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Wildlife Research Wildlife Research Society
Ecology, management and conservation in natural and modified habitats
RESEARCH ARTICLE

Soft-release versus hard-release for reintroduction of an endangered species: an experimental comparison using eastern barred bandicoots (Perameles gunnii)

Jasmine de Milliano A B F , Julian Di Stefano C , Peter Courtney B , Peter Temple-Smith A B D and Graeme Coulson A E
+ Author Affiliations
- Author Affiliations

A School of BioSciences, The University of Melbourne, Vic. 3010, Australia.

B Zoos Victoria, Elliot Avenue, Parkville, Vic. 3052, Australia.

C School of Ecosystem and Forest Sciences, The University of Melbourne, Creswick, Vic. 3363, Australia.

D Current address: Department of Obstetrics and Gynaecology, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, Vic. 3168, Australia.

E Macropus Consulting, 105 Canning Street, Carlton, Vic. 3053, Australia.

F Corresponding author. Current address: Zoos Victoria, Elliot Avenue, Parkville, Vic 3052, Australia. Email: jdemilliano@zoo.org.au

Wildlife Research 43(1) 1-12 https://doi.org/10.1071/WR14257
Submitted: 17 December 2014  Accepted: 23 November 2015   Published: 11 March 2016

Abstract

Context: Reintroduction is a popular tool for conserving endangered species, yet many attempts fail. Soft-release measures, including acclimatisation, have been used for many species around the world, based on the reasoning that gradual and supported reintroductions should improve the success of animals released into an unfamiliar wild environment. However, experimental testing of soft-release methods is rare.

Aims: To experimentally test the effect of a soft-release method versus a hard-release method on the initial reintroduction success of the eastern barred bandicoot (Perameles gunnii).

Methods: We released 12 captive-bred eastern barred bandicoots into a predator-proof reserve using two methods: soft-release (7 days of on-site acclimatisation with supplementary food before release) and hard-release (no acclimatisation and no supplementary food). We monitored the bandicoots intensively via radio-tracking and live-trapping for 4 weeks after release. Compared with hard-release bandicoots, we predicted that soft-release bandicoots would have (1) reduced movement (first night dispersal, site fidelity and activity range), (2) more directed patterns of habitat selection, (3) improved bodyweights and (4) improved survival.

Key results: There was no detectable difference in habitat selection, overall weight change and survival between the soft-release and hard-release groups. There was moderate evidence that, compared with the hard-release group, soft-release bandicoots moved less, demonstrated lower individual variation in all measures of movement, and lost weight more gradually after release. In most cases, effect sizes were moderate to large but had large standard errors owing to both small sample size and high variance. Consequently, statistical testing failed to detect significant differences at the 5% level.

Conclusions: Despite evidence that the release method influenced some of the monitored behaviours, soft-release did not confer a consistent and substantive advantage for captive-bred eastern barred bandicoots at our site. We conclude that soft-release is unlikely to improve overall reintroduction success for this species at fenced predator-free sites.

Implications: The present study suggests that the preferred option for reintroductions of eastern barred bandicoots to fenced sites is a hard-release, information that is now being used to guide reintroductions of this species. Similar experiments should be undertaken to improve reintroduction practice for other endangered species.

Additional keywords: acclimatisation, activity range, captive-bred, dispersal, delayed release, establishment phase, habitat selection, movement, site fidelity, success, supplementary food, survival, weight loss.


References

Aebischer, N. J., Robertson, P. A., and Kenward, R. E. (1993). Compositional analysis of habitat use from animal radio-tracking data. Ecology 74, 1313–1325.
Compositional analysis of habitat use from animal radio-tracking data.Crossref | GoogleScholarGoogle Scholar |

Armstrong, D. P., and Seddon, P. J. (2008). Directions in reintroduction biology. Trends in Ecology & Evolution 23, 20–25.
Directions in reintroduction biology.Crossref | GoogleScholarGoogle Scholar |

Barton, K. (2014). ‘MuMIn: Multi-model Inference. R Package Version 1.10.5.’ Available at http://CRAN.R-project.org/package=MuMIn [Verified 30 October 2015]

Beck, B. B., Rapaport, L. G., Stanley Price, M. R., and Wilson, A. C. (1994). Reintroduction of captive-born animals. In ‘Creative Conservation: Interactive Management of Wild and Captive Animals’. (Eds P. J. S. Olney, G. M. Mace and A. T. C. Feistner.) pp. 265–296. (Chapman & Hall: London.)

