Population dynamics of feral horses (Equus caballus) in an exotic coniferous plantation in Australia
Magdalena A. Zabek A D , David M. Berman B , Simon P. Blomberg C , Christina W. Collins A and John Wright A
+ Author Affiliations
- Author Affiliations
A The University of Queensland, School of Veterinary Science, Gatton, Qld 4343, Australia.
B Queensland Murray–Darling Committee, Toowoomba, Qld 4350, Australia.
C The University of Queensland, School of Biological Sciences, Brisbane, Qld 4072, Australia.
D Corresponding author. Email: m.zabek@uq.edu.au
Wildlife Research 43(4) 358-367 https://doi.org/10.1071/WR15209
Submitted: 5 November 2015 Accepted: 4 June 2016 Published: 6 July 2016
Abstract
Context: Understanding population dynamics of invasive species is crucial for the development of management strategies. Feral horses (Equus caballus) are a growing problem in the Tuan–Toolara State Forest (TTSF), a coniferous plantation in south-eastern Queensland, Australia.
Aim: The population dynamics of the TTSF feral horses was not known. Therefore, the study was designed to characterise the major vital parameters of this population and, using these data, develop a long-term management plan.
Methods: The study was conducted over 3 years (2011–14) involving 522 individually identified horses. Foaling rates were used to calculate fecundity. Body fat distribution was estimated using body condition score (BCS), which reflects the nutritional, metabolic and general health of individual animals. Multi state mark–capture population models were used to estimate age-specific survival, and the Leslie age-structured projection matrix model was used to determine the annual rate at which the population increased.
Key results: The mean annual fecundity was low (0.23 ± 0.07 s.d.). The mean BCS of the population was mid-range (2.55 ± 0.51 s.d.) with adult females having lower scores than other age and gender groups. Survival estimates were consistently high (0.92–0.95) across all age groups. The average annual finite rate of population increase (λ) for the 3 years of the study was 1.09. Sensitivity analysis demonstrated that the population growth rate was almost seven times more sensitive to changes in adult survival compared with juvenile survival, and almost twice as sensitive to changes in fecundity.
Key conclusions: Population dynamics of the TTSF feral horses were comparable to other feral horse populations similarly challenged by environmental nutritional limitations.
Implications: Defining population dynamics of the TTSF feral horses permits the formulation of management goals that can be audited and adapted as required. The most effective strategy for controlling population growth in the TTSF would involve the continuing removal of substantial numbers of adult females or manipulation of survival and/or fecundity. As selective removal will likely alter the adult sex ratio and age structure of the population, ongoing assessment is necessary to minimise adverse welfare outcomes.
Additional keywords: invasive species, fertility, mark–recapture, population ecology, population dynamics, population growth, population management, population modelling, survival, reproduction.
References
Anderson, D. R., Burnham, K. P., and White, G. C. (1994). AIC model selection in overdispersed capture–recapture data. Ecology 75, 1780–1793.| AIC model selection in overdispersed capture–recapture data.Crossref | GoogleScholarGoogle Scholar |
Baynes, J. (2004). Assessing forest canopy density in a highly variable landscape using Landsat data and FCD Mapper software. Australian Forestry 67, 247–253.
| Assessing forest canopy density in a highly variable landscape using Landsat data and FCD Mapper software.Crossref | GoogleScholarGoogle Scholar |
Begon, M., Harper, J. L., and Townsend, C. R. (1990). ‘Ecology: individuals, populations and communities’. (Blackwell Science: Boston).
Berger, J. (1986). ‘Wild horses of the Great Basin’. (University of Chicago Press).
Berman, D. M. (1991). The ecology of feral horses in central Australia. Ph.D. Thesis, University of New England, Armidale.
Berman, D. M. (2013). Wild horse trapping and relocation: Tuan and Toolara State Forests 2009 to 2013. Forestry Plantations Queensland, Gympie.
