Research Questions/Objectives:
Brief Description of the Project:
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Data for environmental variables will be downloaded from WEBSITE. These will include minimum temperature, daily rainfall totals in addition to 3-day and 5 day totals, humidity, wind speed, and moon illumination (from WEBSITE). These variables have been shown to be relevant to calling patterns in other Australian amphibians (e.g., Brodie et al. 2021). I will determine the factors influencing calling in Notaden species. Incidently, this will also indicate the amount of time each species spends on the surface, and how long they spend buried.
Background and Significance of the Research Question to drought risk, vulnerability, preparedness, or resilience:
Bioturbation by frogs has the potential to significantly improve drought resilience in ecosystems, particularly in grazing lands. Frogs have surprisingly high biomass in and around water bodies.
By burrowing into and loosening soil, burrowing frogs enhance its ability to retain water, which is essential for maintaining moisture levels during dry periods. This improved water infiltration helps plants access deeper soil moisture, supporting vegetation growth even in low-rainfall conditions. Healthier plant cover not only stabilises the soil but also reduces evaporation from the ground, further conserving moisture. Additionally, frogs contribute to organic matter decomposition, enriching the soil with nutrients that boost plant resilience under drought stress, and they help control insect populations, which can reduce the need for chemical pest control methods. By supporting soil structure and water retention, bioturbation by frogs increases the land’s drought resilience, helping reduce vulnerability and enhancing preparedness against prolonged dry spells.
We think this project can contribute to ensuring farming systems are productive, sustainable and adapted to future drought (e.g. through improved soil and landscape health.
Academic and research experience relevant to the honours project:Â
I have an undergraduate degree in Zoology & Ecology from James Cook University, and take a personal interest in frogs and herpetology. Reflecting this interest, in 3rd year, my undergraduate capstone subject major project was on rainforest frog jumping behaviour.
Principal Supervisor’s skills and experience in relation to this project topic:
Lin Schwarzkopf is a herpetologist with 33 year’s experience studying frogs and frog behaviour. She has also studied the impact of grazing strategies on biodiversity, including frogs, and is interested in the roles biodiversity can play providing ecosystem services to graziers. She has supervised 24 honours students to completion.
I have lived most of my life in the Northern Territory, surrounded by the breathtaking and vast environment that encapsulates Northern Australia. The uniqueness of the environment and my natural curiosity ultimately lead to my love for the unique and wonderful fauna found throughout Australia. However, frogs have always intrigued me due to their complex life history/calling patterns and differing survival strategies.
During my Zoology and Ecology major, I further explored my interest in the environment and frogs through both classes that explored flora and fauna and electives that explored the role of soil in the environment. As a result, I have gained a deeper understanding of frogs and a new interest and appreciation of soil and its importance in maintaining the status quo of the environment. Naturally, the next step was to join these two interests, which led to a new interest in burrowing frogs, which have found a method to thrive even in Australia’s dry and arid areas.
My research will develop a better understanding of the interaction between these unique frogs and their immediate environment. The results will also shed light on how burrowing frogs influence soil movement. This endeavour aligns with my academic interests and my commitment to developing a better understanding of our environment.
Future Career Goals:
After completing my Honours, I would like to continue analysing and monitoring frog populations/communities while exploring the practical usage of passive acoustic monitoring (PAM). Lastly, I will continue to seek future opportunities to learn about frogs, PAM, and the environment.
Bioturbation contribution by a community of burrowing frogs
Background
Bioturbators play a crucial role in reworking soil and sediments, with common examples including earthworms, ants, and large mammals, which are often the focus of research (Beca et al., 2022; Ruiz & Lavelle, 2008). However, an often-overlooked group of bioturbators—burrowing frogs—may contribute to overall soil movement and can be found throughout Australia and on every continent except Antarctica (Bolochio et al., 2020). These frogs spend the majority of their lives underground, emerging under certain climatic conditions to breed and forage for brief periods, after which they burrow back underground. This underground lifestyle, coupled with their often remote distribution, contributes to a general lack of awareness about their ecological importance.
However, novel monitoring methods, such as acoustic monitoring (PAM), are showing promise for addressing these issues, which is a non-invasive method of recording and analysing the natural soundscape. The act of burrowing to and from the surface promotes increased porosity, disperses organic matter, and enhances microbial communities throughout the soil profile (Beca et al., 2022). Creating passive soil health benefits for agricultural and farm land throughout Australia and improving soil resilience to drought-like conditions. This study aims to investigate the contribution of a community of burrowing frogs to overall soil movement and to evaluate the efficacy of using PAM in detecting and monitoring these frogs.
