Urban Ecosystems

, Volume 17, Issue 2, pp 533–546

Squirrels in suburbia: influence of urbanisation on the occurrence and distribution of a common exotic mammal

  • Colin Bonnington
  • Kevin J. Gaston
  • Karl L. Evans
Article

Abstract

Urbanisation is widely considered to promote the establishment of non-native species, but there is limited empirical evidence of the ecological factors driving their responses. The grey squirrel Sciurus carolinensis (Gmelin 1788) is native to North America, but is widespread in the UK and is starting to spread across Europe. It is regarded as one of the world’s worst invasive animals due to its adverse impacts on native biodiversity. We use the non-native grey squirrel population in Sheffield (UK) as a case study to assess which factors limit its distribution and abundance in urban environments. In 2010 the city-wide population of adult squirrels peaked at an estimated 6539 in autumn (0.46 squirrels/ha), with maximum local densities of 8.29/ha. These densities appear to be slightly lower than those recorded in urban environments in the species’ native range. Grey squirrels occurred more frequently at urban sites with larger amounts of green-space in the surrounding region. Local habitat characteristics were, however, more powerful predictors of urban grey squirrel occurrence and abundance than regional availability of green space. Canopy cover, seed bearing trees and supplementary feeders, provided for garden birds, positively influenced grey squirrels. The potential for grey squirrels to connect city dwellers with nature thus appears to be highest in urban locations that have considerable capacity to support native biodiversity. The beneficial impacts of supplementary feeding on grey squirrel populations is notable given concerns that squirrels can adversely influence bird populations. These habitat associations also imply that grey squirrels typically respond negatively to urbanisation, which challenges arguments that urbanisation favours exotic species.

Keywords

Alien invasive species Gray squirrel Habitat structure Landscape ecology Non-native Urban avifauna 

Supplementary material

11252_2013_331_MOESM1_ESM.docx (32 kb)
Table S1(DOCX 32.3 kb)
11252_2013_331_MOESM2_ESM.docx (29 kb)
Table S2(DOCX 28 kb)
11252_2013_331_MOESM3_ESM.docx (32 kb)
Table S3(DOCX 32 kb)

