possums

Fur and Flowers: Melbourne's Mammalian Pollinators

This is a guest post by Mackenzie Kwak.

These days there’s a lot of buzz surrounding pollinators. When most of us think of them, our minds quickly turn to bees and butterflies. However, in Australia we have a diverse range of warm-blooded pollinators working through the night to keep our forests growing strong, and many of them call our city home.

Ancient Australia

Australia is a global hot spot for mammal pollinators. To better understand the close relationships between these warm-blooded creatures and their floral friends, we must turn our minds back millions of years to prehistoric Australia when flowers first appeared on the continent. For a very long time before the present day, Australia sat much farther south and at one point even stood where Antarctica now rests. At that time though, the globe was much warmer and plants could survive on this cool, southern continent known as Gondwana. Although polar forests flourished, temperatures still remained low, especially in winter when the forests often froze over. This provided a real challenge for plants eager to be pollinated.

Brushtail possums are one of the most common mammalian pollinators encountered around Melbourne.  Image: Wikimedia Commons

Brushtail possums are one of the most common mammalian pollinators encountered around Melbourne. Image: Wikimedia Commons

Insect pollinators were not common in Gondwana at this time due to one basic problem with their biology: cold blood. Insects are commonly described as cold-blooded or more accurately poikilothermic, meaning their body temperature fluctuates with the ambient temperature. However, insect body temperature can fluctuate so much that sometimes it rises far above that of mammals and birds,  making the term ‘cold-blooded’ a little erroneous. Fluctuating body temperature creates some major difficulties for insect pollinators - especially when the ambient temperature is close to freezing and pollination activity becomes impossible. It was these cool conditions that gave mammals their first real go at pollination in Australia. Mammals are warm-blooded, or, more technically, homeothermic, and can control their internal temperature even when the ambient temperature majorly fluctuates. This means that they remain active at much lower temperatures than their six-legged competitors and can exploit the rich nectar resources that plants have to offer. Over time, many mammals specialised to feed on this rich food and plants in turn modified their flowers to attract warm-blooded pollinators. 

Possums

Ringtail possums are another extremely common possum species of Melbourne.  Image: Emma Walsh

Ringtail possums are another extremely common possum species of Melbourne. Image: Emma Walsh

Possums are perhaps the most commonly encountered native mammals in the greater Melbourne region. Most folks view them with a strange combination of weak interest and mild irritation because of their all too common habit of taking up residency in our roofs. Possums, though, are important pollinators of many native trees and shrubs throughout Australia. We are most familiar with the common brushtail possum (Trichosurus vulpecula) and common ringtail possum (Pseudocheirus peregrinus) that are regular visitors to the flowers of gum trees. But while these two species supplement their diets of leaves with whole flowers, nectar and pollen, the real heavy lifters among the pollinating possums are the gliders.

In the greater Melbourne region the most common of these is the sugar glider (Petaurus breviceps), which incorporates a huge amount of pollen and nectar into its diet along with insects and tree sap. These little possums live in family groups, reside in tree hollows, and are important pollinators of Eucalyptus trees. Melbourne is also home to the world’s smallest glider, the feathertail glider (Acrobates pygmaeus), which weighs about 14 grams and is small enough to fit in the palm of your hand. While these little possums are far from common, they can still be found in the forests near Frankston and in Melbourne’s north-east. Like the sugar glider, they are also voracious pollen feeders but supplement their diet with insects.  

