Population dynamics of feral horses (Equus caballus) in an exotic coniferous plantation in Australia

Zabek, Magdalena A., Berman, David M., Blomberg, Simon P., Collins, Christina W. and Wright, John (2016) Population dynamics of feral horses (Equus caballus) in an exotic coniferous plantation in Australia. Wildlife Research, 43 4: 358-367. doi:10.1071/WR15209

Author Zabek, Magdalena A.
Berman, David M.
Blomberg, Simon P.
Collins, Christina W.
Wright, John
Title Population dynamics of feral horses (Equus caballus) in an exotic coniferous plantation in Australia
Formatted title
Population dynamics of feral horses (Equus caballus) in an exotic coniferous plantation in Australia
Journal name Wildlife Research   Check publisher's open access policy
ISSN 1035-3712
Publication date 2016-07-06
Year available 2016
Sub-type Article (original research)
DOI 10.1071/WR15209
Open Access Status Not yet assessed
Volume 43
Issue 4
Start page 358
End page 367
Total pages 10
Place of publication Clayton, VIC, Australia
Publisher C S I R O Publishing
Collection year 2017
Language eng
Formatted 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±0.07s.d.). The mean BCS of the population was mid-range (2.55±0.51s.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 () 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.
Keyword Fertility
Invasive species
Population dynamics
Population ecology
Population growth
Population management
Population modelling
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: HERDC Pre-Audit
School of Biological Sciences Publications
School of Veterinary Science Publications
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