DOI: 10.5061/dryad.fxpnvx0nw
title: Domestic and wild native herbivores combined are still overgrazing Patagonia rangelands: A response to Marino et al. (2019)

description: 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
description: This data set of Guanaco (<em>Lama guanicoe</em>)
 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 km<sup>2</sup>. 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.  
description: There are missing values in the transect names in the Los Machos
 farm rows 1174-1250