ORCID Profile
0000-0002-7712-4373
Current Organisation
NSW Department of Planning, Industry and Environment
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Wiley
Date: 12-03-2020
DOI: 10.1111/GCB.15032
Publisher: Wiley
Date: 21-06-2021
DOI: 10.1111/REC.13419
Abstract: Increasingly threatened species and their habitats require multiple successful management actions to ensure persistence. Introduced predator exclusion and suppression programs are key conservation actions used to retain or restore Australian ecosystems. Nevertheless, few direct comparisons are made to ascertain the in idual and combined efficacy of multiple introduced predator conservation actions to benefit bio ersity. When colocated, both management actions could generate additive conservation benefits that greatly assist the recovery or persistence of threatened native species. Varanid lizards are key functional components in Australian predator guilds and could benefit, via ecological release, when introduced predator management actions are successful. Here we tested the effects of a colocated predator‐exclusion fence and lethal fox baiting on varanid site occupancy in a semiarid protected area. Varanid site occupancy was higher at sites inside (Ψ = 0.90 ± 0.26) compared to sites outside (Ψ = 0.61 ± 0.28) the introduced predator‐proof fenced enclosure. There was only weak evidence of increased varanid site occupancy at fox baited sites (Ψ = 0.037 ± 0.024) compared to nonfox baited (Ψ = 0.00) sites. Overall, colocated introduced predator management actions achieved some additive benefits via possible spillover fencing effects for native mesopredator populations. However, most potential benefits to varanid populations outside of the predator‐proof fenced enclosure were absent due to unsuccessful lethal‐baiting effects on fox populations. The predator‐proof fenced enclosure nevertheless provides important habitat refugia for future source populations for reintroduction once adjacent protected areas become suitable.
Publisher: The Royal Society
Date: 14-11-2018
Abstract: Loss of dispersal typifies island biotas, but the selective processes driving this phenomenon remain contentious. This is because selection via, both indirect (e.g. relaxed selection or island syndromes) and direct (e.g. natural selection or spatial sorting) processes may be involved, and no study has yet convincingly distinguished between these alternatives. Here, we combined observational and experimental analyses of an island lizard, the Komodo dragon ( Varanus komodoensis , the world's largest lizard), to provide evidence for the actions of multiple processes that could contribute to island dispersal loss. In the Komodo dragon, concordant results from telemetry, simulations, experimental translocations, mark-recapture, and gene flow studies indicated that despite impressive physical and sensory capabilities for long-distance movement, Komodo dragons exhibited near complete dispersal restriction: in iduals rarely moved beyond the valleys they were born/captured in. Importantly, lizard site-fidelity was insensitive to common agents of dispersal evolution (i.e. indices of risk for inbreeding, kin and intraspecific competition, and low habitat quality) that consequently reduced survival of resident in iduals. We suggest that direct selection restricts movement capacity (e.g. via benefits of spatial philopatry and increased costs of dispersal) alongside use of dispersal-compensating traits (e.g. intraspecific niche partitioning) to constrain dispersal in island species.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 24-06-2022
Abstract: Comparative studies of mortality in the wild are necessary to understand the evolution of aging yet, ectothermic tetrapods are underrepresented in this comparative landscape, despite their suitability for testing evolutionary hypotheses. We present a study of aging rates and longevity across wild tetrapod ectotherms, using data from 107 populations (77 species) of nonavian reptiles and hibians. We test hypotheses of how thermoregulatory mode, environmental temperature, protective phenotypes, and pace of life history contribute to demographic aging. Controlling for phylogeny and body size, ectotherms display a higher ersity of aging rates compared with endotherms and include phylogenetically widespread evidence of negligible aging. Protective phenotypes and life-history strategies further explain macroevolutionary patterns of aging. Analyzing ectothermic tetrapods in a comparative context enhances our understanding of the evolution of aging.
Publisher: CSIRO Publishing
Date: 16-12-2021
DOI: 10.1071/WR21057
Abstract: Abstract Context Detection probability is a key attribute influencing population-level wildlife estimates necessary for conservation inference. Increasingly, camera traps are used to monitor threatened reptile populations and communities. Komodo dragon (Varanus komodoensis) populations have been previously monitored using camera traps however, considerations for improving detection probability estimates for very low-density populations have not been well investigated. Aims Here we compare the effects of baited versus non-baited camera monitoring protocols to influence Komodo dragon detection and occupancy estimates alongside monitoring survey design and cost considerations for ongoing population monitoring within the Wae Wuul Nature Reserve on Flores Island, Indonesia. Methods Twenty-six camera monitoring stations (CMS) were deployed throughout the study area with a minimum of 400 m among CMS to achieve independent s ling units. Each CMS was randomly assigned as a baited or non-baited camera monitoring station and deployed for 6 or 30 daily s ling events. Key results Baited camera monitoring produced higher site occupancy estimates with reduced variance. Komodo dragon detection probability estimates were 0.15 ± 0.092–0.22 (95% CI), 0.01 ± 0.001–0.03, and 0.03 ± 0.01–0.04 for baited (6 daily survey s ling events), unbaited (6 daily survey s ling events) and long-unbaited (30 daily survey s ling events) s ling durations respectively. Additionally, the provision of baited lures at cameras had additional benefits for Komodo detection, survey design and s ling effort costs. Conclusions Our study indicated that baited cameras provide the most effective monitoring method to survey low-density Komodo dragon populations in protected areas on Flores. Implications We believe our monitoring approach now lends itself to evaluating population responses to ecological and anthropogenic factors, hence informing conservation efforts in this nature reserve.
