Philoria, fungus and fire

David Newell

I work predominantly on rainforest frogs in north-east New South Wales. There is a group of frogs called the mountain frogs, the genus Philoria. They are a really specialised group, with ancient lineages that evolved with the break-up of the Gondwana rainforests. Some of them occur on single mountaintops. Currently we have just five species that are described: one on the Richmond Range – the Richmond Range Mountain frog; another in Main Range in South East Queensland, coming down into Tooloom, which is the yellow-bellied mountain frog, Philoria kundagungan; we have another one called Pugh’s frog, it was named in honour of Dailan Pugh. It occurs up on the Timbarra tablelands. We have Loveridge’s frog, which occurs in Nightcap, Wollumbin, Border Ranges, and into South East Queensland, into Lamington and Springbrook. Then we have Philoria sphagnicola, which occurs further south. It’s relatively common, but all the other ones are listed as endangered. 

They were already in a lot of trouble before the fires. Their breeding is very intimately linked to climate. They live in the headwater streams of mountaintops, where they breed in subterranean burrows, and only lay about between 25-30 eggs. When you live on a mountain-top, you have evolved to very specific habitat requirements. If temperature rises, you can’t go further up the mountain to get cooler. 

They are not evolved to cope with fire. During 2018-19 it was incredibly dry and then the Black Summer fires burnt through large tracts of their habitat. For some of them, up to 50% of their habitat was burnt. We had pre-fire monitoring data for a couple of the species. We had already worked out detailed occupancy studies to understand where their habitat is. We knew that we were losing populations from lower elevations. We had some populations that had disappeared already, because of a climate change response, following the drying of habitat at lower elevations.

Up to 50% of their habitat was burnt

Subtropical rainforest. Photo: Hugh Nicholson

To monitor them, we put sound recording devices in the field, and set them up to record ten minutes of audio every hour, and we leave them out there 24/7 for months at a time. From that we have been able to establish their call phenology. When they call, what time of day, what time of year, what the temperature profiles are that they need. Calling is an analogue for breeding. 

In the lead-up to the fires, we’d go early in the morning, go to as many sites as we can, and count the number of frogs [calling]. When we saw impacts of those fires, we would go back to some of the sites that were burnt, and we weren’t finding any frogs at all. Some sites still have frogs, so they were able to cope to some extent with some fire, but the picture is not looking great. 

For other species like the hip-pocket frogs, we know they live in the leaf-litter. If you have a fire that comes through and totally destroys all the leaf-litter layer, you’ve destroyed all their habitat. That species lays its eggs in the leaf-litter, the eggs hatch in the leaf-litter, the male will come sit on the frogs, they will hatch, and swim into tiny little hip-pockets on his back, hence the name, and then they hatch out the back of the male as baby frogs. So that species was probably severely impacted by the fires. 

I think increasingly people are becoming concerned about the plight of frogs. I think since we started losing species, there’s been a lot of community support for frog research. We’ve seen locally, right along the east coast of Australia over this winter past, we’ve seen massive disease impacts and lots of people finding sick and dying frogs so that’s certainly renewed interest in the fate of our frogs. 

In the late 1970s we had a disease brought into the country, a pathogen called the amphibian chytrid fungus. By the late 1980s, globally, we were noticing that frogs were in decline and disappearing. The first extinction that occurred on the east coast of Australia was the gastric-brooding frog, from up in the Conondale Range, north-west of Brisbane. And then we saw declines in a bunch of other species, and disappearances. Fleay’s Barred Frog, for example, disappeared from a number of sites and declined really severely, up until about the late 1990s, and then what we saw was that populations that had survived actually started to recover. They are able to deal with the fungus now. So we’re looking at trying to understand the factors that have led to that immune response. And then if we can do that, we can look at applying it to other species globally, such as the corroboree frog, in Alpine regions in NSW, Victoria. 

Part of what we’re interested in is what is that immune response in that frog? We’ve got a captive husbandry facility for endangered frogs here at Southern Cross University. We have special tanks that are designed so that they’ve got a gravel stream flowing through them. They need a highly humid habitat, because they’re rainforest frogs.  At the moment there are 50-odd adults in there, raised from eggs. We know that very few eggs actually survive through to adulthood in the wild, so we are not having a population-level impact by taking eggs from the wild. But we also know that if we collect eggs, that they are free of the disease, because they don’t have any keratin on them. 

Richmond Range Mountain frog (Philoria richmondensis). Photo: Dr David Newell

When I started doing frog research there seemed to be very few frog researchers. I started researching frogs that were just really difficult to find at the time, and it was because of the disease. I’ve been fortunate enough to monitor those populations through their recovery and now taking it to the next level. At Wollumbin, populations of Fleay’s barred frog completely disappeared. Part of the hope is that we can take animals from a nearby recovered population and reintroduce them to the mountain. We’re talking to elders at the moment and hoping to get their blessing for the project.

There’s been very few successful translocations of frogs. We’re looking at the order of 40 individuals. And we want to be able to follow them through time, so we need to do radio-tracking studies when we reintroduce them. We use really small radio transmitters, about the size of a button, and we make a little waist-harness out of micropore tape. We fold up a little harness, and we put it around the waist of the frog. When it gets wet or after a couple of weeks, the material actually breaks down so the transmitter will just fall off. 

I’m pushing 30 years of walking in rainforest streams now but we have this amazing data set that’s probably one of the longest-standing amphibian surveys anywhere. With that data we are able to answer bigger questions now about disease risk. We were out there monitoring a group of frogs that nobody really knew anything about, and now we know exactly when they call, exactly what their habitat requirements are, how many there were prior to the fires, and now we can say what happened, post-fire.

Mountain streams bordered by flowering Helmholtzia glaberrima (stream lily). Photo: Anastasia Guise

One of the big concerns is that those kind of fire events really change the whole forest structure. They open up the canopy, which leads to further drying of those habitats, and importantly we are also seeing incursions of feral pigs in the landscape. If you’ve ever seen what a pig does in a muddy bog, it totally destroys all of this frog habitat. So pigs are going to be the next problem. 

The Richmond Range mountain frog was only described in 2014. There’s a new species that’s just been described last week in northern NSW, a new species of hip-pocket frog, called Assa wollumbin, which only occurs on Wollumbin. 

We’ve just got to hope that we don’t get another big fire event in the foreseeable future. We’ve got to act now because we don’t even know if we can hold them in captivity. Because if you’re going to do it, you know, at one minute to midnight on the Doomsday Clock, then there are a lot of lessons that need to be learned along the way to hold those animals in captivity for starters and get them to breed. You want to do it now, before they go extinct.