Bester, A. J., and Rusten, K. (2009). Trial translocation of the numbat (Myrmecobius fasciatus) into arid Australia. Australian Mammalogy 31, 9–16.
Trial translocation of the numbat (Myrmecobius fasciatus) into arid Australia.Crossref | GoogleScholarGoogle Scholar |

Bright, P. W., and Morris, P. A. (1994). Animal translocation for conservation: performance of dormice in relation to release methods, origin and season. Journal of Applied Ecology 31, 699–708.
Animal translocation for conservation: performance of dormice in relation to release methods, origin and season.Crossref | GoogleScholarGoogle Scholar |

Brown, C., and Day, R. L. (2002). The future of stock enhancements: lessons for hatchery practice from conservation biology. Fish and Fisheries 3, 79–94.
The future of stock enhancements: lessons for hatchery practice from conservation biology.Crossref | GoogleScholarGoogle Scholar |

Brown, P. B., Holdsworth, M. C., and Rounsevell, D. E. (1995). Captive breeding and release as a means of increasing the orange-bellied parrot population in the wild. In ‘Reintroduction Biology of Australian and New Zealand Fauna’. (Ed. M. Serena.) pp. 135-141. (Surrey Beatty: Sydney.)

Carbyn, L. N., Armbuster, H. J., and Mamo, C. (1994). The swift fox reintroduction program in Canada from 1983 to 1992. In ‘Restoration of Endangered Species: Conceptual Issues, Planning and Implementation’. (Eds M. L. Bowles and C. J. Whelan.) pp. 247–271. (Cambridge University Press: Cambridge, UK.)

Castro, I., Alley, J. C., Empson, R. A., and Minot, E. O. (1995). Translocation of hihi or stitchbird Notiomystis cincta to Kapiti Island, New Zealand: transfer techniques and comparison of release strategies. In ‘Reintroduction Biology of Australian and New Zealand Fauna’. (Ed. M. Serena.) pp. 113–120. (Surrey, Beatty: Sydney.)

Clarke, R. H., Boulton, R. L., and Clarke, M. F. (2002). Translocation of the socially complex black-eared miner Manorina melanotis: a trial using hard and soft techniques. Pacific Conservation Biology 8, 223–234.

Davis, M. H. (1983). Post-release movements of introduced marten. The Journal of Wildlife Management 47, 59–66.
Post-release movements of introduced marten.Crossref | GoogleScholarGoogle Scholar |

Delroy, L. B., Earl, J., Radbone, I., Robsion, A. C., and Hewett, M. (1986). The breeding and re-establishment of the brush-tailed bettong, Bettongia penicillata, in South Australia. Australian Wildlife Research 13, 387–396.
The breeding and re-establishment of the brush-tailed bettong, Bettongia penicillata, in South Australia.Crossref | GoogleScholarGoogle Scholar |

Dickens, M. J., Delehanty, D. J., and Romero, L. M. (2010). Stress: an inevitable component of animal translocation. Biological Conservation 143, 1329–1341.
Stress: an inevitable component of animal translocation.Crossref | GoogleScholarGoogle Scholar |

DSE (2009). ‘Action Statement No. 4 for the Eastern Barred Bandicoot (Mainland).’ Prepared under section 19 of the Flora and Fauna Guarantee Act 1988. (The State of Victoria Government Department of Sustainability and Environment: Melbourne.)

Dufty, A. (1991). Some population characteristics of Perameles gunnii in Victoria. Wildlife Research 18, 355–366.
Some population characteristics of Perameles gunnii in Victoria.Crossref | GoogleScholarGoogle Scholar |

Dufty, A. (1994a). Population demography of the eastern barred bandicoot (Perameles gunnii) at Hamilton, Victoria. Wildlife Research 21, 445–457.
Population demography of the eastern barred bandicoot (Perameles gunnii) at Hamilton, Victoria.Crossref | GoogleScholarGoogle Scholar |

Dufty, A. C. (1994b). Habitat and spatial requirements of the eastern barred bandicoot at Hamilton, Victoria. Wildlife Research 21, 459–472.
Habitat and spatial requirements of the eastern barred bandicoot at Hamilton, Victoria.Crossref | GoogleScholarGoogle Scholar |

Dufty, A. C. (1995). The growth and development of the eastern barred bandicoot Perameles gunnii in Victoria. Victorian Naturalist 112, 79–85.

