for several species, such as planting the right food plants for the Australian fritillary around Port Macquarie, and for the Bathurst copper.

Brown and green butterfly on a log
The Bathurst copper in NSW is benefiting from community planting of its food plant sweet bursaria.
Tessa Barratt

Indeed, most of the identified at-risk species occur across a mix of land types, including conservation, public and private land. In most cases, conservation reserves alone aren’t enough to ensure the long-term survival of the species.

Many landowners don’t realise they’re important custodians of such rare and threatened butterflies, and how important it is not to clear remaining patches of remnant native vegetation on their properties and adjoining road reserves.

People wanting to learn more about the butterfly species near them can use the free Butterflies Australia app to look up photos and information. You can also be a citizen scientist by recording and uploading sightings on the app.




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The Conversation


Michael F. Braby, Associate Professor, Australian National University; Hayley Geyle, Research Assistant, Charles Darwin University; Jaana Dielenberg, University Fellow, Charles Darwin University; Phillip John Bell, University Associate, School of Natural Sciences, University of Tasmania; Richard V Glatz, Associate research scientist; Roger Kitching, Emeritus Professor, Griffith University, and Tim R New, Retired: Emeritus Professor in Zoology, La Trobe University

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

Meet 5 of Australia’s tiniest mammals, who tread a tightrope between life and death every night


Andrew Baker, Queensland University of TechnologyAustralia has a rich diversity of mammals, with around 320 native, land-based species, 87% of which are found here and nowhere else. Many of these mammals are secretive, only active at night, and small, weighing less than one kilogram.

Mammals are “endotherms”, which means they must generate their own heat and maintain the temperature within a narrow range. This requires a lot of food.

For small mammals, which have a high surface area to volume ratio, the energetic cost is even higher. This makes them particularly prone to heat gain and loss, putting them in peril every night.

The silver-headed antechinus, which weighs up to the equivalent of six $1 coins.
Gary Cranitch/QueenslandMuseum, Author provided

So how on earth do they cope?

Well, there are some advantages to being small. It’s harder to be seen by predators, and there are more places to hide. If the soil type is right, there’s no shortage of cracks and holes to slip into.

Such habitats not only keep small mammals concealed from predators during the day and parts of the night, but the temperature and humidity is also more stable underground, which means they expend less energy in maintaining body temperature.

To further conserve energy, many small mammals will also enter “torpor” — an inactive period that slows down their energy-burning metabolism. Torpor is like a mini hibernation that typically lasts for hours, rather than days.

A long-tailed planigale feasting on a grasshopper. In the corner, you can see it sitting on scientist Euan Ritchie’s finger for scale.
Euan Ritchie

For small mammals — prone to losing heat and needing to catch and eat up to half their body weight in food each night — having some periods of down-time during energy-conserving torpor can mean the difference between life and death.

In addition to the nightly challenge of finding enough food to maintain a stable body temperature, keep a complex brain functioning and have enough energy to move up to several kilometres, Australia’s small mammals face a host of human-caused threats. These include habitat clearing, climate change and feral predators.

The combined pressures have too often proven insurmountable. With 34 species lost forever, Australia has the worst modern-day mammal extinction record of any country on Earth.

So how can we turn this appalling situation around?

First, we humans must appreciate these unique animals and decide they need to be saved. That requires knowledge and understanding, so let’s get to know some of these mysterious mammals a little better.

1. Long-tailed planigale (Planigale ingrami)

Weight: 2.6-6.6 grams (up to two 10c coins)

Can you imagine a mammal that can weigh less than a ten-cent piece yet leaps five times its own height to bring down prey far larger than itself with persistent, savage biting to the head and neck?

This is the long-tailed planigale, the smallest Australian marsupial and one of the world’s smallest mammals.

Long-tailed planigale
Long-tailed planigales may be tiny, but they’re ferocious predators.
Anders Zimney, Author provided

They are ferocious predators, and anything that can be subdued is viciously attacked, including large centipedes, spiders, insects, small lizards, and even other small mammals.

