Action: Exclude domestic animals or wild hogs by fencing
- Three replicated, site comparison studies in the USA found that excluding livestock from streams or ponds did not increase numbers of amphibian species or overall abundance, but did increase larval abundance and abundance of green frog metamorphs. Two studies found that the abundance of green frogs and/or American toads was higher with grazing.
- One randomized, replicated, controlled, before-and-after study in the USA found that excluding cattle from ponds did not increase numbers of eggs or larval survival of Columbia spotted frogs. One before-and-after study in the UK found that pond restoration that included livestock exclusion increased pond use by breeding natterjack toads.
Livestock grazing can have significant effects on aquatic habitats through disturbance, trampling, erosion, reduced water quality and changes in vegetation structure and composition. Such changes may have detrimental effects on amphibian populations. However, grazing can also have beneficial effects on amphibians and their habitats. For example, a study found that three years after excluding livestock grazing by fencing, ungrazed temporary pools dried 50 days earlier than grazed pools (Pyke & Marty 2005). Other studies investigating the effects of grazing on amphibians are discussed in ‘Manage grazing regime’.
Pyke C.R. & Marty J. (2005) Cattle grazing mediates climate change impacts on ephemeral wetlands. Conservation Biology, 19, 1619–1625.
Supporting evidence from individual studies
A replicated, site comparison study in 1998–1999 of streams in pasture in Pennsylvania, USA (Homyack & Giuliano 2002) found that excluding livestock from stream banks did not increase amphibian species richness or abundance overall, but did increase tadpole numbers. There was no significant difference in overall species richness, abundance or biomass, or in the abundance of salamanders, bullfrogs Rana catesbeiana or wood frog Rana sylvatica between fenced and unfenced streams. However, tadpole captures were higher in fenced compared to unfenced areas (20 vs 6). In comparison, captures were higher in unfenced compared to fenced areas for green frogs Rana clamitans (8 vs 5/site) and American toads Bufo americanus (2.4 vs 1.5). Ten grazed and 10 recently fenced (1–2 yrs) streams were selected over 20 farms. Sites were 100m long by 10–15 m wide on both banks. Monitoring was undertaken using two drift-fences per site. Each fence had a pitfall trap, side-flap pail-trap and funnel trap that were checked 3–4 times/week in April–July.
A before-and-after study in 1991–1999 of 17 ponds in a reserve in Caerlaverock, Scotland, UK (Phillips, Patterson & Shimmings 2002) found that pond restoration with livestock exclusion increased natterjack toad Bufo calamita use of ponds for breeding. Out of 12 ponds restored in 1995–1998, 11 were used for breeding every year until 1999, compared to just four before restoration. Toads started to breed in the additional ponds one or two years after restoration. Toads continued to breed in ponds used before restoration and there was little change in use of unmanaged ponds. Of the 11 ponds restored in 1995–1996, 10 were used for breeding every year until 1999. In 1995–1999, 17 ponds were restored by clearing aquatic vegetation and excavation. Electric fences were installed around ponds during the summer to exclude cattle and sheep. Fences were removed after toadlet emergence. Eggs, tadpoles and toadlets were counted at least four times in each pond in May–August 1991–1992 and 1994–1999.
A replicated, site comparison study in 2002–2003 of streams within pasture in southwestern Georgia, USA (Muenz et al. 2006) found that excluding cattle did not result in increased amphibian species richness or abundance along stream banks, but did result in significantly higher numbers of in-stream larvae. There was no significant difference in amphibian species richness between buffered and unbuffered streams, although species richness tended to be higher where cattle were excluded. Abundance of adult salamanders and treefrogs Hyla spp. did not differ between sites. At three sites cattle grazed stream banks and at two other sites cattle had been excluded by fencing for over 25 years. Amphibians were monitored by walking a transect (100 x 4 m) along one side of each stream from March 2002 to March 2003. Bimonthly surveys under natural and artificial cover objects (30 tiles/site) and monthly surveys using tree pipes (10/site) and stream bottom samplers were undertaken.
A randomized, replicated, controlled, before-and-after study in 2002–2006 of 12 ponds in Oregon, USA (Adams et al. 2009) found that there was no effect of complete or partial cattle exclusion on Columbia spotted frog Rana luteiventris egg numbers, larval survival or size at metamorphosis. There was no significant difference between treatments for egg mass counts (exclusion: 8; partial exclusion: 4; access: 7); pre-treatment counts were 6–11. The same was true for larval survival index (exclusion: 25; partial exclusion: 52; access: 33; pre-treatment: 30–72) and size at metamorphosis (pre-treatment: 28–33 mm; post-treatment: 29–31). Fishless ponds within four blocks were randomly assigned to one of three treatments: complete cattle exclusion, exclusion from a section of pond (where most eggs were laid) or no exclusion. Fences were installed in 2003–2005 creating a 1–5 m buffer around ponds. Cattle were present in June–September (25–31 ha/cow-calf pair). Egg masses were counted and a sample of juveniles marked in 2002–2006.
A replicated, site comparison study in 2005–2006 of eight farm ponds in Tennessee, USA (Burton et al. 2009) found that the effects of excluding cattle from ponds depended on amphibian species. There was no significant difference in captures or egg mass abundance for 12 species. However, significantly higher numbers of green frog Rana clamitans metamorphs were captured at exclusion ponds compared to those with cattle grazing (0.06–0.10 vs 0.01–0.03 relative captures/day). The opposite was true for American toads Bufo americanus (0 vs 0.01–0.03). Length and/or mass were significantly greater at exclusion ponds for one and grazed ponds for four species. Four ponds had been exposed to grazing (132 cattle/pond ha/month) and four fenced to prevent grazing for 10 years. Ponds were 0.1–1.0 ha and within similar habitat. Amphibians were monitored using pitfall traps both sides of drift fencing enclosing half of each pond. Traps were set for two days/week in March–August 2005–2006. Weekly egg mass counts were also undertaken along transects.
- Homyack J.D. & Giuliano W.M (2002) Effect of streambank fencing on herpetofauna in pasture stream zones. Wildlife Society Bulletin, 30, 361–369
- Phillips R.A., Patterson D. & Shimmings P. (2002) Increased use of ponds by breeding natterjack toads, Bufo calamita, following management. Herpetological Journal, 12, 75-78
- Muenz T.K., Golladay S.W., Vellidis G. & Smith L.L. (2006) Stream buffer effectiveness in an agriculturally influenced area, Southwestern Georgia: Responses of water quality, macroinvertebrates, and amphibians. Journal of Environmental Quality, 35, 1924–1938
- Adams M.J., Pearl C.A., Mccreary B., Galvan K., Wessell S.J., Wente W.H., Anderson C.W. & Kuehl A.B. (2009) Short-term effect of cattle exclosures on Columbia spotted frog (Rana luteiventris) populations and habitat in northeastern Oregon. Journal of Herpetology, 43, 132-138
- Burton E.C., Gray M.J., Schmutzer A.C. & Miller DebraL. (2009) Differential responses of postmetamorphic amphibians to cattle grazing in wetlands. Journal of Wildlife Management, 73, 269-277