Removing invasive rodents from islands has many ecological and social benefits. However, eradications fail more frequently on tropical than on temperate islands, and causes for these failures are not yet well understood. We addressed two major plausible reasons for eradication failure, testing whether actively reproducing females and pre-weaned pups may not consume bait during an experimental eradication of Rattus exulans on a tropical island (22 ha). We tested four hypotheses, namely that: (1) lactating female rats take longer than non-lactating conspecifics to consume rodent bait, (2) pre-weaned rats orphaned following bait application survive when their mother dies, (3) surviving pre-weaned rats are not exposed to rodent bait and (4) lactating females have different natural diets than non-lactating females. Our experimental eradication was successful, despite conditions that are typically associated with eradication failures: rat density was high (95% CI 65–153 rats/ha), rats were breeding and juveniles of all age-classes were present, land crabs were abundant, bait was only widely available for two nights after bait application (i.e. > 90% of bait disappeared within 36 h; bait was undetectable after 60 h), and alternative foods (e.g. coconut) were abundantly available. We found no evidence to support hypotheses that rat breeding and diet specialisation limit bait uptake because all rats consumed bait. Rat eradication was achieved with a relatively low bait application rate (32 kg/ha; 16 kg/ha per application) and a short (7 day) interval between the two bait applications. We recommend further experimental eradications targeting R. exulans and other invasive Rattus and Mus species on larger islands, but conclude that with comprehensive bait coverage eradications on tropical islands can be successful despite abundant natural food and a high density of reproductively active rats.
This is a preview of subscription content, access via your institution.
Buy single article
Instant access to the full article PDF.
Tax calculation will be finalised during checkout.
Subscribe to journal
Immediate online access to all issues from 2019. Subscription will auto renew annually.
Tax calculation will be finalised during checkout.
Amos W, Nichols HJ, Churchyard T, Brooke MdL (2016) Rat eradication comes within a whisker! A case study of a failed project from the South Pacific. R Soc Open Sci 3:160110. https://doi.org/10.1098/rsos.160110
Borchers DL, Efford MG (2008) Spatially explicit maximum likelihood methods for capture–recapture studies. Biometrics 64:377–385. https://doi.org/10.1111/j.1541-0420.2007.00927.x
Broome KG et al (2014) Rat eradication using aerial baiting: current agreed best practice used in New Zealand (Version 3.0). New Zealand Department of Conservation, Wellington
Burnham KP, Anderson DR (2004) Multimodel inference - understanding AIC and BIC in model selection. Sociol Methods Res 33:261–304. https://doi.org/10.1177/0049124104268644
Butaud J-F (2013) Actualisation de l’état des lieux floristique des différents motu de l’atoll de Tetiaroa en vue d’un classement en espace protégé. Ministère en charge de l’Environnement, Tahiti
Cromarty PL, Broome KG, Cox A, Empson RA, Hutchinson WM, McFadden I (2002) Eradication planning for invasive alien animal species on islands. The approach developed by the New Zealand Department of Conservation. In: Veitch CR, Clout MN (eds) Turning the tide: the eradication of invasive species. IUCN, Gland, pp 85–91
Efford MG (2019) secr: spatially explicit capture-recapture models. R package version 3.2.0. https://CRAN.R-project.org/package=secr. Accessed Apr 2019
Genet Q, Gaspar C (2017) Etude d’inventaire et de suivi des populations de crabes de cocotier (Birgus latro) sur l’atoll de Tetiaroa. Te Mana o Te Moana report, Tahiti
Griffiths R, Miller A, Climo G (2011) Addressing the impact of land crabs on rodent eradications on islands. Pac Conserv Biol 17:347–353. https://doi.org/10.1071/PC110347
Griffiths R, Brown D, Tershy B, Pitt WC, Cuthbert RJ, Wegmann A, Keitt B, Cranwell S, Howald G (2019) Successes and failures of rat eradications on tropical islands: a comparative review of eight recent projects. In: Veitch CR, Clout MN, Martin AR, Russell JC, West CJ (eds) Island Invasives: scaling up to meet the challenge. IUCN, Gland, pp 120–130
Harper GA, Bunbury N (2015) Invasive rats on tropical islands: their population biology and impacts on native species. Glob Ecol Conserv 3:607–627. https://doi.org/10.1016/j.gecco.2015.02.010
Holmes ND, Griffiths R, Pott M, Alifano A, Will D, Wegmann AS, Russell JC (2015) Factors associated with rodent eradication failure. Biol Conserv 185:8–16. https://doi.org/10.1016/j.biocon.2014.12.018
Holmes ND et al (2019) Globally important islands where eradicating invasive mammals will benefit highly threatened vertebrates. PLoS ONE 14:e0212128. https://doi.org/10.1371/journal.pone.0212128
Jones HP et al (2016) Invasive mammal eradication on islands results in substantial conservation gains. Proc Natl Acad Sci 113:4033–4038. https://doi.org/10.1073/pnas.1521179113
Keitt B et al (2015) Best practice guidelines for rat eradication on tropical islands. Biol Conserv 185:17–26. https://doi.org/10.1016/j.biocon.2014.10.014
Meyer J-Y (2018) Inventaire de la flore et mise en place d’un protocole de suivi de la vegetation sur le motu Reiono. Technical report. Délégation à la Recherche, Gouvernement de la Polynésie française, Papeete
