Ontogenetic shifts in the nesting behaviour of female crocodiles

Baker, Cameron J.; Franklin, Craig E.; Campbell, Hamish A.; Irwin, Terri R.; Dwyer, Ross G.

doi:10.1007/s00442-019-04382-4

Cited by 9 publications

(9 citation statements)

References 55 publications

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“…While overland movement is more frequently reported for other crocodilian species such as Alligator mississippiensis (Woolard et al, 2004 ) and Crocodylus niloticus (Combrink, 2015 ), such movement is rare for C . porosus as shown by tracking of over 100 crocodiles in Australia (Baker et al, 2019 ; Fukuda et al, 2019 ). It should be noted that the open sea had a relatively high resistance (707.0) compared to the other estuarine or freshwater habitat types (marginal habitats whether breeding 125.7 or nonbreeding 122.7).…”

Section: Discussionmentioning

confidence: 99%

Environmental resistance and habitat quality influence dispersal of the saltwater crocodile

Fukuda

Christian

Campbell³

et al. 2021

Molecular Ecology

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Landscape genetics commonly focuses on the effects of environmental resistance on animal dispersal patterns, but there is an emerging focus on testing environmental effects on emigration and settlement choices. In this study, we used landscape genetics approaches to quantify dispersal patterns in the world's largest crocodilian, the saltwater crocodile (Crocodylus porosus), and demonstrated environmental influences on three processes that comprise dispersal: emigration, movement and settlement. We found that both environmental resistance and properties of the source and destination catchments (proportion of breeding habitat) were important factors influencing observed dispersal events. Our habitat quality variables related to hypotheses about resource competition and represented the ratio of breeding habitat (which limits carrying capacity), suggesting that competition for habitat influences emigration and settlement choices, together with the strong effect of environmental resistance to movement (where high‐quality habitat was associated with greatest environmental permeability). Approximately 42% of crocodiles were migrants from populations other than their sampling locations and some outstandingly productive populations had a much higher proportion of emigration rather than immigration. The distance most commonly travelled between source and destination was 150–200 km although a few travelled much longer distances, up to 600–700 km. Given the extensive dispersal range, individual catchments or hydrographic regions that combine two or three adjacent catchments are an appropriate scale for population management.

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Section: Discussionmentioning

confidence: 99%

Environmental resistance and habitat quality influence dispersal of the saltwater crocodile

Fukuda

Christian

Campbell³

et al. 2021

Molecular Ecology

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“…Crocodilians are a particularly understudied group, despite the role they play in wetland ecosystems as top generalist predators. To date, satellite tracking in crocodilians has only been carried out in the estuarine crocodile ( Crocodylus porosus , [46,47,57–59]). Given our observations during the first two sampling periods (D 1 : October 2013 and W 2 : May 2014), we hypothesized that there would be major differences in the black caiman’s movement patterns across seasons due to differences in prey availability and/or access to breeding and nesting areas (whose precise locations remain unknown).…”

Section: Resultsmentioning

confidence: 99%

The dark side of the black caiman: Shedding light on species dietary ecology and movement in Agami Pond, French Guiana

