Behavioural Indicators of Intra- and Inter-Specific Competition: Sheep Co-Grazing with Guanaco in the Patagonian Steppe

Abstract

In extensive livestock production, high densities may inhibit regulation processes, maintaining high levels of intraspecific competition over time. During competition, individuals typically modify their behaviours, particularly feeding and bite rates, which can therefore be used as indicators of competition. Over eight consecutive seasons, we investigated if variation in herd density, food availability, and the presence of a potential competitor, the guanaco (Lama guanicoe), was related with behavioural changes in domestic sheep in Chilean Patagonia. Focal sampling, instantaneous scan sampling, measures of bite and movement rates were used to quantify behavioural changes in domestic sheep. We found that food availability increased time spent feeding, while herd density was associated with an increase in vigilant behaviour and a decrease in bite rate, but only when food availability was low. Guanaco presence appeared to have no impact on sheep behaviour. Our results suggest that the observed behavioural changes in domestic sheep are more likely due to intraspecific competition rather than interspecific competition. Consideration of intraspecific competition where guanaco and sheep co-graze on pastures could allow management strategies to focus on herd density, according to rangeland carrying capacity.

Changes in foraging behaviour suggest competition between wild and domestic ungulates: Guanaco and domestic sheep in southern Patagonia

“…Study sites included two national parks (areas not-shared with sheep, hereafter 'nonshared areas'): Torres del Paine National Park (TPNP) (50°55 0 44.4″ S, 72°38 0 47.1″ W) and Pali Aike National Park (PANP) (52°6 0 36.0″ S, 69°42 0 39.6″ W); and two sheep ranches (shared areas): Serena ranch (SER) (53°20 0 56.4″S, 68°52 0 33.6″ W) and Cañad on Grande ranch (CAN), (52°8 0 13.2″S, 52°8 0 13.2″ S). The two ranches averaged sheep stocking densities of 1.10 AE 1.20 and 1.81 AE 0.51 individuals ha À1 for SER and CAN respectively (Fern andez et al, 2021). Average temperatures range from À4°C in winter to 10°C in summer (Peel et al, 2007).…”

“…For details on distance sampling analysis, see the supplementary materials. Sheep densities are reported in Fern andez et al (2021). To estimate quantities of vegetation biomass available to guanaco and sheep, between three and five stops were made to collect vegetation samples along transects every 500 m. At each stop, a 20-m square grid was set up and three randomly placed 0.5 9 0.2 m 2 vegetation Daubenmire quadrats (Daubenmire, 1959) were clipped to ground level within it, collecting all above ground vegetation in the quadrat.…”