Blomberg, S. P., and Shine, R. (2001). Modelling life history strategies with capture–recapture data: evolutionary demography of the water skink Eulamprus tympanum. Austral Ecology 26, 349–359.
| Modelling life history strategies with capture–recapture data: evolutionary demography of the water skink Eulamprus tympanum.Crossref | GoogleScholarGoogle Scholar |
Boyd, L. (1979). The mare–foal demography of feral horses in Wyoming’s Red Desert. In ‘Symposium on the Ecology and Behaviour of Wild and Feral Equids’. (Ed. R. H. Denniston.) pp. 6–8. (University of Wyoming: Laramie,WY.)
Burnham, K. P., and Anderson, D. R. (Ed.) (1998). ‘Model selection and inference – a practical information-theoretic approach’. (Springer-Verlag: New York).
Cameron, E. Z., and Linklater, W. L. (2000). Individual mares bias investment in sons and daughters in relation to their condition. Animal Behaviour 60, 359–367.
| Individual mares bias investment in sons and daughters in relation to their condition.Crossref | GoogleScholarGoogle Scholar | 11007645PubMed |
Cameron, E. Z., Linklater, W. L., Minot, E. O., and Stafford, J. K. (2001). Population dynamics 1994–98 and management of Kaimanawa wild horses. Science for Conservation No. 171. Department of Conservation, Wellington.
Carroll, C. L., and Huntington, P. J. (1988). Body condition scoring and weight estimation of horses. Equine Veterinary Journal 20, 41–45.
| Body condition scoring and weight estimation of horses.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DyaL1c3htFGgsg%3D%3D&md5=67a8796f9701f8bdd97a0db39975368cCAS | 3366105PubMed |
Caswell, H. (Ed.) (2001). ‘Matrix Population Models. Construction, Analysis, and Interpretation’. (Sinauer Associates: Sunderland, MA.)
Caughley, G., and Sinclair, A. R. E. (Ed.) (1994). ‘Wildlife Ecology and Management’. (Blackwell Publishing: Cambridge.)
Cooch, E., and White, G. (2002). ‘Program MARK: a gentle introduction’. Available at http://www.phidot.org/software/mark/docs/book/ [Accessed 19 May 2012].
Crittle, T., and Jackson, S. (2004). Risk assessment-collisions between motor vehicles and feral horses on high use roads in Tuan and Toolara State Forests. Queensland Parks and Wildlife Services, Gympie.
Dawson, M. J. (2005). The population ecology of feral horses in the Australian Alps Management Summary. Australian Alps Liaison Committee, Canberra.
Dawson, M. J., and Hone, J. (2012). Demography and dynamics of three wild horse populations in the Australian Alps. Austral Ecology 37, 97–109.
| Demography and dynamics of three wild horse populations in the Australian Alps.Crossref | GoogleScholarGoogle Scholar |
Dawson, M. J., Lane, C., and Saunders, G. (Ed.) (2006). ‘Proceedings of the National Feral Horse Management Workshop’. (Invasive Animals Cooperative Research Centre, University of Canberra).
Dhont, B. (2011). Developing methods to assess the extent of naturalized slash pine populations and their habitats characteristics in South East Queensland, Australia. M.Sc. Thesis, University of Queensland, Brisbane.
Dobbie, W. R., and Berman, D. M. (1992). Control of brumbies in central Australia. Conservation Commission of the Northern Territory. Department of Primary Industry and Fisheries, Alice Springs.
Duncan, P. (1992). ‘Horses and Grasses: the Nutritional Ecology of Equids and their Impact on the Camargue.’ (Springer-Verlag: New York).
Dyring, J. (1990). The impact of feral horses (Equus caballus) on subalpine and montane environments in Australia. M.Sc. Thesis, University of Canberra, Canberra.
Eberhardt, L. L. (1977). Optimal management policies for marine mammals. Wildlife Society Bulletin 5, 162–169.
