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

Yusuke Fukuda, Craig Moritz, Nancy N. FitzSimmons, Namchul Jang, Grahame Webb, Garry Lindner, Hamish Campbell, Keith Christian, Steven Leeder, Sam Banks

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Abstract

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.

Original languageEnglish
Article numbere22525
Pages (from-to)1-18
Number of pages18
JournalJournal of Wildlife Management
Volume88
Issue number2
Early online date2023
DOIs
Publication statusPublished - Feb 2024

Bibliographical note

Funding Information:
The findings and views expressed are those of the authors and do not necessarily represent the views of Parks Australia, the Director of National Parks, the Australian Government, the Northern Territory Government, Queensland Government, or Western Australia Government. E. Anderson, R. Ani, V. de Araujo, L. Baroro, D. Barrow, D. Best, D. Bickford, J. Binaday, I. Buvanoka, T. Clancy, J. Cliff, G. Dally, B. Douma, S. Dwyer, G. Edwards, L. Engkamat, A. Fisher, C. Giru, M. Gorea, J. Gratten, G. Grigg, J. Gus, M. Gusmao, A. Halford, K. Hay, S. Heaton, S. Horner, C. B. How, I. Hunt, F. Hunter, A. Inus Surubai, F. Isi, D. Jacobson, J. Joe, R. Josh, D. Kenesi, R. Kerr, S. Kessner, A. Kipma, Y. Kok Yen, V. Kula, H. Kurniati, E. Lading, G. Laku, E. Langelet, D. Low Choy, R. Manalo, C. Manolis, J. McLachlan, C. Moore, S. Meti, J. Munro, M. Nagta, T. Nichols, Northern Territory Crocodile Farmer Association, H. Onuki, C. Palmer, G. Peckham, L. K. Peng, T. Pine, J. Pridham, O. Pugh, B. Rae, M. Read, A. Ruswan, K. Saalfeld, G. Saputra, H. Saul Suriwa, B. Seah, N. Sua, T. Sugiarto, Sumarmo, C. V. Sumber Murni, C. V. Surya Raya, N. Thuok, A. Underhill, P. Van Muoi, D. Wade, J. Weedon, J. Wilson, D. William, S. Woerle, J. Worthington Wilmer, F. Xavier, S. Yang, and K. Yesinduma provided field support or provided the genetic samples for the study. This study was funded by the Australian National University, Northern Territory Government, National Geographic Society (grant number 51‐16), Holsworth Wildlife Research Endowment (grant number HWRE2016R2027NEW), International Union for Conservation of Nature‐Species Survival Commission Crocodile Specialist Group Student Research Assistance Scheme (grant number 15/5), and ACT Herpetological Association. Open access publishing facilitated by Charles Darwin University, as part of the Wiley ‐ Charles Darwin University agreement via the Council of Australian University Librarians.

Funding Information:
The findings and views expressed are those of the authors and do not necessarily represent the views of Parks Australia, the Director of National Parks, the Australian Government, the Northern Territory Government, Queensland Government, or Western Australia Government. E. Anderson, R. Ani, V. de Araujo, L. Baroro, D. Barrow, D. Best, D. Bickford, J. Binaday, I. Buvanoka, T. Clancy, J. Cliff, G. Dally, B. Douma, S. Dwyer, G. Edwards, L. Engkamat, A. Fisher, C. Giru, M. Gorea, J. Gratten, G. Grigg, J. Gus, M. Gusmao, A. Halford, K. Hay, S. Heaton, S. Horner, C. B. How, I. Hunt, F. Hunter, A. Inus Surubai, F. Isi, D. Jacobson, J. Joe, R. Josh, D. Kenesi, R. Kerr, S. Kessner, A. Kipma, Y. Kok Yen, V. Kula, H. Kurniati, E. Lading, G. Laku, E. Langelet, D. Low Choy, R. Manalo, C. Manolis, J. McLachlan, C. Moore, S. Meti, J. Munro, M. Nagta, T. Nichols, Northern Territory Crocodile Farmer Association, H. Onuki, C. Palmer, G. Peckham, L. K. Peng, T. Pine, J. Pridham, O. Pugh, B. Rae, M. Read, A. Ruswan, K. Saalfeld, G. Saputra, H. Saul Suriwa, B. Seah, N. Sua, T. Sugiarto, Sumarmo, C. V. Sumber Murni, C. V. Surya Raya, N. Thuok, A. Underhill, P. Van Muoi, D. Wade, J. Weedon, J. Wilson, D. William, S. Woerle, J. Worthington Wilmer, F. Xavier, S. Yang, and K. Yesinduma provided field support or provided the genetic samples for the study. This study was funded by the Australian National University, Northern Territory Government, National Geographic Society (grant number 51-16), Holsworth Wildlife Research Endowment (grant number HWRE2016R2027NEW), International Union for Conservation of Nature-Species Survival Commission Crocodile Specialist Group Student Research Assistance Scheme (grant number 15/5), and ACT Herpetological Association. Open access publishing facilitated by Charles Darwin University, as part of the Wiley - Charles Darwin University agreement via the Council of Australian University Librarians.

Publisher Copyright:
© 2023 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.

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