10.5061/DRYAD.FXPNVX0NW
Oliva, Gabriel Esteban
0000-0002-7839-8851
National Agricultural Technology Institute
Paredes, Paula
National Agricultural Technology Institute
Ferrante, Daniela
National Agricultural Technology Institute
Cepeda, Carla
National Agricultural Technology Institute
Rabinovich, Jorge
National Scientific and Technical Research Council
Domestic and wild native herbivores combined are still overgrazing
Patagonia rangelands: A response to Marino et al. (2019)
Dryad
dataset
2020
Guanacos; Patagonia; fauna; animal density; Lama guanicoe; Distance analysis
guanacos
Carrying capacity
Populations
fauna
Sheep
rangelands
National Agricultural Technology Institute
https://ror.org/04wm52x94
2019-PD-E2-I038-002
2020-04-10T00:00:00Z
2020-04-10T00:00:00Z
en
https://doi.org/10.1111/1365-2664.13753
1790457 bytes
4
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
1. Oliva et al. (2019) based upon primary productivity estimates
concluded that, after long periods of overgrazing, Patagonia´s domestic
stocks adjusted to regional-scale herbivore carrying capacity at the end
of last century. Guanaco populations, a native camelid, increased
thereafter driving combined grazing pressures once again over carrying
capacity in some areas. 2. Marino, Rodriguez and Schroeder (2019)
argued that domestic grazing is not really at equilibrium because domestic
stocks are concentrated in areas that remain overgrazed. They support the
idea that guanacos auto-regulate their density by resource-defence
territoriality and are weak competitors with domestic herbivores,
occupying marginal areas. In their view Oliva et al. (2019) put guanacos
in the role of scapegoats, leaving domestic stocks unchecked. 3.
Equilibrium at regional scale does not preclude over and under-grazing at
smaller (local) scales. By separating areas with and without domestic
stocks Marino et al. (2019) estimated 28% and 73% overgrazing in the
provinces of Chubut and Santa Cruz, respectively. We recalculated these
estimates and found overgrazing of 28% and 47% for Chubut and Santa Cruz,
respectively. But when combined with guanaco densities overgrazing
increases to 48 and 108% for Chubut and Santa Cruz, respectively. 4. We
question the hypothesised lack of competitive value and effective
self-regulating mechanisms in guanacos. A data set of 13 sheep farms show
densities of 12-61 (mean 27) guanacos.km-2 with a combined grazing
pressure above carrying capacity. Populations in a protected area in
Chubut reached 42 guanacos.km-2, crashed during drought with 60%
mortality, and increased thereafter to 70 guanacos.km-2, but even at peak
numbers recruitment population rates remained extremely high. 5.
Synthesis and applications. Marino et al 2019 are right to question the
apparent equilibrium of domestic stocks with carrying capacity, as they
are concentrated in part of the territory that may be still overgrazed.
But ground assessments show that guanaco populations can reach densities
well over carrying capacity with or without sheep. This only stresses our
conclusion that joint management of the native-domestic herbivore system
is urgently needed. Farm management plans may transform an apparent
competitor into a valuable natural complementary resource to sheep raising
This data set of Guanaco (Lama guanicoe) presents the results of 323 km
of ground surveys performed in southern Patagonia. They were subdivided
in 361 transects from 0.8 to 10 km in length designed to evaluate guanaco
density in 13 farms with a total area of 4,740 km2. Guanaco groups were
spotted along the transects using Bushnell 10x25 1000 laser telemeter.
Data is presented in an excel .xls file that includes the variables: Farm
(name); Farm area (km2); Date of survey; Transect n°; Length of transect
(km); Latitude and Longitude in degrees, minutes, seconds (Datum WGS84);
Latitude (X) and Longitude (Y) in Transverse Mercator coordinates (Central
meridian -69, False northing 10001965.73 m) of the vehicle position,
Azimuth of the road (angle of deviation of the road direction in degrees,
where north=0); Angle (deviation of the guanaco group in relation to the
main road direction in degrees); Distance to the guanaco group (measured
by laser distanciometer, meters), Number of guanacos, Category (Adult,
Juvenile or Undetermined). Each row represents a guanaco group spotted.
Transects that did not spot any guanacos are presented without coordinates
and show 0 guanacos. This data was processed using Distance Sampling 7.0
(Buckland et al. 2005) software for density analysis. It was stratified by
date using global density with a Half-normal detectability function and
cosine expansion series in order to produce density estimations included
in the Table 2 of the paper. The .klm file includes cadastral outlines of
these farms, tracks of guanaco survey transects and position of the
guanaco groups.
There are missing values in the transect names in the Los Machos farm rows
1174-1250