Australian Wet-dry Tropics Research Articles

Within‐population variation in dietary traits: implications for vulnerability and impact of imperiled keystone predators

AbstractWithin a population of apex predators, differences among individuals can influence both their ecological impact and their vulnerability to threatening processes. Our field studies on a large monitor lizard (Varanus panoptes) in the Australian wet–dry tropics show that diets shift seasonally and depend upon a lizard’s sex and body size. Individuals that had previously been recorded to consume frogs were most at risk following biological invasion by toxic cane toads (Rhinella marina), as were individuals with broad diets during the wet season. As a result, mortality of those individual predators likely reduced predation pressure on other taxa (invertebrates and reptiles) that were frequently consumed by the same lizards that ate frogs, but with less benefit for taxa (e.g., rodents) that were consumed by non‐anuran‐eating individuals within the predator population. In particular, individuals killed by cane toads often had consumed agamid lizards, a group whose abundance has been reported to increase due to toad‐induced mortality of V. panoptes. To understand the vulnerability of apex predators, or the ecological consequences of their extirpation, we need to incorporate the role of variation among individuals in critical ecological traits.

Predicting hot spots of aquatic plant biomass in a large floodplain river catchment in the Australian wet-dry tropics

Conservation planning processes and wetland management require spatial estimations of aquatic habitats to support the maintenance of aquatic biodiversity. However, physical access to several wetlands and freshwater habitats can be restricted due to difficult topography and technological limitations associated with ground-based observations. In addition to these constraints, the distribution of some aquatic primary producers in freshwater habitats and floodplains that are difficult to reach further complicates large-scale assessment of aquatic habitats using traditional field-based techniques. The main objective of this study is to predict the spatial distribution of hot spots of primary producers (aquatic plant biomass) and assess large-scale inundation patterns in a large floodplain wetland (Flinders catchment) in the wet-dry tropics of Australia. To this end, remote sensing biophysical indicators (vegetation and inundation) were integrated with flood water depth in a classification tree model. Results indicate that in terms of floodplain total inundation, the Flinders wetland hydrology is rather restricted immediately after the summer wet season, the period when most primary production happens. While this can be attributed to the fact that much of the observed annual variability (93%) in rainfall and surface runoff (95%) occur during the wet season, post flood recession patterns are indicators that underpin the somewhat limited alimentation of the Flinders floodplain during this period. As observed in this study, post flood inundation extents in the summers of 2009 and 2019 declined by approximately 89% and 87% within fourteen and ten days, respectively. Despite having a significantly higher magnitude than the 2009 summer flood event, the 2019 extreme ‘big wet’ period did not translate to higher floodplain productivity (aquatic plant biomass and surface water distribution) immediately after summer as was the case in 2009. Furthermore, the predicted extents of aquatic plant biomass and total floodplain inundation in the downstream Flinders show substantial temporal variation and suggest the floodplain wetland hydrology is largely driven by inter-annual changes in annual rainfall. The extents of these hot spots of biomass accumulation were found to be considerably associated with total floodplain inundation extent (r=0.94), rainfall (r=0.81), and discharge (r=0.68). Furthermore, advance statistical analyses show that downstream discharge and rainfall over the Flinders are significantly correlated (r=0.72). In addition to this, observed amplitudes of discharge and rainfall in extreme wet and dry years coincided with floodplain inundation patterns and distribution of hot spots of primary producers. While these relationships emphasize the importance of flow in the nourishment of the downstream catchment, they further corroborate the composite influence of local rainfall and discharge on total floodplain inundation and hot spots of primary producers.

Radon-222 diffusion length and exhalation characteristics of uraniferous waste rock and application to mine site remediation in the Australian wet-dry tropics

The diffusion length of 222Rn in uraniferous waste rock was determined through a novel experiment. Large PVC columns were filled to different depths in the range from 0.5 m to 3.0 m with waste rock material from the Ranger uranium mine and the build-up of 222Rn activity concentration in the column headspace above the material was measured after closing the columns with a lid. Measurements were made approximately one month after filling the columns and again after approximately one and two years. The average 222Rn diffusion length derived from the measurements was 1.9 ± 0.2 m in the dry material. The corresponding diffusion coefficient was (7.3 ± 0.7) × 10−6 m2 s−1. For an infinitely thick layer of the dry material, the average value of the 222Rn exhalation flux density relative to the 226Ra activity concentration was estimated as (5.3 ± 0.3) × 10−4 Bq m−2 s−1 per Bq kg−1. From the diffusion length, the waste rock material was characterised as both a source and attenuator of 222Rn for its proposed use as the surface cover on the final landform of the remediated Ranger uranium mine.