Dufty, A., Seebeck, J., McKay, J., and Watson, A. (1995). Reintroduction of the eastern barred bandicoot Perameles gunnii at Gellibrand Hill Park, Victoria. In ‘Reintroduction Biology of Australian and New Zealand Fauna’. (Ed. M. Serena.) pp. 219-225. (Surrey Beatty: Sydney.)

Engler, R., Guisan, A., and Rechsteiner, L. (2004). An improved approach for predicting the distribution of rare and endangered species from occurrence and pseudo-absence data. Journal of Applied Ecology 41, 263–274.
An improved approach for predicting the distribution of rare and endangered species from occurrence and pseudo-absence data.Crossref | GoogleScholarGoogle Scholar |

Fischer, J., and Lindenmayer, D. B. (2000). An assessment of published results of animal relocations. Biological Conservation 96, 1–11.
An assessment of published results of animal relocations.Crossref | GoogleScholarGoogle Scholar |

Fritts, S. H., Bangs, E. E., Fontaine, J. A., Johnson, M. R., Phillips, M. K., Koch, E. D., and Gunson, J. R. (1997). Planning and implementing a reintroduction of wolves to Yellowstone National Park and central Idaho. Restoration Ecology 5, 7–27.
Planning and implementing a reintroduction of wolves to Yellowstone National Park and central Idaho.Crossref | GoogleScholarGoogle Scholar |

Griffith, B., Scott, J. M., and Reed, C. (1989). Translocation as a species conservation tool: status and strategy. Science 245, 477–480.
Translocation as a species conservation tool: status and strategy.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BC3cvitlKqsA%3D%3D&md5=de6fb9f4f9b24852ce51ebaf19069fcaCAS | 17750257PubMed |

Hardman, B., and Moro, D. (2006). Optimising reintroduction success by delayed dispersal: is the release protocol important for hare-wallabies? Biological Conservation 128, 403–411.
Optimising reintroduction success by delayed dispersal: is the release protocol important for hare-wallabies?Crossref | GoogleScholarGoogle Scholar |

Hood, G. M. (2011). ‘Pop Tools v. 3.2.5.’ Available at http://www.poptools.org [Verified 30 October 2015]

Howard, D., and Bedford, F. (1999). Survivability and ecology of captive-bred eastern barred bandicoots (Perameles gunnii) released at Cobra Killuc Wildlife Reserve. Unpublished report. Melbourne Zoo, Melbourne.

IUCN–SSC (2013). ‘Guidelines for Reintroductions and other Conservation Translocations. Version 1.0.’ (IUCN Species Survival Commission: Gland, Switzerland.)

Jefferies, D. J., Wayre, P., Jessop, R. M., and Mitchell-Jones, A. J. (1986). Reinforcing the native offer Lutra lutra population in East Anglia: an analysis of the behaviour and range development of the first release group. Mammal Review 16, 65–79.
Reinforcing the native offer Lutra lutra population in East Anglia: an analysis of the behaviour and range development of the first release group.Crossref | GoogleScholarGoogle Scholar |

Jenkins, S. L. (1998). The ecology, life history and conservation management of the endangered eastern barred bandicoot (Perameles gunnii) in a re-introduced population. Unpublished M.Sc Thesis. Monash University, Melbourne.

Jonssonn, S., Brännäs, E., and Lundqvist, H. (1999). Stocking of brown trout, Salmo trutta L.: effects of acclimatization. Fisheries Management and Ecology 6, 459–473.
Stocking of brown trout, Salmo trutta L.: effects of acclimatization.Crossref | GoogleScholarGoogle Scholar |

Jule, K. R., Leaver, L. A., and Lea, S. E. G. (2008). The effects of captive experience on reintroduction survival in carnivores: a review and analysis. Biological Conservation 141, 355–363.
The effects of captive experience on reintroduction survival in carnivores: a review and analysis.Crossref | GoogleScholarGoogle Scholar |

