INVESTIGADORES
BALDI Ricardo
artículos
Título:
Guanacos and sheep: evidence for continuing competition in arid Patagonia
Autor/es:
BALDI R.; ALBON S.D.; ELSTON D.
Revista:
OECOLOGIA
Editorial:
Springer-Verlag
Referencias:
Año: 2001 vol. 129 p. 561 - 570
ISSN:
0029-8549
Resumen:
Guanacos (Lama guanicoe) are the only wild
ungulate species widely distributed across the Patagonian
steppe and have undergone a precipitous population
decline since the introduction of domestic sheep (Ovis
aries) 100 years ago. There has been speculation that
sheep ranching may have played a major role in guanaco
population decline after monopolising the most productive
land because of competition for forage plants. Our
aim in this work was to estimate guanaco abundance and
account for its variation across nine different sites, two
seasons and two years. We conducted over 100 ground
surveys of both guanacos and sheep and estimated the
availability of the preferred plant species both animal
species might select in their diet. We found that (1)
sheep densities were up to 23 times higher than guanaco
densities in sympatric conditions, (2) at a protected site
without sheep, guanaco density was one order of magnitude
higher than at the rest of the sites, (3) across nine
different sites, sheep densities alone accounted for
around 60% of the variation in guanaco abundance, (4)
guanaco densities were negatively related to both total
plant cover and availability of the preferred plant species
in their diet, which were both positively associated with
sheep density, and (5) within-site changes in guanaco
densities between seasons and years were negatively related
to changes in sheep densities. Our results are consistent
with predictions on interspecific competition for
food resources, although we cannot rule out possible effects
of other human-related activities influencing guanaco
abundance. We conclude that sheep compete with
guanacos for forage in arid Patagonia.Lama guanicoe) are the only wild
ungulate species widely distributed across the Patagonian
steppe and have undergone a precipitous population
decline since the introduction of domestic sheep (Ovis
aries) 100 years ago. There has been speculation that
sheep ranching may have played a major role in guanaco
population decline after monopolising the most productive
land because of competition for forage plants. Our
aim in this work was to estimate guanaco abundance and
account for its variation across nine different sites, two
seasons and two years. We conducted over 100 ground
surveys of both guanacos and sheep and estimated the
availability of the preferred plant species both animal
species might select in their diet. We found that (1)
sheep densities were up to 23 times higher than guanaco
densities in sympatric conditions, (2) at a protected site
without sheep, guanaco density was one order of magnitude
higher than at the rest of the sites, (3) across nine
different sites, sheep densities alone accounted for
around 60% of the variation in guanaco abundance, (4)
guanaco densities were negatively related to both total
plant cover and availability of the preferred plant species
in their diet, which were both positively associated with
sheep density, and (5) within-site changes in guanaco
densities between seasons and years were negatively related
to changes in sheep densities. Our results are consistent
with predictions on interspecific competition for
food resources, although we cannot rule out possible effects
of other human-related activities influencing guanaco
abundance. We conclude that sheep compete with
guanacos for forage in arid Patagonia.Ovis
aries) 100 years ago. There has been speculation that
sheep ranching may have played a major role in guanaco
population decline after monopolising the most productive
land because of competition for forage plants. Our
aim in this work was to estimate guanaco abundance and
account for its variation across nine different sites, two
seasons and two years. We conducted over 100 ground
surveys of both guanacos and sheep and estimated the
availability of the preferred plant species both animal
species might select in their diet. We found that (1)
sheep densities were up to 23 times higher than guanaco
densities in sympatric conditions, (2) at a protected site
without sheep, guanaco density was one order of magnitude
higher than at the rest of the sites, (3) across nine
different sites, sheep densities alone accounted for
around 60% of the variation in guanaco abundance, (4)
guanaco densities were negatively related to both total
plant cover and availability of the preferred plant species
in their diet, which were both positively associated with
sheep density, and (5) within-site changes in guanaco
densities between seasons and years were negatively related
to changes in sheep densities. Our results are consistent
with predictions on interspecific competition for
food resources, although we cannot rule out possible effects
of other human-related activities influencing guanaco
abundance. We conclude that sheep compete with
guanacos for forage in arid Patagonia.) 100 years ago. There has been speculation that
sheep ranching may have played a major role in guanaco
population decline after monopolising the most productive
land because of competition for forage plants. Our
aim in this work was to estimate guanaco abundance and
account for its variation across nine different sites, two
seasons and two years. We conducted over 100 ground
surveys of both guanacos and sheep and estimated the
availability of the preferred plant species both animal
species might select in their diet. We found that (1)
sheep densities were up to 23 times higher than guanaco
densities in sympatric conditions, (2) at a protected site
without sheep, guanaco density was one order of magnitude
higher than at the rest of the sites, (3) across nine
different sites, sheep densities alone accounted for
around 60% of the variation in guanaco abundance, (4)
guanaco densities were negatively related to both total
plant cover and availability of the preferred plant species
in their diet, which were both positively associated with
sheep density, and (5) within-site changes in guanaco
densities between seasons and years were negatively related
to changes in sheep densities. Our results are consistent
with predictions on interspecific competition for
food resources, although we cannot rule out possible effects
of other human-related activities influencing guanaco
abundance. We conclude that sheep compete with
guanacos for forage in arid Patagonia.