Meyer J-Y (2019) Field trip report to Tetiaroa Atoll (22–24 August 2019): plant recruitment after rat eradication on motu Reiono. Technical report. Délégation à la Recherche, Gouvernement de la Polynésie française, Papeete
Meyer J-Y, Thibault J-C, Butaud J-F, Coote T, Florence J (2005) Sites de conservation importants et prioritaires en Polynésie française No.13 vol 13. Délégation à la Recherche, Gouvernement de la Polynésie française, Papeete
Oppel S et al (2019) Seasonal variation in movements and survival of invasive Pacific rats on sub-tropical Henderson Island: implications for eradication. In: Veitch CR, Clout MN, Martin AR, Russell JC, West CJ (eds) Island Invasives: scaling up to meet the challenge, vol 62. IUCN, Gland, pp 200–208
PII (2011) Resource kit for rodent and cat eradication. Pacific Invasives Initiative. http://rce.pacificinvasivesinitiative.org/. Accessed Apr 2019
Royle JA, Chandler RB, Sollmann R, Gardner B (2014) Spatial capture–recapture. Academic Press, Amsterdam. https://doi.org/10.1016/b978-0-12-405939-9.00005-0
Russell JC, Holmes ND (2015) Tropical island conservation: rat eradication for species recovery. Biol Conserv 185:1–7. https://doi.org/10.1016/j.biocon.2015.01.009
Russell J, Faulquier L, Tonione M (2011) Rat invasion of tetiaroa Atoll, French Polynesia. In: Veitch CR, Clout MN, Towns DR (eds) Island invasives: eradication and management. IUCN, Gland, pp 118–123
Russell JC, Binnie HR, Oh J, Anderson D, Samaniego-Herrera A (2017) Optimizing confirmation of invasive species eradication with rapid eradication assessment. J Appl Ecol 54:160–169. https://doi.org/10.1111/1365-2664.12753
Samaniego A, Anderson DP, Parkes JP, Aguirre-Muñoz A (2013) Rapid assessment of rat eradication after aerial baiting. J Appl Ecol 50:1415–1421. https://doi.org/10.1111/1365-2664.12147
Samaniego A, Clout MN, Aguirre-Muñoz A, Russell JC (2017) Rodent eradications as ecosystem experiments: a case study from the Mexican tropics. Biol Invasions 19:1761–1779. https://doi.org/10.1007/s10530-017-1388-2
Samaniego A et al (2018) Eradicating invasive rodents from wet and dry tropical islands in Mexico. Oryx 52:559–570. https://doi.org/10.1017/S0030605316001150
Samaniego A, Boudjelas S, Harper GA, Russell JC (2019) Assessing the critical role that land crabs play in tropical island rodent eradications and ecological restoration. In: Veitch CR, Clout MN, Martin AR, Russell JC, West CJ (eds) Island Invasives: scaling up to meet the challenge. IUCN, Gland, pp 209–222
Shiels AB, Flores CA, Khamsing A, Krushelnycky PD, Mosher SM, Drake DR (2013) Dietary niche differentiation among three species of invasive rodents (Rattus rattus, R. exulans, Mus musculus). Biol Invasions 15:1037–1048. https://doi.org/10.1007/s10530-012-0348-0
Towns DR, West CJ, Broome KG (2013) Purposes, outcomes and challenges of eradicating invasive mammals from New Zealand islands: an historical perspective. Wildl Res 40:94–107. https://doi.org/10.1071/wr12064
USFWS (2011) Palmyra atoll national wildlife refuge rat eradication project – final environmental impact statement. US Fish and Wildlife Service, Portland
Wolf CA, Young HS, Zilliacus KM, Wegmann AS, McKown M, Holmes ND et al (2018) Invasive rat eradication strongly impacts plant recruitment on a tropical atoll. PLoS ONE 13(7):e0200743. https://doi.org/10.1371/journal.pone.0200743
We thank SOP-Manu for kindly recruiting volunteers, all the volunteers for their hard work despite difficult conditions, Tetiaroa Society for local support, Te Mana o Te Moana for sharing results on their monthly coconut crab surveys and Carl Smith for disseminating our work through ABC/BBC science podcasts and articles. We also thank the Délégation à la Recherche de la Polynésie française and the Haut-Commissariat de la République en Polynésie française for providing the main author a research permit for French Polynesia. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the opinions of the funding institutions. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement.
This project was supported logistically and financially by Island Conservation, the Royal Society for the Protection of Birds, University of Auckland and Tetiaroa Society (Grant Number Tetiaroa Phase I). These funding sources, through their employees (AS, RG, NH, SO, BS, JR), were involved in study design, collection of data, analysis and interpretation of data, writing of the manuscript and decision to submit the article for publication. The project was also financially supported by National Fish and Wildlife Foundation and The David and Lucile Packard Foundation (Grant Number 59943). These funding sources were not involved in study design, collection of data, analysis and interpretation of data, writing of the manuscript or decision to submit the article for publication.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Electronic supplementary material
Below is the link to the electronic supplementary material.
About this article
Cite this article
Samaniego, A., Griffiths, R., Gronwald, M. et al. Risks posed by rat reproduction and diet to eradications on tropical islands. Biol Invasions 22, 1365–1378 (2020). https://doi.org/10.1007/s10530-019-02188-2
- Best practice
- Eradication failure
- Rat ecology
- Rattus exulans