It's no secret why we call this little possum species the feathertail glider!  Image: Wikimedia Commons

It's no secret why we call this little possum species the feathertail glider! Image: Wikimedia Commons

Bats

Bats are another group of mammal pollinators often viewed with some antipathy by the general public because of their noisiness and propensity towards raiding fruit trees. However, bats are much more important to Australia’s ecosystems than many people realise. It’s important to note that the majority of bats that call Melbourne home do not act as pollinators - these are the microbats and they are in fact carnivores or insectivores. The grey-headed flying fox (Pteropus poliocephalus) is Melbourne’s only bat pollinator and reaches sizes far greater than its small carnivorous relatives, with wingspans up to one metre. Grey-headed flying foxes feed on a range of different flowers throughout the year but particularly favour the Myrtaceae family which includes the eucalypts, honey myrtles and tea trees, as well as the Proteaceae which includes the banksias and grevilleas. Fruit bats are not only important pollinators, but also critical seed dispersers for many native plants as well.

Dasyurids

Perhaps the strangest mammal pollinators to call the Melbourne region home are the Dasyurids, a group which few people have even heard of let alone considered as pollinators. For those unfamiliar with the often complex world of mammal taxonomy, the Dasyuridae is a family of mammals that includes quolls, Tasmanian devils, the now extinct Tasmanian tiger, and a range of other small, carnivorous marsupials. Many small Dasyurids resemble rodents superficially, but all possess a pouch which sets them apart. The genus Antechinus is one of these rodent-like groups of marsupials and Melbourne is home to three species: the swamp antechinus (Antechinus minimus), dusky antechinus (Antechinus swainsonii) and agile antechinus (Antechinus agilis). In other parts of Australia, Antechinus species are known as excellent pollinators of Banksia sp. but it remains unclear what role our Melburnian species may play in the pollination of local flora.

The agile antechinus is one of three  Antechinus  species to call Melbourne home.  Image: Wikimedia Commons

The agile antechinus is one of three Antechinus species to call Melbourne home. Image: Wikimedia Commons

It is not yet clear what role Melbourne's  Antechinus  species play in pollination.  Image: Wikimedia Commons

It is not yet clear what role Melbourne's Antechinus species play in pollination. Image: Wikimedia Commons

One Melbourne resident known to be a good pollinator is the brush-tailed phascogale, which resembles a squirrel but is actually a nocturnal, carnivorous marsupial. These secretive little mammals have been recorded gorging themselves on nectar and pollinating flowers with masses of pollen adhering to their furry muzzles. However, like many of our shy native marsupials, it is believed that the brush-tailed phascogale is sadly declining around the Melbourne region due to habitat loss.

So next time you see fruit bats glide overhead or hear a possum scurry across your roof, just remember the surprising task that these pollinators undertake. Although they may not be as glamorous or well-liked as native bees or butterflies, mammals are key pollinators of many of our native plants. It's now our responsibility to halt their decline, as losing them could be catastrophic. 


Mackenzie Kwak is a zoologist with a broad interest in Australia's diverse flora and fauna. His research focuses on the biogeography, systematics and ecology of Australasian ectoparasites, particularly ticks, fleas and lice. 

Banner image of a grey-headed flying fox courtesy of Wikimedia Commons.

Friendly Neighbourhood Possums

Possums are the backyard bandits that we love to hate. These stealthy marsupials are notorious for snacking on our garden plants, nesting in our rooves, and causing a ruckus while we’re trying to sleep. However, our furry neighbours are not to be blamed - they are simply trying to survive in the environment that they too call home. It seems that residents of suburbia have forgotten that possums are native animals to be appreciated and treasured, and that they’re not just another invasive pest that needs to be eradicated.

There are two species of possum that are common in the city of Melbourne. These are the Common Brushtail Possum (Trichosurus vulpecular) and the Common Ringtail Possum (Psuedocheirus peregrinus). Brushtail possums are solidly built, and are around the size of a domestic cat. As their name suggests, the most identifiable characteristic of this species is their bushy tail, but also their loud, guttural calls. They can inhabit a range of environments, such as suburban parks and gardens, but prefer dry eucalypt forests and woodlands. Brushtail Possums have a varied diet, feeding mostly on leaves, fruits and flowers, and also occasionally on insects and meat. In contrast, Ringtail Possums have a slighter build, and are smaller than Brushtrails. They have a slender, white-tipped tail that is prehensile (meaning that it functions as a fifth limb), as it is used to grasp onto branches or carry nesting material. Ringtail Possums inhabit forested environments, as well as coastal scrub and suburban gardens. These shy marsupials feed primarily on leaves, but also on flowers and fruits. Not as loud as their bushy relatives, these possums instead make a soft, high-pitched, twittering call. Like many Australian marsupials and birds, both species nest in tree hollows. However, if tree hollows are unavailable, these possums will nest in any dark and dry nook, such as those found in the rooves of suburban houses.

