Environmental resistance and habitat quality influence dispersal of the saltwater crocodile

Fukuda, Yusuke; Christian, Keith A.; Campbell, Hamish A.; Moritz, Craig; Webb, Grahame J. W.; Jang, Namchul; Lindner, Gary; Banks, Sam C.

doi:10.1111/mec.16310

Cited by 15 publications

(22 citation statements)

References 97 publications

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“…Estuarine crocodiles are highly mobile individuals and regularly travel over 400 km in a few weeks, connecting populations across broad regions [33,34]. In the study region, individuals regularly travel between coastal, estuarine and freshwater environments [35]. Therefore, our SIA results present a broad picture of the isotopic landscape of the estuarine crocodile population over two different periods.…”

Section: Resultsmentioning

confidence: 99%

Dietary shifts may underpin the recovery of a large carnivore population

et al. 2022

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Supporting the recovery of large carnivores is a popular yet challenging endeavour. Estuarine crocodiles in Australia are a large carnivore conservation success story, with the population having extensively recovered from past heavy exploitation. Here, we explored if dietary changes had accompanied this large population recovery by comparing the isotopes δ 13 C and δ 15 N in bones of crocodiles sampled 40 to 55 years ago (small population) with bones from contemporary individuals (large population). We found that δ 13 C and δ 15 N values were significantly lower in contemporary crocodiles than in the historical cohort, inferring a shift in prey preference away from marine and into terrestrial food webs. We propose that an increase in intraspecific competition within the recovering crocodile population, alongside an increased abundance of feral ungulates occupying the floodplains, may have resulted in the crocodile population shifting to feed predominantly upon terrestrial food sources. The number of feral pigs consumed to sustain and grow crocodile biomass may help suppress pig population growth and increase the flow of terrestrially derived nutrients into aquatic ecosystems. The study highlights the significance of prey availability in contributing to large carnivore population recovery.

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Section: Resultsmentioning

confidence: 99%

Dietary shifts may underpin the recovery of a large carnivore population

et al. 2022

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“…The cost distance calculated from the transformed resistance surfaces was used as a predictor to find the best model that explains the genetic distance. A linear mixed-effects model with a maximum likelihood population effect (MLPE) was fitted to the data [90, 91]. We optimised single surfaces of environmental variables and used the log-likelihood as the objective function for the MLPE model.…”

Section: Methodsmentioning

confidence: 99%

Synthesising environmental, epidemiological, and genetic data to assist decision making for onchocerciasis elimination

Shrestha

McCulloch

Chisholm

et al. 2023

Preprint

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Background: Population genetics is crucial for understanding the transmission dynamics of diseases like onchocerciasis. Landscape genetics identifies the ecological features that impact genetic variation between sampling sites. Here, we have used a landscape genetics framework to understand the relationship between environmental features and gene flow of the filarial parasiteOnchocerca volvulusand of its intermediate host and vector, blackflies in the genusSimulium. We analysed samples from the ecological transition region separating the savannah and forest ecological regions of Ghana, where the transmission ofO. volvulushas persisted despite almost half a century of onchocerciasis control efforts. Methods: We generated a baseline microfilarial prevalence map from the point estimates of pre-ivermectin microfilarial prevalence from 47 locations in the study area. We analysed mitochondrial data from 164 parasites and 93 blackflies collected from 15 communities and four breeding sites, respectively. We estimated population genetic diversity and identified correlations with environmental variables. Finally, we compared baseline prevalence maps to movement suitability maps that were based on significant environmental variables. Results: We found that the resistance surfaces derived from elevation (r = 0.793, p = 0.005) and soil moisture (r = 0.507, p = 0.002) were significantly associated with genetic distance between parasite sampling locations. Similarly, for the vector populations, the resistance surfaces derived from soil moisture (r = 0.788, p = 0.0417) and precipitation (r = 0.835, p = 0.0417) were significant. The correlation between the baseline parasite prevalence map and the parasite resistance surface map was stronger than the correlation between baseline prevalence and the vector resistance surface map. The central parts of the transition region which were conducive for both the parasite and the vector gene flow were most strongly associated with high baseline onchocerciasis prevalence. Conclusions: We present a framework for incorporating environmental, genetic, and prevalence data for identifying when ecological conditions are favourable for onchocerciasis transmission between communities. We identified areas with higher suitability for parasite and vector gene flow, which ultimately might help us gain deeper insights into defining transmission zones for onchocerciasis. Furthermore, this framework is translatable to other onchocerciasis endemic areas and to other vector-borne diseases.

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“…Studies on saltwater crocodile movement patterns have largely been carried out in Australia (Campbell et al, 2010;Fukuda et al, 2019;Fukuda et al, 2022). Although long-distance movements of individuals out of their typical distribution range have been recorded (e.g., Marshall Islands; Manolis, 2005;Spennemann, 2020), these appear to be the exception rather than the rule.…”

Section: Crocodyliansmentioning

confidence: 99%

Widespread Use of Migratory Megafauna for Aquatic Wild Meat in the Tropics and Subtropics

Ingram

Prideaux²,

Hodgins³

et al. 2022

Front. Mar. Sci.

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Wild animals are captured or taken opportunistically, and the meat, body parts, and/or eggs are consumed for local subsistence or used for traditional purposes to some extent across most of the world, particularly in the tropics and subtropics. The consumption of aquatic animals is widespread, in some places has been sustained for millennia, and can be an important source of nutrition, income, and cultural identity to communities. Yet, economic opportunities to exploit wildlife at higher levels have led to unsustainable exploitation of some species. In the literature, there has been limited focus on the exploitation of aquatic non-fish animals for food and other purposes. Understanding the scope and potential threat of aquatic wild meat exploitation is an important first step toward appropriate inclusion on the international policy and conservation management agenda. Here, we conduct a review of the literature, and present an overview of the contemporary use of aquatic megafauna (cetaceans, sirenians, chelonians, and crocodylians) in the global tropics and subtropics, for species listed on the Appendices of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). We find that consumption of aquatic megafauna is widespread in coastal regions, although to varying degrees, and that some species are likely to be at risk from overexploitation, particularly riverine megafauna. Finally, we provide recommendations for CMS in the context of the mandate of the Aquatic Wild Meat Working Group.

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Environmental resistance and habitat quality influence dispersal of the saltwater crocodile

Cited by 15 publications

References 97 publications

Dietary shifts may underpin the recovery of a large carnivore population

Dietary shifts may underpin the recovery of a large carnivore population

Synthesising environmental, epidemiological, and genetic data to assist decision making for onchocerciasis elimination

Widespread Use of Migratory Megafauna for Aquatic Wild Meat in the Tropics and Subtropics

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