They live in narrow crevices of cracking clays in blacksoil plains and move below and above the surface at night in search of food. Here, they run the risk of being eaten by predators, such as owls and feral cats.




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The conversion of grassland to agriculture and cattle grazing causes the soil to become compacted, which also poses a threat to this species.

2. Little forest-bat (Vespadelus vulturnus)

Weight: 2.6-5.5 grams (up to two 10c coins)

The little forest-bat is a denizen of various forest types found throughout southeastern Australia.

Its activity depends on temperature — in some parts of southern Australia, during cold periods, individuals may not emerge from roosts for several weeks.

Profile of the little forest-bat
When it’s cold, the little forest-bat won’t emerge from roosts.
Chris Lindorff CC-BY

This species feeds exclusively on flying insects, including moths and mosquitoes.

And they’re not considered threatened — unlike most Australian mammals, they appear to be tolerant of disturbance and will utilise agricultural or urban landscapes if no woodland habitat is available.

3. Eastern pebble-mouse (Pseudomys patrius)

Weight: 10-19 grams (up to seven 10c coins)

This is one of four species of tiny native mice that construct mounds of pebbles that comprise conical, volcano-like ramparts built around burrow entrances. This is unique behaviour among the world’s mammals.

The pebble mounds can be large, weighing more than 50 kilograms and encompassing 10 square metres — astonishing constructions given the architects weigh as little as 10 grams!

Eastern pebble mouse with a pebble in its mouth
Mouse-built pebble mounds can weigh more than 50kg.
Anders Zimny, Author provided

Mounds are energetically expensive to build. They are a critical limiting resource for eastern pebble-mice because females raise their litters in the mounds and their female offspring tend to disperse only as far as the next available mound. Some mounds may even remain in use for centuries, re-used by successive generations.

The erosion of hills and spread of dune fields in arid Australia are reducing the distributions of pebble-mice.

4. Mountain pygmy possum (Burramys parvus)

Weight: 30-82 grams (up to nine $1 coins)

The famously adorable mountain pygmy possum is the only Australian mammal limited to alpine and sub-alpine regions, where snow covers the ground for up to six months of the year.

The possums may move more than one kilometre each night in search of food, which includes seeds, fruits, spiders and insects. They have a preference for Bogong moths (Agrotis infusa).

They double their body weight prior to hibernation, which lasts between five and seven months. During this time, their body temperatures may drop down to 2℃ for up to 20 days at a time.

This species is endangered, and there may be as few as several thousand individuals in total across three isolated populations.




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Their biggest threats include droughts due to climate change, predation by feral cats and foxes, and habitat destruction, particularly after the devastating 2019-20 bushfires razed 15% of the species’ range.

5. Silver-headed antechinus (Antechinus argentus)

Weight: 16-52 grams (up to six $1 coins)

The 15 species in the genus Antechinus are “suicidal reproducers”. All males drop dead at the end of the breeding season, poisoned by their own raging hormones.

This is because the stress hormone cortisol rises during the two-week breeding period. At the same time, surging testosterone from the super-sized testes in males causes a failure in the biological switch that turns off the cortisol. The flood of unbound cortisol results in systemic organ failure and the inevitable death of every male.

But this happens only after they’ve unloaded their precious cargo of sperm, mating with as many promiscuous females as possible in marathon sessions lasting up to 14 hours.

Profile of the silver-headed antechinus
Antechinus species are famous for their marathon breeding sessions.
Gary Cranitch/Queensland Museum, Author provided

Silver-headed antechinuses are found only patchily in a few isolated populations of high-altitude wet forest in mid-eastern Australia. They eat mostly insects and spiders and are likely preyed upon by owls and feral cats.

The silver-headed antechinus is endangered and threatened by climate change. The species lost almost one-third of its core habitat in the 2019-20 megafires.