A study of soil erosion rates using 239Pu, in the wet-dry tropics of northern Australia

The Daly River drains a large (52500 km2) and mainly undisturbed catchment in the Australian wet–dry tropics. The basin landscapes are mantled by a thick veneer of kandosol soil which has developed under varying rates of erosion, uplift, bedrock type and climate and has been identified as being suitable for agriculture. Commencement of large scale clearing and cropping since 2002 have raised concerns about the increased loss of top soil from the land clearing and cultivation activities adjacent to the Daly River. This study was undertaken to determine the modern soil loss rates which can be used to develop a sustainable soil conservation strategy for this catchment. 239Pu, released in the 1950s and 1960s by atmospheric nuclear weapons tests, is used to obtain a quantitative assessment of recent rates of soil loss. Soil cores 30–40 cm deep have been collected from fields with various land uses including peanut and hay cropping and cattle grazing. Cores taken from undisturbed and unburnt areas in open eucalypt woodland have been used as reference sites. The soil loss rates have been established by comparing the excess or deficiency of the 239Pu tracer over that of the reference sites. Since land use practices in the catchment are similar, it is likely that the measured soil loss rates are indicative of soil loss rates over the Daly Basin as well.The development of 239Pu as a soil tracer represents a viable alternative to the traditionally used 137Cs tracer. This also represents a new tool in the quantification of catchment soil loss and the adoption of appropriate soil conservation strategies for the tropical regions and regions where increasing settlement and agriculture are encroaching on catchment slopes.

Do active‐dispersing insects dominate the invertebrate fauna of rock pools in the wet–dry tropics, Kimberley, Australia?

Abstract Invertebrate assemblages of tropical freshwater rock pools (FRPs) are poorly known compared with temperate regions, where FRPs contain specialized, endemic taxa of high conservation value. Invertebrates were sampled from pristine FRPs in the Morgan River catchment in the Australian wet–dry tropics in the 2015 and 2016 wet seasons. Taxa were classified as either active or passive dispersers and by functional feeding groups. A range of physical variables were examined to identify associations with invertebrate assemblages. Forty‐seven taxa were identified from FRPs; most were actively dispersing predatory insects, primarily Coleoptera and Hemiptera. Five adult insect species were found in most pools; other taxa were rare and scattered across FRPs. Two previously undescribed species of Spinicaudata were collected, but few crustacean taxa were recorded, and passively dispersing taxa were rare. Species accumulation curves indicated that had more pools been sampled, more taxa would have been collected in 2015, but in 2016 most species were collected. There was no pattern in FRP assemblages related to any physical variable, but the assemblages in pools were correlated between sampling times. An opportunistic and mobile assemblage composed mostly of actively dispersing predatory insects may explain the absence of relationships with measured variables. Low hydrological stability in the wet–dry tropics may be associated with low taxon richness. The dominance of actively dispersing insects is in contrast with FRP assemblages in temperate and arid regions. Studies of a wider range of FRPs from tropical regions are required to determine whether the fauna of these Kimberley FRPs are typical, and to fully describe short‐range endemic species across the Kimberley and elsewhere. The FRPs have conservation value as habitat for endemic, specialist rock‐pool taxa, contributing to regional species pools. At present, a lack of knowledge of endemic FRP specialist species in tropical regions, including the Kimberley, impedes our ability to protect and conserve these species from disturbance.

A NEW BACKGROUND SUBTRACTION METHOD FOR ASSESSING PUBLIC RADIATION EXPOSURE DUE TO RADON TRANSPORT FROM A URANIUM MINE.

Environmental radon progeny concentration data for the Ranger mine in the Australian wet-dry tropics were analysed. Concentrations in air at public receptor locations correlated with wind direction and were generally higher when the wind had a southerly component. The regional setting suggested that correlations were due to geography rather than the mine. The line of best fit to the radon progeny data when plotted against angle of wind direction was used to estimate background concentrations when the wind was from the direction of the mine. This differed from the standard approach of averaging concentrations when the wind was not from the direction of the mine. Background concentrations in mine-related wind directions using the line of best fit approach were generally higher than those predicted from averaging, as mine-related wind directions included a southerly component. Estimates of mine-related doses to the public were generally lower as a result.

