Biological Invasions

, Volume 12, Issue 9, pp 3351–3361 | Cite as

Disruption of recruitment in two endemic palms on Lord Howe Island by invasive rats

  • Tony D. AuldEmail author
  • Ian Hutton
  • Mark K. J. Ooi
  • Andrew J. Denham
Original Paper


Invasive species may have negative impacts on many narrow range endemics and species restricted to oceanic islands. Predicting recent impacts of invasive species on long-lived trees is difficult because the presence of adult plants may mask population changes. We examined the impact of introduced black rats (Rattus rattus) on two palm species restricted to cloud forests and endemic to Lord Howe Island, a small oceanic island in the southern Pacific. We combined estimates of the standing size distribution of these palms with the proximal impacts of rats on fruit survival in areas baited to control rats and in unbaited areas. The size distribution of palms with trunks was comparable across baited and unbaited sites. Small juvenile palms lacking a trunk (<50 cm tall) were abundant in baited areas, but rare in unbaited sites for Lepidorrhachis mooreana, and rare or absent in 3 out of 4 unbaited Hedyscepe canterburyana sites. All ripe fruits were lost to rats in the small fruited L. mooreana. Fruit removal was widespread but less (20–54%) in H. canterburyana. Both palms showed evidence of a reduced capacity to maintain a juvenile bank of palms through regular recruitment as a consequence of over 90 years of rat impact. This will limit the ability of these species to take advantage of episodic canopy gaps. Baiting for rat control reduced fruit losses and resulted in the re-establishment of a juvenile palm bank. Conservation of both endemic palms necessitates control (or eradication) of rat populations on the unique cloud forest summits of the island.


Seed predation Lord Howe Island Australia Palms Black rat Rattus rattus 



We thank the Lord Howe Island Board for permission to carry out this study and for support in the use of a research facility for TA, MO and AD. William Baker made helpful comments on the manuscript.