Yet, torpor can assist here as well, even after such extreme events. Antechinuses (and other small mammals) are known to use torpor more often after fire, when food is scarce and the risk of predation is higher, as there are fewer places to hide in a scorched landscape.




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The Conversation


Andrew Baker, Senior Lecturer, Queensland University of Technology

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

Humpback whales may have bounced back from near-extinction, but it’s too soon to declare them safe


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Olaf Meynecke, Griffith UniversityThe resurgence in humpback whale populations over the past five decades is hailed as one of the great success stories of global conservation. And right now, the federal Department of Agriculture, Water and the Environment is considering removing the species from Australia’s threatened list.

But humpback whales face new and emerging threats, including climate change. Surveying whales is notoriously hard, and the government has not announced monitoring plans to ensure humpback populations remain strong after delisting. We need a plan to keep them safe.

Australia’s whale season is about to begin. Each year between May and November, the mammals migrate north along Australia’s coastline from their feeding grounds in Antarctica to warmer waters. There, they breed before returning south.

So now’s a good time to take a closer look at the status of this iconic, charismatic species.

A pod of humpback whales lunge feeding.
The resurgence of humpback whales is one of conservation’s greatest success stories.
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A host of threats

Humpback whales live in every ocean in the world, and have one of the longest migrations of any mammal.

Humpback whale numbers dwindled as a result of commercial whaling, which in Australia began in the late 18th Century. Whaling and the export of whale products was Australia’s first primary industry. Between 1949 and 1962 Australia’s whalers killed about 8,300 humpback whales off the east coast, until only a few hundred were left.

The International Whaling Commission banned humpback whaling in the Southern Hemisphere in 1963. By then, humpback populations had fallen to about 5% of pre-whaling numbers. In the years since, some whaling continued, but has now largely ceased.

Today humpback whales face new threats. These include:

  • underwater noise which interferes with whale communication
  • pollution
  • vehicle collisions
  • getting caught in fishing gear
  • over-harvesting prey such as krill
  • marine debris
  • habitat degradation
  • climate change.

In particular, the effects of climate change – such as warming waters, shifting currents and ocean acidification – may affect the availability of prey that humpback whales need to survive.

Combined, these worsening threats could disrupt humpback whales’ recent resurgence. Indeed, under one scenario, scientists predict the increase Australia’s humpback numbers could stall — or worse, start declining – in the next five to ten years.




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A humpback whale calf caught in a fishing net.
A humpback whale calf caught in a fishing net.
SeaPix, Author provided

The humpback whales’ plight

According to the federal government’s delisting assessment, humpback whales’ strong recovery suggests current threats are not a risk to the population. But this assessment has shortcomings.

It states humpback whales on Australia’s east and west coast have reached, or are exceeding, the original population size – increasing by 10-11% a year over the past decade or longer.

But this information is based on models using data collected prior 2010 for Australia’s west coast, and prior to 2015 for the east coast. This data isn’t readily available to the public and does not include recent population trends.

The predicted population growth from these models doesn’t account for current and future impacts from major threats, including climate change. This is despite recent research and observations suggesting changes in the humpback population.

For example, 2019 research showed potential shifts in calving locations, with newborn humpback whales now frequently spotted outside Australian tropical waters. This — along with the early arrival of migrating humpback whales in Australia in the past years — may be a first sign of changes in breeding and migration habits.

It’s also important to compare humpback whale populations in Australia with those elsewhere, such as in the North Pacific. There, calving rates are declining, and whale abundance and distribution is showing marked shifts. The risk of entanglements with fishing gear is also rising.




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A whale tail with a fishing line caught in it
Whales can get caught in fishing gear.
Todd Burrows, Author provided

The problem with counting whales

The pre-whaling population size of humpback whales on the east and west coast of Australia is thought to be between 40,000 and 60,000. But information is limited and the actual number may have been much higher

Today, the estimated numbers from population models are similar: roughly 28,000 on the east cost and up to 30,000 on the west coast. But counting humpback whales accurately is very difficult. For example, on the east coast of Australia humpback whales frequently move between populations and during a census may not be attributed to their original population.

