https://nova.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:45287 Wed 26 Oct 2022 17:20:21 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:46841 Lechriodus fletcheri. We quantified preferences for spawning in pools that were unused by conspecifics, as well as pools with conspecific spawn or tadpoles present, or both. The study included two ecological contexts: a system of naturally occurring breeding pools and a field experiment with 40 artificial pools that controlled for habitat variation. Mothers preferred to oviposit in pools that already contained conspecific spawn, despite the likelihood of intense resource competition upon offspring hatching. This could be due to the potential benefits obtained by providing offspring access to a significant nutrient supply upon hatching via cannibalism of conspecific tadpoles and might be an important adaptation for completing tadpole development in highly ephemeral and resource-limited pools prior to desiccation. In contrast, mothers avoided ovipositing in pools with conspecific tadpoles, a probable adaptation to avoid their own offspring from becoming victims of cannibalism themselves prior to hatching. Such nuances in the effect of conspecific presence on offspring survival highlight the often complex decision-making process that amphibians need to make when selecting oviposition sites, as well as the influence cannibalism can have on the evolution of reproductive behaviour.]]> Wed 22 Mar 2023 17:31:21 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:30395 Rhinella marina) in Australia, which has caused severe population declines in monitor lizards, triggering trophic cascades that facilitated dramatic and sometimes unexpected increases in several prey of the predators, including smaller lizards, snakes, turtles, crocodiles, and birds. Persistence of isolated populations of these predators with a decades-long sympatry with toads suggests the possibility of recovery, but alternative explanations are possible. Confirming predator recovery requires longer-term study of populations with both baseline and immediate post-invasion densities. Previously, we quantified short-term impacts of invasive cane toads on animal communities over seven years at two sites in tropical Australia. Herein, we test the hypothesis that predators have begun to recover by repeating the study 12 yr after the initial toad invasion. The three predatory lizards that experienced 71–97% declines in the short-term study showed no sign of recovery, and indeed a worse fate: two of the three species were no longer detectable in 630 km of river surveys, suggesting local extirpation. Two mesopredators that had increased markedly in the short term due to these predator losses showed diverse responses in the medium term; a small lizard species increased by ~500%, while populations of a snake species showed little change. Our results indicate a system still in ecological turmoil, having not yet reached a “new equilibrium” more than a decade after the initial invasion; predator losses due to this toxic invasive species, and thus downstream effects, were not transient. Given that cane toads have proven too prolific to eradicate or control, we suggest that recovery of impacted predators must occur unassisted by evolutionary means: dispersal into extinction sites from surviving populations with alleles for toxin resistance or toad avoidance. Evolution and subsequent dispersal may be the only solution for a number of species or communities affected by invasive species for which control is either prohibitively expensive, or not possible.]]> Wed 11 Apr 2018 17:13:14 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:26932 Wed 11 Apr 2018 12:31:24 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:53680 10-fold mean increase in detection rates of cats by 5 years after the loss of V. panoptes, reflecting relative increases of 3.3–8.7 individual cats per site. Conclusions: Although some unknown factor may have caused an increase in cats, their similar trophic position and niche to V. panoptes suggests that toads facilitated cats by effectively removing the lizards from the animal community. This interaction likely reflects one type of invasional meltdown, whereby a non-native species (cane toad) facilitated any aspect of another’s (feral cat) invasion (e.g. survival, reproduction, resource acquisition), but the latter has no detected influence on the former (+/0 interaction). Implications: Because both invaders cause declines in animal populations and are difficult to control, the potentially synergistic tandem of cane toads and feral cats could have chronic, irreversible effects on animal communities.]]> Wed 10 Jan 2024 10:20:29 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:43087 Tue 14 May 2024 11:04:41 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:39162 Thu 19 May 2022 19:17:48 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:40299 Thu 07 Jul 2022 15:39:36 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:35232 Rhinella marina) has invaded over 50 countries and is a serious conservation issue in Australia. Because the cane toad has taken several decades to colonise northern Australia, due to the large size of the continent and the east–west invasion axis, there is scope for making testable predictions about how toads will invade new areas. The western toad invasion front is far from linear, providing clear evidence for heterogeneity in invasion speed. Aims: Several ad hoc hypotheses have been offered to explain this heterogeneity, including the evolution of traits that could facilitate dispersal, and spatial heterogeneity in climate patterns. Here an alternative hypothesis is offered, and a prediction generated for the spatiotemporal pattern of invasion into the Kimberley Region – the next frontier for the invading toads in Australia. Methods: Using observations of spatiotemporal patterns of cane toad colonisation in northern Australia over the last 15 years, a conceptual model is offered, based on the orientation of wet season river flows relative to the invasion axis, as well as toad rafting and floating behaviour during the wet season. Key results: Our model predicts that toads will invade southern areas before northern areas; an alternative model based on rainfall amounts makes the opposite prediction. The models can now be tested by monitoring the spread of invasion front over the next 5–10 years. Conclusions: Our conceptual models present a pleuralistic approach to understanding the spatiotemporal invasion dynamics of toads; such an approach and evaluation of the models could prove useful for managing other invasive species. Implications: Although control of cane toads has largely proved ineffective, knowledge of the spatiotemporal pattern of the toad invasion in the Kimberley could: (1) facilitate potential management tools for slowing the spread of toads; (2) inform stakeholders in the local planning for the invasion; (3) provide researchers with a temporal context for quantifying toad impacts on animal communities; and (4) reveal the mechanism(s) causing the heterogeneity in invasion speed.]]