Eberhardt, L. L., Majorowicz, A. K., and Wilcox, J. A. (1982). Apparent rates of increase for two feral horse herds. The Journal of Wildlife Management 46, 367–374.
| Apparent rates of increase for two feral horse herds.Crossref | GoogleScholarGoogle Scholar |
English, A. W. (2001). A report on the management of feral horses in national parks in New South Wales. University of Sydney, Sydney.
Escos, J., and Alados, C. L. (1991). Influence of weather and population characteristics of free-ranging Spanish ibex in the Sierra de Cazorla Segura and in the eastern Sierra Nevada. Mammalia 55, 67–78.
| Influence of weather and population characteristics of free-ranging Spanish ibex in the Sierra de Cazorla Segura and in the eastern Sierra Nevada.Crossref | GoogleScholarGoogle Scholar |
Escos, J., Alados, C. L., and Emlen, J. M. (1994). Application of the stage-projection model with density-dependent fecundity to the population dynamics of Spanish ibex. Canadian Journal of Zoology 72, 731–737.
| Application of the stage-projection model with density-dependent fecundity to the population dynamics of Spanish ibex.Crossref | GoogleScholarGoogle Scholar |
Feist, J. D., and McCullough, D. R. (1976). Behaviour patterns and communication in feral horses. Zeitschrift für Tierpsychologie 41, 337–371.
| Behaviour patterns and communication in feral horses.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DyaE2s%2FktVyrtQ%3D%3D&md5=471730e39460066a254145d89bf3916eCAS | 983427PubMed |
Festa-Bianchet, M. (1988). Birthdate and survival in bighorn lambs (Ovis canadensis). Journal of Zoology 214, 653–661.
| Birthdate and survival in bighorn lambs (Ovis canadensis).Crossref | GoogleScholarGoogle Scholar |
Gaillard, J. M., Festa-Bianchet, M., and Yoccoz, N. G. (1998). Population dynamics of large herbivores: variable recruitment with constant adult survival. Trends in Ecology & Evolution 13, 58–63.
| Population dynamics of large herbivores: variable recruitment with constant adult survival.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BC3M7itFyhtw%3D%3D&md5=caf666562bc6c483026f17dc3518d615CAS |
Gaillard, J. M., Festa-Bianchet, M., Yoccoz, N. G., Loison, A., and Toigo, C. (2000). Temporal variation in fitness components and population dynamics of large herbivores. Annual Review of Ecology and Systematics 31, 367–393.
| Temporal variation in fitness components and population dynamics of large herbivores.Crossref | GoogleScholarGoogle Scholar |
Ganskopp, D., and Vavra, M. (1986). Habitat use by feral horses in the northern sagebrush steppe. Journal of Range Management 39, 207–212.
| Habitat use by feral horses in the northern sagebrush steppe.Crossref | GoogleScholarGoogle Scholar |
Garrott, R. A. (1991). Sex ratios and differential survival of feral horses. Journal of Animal Ecology 60, 929–937.
| Sex ratios and differential survival of feral horses.Crossref | GoogleScholarGoogle Scholar |
Garrott, R. A., and Taylor, L. (1990). Dynamics of a feral horse population in Montana. The Journal of Wildlife Management 54, 603–612.
| Dynamics of a feral horse population in Montana.Crossref | GoogleScholarGoogle Scholar |
Garrott, R. A., Eagle, T. C., and Plotka, E. D. (1991a). Age-specific reproduction in feral horses. Canadian Journal of Zoology 69, 738–743.
| Age-specific reproduction in feral horses.Crossref | GoogleScholarGoogle Scholar |
Garrott, R. A., Siniff, D. B., and Eberhardt, L. L. (1991b). Growth rates of feral horse populations. The Journal of Wildlife Management 55, 641–648.
| Growth rates of feral horse populations.Crossref | GoogleScholarGoogle Scholar |
Gates, S. (1979). A study of the home ranges of free-ranging Exmoor ponies. Mammal Review 9, 3–18.