Sediment fluxes and sinks for Magela Creek, Northern Territory, Australia

Sediment fluxes and sinks based on total sediment load for Magela Creek in the Australian wet–dry tropics have been constructed from detailed measurements of stream suspended sediment (turbidity and suspended sand) and bed load for the 10-year period, 2001–2002 to 2010–2011. This work shows that the sediment trap efficiency of the vegetated wetlands on lower Magela is high at ~89.5%. Sediment fluxes are the lowest in the world because of low soil erosion rates and because upstream floodplains and downstream wetlands trap and store sediment. Bedload yields are less than suspended sediment yields, but the amount of silt and clay is much less than the amount of sand (suspended sand and bedload). All sand is stored upstream of the East Alligator River. Downstream connectivity of sediment movement does not occur. Therefore, sediment moves discontinuously from the upper to the lower catchment.

Fish assemblage dynamics in an intermittent river of the northern Australian wet–dry tropics

AbstractIntermittent rivers make up a large portion of the global river network and are the dominant river type in northern Australia. Increased pressure is being placed on such systems, and a better understanding of their ecology is needed. We examined, over a 7‐year period, the fish fauna of the intermittent Fergusson River, a major tributary of the Daly River of the northern Australia. Changes in habitat structure with the onset of the dry season involved contraction of the riffle/run/pool habitat to a single refugial pool, the size of which was determined by antecedent wet season hydrology. The fishes present comprised a subset of species present within the Daly River main channel and consisted of the most widely distributed of northern Australia's freshwater fishes. The Fergusson River provides suitable spawning habitat for species during the wet season (e.g. Hephaestus fuliginosus, Leiopotherapon unicolor and Neosilurus catfishes) and during the dry season for a different set of species (e.g. Amniataba percoides, Melanotaenia australis and Glossogobius aureus). Little year‐to‐year variation in assemblage structure was observed early in the dry season, whereas interannual variation in late dry season assemblages was substantial. Dry season recruitment imparted some of the interannual variability in assemblage structure recorded between late dry season samples. Piscivorous fishes were an important, but temporally variable, component of the assemblage present in the late dry season refugial habitat, and predation was potentially another important source of variation in assemblage structure.

Frogs in the spotlight: a 16-year survey of native frogs and invasive toads on a floodplain in tropical Australia.

Although widespread declines in anuran populations have attracted considerable concern, the stochastic demographics of these animals make it difficult to detect consistent trends against a background of spatial and temporal variation. To identify long‐term trends, we need datasets gathered over long time periods, especially from tropical areas where anuran biodiversity is highest. We conducted road surveys of four anurans in the Australian wet–dry tropics on 4637 nights over a 16‐year period. Our surveys spanned the arrival of invasive cane toads (Rhinella marina), allowing us to assess the invader's impact on native anuran populations. Our counts demonstrate abrupt and asynchronous shifts in abundance and species composition from one year to the next, not clearly linked to rainfall patterns. Typically, periods of decline in numbers of a species were limited to 1–2 years and were followed by 1‐ to 2‐year periods of increase. No taxa showed consistent declines over time, although trajectories for some species showed significant perturbations coincident with the arrival of toads. None of the four focal frog species was less common at the end of the study than at the beginning, and three of the species reached peak abundances after toad arrival. Survey counts of cane toads increased rapidly during the initial stage of invasion but have subsequently declined and fluctuated. Distinguishing consistent declines versus stochastic fluctuations in anuran populations requires extensive time‐series analysis, coupled with an understanding of the shifts expected under local climatic conditions. This is especially pertinent when assessing impacts of specific perturbations such as invasive species.

A database of radionuclide activity and metal concentrations for the Alligator Rivers Region uranium province

This paper presents a database of radionuclide activity and metal concentrations for the Alligator Rivers Region (ARR) uranium province in the Australian wet-dry tropics. The database contains 5060 sample records and 57,473 concentration values. The data are for animal, plant, soil, sediment and water samples collected by the Environmental Research Institute of the Supervising Scientist (ERISS) as part of its statutory role to undertake research and monitoring into the impacts of uranium mining on the environment of the ARR. Concentration values are provided in the database for 11 radionuclides (227Ac, 40K, 210Pb, 210Po, 226Ra, 228Ra, 228Th, 230Th, 232Th, 234U, 238U) and 26 metals (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, P, Pb, Rb, S, Sb, Se, Sr, Th, U, V, Zn). Potential uses of the database are discussed.