> Thu 04 Jul 2019 13:56:20 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:20801 Sat 24 Mar 2018 08:05:53 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:20296 Sat 24 Mar 2018 07:55:14 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:27419 1 m, suggesting that deep nesting in V. panoptes may be an evolutionary response to egg desiccation during the long (approximately 8 months) dry season incubation period. Alternatively, lizards may avoid shallower nesting because even slight daily temperature fluctuations are detrimental to developing embryos; our data show that this species may have the most stable incubation environment of any reptile and possibly any ectotherm. Soil-filled burrows do not support the hypothesis generated for Daimonelix that the helix would provide more consistent temperature and humidity as a result of limited air circulation in dry palaeoclimates. We suggest that Daimonelix were used mainly for nesting or rearing young, because helical burrows of extant vertebrates are generally associated with a nest. The extraordinary nesting in this lizard reflects a system in which adaptive hypotheses for the function of fossil helical burrows can be readily tested.]]> Sat 24 Mar 2018 07:35:23 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:26367 Rhinella marina), however, offered a unique opportunity to quantify cascading effects. In northern Australia, three species of predatory monitor lizards suffered severe population declines due to toad-induced lethal toxic ingestion (yellow-spotted monitor [Varanus panoptes], Mertens' water monitor [V. mertensi], Mitchell's water monitor [V. mitchelli]). We, thus, predicted subsequent increases in the abundance and recruitment of prey species due to the reduction of those predators. Toad-induced population-level declines in the water monitor species approached 50% over a five-year period spanning the toad invasion, apparently causing fledging success of the Crimson Finch (Neochmia phaeton) to increase from 55% to 81%. The consensus of our original and published long-term data is that invasive cane toads are causing predators to lose a foothold on top-down regulation of their prey, triggering shifts in the relative densities of predator and prey in the Australian tropical savannah ecosystem.]]> Sat 24 Mar 2018 07:33:08 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:47499 Mon 23 Jan 2023 11:54:33 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:35384 Varanus panoptes and V. gouldii) have been discovered at depths of 2.3–3.0 m, suggesting that nesting at extreme depths in these species is an adaptive response to the lack of sufficient soil moisture at shallower depths. Herein, we examine this idea with V. panoptes, specifically predicting that deeper nests in a desert ecosystem compared with those in a savannah ecosystem are attributable to differences in the magnitude of rainfall. We excavated a communal nesting warren to a depth of 4 m and identified 11 fresh nests and 99 hatched nests. Mean nest depth in the present study was greater than that in savannah. However, nests were shallower than those of V. gouldii in the same general location, possibly because of local heterogeneity in soil moisture. Hatchlings excavated their own emergence burrows rather than following the burrows of their mothers, despite relatively great distances through resistant soils. Collectively, deep nesting creates energetic challenges for mothers and hatchlings, suggesting an adaptive function for the behavior.]]> Mon 22 Jul 2019 16:49:19 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:40429 Rhinella marina) has decimated populations of a keystone predator, the yellow-spotted monitor (Varanus panoptes), causing trophic cascades in Australian animal communities. Paradoxically, some V. panoptes populations coexist with toads. Demonstrating patterns in heterogeneous population-level impacts could reveal mechanisms that mediate individual effects, and provide managers with the ability to predict future impacts and assist in population recovery. Aims: The aim of the present study was to search for spatial patterns of population resilience of V. panoptes to invasive cane toads. Methods: Published literature, unpublished data, reports and anecdotal information from trained herpetologists were used to test the emerging hypothesis that resilient predator populations are mainly coastal, whereas non-resilient populations are mostly inland. Key results: Post-toad invasion data from 23 V. panoptes populations supported the idea that toad impacts on V. panoptes were heterogeneous; roughly half the populations could be designated as resilient (n = 13) and half as non-resilient (n = 10). Resilient populations had longer times since toad invasion than did non-resilient populations (39 versus 9 years respectively), supporting the idea that some recovery can occur. Non-resilient populations were exclusively inland (n = 10), whereas resilient populations were split between inland (n = 5) and coastal (n = 8) populations. Resilient inland populations, however, were mainly confined to areas in which decades had passed since toad invasion. Conclusions: The findings suggest that coastal V. panoptes populations fare much better than inland populations when it comes to surviving invading cane toads. Implications: Unambiguous recovery of monitor populations remains undemonstrated and will require long-term population monitoring before and after toad invasion.]]> Fri 22 Jul 2022 14:30:26 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:39954 Rhinella marina) and native water rats (Hydromys chrysogaster), where toads are novel prey. We show that wild water rats preferentially targeted larger toads, and consumed specific non-toxic organs only. Rats either rapidly learned these behaviours, or adapted them from hunting native frogs.]]> Fri 22 Jul 2022 11:49:25 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:47226 Fri 16 Dec 2022 10:44:38 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:38175 Fri 06 Aug 2021 14:14:50 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:49196 Fri 05 May 2023 15:51:18 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:49805 Fri 02 Jun 2023 16:59:49 AEST ]]>