Demography of the Pryor Mountain wild horses, 1993-2007

Abstract

Wild horses (Equus caballus) at Pryor Mountain were studied by direct observation from 1993 through 2007. All horses present were individually identifiable on the basis of coat coloration, head and leg markings, gender, and band associations. Of the 609 horses either present prior to foaling in 1993 or born since, ages were precisely known for density-dependent population regulation, as both population growth rate and survival rate were negatively correlated with population size from the previous year. These and other factors were not sufficient to stabilize the population during our period of study, however, as evidenced by the necessity for large removals in several years.

Understanding population dynamics of feral horses in the Tuan and Toolara State Forest for successful long-term population management

“…Evidence from previous studies shows that the majority of sub-adult feral horses (both females and males) disperse from their natal harems between 1-3 years of age (Klingel 1969;Tyler 1972;Welsh 1975;Pezhorn 1984;Kirkpatrick and Turner 1986;Roelle et al 2010) but later dispersal of males at four and five years of age has also been recorded (Roelle et al 2010). In addition, offspring born to first time mothers develop stronger and longer lasting associations with their dams, which often results in delayed dispersal (Khalil and Kaseda 1997;Khalil et al 2010).…”

“…The overall proportions of females and males at birth are usually equal in feral and freeranging horse populations (Berger 1986;Roelle et al 2010), with insignificant fluctuations occurring from year to year (Keiper and Houpt 1984;. These fluctuations usually arise due to natural reasons, such as the availability of resources, which impacts on the survival of neonates and mare fertility.…”

“…Despite an equal gender ratio at birth (Monard et al 1997;Roelle et al 2010), most adult feral horse populations show gender asymmetry with females being in the majority (Greger and Romney 1999;, although an equal adult gender ratio has been noted in khulans (Equus hemionus, Feh et al 2001). Adult age group mortality is usually the result of injuries sustained in males when competing for females and in females because of the demands of reproduction (Welsh 1973;Berger 1986;Garrott and Taylor 1990).…”

“…Population studies of wild and feral equids often differ in age group classification because of the variability that exists in determining the ages of horses being studied Roelle et al 2010). In some studies, birth dates were available, which obviously provided an exact age and, as there is a close correlation between dental characteristics and age, this allowed observers (where the mouth could be examined) to determine with considerable accuracy the animal's age Garrott 1991b;Grange et al 2009).…”

“…Camargue horses in France (Duncan 1992), Retuertas horses in Spain (Vega-Pla et al 2006;Brandariz-Fontes et al 2013), and feral horses in Australia , New Zealand (Linklater 2000a;, Argentina (Scorolli 2007), Northern America (Ransom and Cade 2009), England (Putman 1986) and Japan (Kaseda et al 1997) are examples of such populations. The term feral is sometimes replaced in the literature by wild but is incorrect (Berger 1986;Putman 1986;Roelle et al 2010). The term feral will be used in this thesis.…”