Caut

François²,

Bacques³

et al. 2019

PLoS ONE

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The black caiman is one of the largest neotropical top predators, which means that it could play a structuring role within swamp ecosystems. However, because of the difficulties inherent to studying black caimans, data are sorely lacking on many aspects of their general biology, natural history, and ecology, especially in French Guiana. We conducted a detailed study of the Agami Pond black caiman population using a multidisciplinary approach. The aim was to better understand the species’ dietary ecology and movements in the pond, and thus its functional role in pond system. We gathered natural history data, tracked caiman movements using satellite transmitters, and characterized feeding ecology via stable isotope analysis. Our study was carried out over three sampling periods and spanned both wet and dry seasons, which differ in their hydrological and ecological conditions. Our results show that black caiman abundance and age demographics differed between seasons in Agami Pond. In the dry season, Agami Pond is one of the only areas within the marsh to hold water. It thus contains large quantities of different fish species, which form the basis of the black caiman’s diet. Caiman body size, a proxy for age class, was around 1.5 meters. During the wet season, which corresponds to the breeding period for migratory birds (e.g., Agami herons), adult black caimans are present in Agami Pond. Adults were most abundant in the inundated forest. There, most individuals measured up to 2 meters. They also exhibited a particular “predatory” behavior near bird nests, preying on fallen chicks and adults. Juveniles and subadults were present during both seasons in the pond’s open waters. These behavioral observations were backed up by stable isotope analysis, which revealed ontogenetic variation in the caiman’s isotopic values. This isotopic variation reflected variation in diet that likely reduced intraspecific competition between adults and young. The telemetry and microchip data show that different age classes had different movement patterns and that seasonal variation in the pond may influence caiman prey availability and reproductive behavior. The new information gathered should help predict this species’ responses to potential ecosystem disturbance (e.g., water pollution, habitat destruction) and inform the development of an effective conservation plan that involves locals and wildlife officials.

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“…This size range includes males, not sexually mature, and females at or near maturity. They may well be dispersing from core habitats in search of new resources or territories (Campbell et al 2013;Baker et al 2019Baker et al , 2022Fukuda et al 2022b). This contrasts situations in QLD where densities are much lower than the NT (Read et al 2004, Brien et al 2017, Taplin et al 2020) and crocodiles display greater site fidelity with their dispersal generally limited to <50 km from the site of origin (Lloyd-Jones et al 2023).…”

Section: Discussionmentioning

confidence: 99%

“…We examined these relationships using generalized liner modeling (GLM) and set the distance from the inferred origin to Darwin Harbor as the response variable and TL, sex, and capture year as the explanatory variables. Because saltwater crocodiles rarely move long distances over land (Baker et al 2019, Fukuda et al 2019, we measured the distance to the harbor along the coastlines rather than overland, using the path distance function in ArcGIS 10.6.1 (Esri, Redlands, CA, USA) with a land cover surface derived from Fukuda et al (2022) being set as the input cost raster. Because the plot of the response variable against the explanatory variable TL showed a somewhat quadratic relationship, we made the variable a quadratic term in the models (and a linear term to compare).…”

Section: Population Assignment-fine Scalementioning

confidence: 99%

Natal origin and dispersal of problem saltwater crocodiles in the Darwin Harbor, Australia

Fukuda,

Moritz,

FitzSimmons

et al. 2023

J Wildl Manag

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Management programs that successfully recovered wild saltwater crocodile (Crocodylus porosus) populations in the Northern Territory of Australia did so with an expanding commitment to maintaining public safety. One aspect of the program is the ongoing removal of resident and immigrant crocodiles within Darwin Harbor (since 1979), the main urban center. We determined the likely sources of crocodiles caught as problem animals between 2015–2017 by comparing recently developed methods for population assignment. Depending on the assignment model used, we estimated that between 30% and 50% of crocodiles in Darwin Harbor originated from the Adelaide and Mary rivers, and the Kakadu region east of Darwin, and between 20% and 30% of crocodiles originated from the Finniss, Reynolds, and Daly rivers southwest of Darwin. Saltwater crocodiles occur at particularly high densities in these catchments. The remainder came from a mixture of different sources across the Northern Territory. The most common animals captured were immature (150–180 cm) males that have traveled 100–200 km. We did not identify any relationships between the distance from the inferred origin to Darwin Harbor and the size and sex of the crocodiles, or the year of capture. The targeted removal of crocodiles from specific sites such as Darwin Harbor, near where most people live, improves public safety in the highest risk areas, without compromising abundant source populations in most areas.

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Ontogenetic shifts in the nesting behaviour of female crocodiles

Cited by 9 publications

References 55 publications

Environmental resistance and habitat quality influence dispersal of the saltwater crocodile

Environmental resistance and habitat quality influence dispersal of the saltwater crocodile

The dark side of the black caiman: Shedding light on species dietary ecology and movement in Agami Pond, French Guiana

Natal origin and dispersal of problem saltwater crocodiles in the Darwin Harbor, Australia

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