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In the land of giants: habitat use and selection of the Aldabra giant tortoise on Aldabra Atoll

  • R. WaltonEmail author
  • R. Baxter
  • N. Bunbury
  • D. Hansen
  • F. Fleischer-Dogley
  • S. Greenwood
  • G. Schaepman-Strub
Original Paper

Abstract

With habitat loss and fragmentation among the greatest threats to biodiversity, a better understanding of the habitat use of keystone species is critical in any conservation management strategy. Aldabra Atoll, in the Seychelles archipelago, has the largest population worldwide of giant tortoises. This endemic species (Aldabrachelys gigantea) could be vulnerable to habitat fragmentation and loss induced by climate change related reduction in rainfall. Here, we assess habitat use and selection by A. gigantea in its natural environment on Aldabra. We quantified the habitat areas of A. gigantea based on the first high-resolution terrestrial habitat map of Aldabra, produced for this purpose using satellite imagery. The resulting map was combined with 4 years of movement data to assess A. gigantea habitat use and selection at landscape and home range scales. Grassland or ‘tortoise turf’ habitat was most preferred by A. gigantea on Aldabra, at the landscape scale across seasons, followed by open mixed scrub. These two habitats cover only 30 km2 (19.2%) of the surface of the atoll (total area: 155.5 km2). At the home range scale, there was no significant preference shown and habitat was used randomly. Our results suggest that Aldabra’s grassland habitat, despite its small area, is of great importance to A. gigantea. Conservation management actions for A. gigantea on Aldabra and elsewhere should therefore focus on the protection and maintenance of this habitat.

Keywords

Habitat mapping Home range Megaherbivore Remote sensing Seychelles Western Indian Ocean 

Notes

Acknowledgements

Aldabra Atoll is managed by the Seychelles Islands Foundation (SIF). We thank SIF’s staff on Aldabra for persistently searching for the GPS-tagged tortoises in inhospitable terrain to download their GPS telemetry data. We are also thankful to the SIF Aldabra and Head Office staff for logistical and administrative support; Philip Haupt for the preparation of the satellite images and discussion; Heather Richards, Christina Quanz and Wilna Accouche for feedback on the results of the classification process; Justin Prosper, Lindsay Chong-Seng, Christina Quanz and Christian Fleischer for the collection of the habitat reference points in 2009 and Environment Trust Fund for funding the flights to Aldabra; Franz Kuemmeth from e-Obs for his generous support with the custom-built GPS tags; and to Global Environment Fund (project ID 3295) for funding the acquisition of the GeoEye satellite imagery, then made available by SIF and Philip Haupt at Rhodes University. We are grateful to the Zurich-Aldabra Research Platform based at the University of Zurich who provided financial and research support, the ‘Forschungskredit’ of the University of Zurich for financial support. G. Schaepman-Strub’s contribution was supported by the University of Zurich Research Priority Program on Global Change and Biodiversity (URPP GCB).