Publisher: CSIRO Publishing
Date: 11-07-2022
DOI: 10.1071/WR22013
Abstract: Context Understanding both the short- and long-term consequences of live animal capture is desirable to limit potential data biases or compromise animal welfare. The short-term elevation of glucocorticoid hormones in animals is an expected short-term stress consequence of trapping and restraint experiences. However, because these hormones also influence behaviour and memory, they may provide a physiological basis through which in iduals vary in their recapture responses to subsequent trapping episodes. Aims This objective of this study was to evaluate the interplay among trapping method, corticosterone responsiveness and recapture likelihood in a lizard, the lace monitor (Varanus varius). The first aim compared how different capture methods and associated restraint durations influenced plasma corticosterone of lace monitors. The second aim evaluated the relationship between capture methodology, corticosterone response and annual recapture frequency. The third aim measured yearly estimates for the probability of lace monitor recapture. Methods Lace monitors were cage-trapped or noose-captured at 76 s ling sites across three annual s ling periods to measure capture experience, obtain blood s les and estimate recapture probabilities. Results As expected, an increased restraint time and exposure to different capture methods significantly influenced corticosterone concentrations in lace monitors. Lace monitor recapture rates were meagre, suggesting that irrespective of the capture method, restraint duration and corticosterone levels, any form of initial capture experience typically leads to long-lasting aversive behaviour. Conclusions Although plasma corticosterone concentrations may be tell-tale of a lace monitor’s duration to short-term capture and restraint, they were not associated with the recapture likelihood in subsequent trapping events. Implications Rapid and seemingly long-lasting trap aversion has apparent implications for the design of population monitoring programs used to study lace monitor population ecology.
Publisher: Springer Science and Business Media LLC
Date: 21-11-2022
Publisher: The Company of Biologists
Date: 2018
DOI: 10.1242/JEB.187930
Abstract: Animals use irruptive movement to avoid exposure to stochastic and pervasive environmental stressors that impact fitness. Beneficial irruptive movements transfer in iduals from high-stress areas (conferring low fitness) to alternate localities that may improve survival or reproduction. However, being stochastic, environmental stressors can limit an animal's preparatory capacity to enhance irruptive movement performance. Thus in iduals must rely on standing, or rapidly induced, physiological and behavioural responses. Rapid elevation of glucocorticoid hormones in response to environmental stressors are widely implicated in adjusting physiological and behaviour processes that could influence irruptive movement capacity. However, there remains little direct evidence to demonstrate that corticosterone regulated movement performance, nor the interaction with the pervasiveness of environmental stress, confers adaptive movement outcomes. Here we compared how movement-related survival of cane toads (Rhinella marina) varied with three different experimental corticosterone phenotypes across four increments of increasing environmental stressor pervasiveness (i.e. distance from water in a semi-arid landscape). Our results indicated that toads with phenotypically increased corticosterone levels attained higher movement-related survival compared to in iduals with control or lowered corticosterone phenotypes. However, the effects of corticosterone phenotypes on movement-related survival to some extent co-varied with stressor pervasiveness. Thus our study demonstrates how the interplay among an in idual's corticosterone phenotype and movement capacity alongside the arising costs of movement and the pervasiveness of the environmental stressor can affect survival outcomes.
Publisher: Springer Science and Business Media LLC
Date: 29-07-2019
DOI: 10.1038/S41559-019-0945-8
Abstract: Monitor lizards are unique among ectothermic reptiles in that they have high aerobic capacity and distinctive cardiovascular physiology resembling that of endothermic mammals. Here, we sequence the genome of the Komodo dragon Varanus komodoensis , the largest extant monitor lizard, and generate a high-resolution de novo chromosome-assigned genome assembly for V. komodoensis using a hybrid approach of long-range sequencing and single-molecule optical mapping. Comparing the genome of V. komodoensis with those of related species, we find evidence of positive selection in pathways related to energy metabolism, cardiovascular homoeostasis, and haemostasis. We also show species-specific expansions of a chemoreceptor gene family related to pheromone and kairomone sensing in V. komodoensis and other lizard lineages. Together, these evolutionary signatures of adaptation reveal the genetic underpinnings of the unique Komodo dragon sensory and cardiovascular systems, and suggest that selective pressure altered haemostasis genes to help Komodo dragons evade the anticoagulant effects of their own saliva. The Komodo dragon genome is an important resource for understanding the biology of monitor lizards and reptiles worldwide.
