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.
Incised river channels are dynamic components of fluvial systems, represent geomorphic degradation, and are encountered worldwide. Ecological effects of incision can be far-reaching, affecting habitat availability and channel processes. Although incision can reflect habitat degradation, some studies suggest that important in-stream habitats do not differ with the degree of incision. Therefore, we tested whether in-stream habitat variables that are important to imperiled fishes differ in river reaches with varying degrees of incision. Because incision (measured using entrenchment ratio) had no discernable effect on in-stream habitat characteristics (i.e., proportion fines, gravel, cobble, and macrophyte occurrence and length), we expanded our analysis to assess the effects of 29 additional geomorphic variables on in-stream habitat. These analyses indicated that bank height, bed mobility, D 84 , cross-sectional area, bankfull width, and wetted perimeter accounted for 42% of macrophyte occurrence and 64% of macrophyte length variance. Postflood surveys indicated that macrophyte occurrence on cobble declined as bank height and bed mobility increased, and sediment size decreased, suggesting that sediment size and bed mobility have a stronger influence on in-stream habitat than incision. Although channel incision often indicates environmental degradation, important aspects of habitat are not described by this measurement. Strategies that depend on incision to identify restoration sites may have limited habitat benefits in Southeastern Piedmont streams and rivers. Instead, landscape or shoal-scale restoration approaches that increase coarse sediment proportions may increase macrophyte occurrence, length, and persistence. Sediment budgets that identify coarse and fine sediment sources and transport may be useful to prioritize restoration approaches.
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