The main dispute that people have with possums is sharing their house with these furry bandits. However, there are a few things that you can do to discourage possums from nesting in your roof. Firstly, the best thing to do is to block up all the holes and entrances to your roof. Make sure to do this after dark while the possums are out foraging. It is best to close up all entrances, but if you are unsure if an entrance is being used, stuff it with newspaper, and check in a few days time to see if the newspaper has been pushed aside by a possum. It is also a good idea to trim any tree branches near your house so that there are none within 1.5 meters of the roof. This way, possums can’t jump from one to the other. Secondly, to encourage possums to nest in places other than your roof, you should install a nest box. You can obtain instructions on how to construct a nest box or where to find a nest box supplier on the DEPI (Department of Environment and Primary Industries) website. Another thing to think about is preserving the mature trees on your property. Tree hollows take over 150 years to develop, and due to land clearing and urbanisation there are few mature trees remaining in the suburbs. As many marsupials and birds require tree hollows for nesting, keeping an old tree in your backyard will encourage possums to nest in the tree and not in your roof. Also, try putting mothballs in your roof – apparently they hate the smell!

These species have a varied diet, and are infamous for feeding on the nonnative plants in our gardens, such as Silver Birch trees. Here a Ringtail Possum snacks on a Crepe Myrtle tree. 

These species have a varied diet, and are infamous for feeding on the nonnative plants in our gardens, such as Silver Birch trees. Here a Ringtail Possum snacks on a Crepe Myrtle tree. 

Another annoying habit of our furry neighbours is snacking on our garden plants. To prevent possums from snacking on your trees, install tree collars on those affected. These should be 60 cm wide, and 60 cm above the ground. For shrubs, try putting large quantities of blood and bone at the base of the plant. Finally, don’t feed possums! It encourages them to return to your home, as they learn to associate you and your house with food.

Furthermore, we should try to reduce our impact on possums. They are only a nuisance to us because we have invaded their environment and cleared their habitat, causing shortages of both food and shelter. Under the Wildlife Act of 1975, it is illegal to capture, transport or otherwise interfere with any native animal without a permit. If you wish to evict your possum by hiring a possum removalist, do not have the possum relocated. As possums are highly territorial, it is highly probable that other possums will move in after the first possum has departed. It can actually be beneficial to you to have a possum inhabiting a nest box on your property, as they will fiercely defend their territory, subsequently warding off any other possums that wish to nest in your roof.

Brushtail Possums have pointed ears, have an unmistakeable bushy tail, and are larger than Ringtail Possums.  Photo: David Cook

Brushtail Possums have pointed ears, have an unmistakeable bushy tail, and are larger than Ringtail Possums. Photo: David Cook

Conversely, if you enjoy our native wildlife and want to encourage possums into your backyard, there are a few things you can do to entice them. Plant indigenous eucalypt species to lure them into your garden, and keep your pets inside your home after dark. As previously mentioned, maintain and cherish mature trees, as much of our wildlife (including possums) require tree hollows for nesting.

Unfortunately, the adaptability of our possums has caused these native treasures to be viewed as pests. On the contrary, both Common Brushtail Possums and Common Ringtail Possums should be viewed as the champions of suburbia; where so many species have been displaced, these possums have persisted and adapted, which is something to be admired. They are our little Aussie battlers, so share your backyards, and bask in the success of our friendly neighbourhood possums.