Langford, D. G., and Burbidge, A. A. (2001). Translocation of mala (Lagorchestes hirsutus) from the Tanami Desert, Northern Territory to Trimouille Island, Western Australia. Australian Mammalogy 23, 37–46.
Translocation of mala (Lagorchestes hirsutus) from the Tanami Desert, Northern Territory to Trimouille Island, Western Australia.Crossref | GoogleScholarGoogle Scholar |

Letty, J., Marchandeau, S., Clobert, J., and Aubinearu, J. (2000). Improving translocation success: an experimental study of anti-stress treatment and release method for wild rabbits. Animal Conservation 3, 211–219.
Improving translocation success: an experimental study of anti-stress treatment and release method for wild rabbits.Crossref | GoogleScholarGoogle Scholar |

Long, K., Robley, A. J., and Lovett, K. (2005). Immediate post-release survival of eastern barred bandicoots Perameles gunnii at Woodlands Historic Park, Victoria, with reference to fox activity. Australian Mammalogy 27, 17–25.

Matějů, J., Říčanová, Š., Poláková, S., Ambros, M., Kala, B., Matějů, K., and Kratochvíl, L. (2012). Method of releasing and number of animals are determinants for the success of European ground squirrel (Spermophilus citellus) reintroductions. European Journal of Wildlife Research 58, 473–482.
Method of releasing and number of animals are determinants for the success of European ground squirrel (Spermophilus citellus) reintroductions.Crossref | GoogleScholarGoogle Scholar |

Miller, B., Biggins, D., Hanebury, L., and Vargas, A. (1994). Reintroduction of the black-footed ferret (Mustela nigripes). In ‘Creative Conservation: Interactive Management of Wild and Captive Animals’. (Eds P. J. S. Olney, G. M. Mace and A. T. C. Feistner.) pp. 455-464. (Chapman & Hall: London.)

Miller, B., Ralls, K., Reading, R. P., Scott, J. M., and Estes, J. (1999). Biological and technical considerations of carnivore translocation: a review. Animal Conservation 2, 59–68.
Biological and technical considerations of carnivore translocation: a review.Crossref | GoogleScholarGoogle Scholar |

Mitchell, A. M., Wellicome, T. I., Brodie, D., and Cheng, K. M. (2011). Captive-reared burrowing owls show higher site-affinity, survival and reproductive performance when reintroduced using a soft-release. Biological Conservation 144, 1382–1391.
Captive-reared burrowing owls show higher site-affinity, survival and reproductive performance when reintroduced using a soft-release.Crossref | GoogleScholarGoogle Scholar |

Moehrenschlager, A., and Macdonald, D. W. (2003). Movement and survival parameters of translocated and resident swift foxes Vulpes velox. Animal Conservation 6, 199–206.
Movement and survival parameters of translocated and resident swift foxes Vulpes velox.Crossref | GoogleScholarGoogle Scholar |

Moro, D. (2003). Translocation of capitve-bred dibblers Parantechinus apicalis (Marsupialia: Dasyuridae) to Escape Island, Western Australia. Biological Conservation 111, 305–315.
Translocation of capitve-bred dibblers Parantechinus apicalis (Marsupialia: Dasyuridae) to Escape Island, Western Australia.Crossref | GoogleScholarGoogle Scholar |

Moseby, K. E., and O’Donnell, E. (2003). Reintroduction of the greater bilby, Macrotis lagotis (Reid) (Marsupialia: Thylacomyidae), to northern South Australia: survival, ecology and notes on reintroduction protocols. Wildlife Research 30, 15–27.
Reintroduction of the greater bilby, Macrotis lagotis (Reid) (Marsupialia: Thylacomyidae), to northern South Australia: survival, ecology and notes on reintroduction protocols.Crossref | GoogleScholarGoogle Scholar |

Moseby, K. E., Hill, B. M., and Lavery, T. H. (2014). Tailoring release protocols to individual species and sites: one size does not fit all. PLoS ONE 9, e99753.
Tailoring release protocols to individual species and sites: one size does not fit all.Crossref | GoogleScholarGoogle Scholar | 24963633PubMed |

Murphy, J. A., and Serena, M. (1993). Results of radio tracking eastern barred bandicoots, Perameles gunnii, (Marsupialia: Peramelidae) at Gellibrand Hill Park, Victoria. Australian Mammalogy 16, 51–54.