References

  1. Baker PJ, Harris S (2007) Urban mammals: what does the future hold? An analysis of the factors affecting patterns of use of residential gardens in Great Britain. Mammal Rev 37:297–315Google Scholar
  2. Baum JK, Myers RA (2004) Shifting baselines and the decline of pelagic sharks in the Gulf of Mexico. Ecol Lett 7:135–145CrossRefGoogle Scholar
  3. Bayne E, Hobson K (2000) Relative use of contiguous and fragmented boreal forest by red squirrels (Tamiasciurus hudsonicus). Can J Zool 78:359–365CrossRefGoogle Scholar
  4. Bertolino S, Lurz PWW, Sanderson R, Rushton SP (2008) Predicting the spread of the American grey squirrel (Sciurus carolinensis) in Europe: a call for a co-ordinated European approach. Biol Conserv 141:2564–2575CrossRefGoogle Scholar
  5. Bivand R, Altman M, Anselin L, Assun R, Berke O, Bernat A, Blanchet G, Blankmeyer E, Carvalho M, Christensen B, Chun Y, Dormann C, Dray S, Halbersma R, Krainski E, Legendre P, Lewin-Koh N, Li H, Ma J, Millo G, Mueller W, Ono H, Peres-Neto P, Piras G, Reder M, Tiefelsdorf M, Yu D (2013) Spatial dependence: weighting schemes, statistics and models. Version 0.5–57. R Foundation for Statistical Computing, ViennaGoogle Scholar
  6. Bonnington C, Gaston KJ, Evans KL (2013) Assessing the potential for Grey Squirrels Sciurus carolinensis to compete with birds at supplementary feeding stations. Ibis doi:10.1111/ibi.12107
  7. Bowers MA, Breland B (1996) Foraging of gray squirrels on an urban–rural gradient: use of the GUD to assess anthropogenic impact. Appl Ecol 6:1135–1142CrossRefGoogle Scholar
  8. Bruemmer CM, Rushton SP, Gurnell J, Lurz PWW, Nettleton P, Sainsbury AW, Duff JP, Gilray J, McInnes CJ (2010) Epidemiology of squirrelpox virus in grey squirrels in the UK. Epidemiol Infect 138:941–950PubMedCrossRefGoogle Scholar
  9. Buckland ST, Anderson DR, Burnham KP, Laake JL, Borchers DL, Thomas L (2001) Introduction to distance sampling: estimating abundance of biological populations. Oxford University Press, OxfordGoogle Scholar
  10. Buckland ST, Anderson DR, Burnham KP, Laake JL, Borchers DL, Thomas L (eds) (2004) Advanced distance sampling. Oxford University Press, OxfordGoogle Scholar
  11. Clergeau P, Savard JL, Mennechez G, Falardeau G (1998) Bird abundance and diversity along an urban–rural gradient: a comparative study between two cities on different continents. Condor 100:413–425CrossRefGoogle Scholar
  12. Crooks KR, Suarez AV, Bolger DT (2004) Avian assemblages along a gradient of urbanization in a highly fragmented landscape. Biol Conserv 115:451–462CrossRefGoogle Scholar
  13. DEFRA (2001) Urban grey squirrels. Rural Development Service Technical Advice Note 09. http://www.snh.org.uk/ukredsquirrelgroup/PDFs/UKRSG%20urban%20gs.pdf Accessed 15/12/2009.
  14. Dobbie MJ, Welsh AH (2001) Modelling correlated zero inflated count data. Aust N Z J Stat 43:431–444CrossRefGoogle Scholar
  15. Dormann CF, McPherson JM, Araújo MB, Bivand R, Bolliger J, Carl G, Davies RG, Hirzel A, Jetz W et al (2007) Methods to account for spatial autocorrelation in the analysis of species distributional data: a review. Ecography 30:609–628CrossRefGoogle Scholar
  16. Dunn RR, Gavin MC, Sanchez MC, Solomon JN (2006) The pigeon paradox: dependence of global conservation on urban nature. Conserv Biol 20:1814–1816PubMedCrossRefGoogle Scholar
  17. Evans KL, Newson SE, Storch D, Greenwood JJD, Gaston KJ (2008) Spatial scale, abundance and the species-energy relationship in British birds. J Anim Ecol 77:395–405PubMedCrossRefGoogle Scholar
  18. Flyger VF (1970) Urban gray squirrels—problems, management, and comparisons with forest populations. T Northeast Fish Wildl 27:107–113Google Scholar
  19. Fuller RA, Warren PH, Armsworth PR, Barbosa O, Gaston KJ (2008) Garden bird feeding predicts the structure of urban avian assemblages. Divers Distrib 14:131–137CrossRefGoogle Scholar