| A study of the home ranges of free-ranging Exmoor ponies.Crossref | GoogleScholarGoogle Scholar |
Gill, R. M. A., Johnson, A. L., Francis, A., Hiscocks, K., and Peace, A. J. (1996). Changes in roe deer (Capreolus capreolus L.) population density in response to forest habitat succession. Forest Ecology and Management 88, 31–41.
| Changes in roe deer (Capreolus capreolus L.) population density in response to forest habitat succession.Crossref | GoogleScholarGoogle Scholar |
Goodloe, R. B., Warren, R. J., Osborn, D. A., and Hall, C. (2000). Population characteristic of feral horses on Cumberland Island, Georgia and their management implications. The Journal of Wildlife Management 64, 114–121.
| Population characteristic of feral horses on Cumberland Island, Georgia and their management implications.Crossref | GoogleScholarGoogle Scholar |
Grange, S., Duncan, P., and Gaillard, J. M. (2009). Poor horse traders: large mammals trade survival for reproduction during the process of feralization. Proceedings. Biological Sciences 276, 1911–1919.
| Poor horse traders: large mammals trade survival for reproduction during the process of feralization.Crossref | GoogleScholarGoogle Scholar |
Gray, M. E., Cameron, E. Z., Peacock, M. M., Thain, D. S., and Kirchoff, V. S. (2012). Are low infidelity rates in feral horses due to infanticide? Behavioral Ecology and Sociobiology 66, 529–537.
| Are low infidelity rates in feral horses due to infanticide?Crossref | GoogleScholarGoogle Scholar |
Greger, P. D., and Romney, E. M. (1999). High foal mortality limits growth of a desert feral horse population in Nevada. The Great Basin Naturalist 59, 374–379.
Hall, R. (1972). Wild horse biology and alternatives for management – Pryor Mountain Wild Horse Range. Bureau of Land Management, Montana.
Kaczensky, P., Ganbaatar, N., Altansukh, N., and Enkhsaikhan, N. (2010). Winter disaster in the Dzungarian Gobi – crash of the Przewalski’s horse population in Takhin Tal 2009/2010. University of Vienna, Vienna.
Kaseda, Y., Khalil, A. M., and Ogawa, H. (1995). Harem stability and reproductive success of Misaki feral mares. Equine Veterinary Journal 27, 368–372.
| Harem stability and reproductive success of Misaki feral mares.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DyaK287htFahtw%3D%3D&md5=4fcbf6960e0a501e54e2da0f51cee3f9CAS | 8654352PubMed |
Keiper, R., and Houpt, K. (1984). Reproduction in feral horses: an eight-year study. American Journal of Veterinary Research 45, 991–995.
| 1:STN:280:DyaL2c3ivFGnsg%3D%3D&md5=3652287f0b548ae0a428c85a3661c127CAS | 6732036PubMed |
Kuiters, A. T., Mohren, G. M. J., and Van Wieren, S. E. (1996). Ungulates in temperate forest ecosystems. Forest Ecology and Management 88, 1–5.
| Ungulates in temperate forest ecosystems.Crossref | GoogleScholarGoogle Scholar |
Lande, R. (1988). Demographic models of the northern spotted owl (Strix occidentalis caurina). Oecologia 75, 601–607.
| Demographic models of the northern spotted owl (Strix occidentalis caurina).Crossref | GoogleScholarGoogle Scholar |
Lebreton, J. D., Burnham, K. P., Clobert, J., and Anderson, D. R. (1992). Modeling survival and testing biological hypotheses using marked animals: a unified approach with case studies. Ecological Monographs 62, 67–118.
| Modeling survival and testing biological hypotheses using marked animals: a unified approach with case studies.Crossref | GoogleScholarGoogle Scholar |
Leslie, P. H. (1945). On the use of matrices in certain population mathemathics. Biometrika 33, 183–212.