Publisher: Oxford University Press (OUP)
Date: 18-01-2019
Publisher: CSIRO Publishing
Date: 04-07-2022
DOI: 10.1071/WR22012
Abstract: Context Management actions that suppress introduced predator densities can benefit the population recovery of native species. Nevertheless, ensuring that predator management produces measurable population-level benefits can be influenced by multiple factors affecting species detection. Monitoring designs using multiple survey methods may perform better than increasing s ling effort with single-method protocols. Aims This study aimed to estimate in idual and cumulative detection probabilities and site occupancy estimates from the use of five different monitoring methods to survey a native mesopredator, the lace monitor (Varanus varius). Second, we assessed the effect of lethal red fox (Vulpes vulpes) baiting on lace monitor detection probabilities and site occupancy estimates collected from each monitoring method. Methods Multi-method s ling for Varanus varius occurred at 76 sites across lethal fox baited and non-baited habitats in East Gippsland, Victoria. Bayesian site occupancy models were used to estimate the effects of detection method and fox-baiting treatments on Varanus varius detection probability and site occupancy. Key results Method-specific detection probabilities (P = 0.00–0.12) and site occupancy estimates (Ψ = 0–0.53) varied considerably among methods, but combinations of multi-method monitoring improved lace monitor detection probability (P = 0.11–0.18) and site occupancy (Ψ = 0.87 ± [0.66–0.93]−0.91 ± [0.76–0.97] mean ± [95% credible intervals]) above any single method. However, there was extreme heterogeneity in the size and direction of the introduced predator baiting effect on method-specific lace monitor detection. Three methods (box traps and two different visual search surveys) all indicated lace monitor detection probabilities increased in fox-baited sites. However, sand pads reported a decrease in lace monitor detection at fox-baited sites, whereas pipe traps obtained no detections. Conclusions Combining detection data from all methods led to the inference of a positive fox-baiting effect, albeit with a smaller magnitude and better certainty than that estimated using a reduced method monitoring design, which had fewer detection data after excluding biased detection from sand pads. Implications Using a multi-method monitoring approach improved lace monitor detection and reduced s ling effort. However, depending on s ling methodology, the management effects on lace monitors can change.
Publisher: Wiley
Date: 15-09-2020
DOI: 10.1002/ECE3.6705
Publisher: Springer Science and Business Media LLC
Date: 18-08-2020
Publisher: Wiley
Date: 20-03-2020
DOI: 10.1111/GEB.13091
Publisher: Wiley
Date: 03-02-2020
DOI: 10.1002/ECY.2970
Abstract: Apex predators can have substantial and complex ecological roles in ecosystems. However, differences in species-specific traits, population densities, and interspecific interactions are likely to determine the strength of apex predators' roles. Here we report complementary studies examining how interactions between predator per capita metabolic rate and population density influenced the biomass, population energy use, and ecological effects of apex predators on their large mammalian prey. We first investigated how large mammal prey resources and field metabolic rates of terrestrial apex predators, comprising large mammals and the Komodo dragon (Varanus komodoensis), influenced their biomass densities and population energy use requirements. We next evaluated whether Komodo dragons, like apex mammalian predators, exerted top-down regulation of their large mammal prey. Comparison of results from field studies demonstrates that Komodo dragons attain mean population biomass densities that are 5.75-231.82 times higher than that of apex mammalian predator species and their guilds in Africa, Asia, and North America. The high biomass of Komodo dragons resulted in 1.96-108.12 times greater population energy use than that of apex mammalian predators. Nevertheless, substantial temporal and spatial variation in Komodo dragon population energy use did not regulate the population growth rates of either of two large mammal prey species, rusa deer (Rusa timorensis) and wild pig (Sus scrofa). We suggest that multiple processes weaken the capacity of Komodo dragons to regulate large mammal prey populations. For ex le, a low per capita metabolic rate requiring an infrequent and inactive hunting strategy (including scavenging), would minimize lethal and nonlethal impacts on prey populations. We conclude that Komodo dragons differ in their predatory role from, including not being the ecological analogs of, apex mammalian predators.
Publisher: Wiley
Date: 04-2020
DOI: 10.1002/BES2.1671
Publisher: Springer Science and Business Media LLC
Date: 21-07-2021
Location: Australia
No related grants have been discovered for Tim S. Jessop.