References

  1. Aebischer NJ, Robertson PA, Kenward RE (1993) Compositional analysis of habitat use from animal radio-tracked data. Ecology 74(5):1313–1325CrossRefGoogle Scholar
  2. Anadon JD, Gimenez A, Perez I, Martinez M, Esteve MA (2006) Habitat selection by the spur-thighed tortoise Testudo graeca in a multisuccessional landscape: implications for habitat management. Biodivers Conserv 15:2287–2299CrossRefGoogle Scholar
  3. Bailey DW, Gross JE, Laca EA, Rittenhouse LR, Coughenour MB, Swift DM, Sims PL (1996) Mechanisms that result in large herbivore grazing distribution patterns. J Range Manag 49:386–400CrossRefGoogle Scholar
  4. Bastille-Rousseau G, Gibbs JP, Campbell K, Yackulic CB, Blake S (2017) Ecosystem implications of conserving endemic versus eradicating introduced large herbivores in the Galapagos Archipelago. Biol Conserv 209:1-10.  https://doi.org/10.1016/j.biocon.2017.02.015 CrossRefGoogle Scholar
  5. Baxter R (2015) Movement and activity drivers of an ecosystem engineer: Aldabrachelys gigantea on Aldabra Atoll. MSc thesis, University of ZurichGoogle Scholar
  6. Bertram BCR (1979a) Homing by a leopard tortoise in the Serengeti. Afr J Ecol 17:245–247CrossRefGoogle Scholar
  7. Bertram BCR (1979b) Home range of a hingeback tortoise in the Serengeti. Afr J Ecol 17:241–244CrossRefGoogle Scholar
  8. Beyer HL, Haydon DT, Morales JM, Frair JL, Hebblewhite M, Mitchell M, Matthiopoulos J (2010) The interpretation of habitat preference metrics under use-availability designs. Philos Trans R Soc Lond B 365:2245–2254CrossRefGoogle Scholar
  9. Blake S, Yackulic CB, Cabrera F, Tapia W, Gibbs JP, Kummeth F, Wikelski M (2013) Vegetation dynamics drive segregation by body size in Galapagos tortoises migrating across altitudinal gradients. J Anim Ecol 82:310–321CrossRefGoogle Scholar
  10. Bourn D, Coe M (1978) The size, structure and distribution of the giant tortoise population of Aldabra. Philos Trans R Soc Lond B 282:139–175CrossRefGoogle Scholar
  11. Bourn D, Gibson C, Augeri D, Wilson CJ, Church J, Hay S (1999) The rise and fall of the Aldabran giant tortoise population. Proc R Soc Lond B 266:1091–1100CrossRefGoogle Scholar
  12. Cagnacci F, Boitani L, Powell RA, Boyce MS (2010) Animal ecology meets GPS-based radiotelemetry: a perfect storm of opportunities and challenges. Philos Trans R Soc Lond B 365:2157–2162CrossRefGoogle Scholar
  13. Calenge C (2006) The package adehabitat for the R software: a tool for the analysis of space and habitat use by animals. Ecol Model 197:516–519CrossRefGoogle Scholar
  14. Calenge C, Dray S, Royer-Carenzi M (2009) The concept of animals’trajectories from a data analysis perspective. Ecol Inform 4:34–41CrossRefGoogle Scholar
  15. Core Team R (2013) R: a language and environment for statistical computing. R Foundation for Statistical Computing, ViennaGoogle Scholar
  16. Digital Globe (2011) Product Order number: 1340507Google Scholar
  17. Digital Globe (2014) GeoEye-1 data sheet. https://www.digitalglobe.com/sites/default/files/DG_GeoEye1.pdf. Accessed 15 Jan 2015
  18. Duhec A, Balderson S, Doak N (2010) Climate data report for Aldabra Atoll: 1949–2009 (Seychelles Islands Foundation, unpublished report)Google Scholar
  19. EXILIS (2016) Calculate confusion matrices. http://www.exelisvis.com/docs/CalculatingConfusionMatrices.html [Accessed on: 08/09/2016]
  20. Falcón W, Baxter RP, Furrer S, Bauert M, Hatt J-M, Schaepman-Strub G, Ozgul A, Bunbury N, Clauss M, Hansen DM (2018) Patterns of activity and body temperature of Aldabra giant tortoises in relation to environmental temperature. Ecol Evol 8:2108–2121.  https://doi.org/10.1002/ece3.3766 Google Scholar