| On the use of matrices in certain population mathemathics.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DyaH28%2FisV2nsg%3D%3D&md5=483db4db7e63a5dfa4aefa6be5015f1fCAS | 21006835PubMed |
Linklater, W. L. (2000). Adaptive explanation in socio-ecology: lessons from Equidae. Biological Reviews of the Cambridge Philosophical Society 75, 1–20.
| Adaptive explanation in socio-ecology: lessons from Equidae.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD3c3gsFSltg%3D%3D&md5=56bd2caa23e10ef16faee1282e70e20aCAS | 10740891PubMed |
Linklater, W. L., Cameron, E. Z., Stafford, K. J., and Minot, E. O. (2001). Estimating Kaimanawa feral horse population size and growth. Science and Research Internal Report No 185. Department of Conservation, Wellington.
Linklater, W. L., Cameron, E. Z., Minot, E. O., and Stafford, K. J. (2004). Feral horse demography and population growth in the Kaimanawa Ranges, New Zealand. Wildlife Research 31, 119–128.
| Feral horse demography and population growth in the Kaimanawa Ranges, New Zealand.Crossref | GoogleScholarGoogle Scholar |
Lucas, Z., Raeside, J. I., and Betteridge, K. J. (1991). Non-invasive assessment of the incidences of pregnancy and pregnancy loss in the feral horses of Sable Island. Journal of Reproduction and Fertility. Supplement 44, 479–488.
| 1:STN:280:DyaK387nslamtA%3D%3D&md5=6d27c0392b3f5837abde9d3da1773992CAS | 1795292PubMed |
Lundie-Jenkins, G., Maag, G., and Manning, B. (2006). A summary of the results of an aerial survey of the feral horse populations in Carnavon National Park and neighbouring properties in Central Queensland. Queensland Parks and Wildlife Services, Brisbane.
Nimmo, D. G., and Miller, K. K. (2007). Ecological and human dimensions of management of feral horses in Australia: a review. Wildlife Research 34, 408–417.
| Ecological and human dimensions of management of feral horses in Australia: a review.Crossref | GoogleScholarGoogle Scholar |
Nuñez, C. M. V., Adelman, J. S., and Rubenstein, D. (2010). Immunocontraception in Wild Horses (Equus caballus) extends reproductive cycling beyond the normal breeding season. PLoS One 5, e13635.
| Immunocontraception in Wild Horses (Equus caballus) extends reproductive cycling beyond the normal breeding season.Crossref | GoogleScholarGoogle Scholar |
Pollock, K. H. (1982). A capture–recapture design robust to unequal probability of capture. The Journal of Wildlife Management 46, 752–757.
| A capture–recapture design robust to unequal probability of capture.Crossref | GoogleScholarGoogle Scholar |
R Development Core Team (2012). R: A Language and Environment for Statistical Computing. R Foundation for statistical computing.Vienna Available at http://www.R-project.org/ [Accessed 9 March 2013].
Ransom, J. I. (2009). Understanding the influences of immunocontraception on equids through competing models of behavior. M.Sc. Thesis, Colorado State University, Fort Collins, CO.
Roelle, J. E., Singer, F. J., Zeigenfuss, L. C., Ransom, J. I., Coates-Markle, L., and Schoenecker, K. (2010). Demography of the Pryor Mountain Wild Horses, 1993–2007. US Geological Survey Scientific Investigations Report 2010–5125; Reston, VA.
Rudman, R., and Keiper, R. R. (1991). The body condition of feral ponies on Assateague Island. Equine Veterinary Journal 23, 453–456.
| The body condition of feral ponies on Assateague Island.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DyaK387jslWmtg%3D%3D&md5=5ad8f258d1fc0a953a850ee6ba9c8764CAS | 1778164PubMed |
Saether, B. E., Engen, S., and Solberg, E. J. (2001). Optimal harvesting of age-structured populations of moose. Alces alces in a fluctuating environment. Wildlife Biology 7, 171–179.