What’s more, conditions prior to whaling are not comparable with today’s conditions. Krill is a major food source for whales, and widespread whaling in the Southern Hemisphere caused krill numbers to increase. Research from 2019 suggests humpback whales’ fast recovery after whaling ceased may have been due to widely available krill.

But krill numbers have declined or their availability has shortened in recent years due to threats such as climate change and industrial fishing.




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Aerial view of humpback under icy water .
Every year humpback whales migrate from Antarctica where they feed, to breed in Australia.
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Proceed with caution

Humpback whales off Australia’s coast will continue to have some protection under the Environment Protection and Biodiversity Conservation Act, even if they’re taken off the threatened species list.

Generally, all marine mammals are protected in Australian waters. But getting delisted means fewer resources devoted to their protection.

Forecasting the complex interactions of today’s threats, in order to predict tomorrow’s humpback whale populations, is challenging. A cautionary approach should therefore be taken.

In 2016, the US delisted some humpback whale populations. But before doing so, it established a ten-year monitoring plan to track population changes, threats and species abundance.

If Australia proceeds with the delisting, it should follow the US’ lead. Humpback whales should remain listed for another five years so a monitoring plan can be developed. Federal and state governments must invest resources into this process, and react swiftly if changes are detected.

A number of whale researchers and organisations concerned about the humpback whale delisting, including the author, prepared a detailed response to the proposal here.The Conversation

Olaf Meynecke, Research Fellow in Marine Science, Griffith University

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

Marine life is fleeing the equator to cooler waters. History tells us this could trigger a mass extinction event


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Anthony Richardson, The University of Queensland; Chhaya Chaudhary, University of Auckland; David Schoeman, University of the Sunshine Coast, and Mark John Costello, University of AucklandThe tropical water at the equator is renowned for having the richest diversity of marine life on Earth, with vibrant coral reefs and large aggregations of tunas, sea turtles, manta rays and whale sharks. The number of marine species naturally tapers off as you head towards the poles.

Ecologists have assumed this global pattern has remained stable over recent centuries — until now. Our recent study found the ocean around the equator has already become too hot for many species to survive, and that global warming is responsible.

In other words, the global pattern is rapidly changing. And as species flee to cooler water towards the poles, it’s likely to have profound implications for marine ecosystems and human livelihoods. When the same thing happened 252 million years ago, 90% of all marine species died.

The bell curve is warping dangerously

This global pattern — where the number of species starts lower at the poles and peaks at the equator — results in a bell-shaped gradient of species richness. We looked at distribution records for nearly 50,000 marine species collected since 1955 and found a growing dip over time in this bell shape.

A chart with three overlapping lines, each representing different decades. It shows that between 1955 and 1974, the bell curve is almost flat at the top. For the lines 1975-1994 and 1995-2015, the dip gets progressively deeper, with peaks either side of the centre.
If you look at each line in this chart, you can see a slight dip in total species richness between 1955 and 1974. This deepens substantially in the following decades.
Anthony Richardson, Author provided

So, as our oceans warm, species have tracked their preferred temperatures by moving towards the poles. Although the warming at the equator of 0.6℃ over the past 50 years is relatively modest compared with warming at higher latitudes, tropical species have to move further to remain in their thermal niche compared with species elsewhere.

As ocean warming has accelerated over recent decades due to climate change, the dip around at the equator has deepened.

We predicted such a change five years ago using a modelling approach, and now we have observational evidence.




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For each of the 10 major groups of species we studied (including pelagic fish, reef fish and molluscs) that live in the water or on the seafloor, their richness either plateaued or declined slightly at latitudes with mean annual sea-surface temperatures above 20℃.

Today, species richness is greatest in the northern hemisphere in latitudes around 30°N (off southern China and Mexico) and in the south around 20°S (off northern Australia and southern Brazil).

school of tuna fish
The tropical water at the equator is renowned for having the richest diversity of marine life, including large aggregations of tuna fish.
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This has happened before

We shouldn’t be surprised global biodiversity has responded so rapidly to global warming. This has happened before, and with dramatic consequences.

