Spring at the Prom

Driving through Wilsons Prom as the sun rises, I can’t help but feel incredibly lucky. Although dragging myself out of a warm cosy bed at 5am required considerable effort, it wasn’t for the spectacular sunrise. My true motivation is the knowledge that there are plump little mice waiting for me.

Sunrise at the Prom
The sun rises over Wilsons Promontory National Park

 

I’m headed to check my traps and see how the New Holland mice on Yanakie Isthmus are faring this month. Arriving at the sites just on sunrise, I walk along the traplines, clambering through the vegetation looking to see which traps have closed doors – indicating an occupant.

Peering into a trap, I pull out the warm fluff to see who has been lured in overnight by the scent of peanut butter, golden syrup, vanilla essence and oats.

New Holland mouse in a trap
A New Holland mouse (and its beloved peanut butter & oat ball) gets a rude early morning wakeup after I remove its warm fluffy bedding.

Discovering a New Holland mouse, I tip it into a bag and get to work weighing it, taking a genetic sample, and checking its gender, age, and reproductive status before releasing him and re-setting the trap.

A New Holland mouse huddles in a cloth handling-bag
A New Holland mouse huddles in a cloth handling-bag

Unconvinced that I’m actually a giant, terrifying predator, the New Holland mouse chooses to explore my lap before heading home to his burrow to sleep until nightfall. I quickly move on to the next trap, not wanting to keep the mice waiting any longer than necessary.

New Holland mouse on lap
Surprisingly chill, considering that I just snipped a tiny bit off his ear for a DNA sample

It’s breeding season for New Holland mice at the moment, and the next individual I encounter is playing her part well. Adult New Holland mice usually weigh about 18-20 grams at these sites. This little lady is a hefty 32g, soon to give birth to up to six babies. She will breastfeed them for the next month, until they’re ready to head out and find tasty seeds, leaves, invertebrates, and fungi to eat.

Pregnant mouse
One heavily pregnant New Holland mouse with engorged nipples

As the New Holland mouse breeding season can last 5-7 months, some of her kids from this litter will mature and have offspring of their own in the next few months. During that time, she will produce a few more litters herself.

Despite what may seem like quite high reproductive potential, New Holland mice are threatened and populations can disappear quickly. Breeding season length and success are highly dependent on resource availability – if there isn’t much food to go around, there will be fewer, smaller litters, with fewer of those offspring surviving to maturity.

Figuring out the specific factors driving population success will help us to protect and conserve the few populations of New Holland mice that remain in Victoria. A challenge definitely worthy of a 5am start.

New Holland mouse
A New Holland mouse wanders home through the prickly groundcover

NHMs head Off Track

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A New Holland mouse bounds home after release. Image: Ann Jones

The New Holland mouse population at Wilsons Promontory was lucky enough to have Ann Jones from Radio National’s Off track program come out and visit them recently. Ann also stopped by to chat with Jim Whelan, expert on all things Yanakie Isthmus, to learn more about the threat to NHMs and many other species posed by coastal tea tree encroachment. Listen to the experience and see some of Ann’s gorgeous photos hereAnd check out the video story here.

 

 

 

New Holland mice on camera

The New Holland mouse (Pseudomys novaehollandiae) is one of Victoria’s threatened native rodents. The charismatic little species has only been recorded from 3 areas across the state in the past 15 years (blue dots in map below) whereas historically it was recorded from 10, including metropolitan Melbourne (red dots in map below). That’s why I’ve embarked on a PhD to determine the status of NHMs across Victoria, and help protect this species from further decline.

New Holland mouse detection sites across Victoria. Red dots indicate sites in areas where the species has not been detected in at least 15 years, blue dots indicate areas with more recent detections. Dates show the range of years during which New Holland mice were known at each site.
New Holland mouse (Pseudomys novaehollandiae) detection sites across Victoria. Red dots indicate sites in areas where the species has not been detected in at least 15 years, blue dots indicate areas with more recent detections. Dates show the range of years during which New Holland mice were known at each site.