Floods and famine: climate‐induced collapse of a tropical predator‐prey community

Summary Will climate change threaten wildlife populations by gradual shifts in mean conditions, or by increased frequency of extreme weather events? Based on long‐term data (from 1991 to 2014), the aim of the present study was to analyse and compare the sensitivity of predator–prey demography to extreme climatic events versus normal, albeit highly variable, annual deviations in climatic conditions in the Australian wet–dry tropics. From 1991 to 2005, predators (water pythons, Liasis fuscus) and their main prey (dusky rats, Rattus colletti) showed significant climate‐driven fluctuations in numbers. These fluctuations were, however, trivial compared to the impact of two massive but brief deluges in 2007 and 2011, which virtually eliminated the dusky rats. The two floods resulted in the pythons experiencing an unprecedented famine in seven out of the last 8 years causing a massive shift in python demography, that is a significant reduction in feeding rates, reproductive output, growth rates, relative body mass, survival, mean body length and numbers (from 3173 in 1992 to 96 in 2013). Our results demonstrate that attempts to predict faunal responses to climate change, even if based on long‐term studies, may be doomed to failure. Consequently, biologists may need to confront the uncomfortable truth that increased frequency of brief unpredictable bouts of extreme weather can influence populations far more than gradual deviations in mean climatic conditions.

Context dependency of top-down and bottom-up effects in a Northern Australian tropical river

AbstractTop-down and bottom-up forces (consumer and resource limitation, respectively) influence biomass of primary producers and primary consumers in natural food webs. Few investigators experimentally examine both in concert, especially in the tropics. Tropical systems probably are more sensitive than temperate systems to eutrophication and other disturbances, such as destruction of riparian canopy cover, because of wide windows of ecological opportunity. We experimentally examined the relative importance of top-down and bottom-up effects at 2 sites in the Edith River in the Australian wet–dry tropics during baseflow conditions. We used large fish-exclusion cages to examine top-down effects of fish, and we used nutrient-diffusing substrates to manipulate bottom-up effects of nutrients. Macroinvertebrates were significantly more abundant in fish-exclusion cages than in open control areas at both sites. At 1 site, chlorophyll a on rock substrate was 1.5× greater and ash-free dry mass was 1.4× greater in f...

Temporal variation in benthic primary production in streams of the Australian wet–dry tropics

In the Australian wet–dry tropics, seasonal changes in hydrology can influence abiotic conditions and consequently influence standing stocks of benthic biomass and production. While there is some understanding of these processes at riverscape scales, effects of seasonal hydrology on benthic biomass and production in low-order streams remain largely unquantified. We observed changes in water quality, algal and macroinvertebrate biomass, and stream benthic primary productivity over a 15-month period in three low-order streams with contrasting flow regimes in the wet–dry tropics of northern Australia. Water quantity and quality showed a distinct seasonal signature reflected in seasonal peaks in algal (maximum 1.29 µg cm−2) and macroinvertebrate biomass (maximum 0.24 g m−2), and productivity (maximum 0.41 g C m−2 days−1). In particular, transitional periods between dry and wet seasons were key times of elevated production and algal biomass. Overall, variation in biomass and benthic primary production was greater between seasons than among streams indicating that extrapolation between seasons may not be appropriate.

Using239Pu as a tracer for fine sediment sources in the Daly River, Northern Australia

The Daly River drains a large (52500 km 2 ) and mainly undisturbed catchment in the Australian wet-dry tropics. Clearing and cropping since 2002 have raised concerns about possible increased sediment input into the river and motivated this study of its fine sediment sources. Using 239 Pu as a tracer it is shown that the fine sediments originate mainly from erosion by gullying and channel change. Although the results also indicate that the surface soil contribution to the river channel sediments from sheet erosion has increased to 5-22% for the Daly River and 7-28% for the Douglas River (a tributary of the Daly River) in 2009 vs. 3- 6% for the Daly River and 4-9% for the Douglas River in 2005. This excess top soil likely originates from the cleared land adjacent to the Daly River since 2005. However, channel widening largely as a result of hydrologic change is still the dominant sediment source in this catchment.