  21. Fosberg FR (1971) Preliminary survey of Aldabra vegetation. Philos Trans R Soc Lond B 260:215–227CrossRefGoogle Scholar
  22. Franks BR, Avery HW, Spotila J (2011) Home range and movement of desert tortoises Gopherus agassizii in the Mojave Desert of California, USA. Endanger Species Res 13:191–201CrossRefGoogle Scholar
  23. Froyd CA, Coffey EED, van der Knaap WO, van Leeuwen JFN, Tye A, Willis KJ (2014) The ecological consequences of megafaunal loss: giant tortoises and wetland biodiversity. Ecol Lett 17(2):144–154CrossRefGoogle Scholar
  24. Gaymer R (1968) The Indian Ocean giant tortoise Testudo gigantea on Aldabra. J Zool Lond 154:341–363CrossRefGoogle Scholar
  25. Getz WM, Fortmann-Roe S, Cross PC, Lyons AJ, Ryan SJ, Wilmers CC (2007) LoCoH: nonparametric kernel methods for constructing home ranges and utilization distributions. PLoS ONE 2(2):e207CrossRefGoogle Scholar
  26. Gibbs JP, Sterling EJ, Zabala FJ (2010) Giant tortoises as ecological Engineers: a long-term quasi-experiment in the Galapagos islands. Biotropica 42:208–214CrossRefGoogle Scholar
  27. Gibson CWD, Hamilton J (1983) Feeding ecology and seasonal movements of giant tortoises on Aldabra Atoll. Oecologia 56:84–92CrossRefGoogle Scholar
  28. Gibson CWD, Phillipson J (1983a) The vegetation of Aldabra Atoll: preliminary analysis and explanation of the vegetation map. Philos Trans R Soc Lond B 302:201–235CrossRefGoogle Scholar
  29. Gibson CWD, Phillipson J (1983b) The primary production of Aldabra Atoll, with reference to habitats used by giant tortoises. Philos Trans R Soc Lond B 302:167–199CrossRefGoogle Scholar
  30. Griffiths CJ, Jones CG, Hansen DM, Puttoo M, Tatayah RV, Muller CB, Harris S (2010) The use of extant non-indigenous tortoises as a restoration tool to replace extinct ecosystem engineers. Restor Ecol 18:1–7CrossRefGoogle Scholar
  31. Grubb P (1971) The growth, ecology and population structure of giant tortoises on Aldabra. Philos Trans R Soc Lond B 260:327–372CrossRefGoogle Scholar
  32. Hansen DM, Galetti M (2009) The forgotten megafauna. Science 324:42–43CrossRefGoogle Scholar
  33. Hansen DM, Donlan CJ, Griffiths CJ, Campbell KJ (2010) Ecological history and latent conservation potential: large and giant tortoises as a model for taxon substitutions. Ecography 33:272–284Google Scholar
  34. Haverkamp PJ, Shekeine J, de Jong R, Schaepman M, Turnbull LA, Baxter R, Hansen D, Bunbury N, Fleischer-Dogley F, Schaepman-Strub G (2017) Giant tortoise habitats under increasing drought conditions on Aldabra Atoll—ecological indicators to monitor rainfall anomalies and related vegetation activity. Ecol Indic 80:354–362CrossRefGoogle Scholar
  35. Hnatiuk RJ, Merton LFH (1979) A perspective of the vegetation of Aldabra. Phil Trans R Soc Lond B 286:79–84CrossRefGoogle Scholar
  36. Hnatiuk R, Woodell S, Bourn D (1976) Giant tortoise and vegetation interactions on Aldabra Atoll—Part 2: coastal. Biol Conserv 9:305–316CrossRefGoogle Scholar
  37. Horning N, Robinson JA, Sterling EJ, Turner W, Spector S (2010) Remote sensing for ecology and conservation. Oxford University Press, OxfordGoogle Scholar
  38. John F, Kostkan V (2009) Compositional analysis and GPS/GIS for study of habitat selection by the European beaver, Castor fiber in the middle reaches of the Morava River. Folia Zool 58:76–86Google Scholar
  39. Johnson D (1980) The comparison of usage and availability measurements for evaluating resource preference. Ecology 61:65–71CrossRefGoogle Scholar
  40. Jones HG, Vaughan RA (2010) Remote sensing of vegetation: principles, techniques and applications. Oxford University Press, OxfordGoogle Scholar