Methods
The site was initially scouted to confirm the presence of burrowing frogs and man-made water bodies (dams). An acoustic recorder (Frontier Labs BarLT) was positioned facing the water body and recorded 24/7. Weekly surveys were conducted involving two 150m transects spaced 5m apart, with a 5-minute tadpole sweep conducted afterwards. Frog density was calculated using the total number of frogs throughout all surveys, assuming no recaptures. The burrow size of each species, sourced from existing literature, and the total soil moved were calculated under the assumption that each frog found during surveys was unique and burrows to and from the surface (Booth, 2006; Thompson et al., 2005).
It is noteworthy that the burrow size attributed to Cyclorana brevipes for the soil movement calculations was derived from a study examining the burrow depth of Cyclorana alboguttata. Additionally, the burrow depth data for Neobatrachus aquilonius were used to replace those of Platyplectrum ornatum, as the two species are closely related and the available literature did not provide information regarding the burrow depth of Platyplectrum ornatum.
Results
In total, three burrowing frog species were detected: Cyclorana alboguttata (Striped Burrowing Frog: Figure 1a), Platyplectrum ornatum (Ornate Burrowing Frog: Figure 1b) and Cyclorana brevipes (Short-footed Frog: Figure 1c). Cyclorana alboguttata accounted for the majority of individuals across all surveys, with the highest estimated soil moved over time and the highest predicted soil moved per density (Figures 2 and 3). The peak of soil movement occurs for all species in mid-to-late December, with both Cyclorana alboguttata and Platyplectrum ornatum showing later soil movement within the survey period (Figure 2). Lastly, PAM was unable to detect individuals as such was not used in calculating soil movement, but was able to identify the calls of every species with high confidence.
Soil health is crucial for successful farming, particularly as extreme weather events, such as droughts, become more frequent and significantly impact crop quality and yield. Understanding the natural resources that maintain and improve soil health is crucial. The most common examples include earthworms, ants, and burrowing mammals, which often overshadow other animals that likely play a role in soil health, such as burrowing frogs.
Burrowing frogs inhabit every continent except Antarctica, with many species throughout Australia. These frogs spend the majority of their lives underground, emerging under certain climatic conditions to breed and forage for brief periods, after which they burrow back underground. This underground lifestyle, coupled with their often remote distribution, contributes to a general lack of awareness about their ecological importance. However, novel monitoring methods, such as acoustic monitoring, are showing promise in addressing these issues. This involves deploying a microphone and analysing the audio recorded for species-specific calls, which is a non-invasive approach.
The burrowing behaviour of these frogs improves soil structure and assists in dispersing organic matter, thereby improving overall soil health and helping soil resist compaction and drought. However, the burrowing frogs’ exact contribution to soil movement/health is a relatively novel concept, due to their cryptic nature. This study aimed to investigate the extent to which a burrowing frog community contributes to soil movement along a man-made dam and to assess the validity of using acoustic monitoring to detect and monitor burrowing frogs.
Over a six-month period, from December to May, weekly site visits were conducted along the edge of the dam. These visits involved two transects that were 150m each, with a 5m spacing in between—ensuring that no frog was counted twice. Burrow sizes were sourced from existing literature for each species found: Striped Burrowing Frog (Cyclorana alboguttata), Short-footed Frog (Cyclorana brevipes) and Ornate Burrowing Frog (Platyplectrum ornatum). Unfortunately, due to the lack of available data on burrow sizes, data substitutions had to be made; the Ornate Burrowing Frog took data from its close relative, the Northern Burrowing Frog (Neobatrachus aquilonius), based on a field survey, while the Short-footed Frog relied on information from the Striped Burrowing Frog through a lab experiment.
Out of the three species, the Striped Burrowing Frog was the dominant species, followed by the Ornate Burrowing and Short-Footed Frogs. Both the Ornate Burrowing and Striped Burrowing Frogs were found to move a larger volume of soil compared to the Short-footed frog. All frogs were estimated to move some volume of soil throughout the study period. Additionally, burrowing activity peaked synchronously amongst all species in mid-late December, while both Striped Burrowing and Ornate Burrowing Frogs displayed burrowing months after the peak. Lastly, an acoustic recorder was set up facing the water and recorded continuously, listening for the calls of the burrowing frogs. While it could not detect individuals, it could identify each species’ call with high confidence, making it a low-cost method for landholders to detect and monitor burrowing frogs.
This study highlighted that while burrowing frogs likely contribute to overall soil movement, further research is needed in five key areas: species burrow characteristics, exploring seasonal trends, increasing spatial scale, investigating more species, and examining possible other effects on soil health.