Assessing the impacts of climate change and dams on floodplain inundation and wetland connectivity in the wet–dry tropics of northern Australia

Summary Floodplain wetlands and their hydrological connectivity with main river channels in the Australian wet–dry tropics are under increasing pressure from global climate change and water resource development, and there is a need for modelling tools to estimate the time dynamics of connectivity. This paper describes an integrated modelling framework combining conceptual rainfall–runoff modelling, river system modelling and hydrodynamic (HD) modelling to estimate hydrological connectivity between wetlands and rivers in the Flinders and Gilbert river catchments in northern Australia. Three historical flood events ranging from a mean annual flood to a 35-year return period flood were investigated using a two dimensional HD model (MIKE 21). Inflows from upstream catchments were estimated using a river network model. Local runoff within the HD modelling domain was simulated using the Sacramento rainfall–runoff model. The Shuttle Radar Topography Mission (SRTM) derived 30 m DEM was used to reproduce floodplain topography, stream networks and wetlands in the HD model. The HD model was calibrated using stream gauge data and inundation maps derived from satellite (MODIS: MODerate resolution Imaging Spectroradiometer) imagery. An algorithm was developed to combine the simulated water heights with the DEM to quantify inundation and flow connection between wetlands and rivers. The connectivity of 18 ecologically important wetlands on the Flinders floodplain and 7 on the Gilbert floodplain were quantified. The impacts of climate change and water resource development on connectivity to individual wetlands were assessed under a projected dry climate (2nd driest of 15 GCMs), wet climate (2nd wettest of 15 GCMs) and dam conditions. The results indicate that changes in rainfall under a wetter and drier future climate could have large impacts on area, duration and frequency of inundation and connectivity. Topographic relief, river bank elevation and flood magnitude were found to be the key factors contributing to the level of connectivity. Under a wetter future climate the average duration of connection of wetlands to the main river channel increased by 7% and under a drier climate it decreased by 18%. Construction of a 248 GL dam in the Flinders catchment and two (498 and 271 GL capacity) in the Gilbert catchment could reduce the average duration of connectivity by 1% and 2% in the Flinders and Gilbert catchments respectively. This information is potentially useful to future studies on the flood-dependent ecology in this region.

Activity Patterns and Movements of Free-Ranging Bluetongue Lizards (Tiliqua scincoides intermediaandTiliqua multifasciata) in the Australian Wet-Dry Tropics

Abstract We used GPS-based radiotelemetry to quantify diel activity patterns and movements by two species of large scincid lizards in the Australian wet-dry tropics. From an average of 63 days tracking of 54 Northern Bluetongues (Tiliqua scincoides intermedia) and 42 days tracking of 8 Centralian Bluetongues (Tiliqua multifasciata), we obtained 53,801 and 8,139 data points, respectively, on lizard locations over a 13-month period. Lizard species, sex, and study site had relatively little effect on distances moved, at both daily and hourly levels. However, Northern Bluetongues moved further per day than did Centralian Bluetongues at a site where they were sympatric. Most movements were <20 m, with longer movements (dispersal between core areas within the wider home range) occurring primarily during midmorning and late afternoon. The only major effect of ambient temperatures on lizard activity patterns likely was that midday movements were precluded by the risk of overheating; at all other times of the day ...

The early toad gets the worm: cane toads at an invasion front benefit from higher prey availability

In biological invasions, rates of range expansion tend to accelerate through time. What kind of benefits to more rapidly dispersing organisms might impose natural selection for faster rates of dispersal, and hence the evolution of range-edge acceleration? We can answer that question by comparing fitness-relevant ecological traits of individuals at the invasion front compared with conspecifics in the same area a few years post-invasion. In tropical Australia, the rate of invasion by cane toads (Rhinella marina) has increased substantially over recent decades, due to shifts in heritable traits. Our data on field-collected cane toads at a recently invaded site in the Australian wet-dry tropics span a 5-year period beginning with toad arrival. Compared with conspecifics that we monitored in the same sites post-invasion, toads in the invasion vanguard exhibited higher feeding rates, larger energy stores, better body condition and faster growth. Three processes may have contributed to this pattern: (i) higher prey availability at the front (perhaps due to reduced competition from conspecifics); (ii) the lack of viability-reducing parasites and pathogens in invasion-front toads; and (iii) distinctive (active, fast-growing) phenotypes of the invasion-front toads. Nutritional benefits to individuals in the invasion vanguard (whether because of higher prey availability, or lower pathogen levels) thus may have conferred a selective advantage to accelerated dispersal in this system.

