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Seasonal variation in movements and survival of invasive Pacific rats on sub-tropical Henderson Island: implications for eradication


Oppel, S and McClelland, GTW and Lavers, JL and Churchyard, T and Donaldson, A and Duffield, N and Havery, S and Kelly, J and Proud, T and Russell, JC and Bond, AL, Seasonal variation in movements and survival of invasive Pacific rats on sub-tropical Henderson Island: implications for eradication, Island invasives: scaling up to meet the challenge: Proceedings of the International Conference on Island Invasives, 10-14 June 2017, Dundee, Scotland, pp. 200-208. ISBN 9782831719627 (2019) [Refereed Conference Paper]

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DOI: doi:10.2305/IUCN.CH.2019.SSC-OP.62.en


Invasive rodents are successful colonists of many ecosystems around the world, and can have very flexible foraging behaviours that lead to differences in spatial ranges and seasonal demography among individuals and islands. Understanding such spatial and temporal information is critical to plan rodent eradication operations, and a detailed examination of an island’s rat population can expand our knowledge about possible variation in behaviour and demography of invasive rats in general. Here we investigated the movements and survival of Pacific rats (Rattus exulans) over five months on sub-tropical Henderson Island in the South Pacific Ocean four years after a failed eradication operation. We estimated movement distances, home range sizes and monthly survival using a spatially-explicit Cormack-Jolly-Seber model and examined how movement and survival varied over time. We captured and marked 810 rats and found a median maximum distance between capture locations of 39 ± 25 m (0–107 m) in a coastal coconut grove and 61 ± 127 m (0–1,023 m) on the inland coral plateau. Estimated home range radii of Pacific rats on the coral plateau varied between ‘territorial’ (median: 134 m; 95% credible interval 106–165 m) and ‘roaming’ rats (median: 778 m; 290–1,633 m). The proportion of rats belonging to the ‘roaming’ movement type varied from 1% in early June to 23% in October. There was no evidence to suggest that rats on Henderson in 2015 had home ranges that would limit their ability to encounter bait, making it unlikely that limited movement contributed to the eradication failure if the pattern we found in 2015 is consistent across years. We found a temporal pattern in monthly survival probability, with monthly survival probabilities of 0.352 (0.081–0.737) in late July and 0.950 (0.846–0.987) in late August. If seasonal variation in survival probability is indicative of resource limitations and consistent across years, an eradication operation in late July would likely have the greatest probability of success.

Item Details

Item Type:Refereed Conference Paper
Keywords:invasive species, island conservation, eradication, rodents, home range, introduced species, island restoration, Pitcairn Islands, Rattus exulans
Research Division:Environmental Sciences
Research Group:Environmental management
Research Field:Conservation and biodiversity
Objective Division:Environmental Management
Objective Group:Marine systems and management
Objective Field:Control of pests, diseases and exotic species in marine environments
UTAS Author:Lavers, JL (Dr Jennifer Lavers)
ID Code:131231
Year Published:2019
Deposited By:Ecology and Biodiversity
Deposited On:2019-03-07
Last Modified:2020-03-17
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