Parker, K. A., Dickens, M. J., Clarke, R. H., and Lovegrove, T. G. (2012). The theory and practice of catching, holding, moving and release animals. In ‘Reintroduction Biology: Integrating Science and Management’. (Eds J. G. Ewen, D. P. Armstrong, K. A. Parker and P. J. Seddon.) pp. 105-137. (Wiley-Blackwell: Hoboken, NJ.)

Pinheiro, J., Bates, D., DebRoy, S., Sarkar, D., and R Core Team (2014). ‘nlme: Linear and Nonlinear Mixed Effects Models. R package version 3.1-117.’ Available at http://CRAN.R-project.org/package=nlme [Verified 30 October 2015]

Pullin, A. S., Knight, T. M., Stone, D. A., and Charman, K. (2004). Do conservation managers use scientific evidence to support their decision-making? Biological Conservation 119, 245–252.
Do conservation managers use scientific evidence to support their decision-making?Crossref | GoogleScholarGoogle Scholar |

R Core Team (2014). ‘A Language and Environment for Statistical Computing.’ (R Foundation for Statistical Computing: Vienna.) Available at http://www.R-project.org/ [Verified 30 October 2015]

Richardson, K., Castro, I. C., Brunton, D. H., and Armstrong, D. P. (2013). Not so soft? Delayed release reduces long-term survival in a passerine reintroduction. Oryx , .
Not so soft? Delayed release reduces long-term survival in a passerine reintroduction.Crossref | GoogleScholarGoogle Scholar |

Scott, J. M., and Carpenter, J. W. (1987). Release of captive-reared or translocated endangered endangered birds: what do we need to know? The Auk 104, 544–545.
Release of captive-reared or translocated endangered endangered birds: what do we need to know?Crossref | GoogleScholarGoogle Scholar |

Seddon, P., Armstrong, D. P., and Maloney, R. F. (2007). Developing the science of reintroduction biology. Conservation Biology 21, 303–312.
Developing the science of reintroduction biology.Crossref | GoogleScholarGoogle Scholar | 17391180PubMed |

Seebeck, J. (1983). The eastern barred bandicoot. In ‘Complete Book of Australian Mammals’. (Ed. R. Strahan.) p. 100. (Angus and Robertson: Sydney.)

Seebeck, J., and Booth, R. (1996). Eastern barred bandicoot recovery: the role of the veterinarian in the management of endangered species. Australian Veterinary Journal 73, 81–83.
Eastern barred bandicoot recovery: the role of the veterinarian in the management of endangered species.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DyaK283mtFaltw%3D%3D&md5=8c57d9f1a13437d7517a5da0050d70b3CAS | 8660217PubMed |

Sheean, V., Manning, A. D., and Lindenmayer, D. B. (2012). An assessment of scientific approaches towards species relocations in Australia. Austral Ecology 37, 204–215.
An assessment of scientific approaches towards species relocations in Australia.Crossref | GoogleScholarGoogle Scholar |

Short, J. (2009). The characteristics and success of vertebrate translocations within Australia: a progress report to Department of Agriculture, Fisheries and Forestry. June 2009. Available at http://www.wildliferesearchmanagement.com.au/translocations.htm [Verified 30 October 2015]

Short, J., and Turner, B. (2000). Reintroduction of the burrowing bettong Bettongia lesueur (Marsupialia: Potoroidae) to mainland Australia. Biological Conservation 96, 185–196.
Reintroduction of the burrowing bettong Bettongia lesueur (Marsupialia: Potoroidae) to mainland Australia.Crossref | GoogleScholarGoogle Scholar |

Soderquist, T. R. (1995). The importance of hypothesis testing in reintroduction biology: examples from the reintroduction of the carnivorous marsupial Phascogale tapoatafa. In ‘Reintroduction Biology of Australian and New Zealand Fauna’. (Ed. M. Serena.) pp. 159-164. (Surrey Beatty: Sydney.)

Stamps, J. A., and Swaisgood, R. R. (2007). Someplace like home: experience, habitat selection and conservation biology. Applied Animal Behaviour Science 102, 392–409.
Someplace like home: experience, habitat selection and conservation biology.Crossref | GoogleScholarGoogle Scholar |

Stanley-Price, M. R. (1989). ‘Animal Re-introductions: the Arabian Oryx in Oman.’ (Cambridge University Press: Cambridge, UK.)

