NEWSTaste of the NSW Forum: Rivers, Streams and Catchments in Northern NSW – your questions answered!

For this endangered freshwater turtle, current fox control measures are not adequate. Each year, foxes are raiding more than 95% of Bell’s Turtle nests and juvenile turtles make up less than 1% of this aging population. Until we have effective fox management, conservation intervention is required to assure the persistence of this turtle species.

My research is looking at conservation strategies that prevent or bypass fox predation with the aim of increasing the number of juvenile turtles in the population. The first strategy is the in-situ protection of turtle nests. So far, this strategy has prevented any predation of the protected nests and more than 700 hatchlings have made it into the river system. Synchronous nesting in response to weather events does make it difficult to locate and protect nests on a large scale – before the foxes find the nests. Nests left in-situ are also vulnerable to environmental extremes (e.g. flooding, drought, increased temperatures) which can have a drastic effect on overall hatching success.

The second conservation strategy I am looking at is the artificial incubation of turtle eggs in the laboratory and release of the hatchlings into the wild. I have been able to achieve 97% hatching success and almost 400 hatchlings have been released.

This spring, a team of ecologists, landowners and Aboriginal rangers will be locating and protecting wild Bell’s Turtle nests. There will also be a hatchling release program starting this season, which aims to produce more than 1000 Bell’s Turtle hatchlings each year.

Other conservation strategies that we are looking at include the use of temporary fencing to exclude foxes from nesting banks, and financial incentives for landowners to undertake fox control, riparian restoration and habitat protection.

The short term measure of success is the recapture of released hatchlings or hatchlings from the protected nests, and confirmation that the hatchlings are surviving and developing normally. The long term measure of success is when turtles from the conservation strategies reach sexual maturity and become part of the breeding population.

Those turtles are too cute!! Well done on your hard work.

My question is have you found fox control in the areas around your nest to impact turtle hatchling success?

I am not directly researching fox control. However, a number of published studies suggest that even with lethal fox control, predation of freshwater turtle nests is still unsustainably high. My research is aimed at bypassing or preventing fox predation. Ex-situ incubation of eggs bypasses nest predation completely. In-situ protection of nests has improved hatching success dramatically.

Protection of individual nests with wire mesh or steel cages has been 100% effective at preventing fox predation over 3 breeding seasons.

You mentioned bare river banks without overhanging, densely vegetated banks are preferred nesting habitat. What do we know of in-channel habitat needs and remediation efforts to provide them?

Bell’s Turtles need deep pools for daytime shelter and winter hibernation, and they need shallow areas for foraging. It is thought that hatchling turtles shelter in dense aquatic vegetation (e.g. ribbon weed and reeds) and forage in riffles. I’m not aware of any current remediation projects for in-channel habitat for Bell’s Turtles. However, Local Land Services provides incentive funding for landholders to protect and restore riparian areas.

Hi Lou, have any geomorpholgists commented on the preferred nesting sites being exposed banks, before European clearing where would they have nested?

As yet, I haven’t spoken to any geomorphologists. I have noticed that even in areas where grazing has been excluded, various bare areas still occur (e.g. sandy banks, gravel and shingle beds) that do support nesting. I imagine that turtle populations were able to persist with a lower quantity of bare nesting habitat when there was an absence of foxes.

Are your findings influencing riparian revegetation activities in known turtle breeding areas? Given your knowledge of types of habitat for turtle nesting locations – ie stock access, no canopy.

Yes, I liaise with Local Land Services and some of their incentive funding is focused on riparian protection through strategic grazing management within Bell’s Turtle nesting areas, and they subsidise the installation of off-stream watering points for livestock.

$600-1,000/lm

You said that riparian revegetation is a touchy issue with landowners in the Hunter. What did the other surrounding land holders think of your project now that you can show how successful it was?

They were interested to see how the project turned out. Some already have a thin riparian vegetation buffer, others weren’t so keen on changing their management of river banks. We’re using this site as a demonstration in the hope that other estuarine river bank landholders see the benefits. It helps to have a champion landholder to tell the story.

Thanks Jenny for the interesting presentation. Wondering if there is an ongoing commitment to monitor the pilot study to quantify improvements in water quality, bank stability etc.? This might help in winning minds?

We’re lucky that Melbourne Uni included our site in a rock fillets study on NSW coastline (transects, sedimentation rates, etc). Field work was completed pre-COVID and we’re eagerly awaiting the results. We’re also monitoring survival of plants and taking photopoints. Water quality improvements are difficult to link to one small scale bank rehab project in a large estuary, however we also have catchment improvement projects in other areas of the Hunter so hopefully the cumulative benefits will be observed over time.

Yes, I would use the same method to calculate Manning’s n in the future if I was to do a similar study. The method I used eliminates subjectivity and takes into account the roughness of all above-ground objects (vegetation, fence posts, etc.). Further, a lot of the pre-calculated values of Manning’s n have been oversimplified for use by engineers in artificial environments such as drainage canals. As a result, these values do not translate accurately to natural settings.

Awesome thesis. Are some species considered to be better at bank roughness than others?

There are definitely particular species that provide better or worse bank stability and/or roughness. For example, giant reed (Arundo donax) has a high amount of above ground vegetative cover but it known to rip up like a carpet during floods due to having shallow rhizomes. Further, species that are more flexible (e.g. grasses or herbs) are more likely to ‘lie down’ during high flows and will provide less flow resistance then a stiffer species.

Bec, have you an estimated cost per lineal metre to address invasive weeds and revegetate based on your study work?

The implementation of invasive weed management and native revegetation was not covered by my study. It would be difficult to determine an average lineal cost as there are many site variables involved.