Salter, R. E., and Hudson, R. J. (1982). Social organization of feral horses in western Canada. Applied Animal Ethology 8, 207–223.
| Social organization of feral horses in western Canada.Crossref | GoogleScholarGoogle Scholar |
Schott, C. J. (2004). Ecology of free-ranging horses in northern Guy Fawkes River National Park NSW, Australia. M.Sc. Thesis, University of New England, Armidale, NSW.
Scorolli, A. L., Lopez-Cazorla, A. C., and Tejera, L. A. (2006). Unusual mass mortality of feral horses during a violent rainstorm in Parque Provincial Tornquist, Argentina. Mastozoología Neotropical 13, 255–258.
Scorolli, A. L., and Lopez-Cazorla, A. C. (2010). Demography of feral horses (Equus caballus): a long-term study in Tornquist Park, Argentina. Wildlife Research 37, 207–214.
| Demography of feral horses (Equus caballus): a long-term study in Tornquist Park, Argentina.Crossref | GoogleScholarGoogle Scholar |
Scorolli, A. L. (2012). Feral horse body condition: a useful tool for population management? In ‘Proceedings of the International Wild Equid Conference’. (Eds P. Kaczensky and J. I. Ransom.) p. 92. (University of Veterinary Medicine: Vienna.)
Seal, U. S., and Plotka, E. D. (1983). Age-specific pregnancy rates in feral horses. The Journal of Wildlife Management 47, 422–429.
| Age-specific pregnancy rates in feral horses.Crossref | GoogleScholarGoogle Scholar |
Seber, G. A. F. (1992). A review of estimating animal abundance II. International Statistical Review 60, 129–166.
| A review of estimating animal abundance II.Crossref | GoogleScholarGoogle Scholar |
Turner, J. W. J., Wolfe, M. L., and Kirkpatrick, J. F. (1992). Seasonal mountain lion predation on a feral horse population. Canadian Journal of Zoology 70, 929–934.
| Seasonal mountain lion predation on a feral horse population.Crossref | GoogleScholarGoogle Scholar |
Vernes, K., Freeman, M., and Nesbitt, B. (2009). Estimating the density of free-ranging wild horses in rugged gorges using a photographic mark–recapture technique. Wildlife Research 36, 361–367.
| Estimating the density of free-ranging wild horses in rugged gorges using a photographic mark–recapture technique.Crossref | GoogleScholarGoogle Scholar |
Walter, M. J. (2002). The population ecology of wild horses in the Australian Alps. Ph.D. Thesis, University of Canberra.
Wang, Q. (2008). Impacts of climate, topography, and weathering profile on vadose zone hydrology and coastal pine plantation management – a multi-scale investigation, southwest Queensland, Australia. Ph.D. Thesis, Queensland University of Technology, Brisbane.
Weber, E. (2003). ‘Invasive Plant Species of the World: a Reference Guide to Environmental Weeds.’ (CABI Publishing: Wallingford, UK.)
Welsh, D. A. (1975). Population, behavioural and grazing ecology of the horses of Sable Island, Nova Scotia. Ph.D. Thesis, Dalhousie University, Nova Scotia.
White, G. C., and Burnham, K. P. (1999). Program MARK: survival estimation from populations of marked animals. Bird Study 46, S120–139.
| Program MARK: survival estimation from populations of marked animals.Crossref | GoogleScholarGoogle Scholar |
Young, P. A. R., and Dillewaard, H. A. (Ed.) (1999). ‘Southeast Queensland. The Conservation Status of Queensland’s Bioregional Ecosystems’. (Queensland Environmental Protection Agency: Brisbane.)
Zabek, M. A. (2015). Understanding population dynamics of feral horses in the Tuan and Toolara State Forest for successful long-term population management. Ph.D. Thesis, University of Queensland, Gatton.