One of the greatest challenges for studying the status and conservation of New Holland mice (and many native Australian rodents) is that they can be very difficult to find; you can’t just see them in your binoculars or hear them calling in the bush. Adding to the challenge – many native rodents, including NHMs, go through natural periods where they persist in such low numbers that traditional survey efforts such as live trapping fail to detect them. New Holland Mice are also particularly fickle about their habitat preferences and may only persist locally for a few years before moving on, making their populations even more difficult to track.

New Holland mouse captured and released using live trapping. (Image: Phoebe Burns)
New Holland mouse (Pseudomys novaehollandiae) captured and released using live trapping. (Image: Phoebe Burns)

That’s why I’ve been trialling the use of cameras to detect the New Holland mouse. Traditional live trapping can be a great method for detecting a species in an area, and it’s critical if I want to know about health and reproduction, estimate abundance, or get DNA samples. However, sometimes when a species is at low densities it takes a huge amount of effort to be reasonably confident that the species isn’t there, which in a world of limited time and funding drastically reduces the area you can survey; a real challenge when a species moves in the landscape. This is where cameras can come in handy – you set them once and rather than having to come back every morning and afternoon to check each trap, you can just leave them in place for weeks at a time. The animals are attracted to a tasty lure (I like to use peanut butter, oats, golden syrup and vanilla essence) and while they investigate, the camera senses the heat and motion and snaps a photo.

Camera trap image of a New Holland mouse clinging to a bait station. (Image: Phoebe Burns)
Camera trap image of a New Holland mouse (Pseudomys novaehollandiae) clinging to a bait station. (Image: Phoebe Burns)

Cameras allow you to survey much wider areas, for longer periods of time with a fraction of the effort of live trapping – at least until you have to sift through the images and identify the animals. Once I know that NHMs are present in an area from the camera trapping, I can target those areas for live trapping to collect the rest of my data. My challenge, and the reason I did a camera trial, rather than just jumping straight into using cameras as a survey method, was identifying New Holland mice in the images.

Camera trap image of a New Holland mouse climbing on a bait station with a house mouse standing up against the base. (Image: Phoebe Burns)
Camera trap image of a New Holland mouse (Pseudomys novaehollandiae) climbing on a bait station with a house mouse (Mus musculus) standing up against the base. (Image: Phoebe Burns)

Rodents tend to look very similar on camera, particularly if the images are in black and white. It doesn’t help that New Holland mice are about the same size as the non-native house mice (Mus musculus); they can be hard for some people to tell apart when they are holding them in their hand. Since the house mouse has infiltrated all known New Holland mouse habitat in Victoria I needed to tell them apart from less than perfect images in colour and in black and white.

Camera trap image of a New Holland mouse clinging to a bait station. (Image: Phoebe Burns)
Infrared images of New Holland mice (Pseudomys novaehollandiae)(left) and house mice (Mus musculus)(right). (Images: Phoebe Burns)

Tens of thousands of images later, I can happily say that New Holland mice and house mice are distinguishable on both colour and black and white images. In the colour images the species can be distinguished by differences in colouration, but in black and white the distinction is all in the shape of the two rodents. New Holland mice have a much sturdier build, thick set neck and snubby nose, whereas house mice are much more slender with a pointed nose; sort of like the difference between rugby and footy players.

Now that I’ve got the IDs sorted, I’ll be using cameras (and live traps) to survey across Victoria and see where the New Holland mouse is persisting so that we can do our best to halt the species’ further decline.

Can you ID a New Holland mouse? Have a go with my quiz!

 

Originally published here

Smoky mice in the Grampians

The endangered and elusive smoky mouse (Pseudomys fumeus) is small native Australian rodent species. The nocturnal species nests in communal burrow systems and consumes a varied diet of fungi, invertebrates, seeds and plant material. While many aspects of the species’ life history appear quite flexible – such as diet, habitat, and timing of the breeding season – smoky mice have been poorly detected across much of their range in recent decades and are thought to be in decline.