Gut content and stable isotope analyses provide complementary understanding of ontogenetic dietary shifts and trophic relationships among fishes in a tropical river

Summary1. Despite widespread recognition of the role of body size in fish trophic ecology, little attention has been focused on this issue in isotopic studies, particularly in tropical systems.2. We used analyses of stomach contents and stable isotopes to examine size‐related shifts in diet in a terapontid fish assemblage in the Australian wet–dry tropics. Stomach content analysis identified substantial ontogenetic dietary shifts in all species, corresponding to changes in body size–isotope trajectories for two species. Shifts away from relatively specialised diets of heavily 13C‐depleted insect larvae to consumption of a range of items across multiple basal carbon sources appeared to be the proximate cause of observed isotopic changes.3. Allochthonous organic matter in the form of C3 riparian vegetation was particularly important to smaller terapontids before larger fish shifted to a broad range of dietary items and similarly broad range of basal carbon sources.4. While there was general agreement between δ13C and stomach content analysis, there was minimal concurrence between the latter and δ15N isotopic derivation of estimates of trophic position. Due to factors such as omnivory, isotopically overlapping basal sources and uncertainties about rates of isotopic fractionation in both predator and prey species, stomach content analysis provides an essential complement to isotopic methodologies in tropical systems.5. Given that basal sources supporting any individual species can change markedly with ontogeny, consideration of intraspecific, size‐related variation is necessary in isotopic studies of food web structure.

Assessing the seasonal dynamics of inundation, turbidity, and aquatic vegetation in the Australian wet–dry tropics using optical remote sensing

ABSTRACTFloodplain wetlands in the wet–dry tropics are under increasing pressure from water resource development, and there is a need for methods to assess the biophysical dynamics of these extensive and often remote ecosystems. This study assessed the capacity of optical remote sensing methods to monitor the seasonal dynamics of inundation, turbidity, and aquatic vegetation cover for a northern Australian savanna catchment. MODIS data were used to map seasonal flood inundation patterns, and Landsat 5 TM data were used to map dry‐season waterbody dynamics. A network of water‐depth loggers and temperature sensors provided ground observations of surface inundation dynamics, and was used to validate the inundation mapping. Post‐flood waterbody surface area declined by 89% over the dry season, with 70% of the decline occurring for Palustrine (floodplain) waterbodies. All aquatic systems became increasingly disconnected as the dry season progressed. Statistical relationships were developed between seasonal measurements of turbidity, aquatic vegetation cover, and Landsat spectral data. Catchment wide predictions showed that turbidity increased and macrophyte cover decreased for the Palustrine and Lacustrine (lake) systems, while the Riverine systems became less turbid over the dry season. These results show that, for open savanna landscapes where cloud cover does not limit waterbody detection, optical remote sensing methods can be effectively applied to assess seasonal patterns of inundation and accompanying biophysical dynamics. This provides an effective tool to evaluate the impact of river flow regime changes from water resource use or climate change in these regions. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Effects of seasonal aridity on the ecology and behaviour of invasive cane toads in the Australian wet–dry tropics

Summary1. Measuring the costs imposed by specific environmental challenges is difficult, because organisms adapt in ways that reduce those costs. Invasive species provide an opportunity to quantify environmental impacts before organisms can make adaptive changes.2. The native range of cane toads (Rhinella marina) lies within the wet neotropics; although part of this range experiences seasonal drought, many of the places recently invaded by this large anuran species are much more arid.3. Five years’ fieldwork from a seasonally arid site in the Australian wet–dry tropics shows strong seasonal shifts in the toads’ (i) population structure, reflecting seasonality in breeding and recruitment; (ii) adult morphology (secondary sexual characteristics in males); (iii) growth rates; (iv) energy balance; (v) spatial ecology (philopatry, dispersal rates) and (vi) adult mortality rates.4. Some of these patterns accord with intuition: for example, wet‐season conditions resulted in higher rates of growth, reproduction and movement, better body condition and more pronounced secondary sexual characteristics. However, seasonal patterns for other traits were non‐intuitive: for example, neither hematocrit levels (reflecting hydration state) nor corticosterone levels (reflecting stress) showed significant seasonal variation, and mortality rates were higher in the wet season than the dry season.5. The toads’ ability to flexibly adjust their behaviour and ecology to local hydric conditions has allowed them to thrive even under climatic conditions that preclude activity, feeding and reproduction for most of the year.