Population Characteristics of Feral Horses on Cumberland Island, Georgia and Their Management Implications

Abstract

Control of feral horse populations (Equus caballus) on public lands is restricted to nonlethal methods. These methods can limit population growth; however, efficacy may vary among populations with differing demography and social structures. Characteristics of many western feral horse populations are well documented, but fewer data are available for Atlantic barrier island populations. Therefore, we monitored a population of feral horses on Cumberland Island, Georgia from 1986 to 1990. Population growth averaged 4.3% annually with a stable age structure. Mean size of bands with 21 stallion was 4.6 horses. The adult sex ratio for the population was 0.6 females:1.0 males. About 66% of mares foaled during a given year and no juvenile females foaled. Annual survival rates averaged 61.1% for female foals, 58.8% for male foals, and 92.4% for mares. Most bands contained a dominant or codominant stallion, mares and-or juvenile females, and foals. Most mares (62.5%) changed bands-1 time during our study. Bachelors represented 50.4% of stallions. These population characteristics differed from other feral horse populations. The small band size, large number of bachelors, high degree of band instability, and codominance of band stallions on Cumberland Island likely will limit the efficacy of some forms of nonlethal population control.

Poor horse traders: large mammals trade survival for reproduction during the process of feralization

“…( Tatin et al 2009;C. Feh 2007, personal communication), feral horses in the Great Basin (Berger 1986), Pryor Mountains (Garrott & Taylor 1990) and Kaimanawa (Cameron et al 2001;Linklater et al 2004), the Camargue horses studied at (this study) low and (this study) high densities and Cumberland Island at carrying capacity (Goodloe et al 2000). (Populations were classed as at or close to carrying capacity when density dependence in r or reproductive success was demonstrated.…”

“…The differences in adult survival between males and females of the Camargue herd also led to a malebiased sex ratio: males over 2 years old represented 30 per cent of adults in 1974 and they reached more than 60 per cent in 1982 (Duncan 1992). Most feral horse populations have female-biased sex ratios (see Linklater 2000 andLinklater et al 2004 for reviews), but the other studies where the population was resource-limited had male-biased adult sex ratios as those in the Camargue: on Sable Island ( Welsh 1975) and Cumberland Island (Goodloe et al 2000). Male-biased sex ratios have also been found in feral populations of other feral ungulates, cattle (Berteaux & Micol 1992) and sheep (Réale 1996), supporting the suggestion that this general principle may be true for all these species of ungulates.…”

Demography and dynamics of three wild horse populations in the Australian Alps

“…Mean annual adult survivorship has been reported to be above 90% and survival rates in 0‐ to 2‐year‐old wild horses varied greatly (27–97%) (Eberhardt et al . 1982; Berger 1986; Ganskopp & Vavra 1986; Garrott & Taylor 1990; Duncan 1992; Goodloe et al . 2000; Linklater et al .…”

Population dynamics of feral horses (Equus caballus) following above‐average rainfall in a semi‐arid environment of Australia

“…The mortality rate of adult feral horses is usually low, with many studies reporting survival rates higher than 90% . When plentiful water and food conditions prevail, in an environment free of predators, diseases and control by humans, the mortality rate of adult feral horses may be negligible.…”