  1. Allen RB, Lee WG, Rance BD (1994) Regeneration in indigenous forest after eradication of Norway rats, Breaksea Island, New Zealand. NZ J Bot 32:429–439Google Scholar
  2. Anderson A (2003) Investigating early settlement on Lord Howe Island. Aust Archaeol 57:98–102Google Scholar
  3. Angel A, Wanless RM, Cooper J (2009) Review of impacts of the introduced house mouse on islands in the Southern Ocean: are mice equivalent to rats? Biol Invas 11:1743–1754CrossRefGoogle Scholar
  4. Athens JS (2009) Rattus exulans and the catastrophic disappearance of Hawai’i’s native lowland forest. Biol Invas 11:1489–1501CrossRefGoogle Scholar
  5. Auld TD, Hutton I (2004) Conservation issues for the vascular flora of Lord Howe Island. Cunninghamia 8:490–500Google Scholar
  6. Baker WJ, Hutton I (2006) Lepidorrhachis. Palms 50:33–38Google Scholar
  7. Billing J (2000) The control of introduced Rattus rattus L. on Lord Howe Island. II. The status of warfarin resistance in rats and mice. Wildl Res 27:659–661CrossRefGoogle Scholar
  8. Billing J, Harden B (2000) Control of introduced Rattus rattus L. on Lord Howe Island. I. The response of mouse populations to warfarin bait used to control rats. Wildl Res 27:655–658CrossRefGoogle Scholar
  9. Blackburn TM, Cassey P, Duncan RP, Evans KL, Gaston KJ (2004) Avian extinction and mammalian introductions on oceanic islands. Science 305:1955–1958CrossRefPubMedGoogle Scholar
  10. Campbell DJ, Atkinson IAE (2002) Depression of tree recruitment by the Pacific rat (Rattus exulans Peale) on New Zealand’s northern offshore islands. Biol Conserv 107:19–35CrossRefGoogle Scholar
  11. Cheke AS (2006) Establishing extinction dates—the curious case of the Dodo Raphus cucullatus and the Red Hen Aphanapteryx bonasia. Ibis 148:155–158CrossRefGoogle Scholar
  12. Coote T, Loeve E (2003) From 61 species to five: endemic tree snails of the Society Islands fall prey to an ill-judged biological control programme. Oryx 37:91–96CrossRefGoogle Scholar
  13. Crisp MD, Lange RT (1976) Age structure, distribution and survival under grazing of the arid-zone shrub Acacia burkittii. Oikos 27:86–92CrossRefGoogle Scholar
  14. Davey A (1986) Plan of management. Lord Howe Island permanent park preserve. NSW National Parks and Wildlife Service, SydneyGoogle Scholar
  15. Delgado García JD (2002) Interaction between introduced rats and a frugivore bird–plant system in a relict island forest. J Nat Hist 36:1247–1258CrossRefGoogle Scholar
  16. Department of Environment and Climate Change NSW (2007) Lord Howe Island Biodiversity Management Plan. Department of Environment and Climate Change (NSW), SydneyGoogle Scholar
  17. Dransfield J, Uhl NW, Asmussen CB, Baker WJ, Harley MM, Lewis CE (2008) Genera Palmarum. The evolution and classification of palms. Kew Publishing, UKGoogle Scholar
  18. Duncan RP, Young JR (2000) Determinants of plant extinction and rarity 145 years after European settlement of Auckland, New Zealand. Ecology 81:3048–3061CrossRefGoogle Scholar
  19. Enright NJ (1985) Age, reproduction and biomass allocation in Rhopalostylis sapida (Nikau palm). Aust J Ecol 10:461–467CrossRefGoogle Scholar
  20. Enright NJ, Watson AD (1992) Population dynamics of the Nikau palm, Rhopalostylis sapida (Wendl et Drude), in a temperate forest remnant near Auckland, New Zealand. NZ J Bot 30:29–43Google Scholar
  21. Fox GA (2001) Failure-time analysis: Studying times to events and rates at which events occur. In: Scheiner SM, Gurevitch J (eds) Design and analysis of ecological experiments. Oxford University Press, Oxford, pp 235–266Google Scholar
  22. Harris R, Cassis G, Auld TD, Hutton I (2005) Patterns in floristic composition and structure in the mossy cloud forest of Mt Gower summit, Lord Howe Island. Pac Conserv Biol 11:246–256Google Scholar
  23. Hindwood KA (1940) The birds of Lord Howe Island. Emu 40:1–86Google Scholar
  24. Holdaway RN (1989) New Zealand’s pre-human avifauna and its vulnerability. NZ J Ecol 12:11–25Google Scholar
  25. Hunt TL (2007) Rethinking Easter Island’s ecological catastrophe. J Archaeol Sci 34:485–502CrossRefGoogle Scholar
  26. Hutton I (1986) Lord Howe Island. Conservation Press, Canberra, ACTGoogle Scholar
  27. Hutton I, Parkes JP, Sinclair ARE (2007) Reassembling island ecosystems: the case of Lord Howe Island. Anim Cons 10:22–29CrossRefGoogle Scholar
  28. Janzen DH (1986) Blurry catastrophes. Oikos 47:1–2CrossRefGoogle Scholar
  29. Lonsdale WM (1999) Global patterns of plant invasions and the concept of invasibility. Ecology 80:1522–1536CrossRefGoogle Scholar