Smoky Mouse (Pseudomys fumeus), Grampians National Park, November 2012. Photo: David Paul, Museum Victoria

There are several hypothesised causes of decline in smoky mice, most notably drought, foxes, feral cats, and fire – all of which play major roles in the Grampians-Gariwerd National Park. My Masters research focused on a smoky mouse population in the Victoria Range, in the west of the park. In November 2012, as part of a team from Museum Victoria and Parks Victoria we surveyed one of the historical smoky mouse sites in the Victoria Range as part of a broader survey of the Grampians. We detected an astounding 28 individuals at the one site, now affectionately known as ‘Supergully,’ – a record high number in the Victoria Range. Three months later Supergully burned in the Victoria Valley fire, along with all other historical smoky mouse sites in the Victoria Range.

'Supergully' before the Victoria Valley fire, November 2012. Image: Heath Warwick, Museum Victoria.
‘Supergully’ before the Victoria Valley fire, November 2012. Image: Heath Warwick, Museum Victoria.

Given the severity and comprehensiveness of the fire, our main concern was that if smoky mice could not persist in the fire scar, there might be no suitable unburned patches nearby from which they could recolonise the Victoria Range. Many small mammal species in the Grampians, such as swamp rats and heath mice, aren’t found within fire scars for a few years post-fire. Based on smoky mouse records in the area and the documented fire responses of similar species, the outlook for smoky mice was grim.

'Supergully' three most after the Victoria Valley fire, May 2013. Image: Heath Warwick, Museum Vitoria.
‘Supergully’ three most after the Victoria Valley fire, May 2013. Image: Heath Warwick, Museum Vitoria.

Prior to our research, smoky mice were recorded in the Victoria Range at two sites in 1974 and three sites in 2002-4. To determine whether smoky mice had declined in the Victoria Range since their initial detection in 1974 and how the species responded to the 2013 fire, I surveyed 42 burned and unburned sites across the Victoria Range from September – December 2013. I detected smoky mice at one known site and five new sites, and confirmed their absence from the two 1974 sites. Although I detected individuals at ‘new’ sites, this may be a reflection of previous sampling effort rather than a shift in the species’ occupancy.

Smoky mouse (Pseudomys fumeus) in the Victoria Valley fire scar, September 2013. Image: Phoebe Burns
Smoky mouse (Pseudomys fumeus) in the Victoria Valley fire scar, September 2013. Image: Phoebe Burns

Contrary to expectation, smoky mice survived the Victoria Valley. Of the six sites at which I detected smoky mice in 2013, five had recently burned. Of nine individuals I captured at Supergully in 2013, three were recaptures from 2012, suggesting the species persisted in situ. All the individuals I captured at burned sites were within a normal weight range and I found evidence of breeding. While this is great news for smoky mice, the species may not respond in the same way to future fires under different weather and habitat conditions.

Juvenile smoky mouse ( Pseudomys fumeus) in the Grampians National Park, October 2013. Image: Phoebe Burns
Juvenile smoky mouse (Pseudomys fumeus) in the Grampians National Park, October 2013. Image: Phoebe Burns

Despite persisting through the fire, smoky mice appear to be currently declining in numbers in a snapshot of one site. Supergully yielded 28, 9 and 3 individuals in 2012, 2013 and 2014 respectively. This may be a delayed response to the fire, part of a natural population cycle, or the result of some other factor such as decreased rainfall.

Smoky mice in the Victoria Range have persisted over the past forty years of droughts and feral predators, as well as the short-term impacts of fire. However, for smoky mice and other threatened species, we need to survey populations regularly to keep track of fluctuations in abundance and isolate these from other threatening declines. Fingers crossed we detect some smokies in our survey this November.

Originally published in the April 2014 Friends of Grampians-Gariwerd newsletter