  20. Gaston KJ, Warren PH, Thompson K, Smith RM (2005) Urban domestic gardens (IV): the extent of the resource and its associated features. Biodivers Conserv 14:3327–3349CrossRefGoogle Scholar
  21. Gorman OT, Roth RR (1989) Consequences of a temporally and spatially variable food supply for an unexploited gray squirrel (Sciurus carolinensis) population. Am Midl Nat 121:41–60CrossRefGoogle Scholar
  22. Gurnell J, Wauters LA, Lurz PWW, Tosi G (2004a) Alien species and interspecific competition: effects of introduced eastern grey squirrels on red squirrel population dynamics. J Anim Ecol 73:26–35CrossRefGoogle Scholar
  23. Gurnell J, Lurz PWW, Shirley MDF, Cartmel S, Garson PJ, Magris L, Steele J (2004b) Monitoring red squirrels Sciurus vulgaris and grey squirrels Sciurus carolinensis in Britain. Mammal Rev 34:51–74CrossRefGoogle Scholar
  24. Hadidian J, Manski D, Flyger V, Cox C, Hodge G (1987) Urban gray squirrel damage and population management: a case study. Third Eastern Wildlife Damage Control Conference. Paper 19. http://digitalcommons.unl.edu/ewdcc3/19 Accessed 23/09/2012.
  25. Harris S, Morris P, Wray S, Yalden D (1995) A review of British mammals: Population estimates and conservation status of British mammals other than cetaceans. JNCC, EnglandGoogle Scholar
  26. Harris S, Yalden DW (eds) (2008) Mammals of the British Isles, 4th edn. Mammal Society Handbook, SouthamptonGoogle Scholar
  27. Hein EW (1997) Demonstration of line transect methodologies to estimate urban grey squirrel density. Environ Manage 21:943–947PubMedCrossRefGoogle Scholar
  28. Hewson CM, Fuller RJ, Mayle B, Smith KW (2004) Possible impacts of Grey Squirrel on birds and other wildlife. Br Wildl 15:183–191Google Scholar
  29. Hurlbert AH, Haskell JP (2003) The effect of energy and seasonality on avian species richness and community composition. Amer Nat 161:83–97CrossRefGoogle Scholar
  30. Jokimäki J, Clergeau P, Kaisanlahti-Jokimäki ML (2002) Winter bird communities in urban habitats: a comparative study between central and northern Europe. J Biogeogr 29:69–79CrossRefGoogle Scholar
  31. Katcher A, Beck A (1987) Health and caring for living things. Anthrozoös 1:175–183CrossRefGoogle Scholar
  32. Kenward RE, Parish T (1986) Bark-stripping by grey squirrels. J Zool 210:473–481CrossRefGoogle Scholar
  33. Kenward RE, Holm JL (1993) On the replacement of the red squirrel in Britain: a phytotoxic explanation. P Roy Soc Lond B Bio 251:187–194CrossRefGoogle Scholar
  34. Koprowski JL (1994) Sciurus carolinensis. Mamm Species 480:1–9Google Scholar
  35. Lowe KA, Taylor CE, Mayor RE (2011) Do common mynas significantly compete with native birds in urban environments? J Ornithol 152:909–921CrossRefGoogle Scholar
  36. Lowe S, Browne M, Boudjelas S, De Poorter M (2000) 100 of the world’s worst invasive alien species a selection from the global invasive species database. Published by The Invasive Species Specialist Group (ISSG) a specialist group of the Species Survival Commission (SSC) of the World Conservation Union (IUCN), 12pp. First published as special lift-out in Aliens 12, December 2000. Updated and reprinted version: November 2004Google Scholar
  37. Manski DA, Van Druff LW, Flyger V (1981) Activities of gray squirrels and people in a downtown Washington, D.C. park: management implications. Trans North Amer Wildl Nat Res Conf 46:439–454Google Scholar
  38. Martin TG, Kuhnert PM, Mengersen K, Possingham HP (2005) The power of expert opinion in ecological models using Bayesian methods: impact of grazing on birds. Ecol Appl 15:266–280CrossRefGoogle Scholar
  39. Mazerolle MJ (2013) Model selection and multimodel inference based on (Q)AIC(c). Version 1.31. R Foundation for Statistical Computing, ViennaGoogle Scholar
  40. McPherson EG, Nilon C (1987) A habitat suitability index model for gray squirrel in an urban cemetery. Landsc J 6:21–30Google Scholar
