TY - JOUR
T1 - Demography and dynamics of three wild horse populations in the Australian Alps
AU - Hone, Jim
PY - 2012
Y1 - 2012
N2 - Wild horses (Equus caballus) are a non-native species occupying over 2800 km2 of the nationally significant Australian Alps National Parks.We estimated key demographic parameters (fecundity, adult and juvenile
survival and annual finite population growth rate) over 3 years and related these to horse body condition and available food for three populations under natural conditions, and found a trend consistent with food limitation. The populations were independent, with different site characteristics and occupied areas, identified by land managers, as areas of concern about possible conservation impacts. Annual fecundity and juvenile survival varied across sites averaging between 0.21 and 0.31 female young per adult female, and 0.83 and 0.90 per annum, respectively, and annual adult survival was consistent across sites averaging 0.91 per annum. One population was increasing (l = 1.09 year-1;95% CI 1.04â¿¿1.14) and two populationswere stable (l ~ 1.0 year-1).Mean body condition of horses was positively correlated with mean pasture biomass rank.Across the three populations, fecundity, recruitment, body condition and annual finite population growth rate were lowest when mean pasture biomass rank was lowest and conversely highest when pasture rank was highest.We conclude that food limitation appears to be operating across these three sites.We used our results to assess the sensitivity of annual finite rate of increase (l) to changes in key demographic parameters and found that l was most sensitive to a change in adult survival, with the second most sensitive parameter being fecundity.Thus, if the aim of management is to reduce the size of the wild horse population then targeting adult survival is most important, followed by fecundity. Finally, we estimated the linear, negative, numerical response for wild horses between annual l and horses per unit pasture biomass.
AB - Wild horses (Equus caballus) are a non-native species occupying over 2800 km2 of the nationally significant Australian Alps National Parks.We estimated key demographic parameters (fecundity, adult and juvenile
survival and annual finite population growth rate) over 3 years and related these to horse body condition and available food for three populations under natural conditions, and found a trend consistent with food limitation. The populations were independent, with different site characteristics and occupied areas, identified by land managers, as areas of concern about possible conservation impacts. Annual fecundity and juvenile survival varied across sites averaging between 0.21 and 0.31 female young per adult female, and 0.83 and 0.90 per annum, respectively, and annual adult survival was consistent across sites averaging 0.91 per annum. One population was increasing (l = 1.09 year-1;95% CI 1.04â¿¿1.14) and two populationswere stable (l ~ 1.0 year-1).Mean body condition of horses was positively correlated with mean pasture biomass rank.Across the three populations, fecundity, recruitment, body condition and annual finite population growth rate were lowest when mean pasture biomass rank was lowest and conversely highest when pasture rank was highest.We conclude that food limitation appears to be operating across these three sites.We used our results to assess the sensitivity of annual finite rate of increase (l) to changes in key demographic parameters and found that l was most sensitive to a change in adult survival, with the second most sensitive parameter being fecundity.Thus, if the aim of management is to reduce the size of the wild horse population then targeting adult survival is most important, followed by fecundity. Finally, we estimated the linear, negative, numerical response for wild horses between annual l and horses per unit pasture biomass.
KW - demographic rate
KW - Equus caballus
KW - feral horse
KW - numerical response
KW - population growth rate
KW - wild horse.
U2 - 10.1111/j.1442-9993.2011.02247.x
DO - 10.1111/j.1442-9993.2011.02247.x
M3 - Article
SN - 1442-9985
VL - 37
SP - 97
EP - 109
JO - Austral Ecology
JF - Austral Ecology
IS - 1
ER -