  41. Kazmaier RT, Hellgren EC, Ruthven DC (2001) Habitat selection by the texas tortoise in a managed thornscrub ecosystem. J Wildl Manag 65:653–660CrossRefGoogle Scholar
  42. Kerr JT, Ostrovsky M (2003) From space to species: ecological applications for remote sensing. Trends Ecol Evol 18:299–305CrossRefGoogle Scholar
  43. Krausman P (1999) Some basic principles of habitat use. Grazing behaviour of livestock and wildlife. Idaho For Wildl Range Exp Stn Bull 70:85–90Google Scholar
  44. Merton LFH, Bourn DM, Hnatiuk RJ (1976) Giant tortoise and vegetation interactions on Aldabra Atoll—part 1: inland. Biol Conserv 9:293–304CrossRefGoogle Scholar
  45. Moulherat S, Delmasa V, Slimanid T, Moudend EHE, Louzizid T, Lagardea F, Bonnet X (2014) How far can a tortoise walk in open habitat before overheating? Implications for conservation. J Nat Conserv 22:186–192CrossRefGoogle Scholar
  46. Pendleton GW, Titus K, DeGayner E, Flatten CJ, Lowell RE (1998) Compositional analysis and GIS for study of habitat selection by Goshawks in southeast Alaska. J Agric Biol Environ Stat 3:280–295CrossRefGoogle Scholar
  47. Rozylowicz L, Popescu VD (2012) Habitat selection and movement ecology of eastern Hermann’s tortoises in a rural Romanian landscape. Eur J Wildl Res 59:47–55CrossRefGoogle Scholar
  48. Rugiero L, Luiselli L (2006) Ecological modelling of habitat use and the annual activity patterns in an urban population of the tortoise, Testudo hermanni. Ital J Zool 73:219–225CrossRefGoogle Scholar
  49. Rutter S (2007) The integration of GPS, vegetation mapping and GIS in ecological and behavioural studies. Rev Bras Zoo 36:63–70CrossRefGoogle Scholar
  50. Shekeine J, Turnbull LA, Cherubini P, de Jong R, Baxter R, Hansen D, Bunbury N, Fleischer-Dogley F, Schaepman-Strub G (2015) Primary productivity and its correlation with rainfall on Aldabra Atoll. Biogeosci Discuss 12:981–1013CrossRefGoogle Scholar
  51. Tso B, Mather PM (2009) Classification methods for remotely sensed data, 2nd edn. CRC Press, London/New YorkGoogle Scholar
  52. Turnbull LA, Ozgul A, Accouche W, Baxter R, Chong-Seng L, Currie JC, Doak N, Hansen DM, Pistorius P, Richards H, van de Crommenacker J, von Brandis R, Fleischer-Dogley F, Bunbury N (2015) Persistence of distinctive morphotypes in the native range of the CITES-listed Aldabra giant tortoise. Ecol Evol 5:5499–5508CrossRefGoogle Scholar
  53. Wall J (2014) Movement ecology tools for ArcGIS® (ArcMET) version: 10.2.2 v3 user manual. www.movementecology.net. Accessed 11 Feb 2015
  54. Walter DW, Fischer JW, Baruch-Mordo S, Vercauteren KC (2011) What is the proper method to delineate home range of an animal using today’s advanced GPS telemetry systems: the initial step. USDA National Wildlife Research Center—Staff Publications, Colorado, p 1375Google Scholar
  55. Zylstra ER, Steidl RJ (2009) Habitat use by Sonoran desert tortoises. J Wildl Manag 73:747–754CrossRefGoogle Scholar

Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  • R. Walton
    • 1
    • 2
    Email author
  • R. Baxter
    • 3
  • N. Bunbury
    • 1
    • 4
  • D. Hansen
    • 3
  • F. Fleischer-Dogley
    • 1
  • S. Greenwood
    • 5
  • G. Schaepman-Strub
    • 3
  1. 1.Seychelles Islands FoundationMahéSeychelles
  2. 2.James Michel Blue Economy Research InstituteUniversity of SeychellesMahéSeychelles
  3. 3.Department of Evolutionary Biology and Environmental StudiesUniversity of ZurichZurichSwitzerland
  4. 4.Centre for Ecology and ConservationUniversity of Exeter, Cornwall CampusPenrynUK
  5. 5.Biomedical Teaching Organisation, Biomedical Sciences, Teviot PlaceUniversity of EdinburghEdinburghUK

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