252 million years ago…

At the end of the Permian geological period about 252 million years ago, global temperatures warmed by 10℃ over 30,000-60,000 years as a result of greenhouse gas emissions from volcano eruptions in Siberia.

A 2020 study of the fossils from that time shows the pronounced peak in biodiversity at the equator flattened and spread. During this mammoth rearranging of global biodiversity, 90% of all marine species were killed.

125,000 years ago…

A 2012 study showed that more recently, during the rapid warming around 125,000 years ago, there was a similar swift movement of reef corals away from the tropics, as documented in the fossil record. The result was a pattern similar to the one we describe, although there was no associated mass extinction.

Authors of the study suggested their results might foreshadow the effects of our current global warming, ominously warning there could be mass extinctions in the near future as species move into the subtropics, where they might struggle to compete and adapt.

Today…

During the last ice age, which ended around 15,000 years ago, the richness of forams (a type of hard-shelled, single-celled plankton) peaked at the equator and has been dropping there ever since. This is significant as plankton is a keystone species in the foodweb.

Our study shows that decline has accelerated in recent decades due to human-driven climate change.

The profound implications

Losing species in tropical ecosystems means ecological resilience to environmental changes is reduced, potentially compromising ecosystem persistence.

In subtropical ecosystems, species richness is increasing. This means there’ll be species invaders, novel predator-prey interactions, and new competitive relationships. For example, tropical fish moving into Sydney Harbour compete with temperate species for food and habitat.

This could result in ecosystem collapse — as was seen at the boundary between the Permian and Triassic periods — in which species go extinct and ecosystem services (such as food supplies) are permanently altered.

The changes we describe will also have profound implications for human livelihoods. For example, many tropical island nations depend on the revenue from tuna fishing fleets through the selling of licenses in their territorial waters. Highly mobile tuna species are likely to move rapidly toward the subtropics, potentially beyond sovereign waters of island nations.




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Similarly, many reef species important for artisanal fishers — and highly mobile megafauna such as whale sharks, manta rays and sea turtles that support tourism — are also likely to move toward the subtropics.

The movement of commercial and artisanal fish and marine megafauna could compromise the ability of tropical nations to meet the Sustainable Development Goals concerning zero hunger and marine life.

Is there anything we can do?

One pathway is laid out in the Paris Climate Accords and involves aggressively reducing our emissions. Other opportunities are also emerging that could help safeguard biodiversity and hopefully minimise the worst impacts of it shifting away from the equator.

Currently 2.7% of the ocean is conserved in fully or highly protected reserves. This is well short of the 10% target by 2020 under the UN Convention on Biological Diversity.

Manta ray with other fish
Manta rays and other marine megafauna leaving the equator will have a huge impact on tourism.
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But a group of 41 nations is pushing to set a new target of protecting 30% of the ocean by 2030.

This “30 by 30” target could ban seafloor mining and remove fishing in reserves that can destroy habitats and release as much carbon dioxide as global aviation. These measures would remove pressures on biodiversity and promote ecological resilience.

Designing climate-smart reserves could further protect biodiversity from future changes. For example, reserves for marine life could be placed in refugia where the climate will be stable over the foreseeable future.

We now have evidence that climate change is impacting the best-known and strongest global pattern in ecology. We should not delay actions to try to mitigate this.

This story is part of Oceans 21

Our series on the global ocean opened with five in-depth profiles. Look out for new articles on the state of our oceans in the lead-up to the UN’s next climate conference, COP26. The series is brought to you by The Conversation’s international network.




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The Conversation


Anthony Richardson, Professor, The University of Queensland; Chhaya Chaudhary, , University of Auckland; David Schoeman, Professor of Global-Change Ecology, University of the Sunshine Coast, and Mark John Costello, Professor, University of Auckland

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