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Providing evidence to improve practice

Action: Manage vegetation using livestock grazing Terrestrial Mammal Conservation

Key messages

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  • Six studies evaluated the effects on mammals of managing vegetation using livestock grazing. Four studies were in the USA, one was in Norway and one was in Mexico.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

BEHAVIOUR (5 STUDIES)

  • Use (4 studies): One of four studies (three replicated controlled studies and a before-and-after study), in the USA and Norway, found that sheep-grazed pasture was used by feeding reindeer more than was ungrazed pasture. One found mixed effects on Rocky Mountain elk use of grazed plots and another found no response of Rocky Mountain elk to spring cattle grazing. The forth study found cattle grazing to increase the proportion of rough fescue biomass utilized by elk in the first, but not second winter after grazing.
  • Behaviour change (1 study): A replicated, paired sites study in Mexico found that in pastures grazed by cattle, Tehuantepec jackrabbits spent more time feeding than they did in pastures not grazed by cattle.

Supporting evidence from individual studies

1 

A before-and-after study in 1948–1974 in a predominantly grassland wildlife management area in Oregon, USA (Anderson & Scherzinger 1975) found that when cattle grazing was reintroduced, there was a mixed effect on Rocky Mountain elk Cervus canadensis abundance. Four years after cattle were first reintroduced, elk numbers (325) were similar to those before cattle reintroduction (120–500), although disturbance by snowmobiles during this period may have reduced abundance. After nine years, elk numbers (1,191) were higher than before reintroduction (120–500). In 1960 the site was designated as a wildlife management area. Cattle grazed ceased in 1960 but was reintroduced in 1965 at a rate of 340 animal unit months (AUMs – a grazing measure based on forage requirement). Cattle grazing was increased to 700 AUMs in 1967 and 900 AUMS in 1969–1974. Cattle grazing was managed to optimise forage conditions and prevent accumulation of residual unpalatable vegetation. Elk were counted from horseback, along fixed routes, five times each winter, in 1948–1974.

2 

A randomized, replicated, controlled study in 1971–1974 of a grassland in Washington, USA (Skovlin et al. 1983) found that spring grazing by cattle did not increase pasture use by Rocky Mountain elk Cervus canadensis nelsoni the following winter. There were no significant differences in the numbers of elk using cattle-grazed and ungrazed plots in the first winter (grazed: 60; ungrazed: 68 elk days/ha) or third winter (grazed: 38; ungrazed: 51 elk days/ha) after cattle grazing commenced. In the second winter, fewer elk used grazed plots (71 elk days/ha) than used ungrazed plots (98 elk days/ha). Three plots (9.3 ha each) were randomly assigned to be grazed by cattle and three were ungrazed. Grazing was at a rate of one mature cow or equivalent/2.4 ha, from mid-April to early-June in 1971–1973. Elk pellets were counted each spring to assess elk use of plots in winters of 1971–1972, 1972–1973, and 1973–1974.

3 

A replicated, controlled study in 1983–1987 of a rough fescue Festuca scabrella-dominated grassland in Montana, USA (Jourdonnais & Bedunah 1990) found that cattle grazing increased the proportion of rough fescue biomass utilized by elk Cervus canadensis nelsoni in the first, but not second winter after grazing. Over the first winter, a higher proportion of rough fescue was utilized by elk in cattle-grazed plots (58%) than in non-cattle-grazed plots (24%). There was no difference between plots the following winter (cattle grazed: 78%; ungrazed: 69%). Additionally, the proportion of rough fescue plants grazed by elk over the four years from outset of the experiment did not differ between plots grazed (26–98%) or ungrazed (15–97%) by cattle. Cattle-grazing entailed 104 cow/calf pairs on a 104-ha pasture, from 18 October 1983 to 22 December 1983. There were three ungrazed control plots, 2 ha each in extent. Six caged and six non-caged samples on each treatment were clipped in April 1985 and 1986 to determine elk utilization by biomass. Additionally, utilization of rough fescue was assessed by determining the proportion of plants grazed by elk by inspecting the closest plant to 50 points along each of two transects per plot.

4 

A replicated, controlled, before-and-after study in 1998–2000 in five grassland sites in California, USA (Kelt et al. 2005) found that using livestock grazing to manage vegetation had mixed effects on the abundance of Stephens’ kangaroo rat Dipodomys stephensi. One year after grazing started, there was no difference in the density of Stephens’ kangaroo rat (9 animals/ha) compared to before grazing started (9 animals/ha). However, after two years, their density had increased to 22 animals/ha. Areas that were grazed had a lower density of kangaroo rats both before grazing started and after one year when compared to ungrazed areas (9 animals/ha vs 28 animals/ha), but after two years there was no longer a significant difference (22 animals/ha vs 28 animals/ha). In 1998 and 1999, two sites were grazed by sheep for between four hours and three days, and two sites were not grazed in either year. An unspecified number of Sherman live traps were placed in each site. In 1996–2000, at unspecified times of year, trapping was conducted over three consecutive nights. Traps were opened in the evening and checked at midnight and at dawn and animals caught were individually marked.

5 

A replicated, controlled study in 2003–2005 of pasture at a site in northern Norway (Colman et al. 2009) found that sheep-grazed pasture was used by feeding reindeer Rangifer tarandus more than was ungrazed pasture. Reindeer spent more time feeding in low-intensity sheep grazed plots (30% of all feeding observations) and high-intensity sheep grazed plots (28%) than in ungrazed plots (17%). Sixteen plots were established in each of two 0.3-ha fields. Each field contained four plots of each high-intensity sheep grazing, low-intensity sheep grazing and ungrazed pasture. Low- and high-intensity sheep grazing comprised two (ewe and yearling) and four (ewe and three lambs) sheep respectively, for 10 days at the beginning of July in 2003 and 2004, contained within temporary internal fencing. Four 2-year-old male reindeer were grazed on each field for two weeks in autumn 2003, spring and autumn 2004 and spring 2005. Reindeer feeding patch choice was determined by timed observations.

6 

A replicated, paired sites study in 2014 in 10 pastures in Oaxaca, Mexico (Luna-Casanova et al. 2016) found that in pastures grazed by cattle, Tehuantepec jackrabbits Lepus flavigularis spent more time feeding than they did in pastures not grazed by cattle. When in pastures with cattle, Tehuantepec jackrabbits spent more time feeding (75%) than when in pastures without cattle (66%). The study was conducted in five pastures with cattle (average of 16 cows/pasture) and five pastures without. Pastures averaged 11 ha extent and were located next to each other. Cattle moved freely within each pasture. In March 2014, twenty-two adult jackrabbits were captured, radio-tagged and released at the capture site. Animals were followed for ≤10 days in March and September 2014. Additionally, jackrabbit behaviour was recorded from five fixed observation sites throughout the study area. The behaviour (eating, resting and socializing) of jackrabbits was recorded between 6:00–10:00 h and 17:00–20:00 h in pastures with or without cattle.

Referenced papers

Please cite as:

Littlewood, N.A., Rocha, R., Smith, R.K., Martin, P.A., Lockhart, S.L., Schoonover, R.F., Wilman, E., Bladon, A.J., Sainsbury, K.A., Pimm S. and Sutherland, W.J. (2020) Terrestrial Mammal Conservation: Global Evidence for the Effects of Interventions for terrestrial mammals excluding bats and primates. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.