  41. Menard S (1995) Applied logistic regression analysis: Sage University series on quantitative applications in the social sciences. Sage, Thousand OaksGoogle Scholar
  42. Møller H (1983) Foods and foraging behaviour of Red (Sciurus vulgaris) and Grey (Sciurus carolinensis) squirrels. Mammal Rev 13:81–98CrossRefGoogle Scholar
  43. Newson SE, Leech DI, Hewson CM, Crick HQP, Grice PV (2010a) Potential impact of grey squirrels Sciurus carolinensis on woodland bird populations in England. J Ornithol 151:211–218CrossRefGoogle Scholar
  44. Newson SE, Rexstad EA, Baillie SR, Buckland ST, Aebischer NJ (2010b) Population change of avian predators and grey squirrels in England: is there evidence for an impact on avian prey populations? J Appl Ecol 47:244–252CrossRefGoogle Scholar
  45. Office for National Statistics (2010) Population estimates for UK, England and Wales, Scotland and Northern Ireland, Mid-2010. http://www.ons.gov.uk/ons/publications/ Accessed 20 May 2011.
  46. Parker TS, Nilon CH (2008) Gray squirrel density, habitat suitability, and behavior in urban parks. Urban Ecosyst 11:243–255CrossRefGoogle Scholar
  47. Parker TS, Nilon CH (2012) Urban landscape characteristics correlated with the synurbization of wildlife. Landsc Urban Plan 106:316–325CrossRefGoogle Scholar
  48. Pautasso M, Gaston KJ (2006) A test of the mechanisms behind avian generalized individuals-area relationships. Global Ecol Biogeogr 15:303–317Google Scholar
  49. R Development Core Team (2011) R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, http://www.R-project.org Google Scholar
  50. Robb GN, McDonald RA, Chamberlain DE, Reynolds SJ, Harrison TJE, Bearhop S (2008) Winter feeding of birds increases productivity in the subsequent breeding season. Biol Lett 4:220–223PubMedCentralPubMedCrossRefGoogle Scholar
  51. Rotherham ID, Boardman S (2006) Who says the public only love red squirrels? ECOS 27:28–35Google Scholar
  52. Russell RE, Lehmkuhl JF, Buckland ST, Saab VA (2010) The short-term responses of red squirrels to prescribed burning in the interior Pacific. Northwest J Wildl Manage 74:12–17CrossRefGoogle Scholar
  53. Shorten M (1954) Squirrels. Collins (The New Naturalist series), LondonGoogle Scholar
  54. Sieving KE, Willson MF (1998) Nest predation and avian species diversity in north-western forest understory. Ecology 79:2391–2402CrossRefGoogle Scholar
  55. Smallwood KS, Schonewald C (1998) Study design and interpretation of mammalian carnivore density estimates. Oecologia 11:474–491CrossRefGoogle Scholar
  56. Thomas L, Laake JL, Rexstad E, Strindberg S, Marques FFC, Buckland ST, Borchers DL, Anderson DR, Burnham KP, Burt ML, Hedley SL, Pollard JH, Bishop JRB, Marques TA (2009) Distance 6.0. Release “6.0”. Research Unit for Wildlife Population Assessment, University of St. Andrews, UK, http://www.ruwpa.st-and.ac.uk/distance/ Google Scholar
  57. Tompkins DM, White AR, Boots M (2003) Ecological replacement of native red squirrels by invasive greys driven by disease. Ecol Lett 6:189–196CrossRefGoogle Scholar
  58. Wauters LA, Gurnell J (1999) The mechanism of replacement of red squirrels by grey squirrels: a test of the interference competition hypothesis. Ethology 105:1053–1071CrossRefGoogle Scholar
  59. Welsh AH, Cunningham RB, Donnelly CF, Lindenmayer DB (1996) Modelling the abundance of rare species: statistical models for counts with extra zeros. Ecol Model 88:297–308CrossRefGoogle Scholar
  60. Williamson RD (1983) Identification of urban habitat components which affect Eastern gray squirrel abundance. Urban Ecol 7:345–356CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  • Colin Bonnington
    • 1
    • 3
  • Kevin J. Gaston
    • 2
  • Karl L. Evans
    • 1
  1. 1.Department of Animal and Plant SciencesUniversity of SheffieldSheffieldUK
  2. 2.Environment and Sustainability InstituteUniversity of ExeterPenrynUK
  3. 3.URS, WestOneLeedsUK

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