Sutherland, W. J. (2000). ‘The Conservation Handbook: Research, Management and Policy.’ (Blackwell Science: Oxford, UK.)

Sutherland, W. J., Pullin, A. S., Doman, P. M., and Knight, T. M. (2004). The need for evidence-based conservation. Trends in Ecology & Evolution 19, 305–308.
The need for evidence-based conservation.Crossref | GoogleScholarGoogle Scholar |

Swaisgood, R. R. (2010). The conservation-welfare nexus in reintroduction programmes: a role for sensory ecology. Animal Welfare 19, 125–137.
| 1:CAS:528:DC%2BC3cXmtFyltro%3D&md5=bde26511ec89c2bcd220fb9c5ef58a42CAS |

Teixeira, C. P., Schetini De Azevedo, C., Mendl, M., Cipreste, C. F., and Young, R. J. (2007). Revisiting translocation and reintroduction programmes: the importance of considering stress. Animal Behaviour 73, 1–13.
Revisiting translocation and reintroduction programmes: the importance of considering stress.Crossref | GoogleScholarGoogle Scholar |

Truett, J. C., Dullan, J. L. D., Matchell, M. R., Owens, E., and Seery, D. (2001). Translocating prairie dogs: a review. Wildlife Society Bulletin 29, 863–872.

Tuberville, T. D., Clark, E. E., Buhlmann, K. A., and Whitfield Gibbons, J. (2005). Translocation as a conservation tool: site fidelity and movement of repatriated gopher tortoises (Gopherus polyphemus). Animal Conservation 8, 349–358.
Translocation as a conservation tool: site fidelity and movement of repatriated gopher tortoises (Gopherus polyphemus).Crossref | GoogleScholarGoogle Scholar |

Wanless, R. M., Cunningham, J., Hockey, P. A. R., Wanless, J., White, R. W., and Wiseman, R. (2002). The success of a soft-release reintroduction of the flightless Aldabra rail (Dryolimnas cuvieri aldabranus) on Aldabra Atoll, Seychelles. Biological Conservation 107, 203–210.
The success of a soft-release reintroduction of the flightless Aldabra rail (Dryolimnas cuvieri aldabranus) on Aldabra Atoll, Seychelles.Crossref | GoogleScholarGoogle Scholar |

White, G. C., and Garrott, R. A. (1990) ‘Analysis of Wildlife Radio-tracking Data.’ (Academic Press: San Diego, CA.)

Winnard, A. L., and Coulson, G. M. (2008). Sixteen years of eastern barred bandicoot Perameles gunnii reintroductions in Victoria: a review. Pacific Conservation Biology 14, 34–53.

Winnard, A., Hill, R., Courtney, P., Coulson, G., Harley, D., and Parrott, M. (2013a). Twenty years of captive breeding and re-introduction of the eastern barred bandicoot in Victoria, Australia. In ‘Global Re-introduction Perspectives: 2013. More Case Studies from Around the Globe’. (Ed. P. S. Soorae.) pp. 204-209. (IUCN–SSC Re-introduction Specialist Group: Gland, Switzerland and Environment Agency-Abu Dhabi: Abu Dhabi, UAE.)

Winnard, A. L., Di Stefano, J., and Coulson, G. (2013b). Habitat use of a critically-endangered species in a predator-free but degraded reserve in Australia. Wildlife Biology 19, 429–438.
Habitat use of a critically-endangered species in a predator-free but degraded reserve in Australia.Crossref | GoogleScholarGoogle Scholar |

Wolf, C. M., Griffith, B., Reed, C., and Temple, S. A. (1996). Avian and mammalian translocations: update and reanalysis of 1987 data. Conservation Biology 10, 1142–1154.
Avian and mammalian translocations: update and reanalysis of 1987 data.Crossref | GoogleScholarGoogle Scholar |

Wood, S., and Scheipl, F. (2014). ‘Gamm4: Generalized Additive Mixed Models Using mgcv and lme4. R Package Version 0.2-3.’ Available at http://CRAN.R-project.org/package=gamm4 [Verified 30 October 2015]

Worton, B. J. (1989). Kernel methods for estimating the utilization distribution in home-range studies. Ecology 70, 164–168.
Kernel methods for estimating the utilization distribution in home-range studies.Crossref | GoogleScholarGoogle Scholar |