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.

The real Tinkerbell: don’t mess with these tiny fairy wasps



gbohne/Flickr, CC BY-SA

Manu Saunders, University of New England

Have you ever seen a fairy? They exist, and may very well be in your garden. But you would need a high-powered microscope to spot the dainty creatures.

Fairy wasps (family Mymaridae) are tiny, feathery-winged parasitoid wasps. They’re often called fairy flies, which is a misnomer. The Mymaridae family includes the smallest known insects in the world. Most species are less than 1mm long – smaller than the average pinhead.




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But two species in particular have the record for being the smallest insects in the world. Measuring 0.15-0.19mm, the smallest recorded winged insects are female Kikiki huna.

Images of a female Kikiki huna body and wings. The scale line represents 0.1mm.
Huber J, Noyes J (2013) via Wikimedia Commons, CC BY-SA

Not much is known of K. huna’s ecology, but the species was first discovered in Hawai’i (the scientific name is made from Hawaiian words for “tiny bit”). Since then, specimens have been recorded from Western Australia and South and Central America, suggesting the species could be distributed much more widely.

In 2013, another closely related species was discovered in Costa Rica and named Tinkerbella nana, after Peter Pan’s fairy friend.

The smallest known insect of all, at around 0.13mm, is a wingless male specimen of another fairy wasp, Dicopomorpha echmepterygis, found in the United States. Many insect species are sexually dimorphic, meaning males and females can look so different they may be confused as different species. For this fairy wasp, females are much larger than the record-breaking males, and have wings.

Eggs in eggs, wheels within wheels

All fairy wasp larvae are parasites. Adult females search for the eggs of other insects in sheltered places, such as under leaves or in leaf litter. When she finds a stash, she lays her own eggs inside the other eggs – an indication of just how tiny these wasps are! The wasp larva uses the nutrients from the egg to develop, killing the other insect in the process, before emerging through a tiny hole in the egg surface. The BBC captured this process in mesmerising underwater footage in 2017.

The smallest kinds of fairy wasp lay their eggs inside the eggs of barklice, who are also extremely tiny.
Katja Schulz/Flickr, CC BY

Adults only live for a couple of days to reproduce and start the cycle again. In fact, some males never leave the egg they develop in – as soon as they emerge from their own egg within an egg, they mate with a female and die.

Despite their diminutive size, fairy wasps pack a punch when it comes to impact. Their dependence on other insects to complete their life cycle means they play an important role in controlling populations of many other insects.

Scientists don’t think these wasps have strong preferences about their host species, which means they seem to pick whatever eggs are available. But very little is known of the ecology of most species, so it is hard to know for certain.




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Most of the known records of fairy wasps have emerged from eggs of Hemiptera species, the group of sucking bugs that includes planthoppers and aphids. But other hosts are known to include thrips (Thysanoptera), beetles (Coleoptera), and psocid (Psocoptera).

The smallest insect in the world, D. echmepterygis, was reared from eggs of a psocid, or barklouse species – another group of small insects that is often overlooked. Barklice and booklice, also called psocids, are in the order Psocoptera; barklice usually feed on lichen and algae on tree trunks, while their cousins the booklice are often found feeding on mould inside book bindings in old libraries.

Other fairy wasp species have become valued for their important role as biological control agents in agricultural systems. Mymarids can control many damaging economic pests, including the glassy-winged sharpshooter, and weevil and sucking bug pests of eucalypt plantations. Many other associations remain to be discovered.

Fairy wasps can help keep down numbers of glassy-winged sharpshooters, which are a pest.
Chuck/Flickr, CC BY-NC-SA

Fairy wasps are a fascinating example of how much biodiversity is still undiscovered. With so much focus on larger, or more charismatic species, the tiny world of the smallest animals on Earth goes by unnoticed.

We still have much to learn about the ecology and life history of minuscule fairy wasps. Most of us would walk past one nearly every day without noticing. But we can support them without seeing them. Like many other flying insects, adults need sugar from floral nectar or insect honeydew for their energy.

This means that encouraging flowering plants to grow in and around crop fields can help production. These wild floral resources support populations of many beneficial insects, including fairy wasps, making them more effective as biological control agents. And, just like many other beneficial insects, pesticides can kill fairy wasps, or make them less effective at controlling other pests.




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The same principle goes for gardens. Next time you find a pesky insect herbivore munching on your plants, consider an experiment: let them be and see how long it takes before fairies have moved into the bottom of your garden.The Conversation

Manu Saunders, Research fellow, University of New England

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

Article: Wildlife – The Christmas Island Pipistrelle


Tiny Native Bat Now Feared Extinct

The following link is to an article reporting on the feared extinction of the Christmas Island Pipistrelle.

For more visit:
http://news.mongabay.com/2012/0523-hance-christmas-island-pipistrelle.html