  30. Mack MC, D’Antonio CM (1998) Impacts of biological invasions on disturbance regimes. Trends Ecol Evol 13:195–198CrossRefGoogle Scholar
  31. McAllan IAW, Curtis BR, Hutton I, Cooper RM (2004) The birds of Lord Howe Island Group: a review of records. Aust Field Ornithologist 21(Suppl):1–82Google Scholar
  32. McDougall I, Embleton BJ, Stone DB (1981) Origin and evolution of Lord Howe Island, southwest Pacific Ocean. J Geol Soc Aust 28:155–176Google Scholar
  33. Meyer JY, Butaud JF (2009) The impacts of rats on the endangered native flora of French Polynesia (Pacific Islands): drivers of plant extinction or coup de grâce species? Biol Invas 11:1569–1585CrossRefGoogle Scholar
  34. Moore HE (1966) Palm hunting around the world. IV Lord Howe Island. Principes 10:13–21Google Scholar
  35. Mueller-Dumbois D, Fosberg FR (1998) Vegetation of the tropical Pacific islands. Springer, New YorkGoogle Scholar
  36. Mulder CPH, Grant-Hoffman MN, Towns DR, Bellingham PJ, Wardle DA, Durrett MS, Fukami T, Bonner KI (2009) Direct and indirect effects of rats: does rat eradication restore ecosystem functioning of New Zealand seabird islands? Biol Invas 11:1671–1688CrossRefGoogle Scholar
  37. Ogden J (1985) An introduction to plant demography with special reference to New Zealand trees. NZ J Bot 23:751–772Google Scholar
  38. Pickard J (1980) The palm seed industry of Lord Howe Island. Principes 24:3–13Google Scholar
  39. Pickard J (1983a) Vegetation of Lord Howe Island. Cunninghamia 1:133–266Google Scholar
  40. Pickard J (1983b) Rare or threatened vascular plants of Lord Howe Island. Biol Conserv 27:125–139CrossRefGoogle Scholar
  41. Prebble M, Dowe JL (2008) The late Quaternary decline and extinction of palms on oceanic Pacific islands. Quatern Sci Rev 27:2546–2567CrossRefGoogle Scholar
  42. Priddel D, Carlile N, Humphrey M, Fellenberg S, Hiscox D (2003) Rediscovery of the ‘extinct’ Lord Howe Island stick-insect (Dryococelus australis (Montrouzier)) (Phasmatodea) and recommendations for its conservation. Biodiversity Conserv 12:1391–1403CrossRefGoogle Scholar
  43. Sakai AK, Wagner WL, Mehrhoff LA (2002) Patterns of endangerment in the Hawaiian flora. Syst Biol 51:276–302CrossRefPubMedGoogle Scholar
  44. Sarukhán J (1980) Demographic problems in tropical systems. In: Solbrig O (ed) Demography and evolution in plant populations. Blackwell Scientific Publications, Oxford, pp 161–188Google Scholar
  45. Silvertown JW (1982) Introduction to plant population ecology. Longman Press, LondonGoogle Scholar
  46. Soule ME (1990) The onslaught of alien species, and other challenges in the coming decades. Conserv Biol 4:233–239CrossRefGoogle Scholar
  47. Tomlinson PB (1979) Systematics and ecology of the Palmae. Annu Rev Ecol Syst 10:85–107CrossRefGoogle Scholar
  48. Towns DR (2009) Eradications as reverse invasions: lessons from Pacific rat (Rattus exulans) removals on New Zealand islands. Biol Invas 11:1719–1733CrossRefGoogle Scholar
  49. Towns DR, Atkinson IAE, Daugherty CH (2006) Have the harmful effects of introduced rats on islands been exaggerated? Biol Invas 8:863–891CrossRefGoogle Scholar
  50. Traveset A, Nogales M, Alcover JA, Delgado JD, López-Darias M, Godoy D, Igual JM, Bover P (2009) A review on the effects of alien rodents in the Balearic (Western Mediterranean Sea) and Canary Islands (Eastern Atlantic Ocean). Biol Invas 11:1653–1670CrossRefGoogle Scholar
  51. Trevino HS, Skibiel AL, Karels TJ, Dobson FS (2007) Threats to avifauna on oceanic islands. Conserv Biol 21:125–132CrossRefPubMedGoogle Scholar
  52. Underwood AJ (1997) Experiments in ecology. Their logical design and interpretation using analysis of variance. Cambridge University Press, CambridgeGoogle Scholar
  53. Walker BH, Stone L, Hendersen L, Verede M (1986) Size structure analysis of the dominant trees in a South African savannah. S Afr J Bot 52:397–402Google Scholar
  54. Wiles GJ, Bart J, Beck RE, Aguon CF (2003) Impacts of the brown tree snake: patterns of decline and species persistence in Guam’s avifauna. Conserv Biol 17:1350–1360CrossRefGoogle Scholar
  55. Zar JH (1974) Biostatistical analysis. Prentice-Hall Inc, NJGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  • Tony D. Auld
    • 1
    Email author
  • Ian Hutton
    • 2
  • Mark K. J. Ooi
    • 3
  • Andrew J. Denham
    • 1
  1. 1.Climate Change Science, Department of EnvironmentClimate Change and Water (NSW)HurstvilleAustralia
  2. 2.Lord Howe IslandAustralia
  3. 3.Department of Animal and Plant SciencesUniversity of SheffieldSheffieldUK

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