The effects of grazing by pygmy goats (Capra hircus) on limestone scrub. Sophie Smith

The effects of grazing by pygmy goats (Capra hircus) on limestone scrub. Sophie Smith

Introduction Site Information Clennon limestone grassland (SX880620) is owned by the Whitley Wildlife Conservation Trust. The Clennon Gorge nature reserve of which the grassland is part covers approximately 24.3 hectares (60 acres). The site has been given the status of County Wildlife Site by Devon Wildlife Trust, due to the limestone grassland and semi-natural ancient woodland, (Weeks 1997). The valley has a Carboniferous limestone plateau on it s eastern side, on this is the grassland. The grassland contains characteristic calcareous grassland species, however the area is being encroached upon by tree and shrub species such as wild privet (Ligustrum vulgare), dogwood (Thelycrania sanguinea), hawthorn (Crataegus monogyna), gorse (Ulex europaea) and ash (Fraxinus excelsior)( Weeks 1997-2002). The limestone grassland is not only an important local habitat but an educational resource, school groups have access to the grassland to study succession. Limestone grassland conservation importance Limestone grassland has largely developed on shallow lime-rich soils, usually over limestone rocks, and is typically managed as part of a pastoral or mixed farming system. It includes a variety of vegetation types but often has a very rich flora. (www.english-nature.org.uk) Only one percent of land in Britain is now limestone grassland,(weeks 1997). Since World War II 97% of wildflower rich grassland has been destroyed. (Devon Wildlife Trust 1991)

Devon wildlife trust (1991) states that the loss of grassland and development of scrub probably resulted from the breakdown in traditional farming practices such as sheep grazing and was exacerbated by the decrease in rabbit populations from disease. Limestone grassland in Devon is restricted to small areas along the southern coast,(weeks 1997). However unimproved calcareous grassland in Torbay covers 22.36ha, 0.36% of the total area of Torbay habitats, therefore Torbay has the most extensive areas of calcareous grassland in Devon (Devon wildlife trust 1991) Figure 1. shows the significance of limestone grassland in England, the Torbay area indicates a nationally significant area of grassland. Figure 1. Map of Britain showing the national and local significant areas of limestone grassland. (National or local significance is based on factors that can include the area of the habitat, its diversity, and presence of rare communities or species.) Torbay & surrounding area 1998-2004 English Nature, Northminster House, Peterborough PE1 1UA England Taken from www.english-nature.org.uk

Background on project There has been a dramatic decrease in limestone grassland since the end of the last world war and with it the specialised flora of this habitat. Clennon is therefore high priority for restoration and maintenance for the Reserves Warden. The limestone grassland requires management to retain the habitat at it s present successional stage, preventing it from developing into scrub and then woodland. The management involves the joining up of fragmented areas of the remaining grassland, the clearance of established and encroaching scrub and trees. (Weeks 1997) In the past the grassland was maintained through the grazing of a colony of rabbits, this kept the grass short and prevented the encroachment of shrub species and woodland. However in recent years the rabbits have become less effective at holding back the surrounding woodland, and human management has been required. This has involved the cutting back of scrub and trees by the warden, however this management has not been satisfactory and a new management technique was needed. The reserves warden decided to try implementing extra grazing in the area as it is a natural and proven method of control. Clennon grassland, like many other limestone grasslands has very shallow soil, this made the use of large livestock which might poach the ground unsuitable. Paignton Zoo houses many pygmy goats (Capra hircus) so these were easily available for an experimental trial.

The pygmy goats are light animals which will not damage the soil, are hardy enough to withstand the conditions out on the hill and are know to selectively graze on scrub species preferentially. Two sites were picked, both were at the edge of the grassland and contained above average scrub and woodland plants. These sites were used for experimental trails into the effects of the goats upon the plants of the grassland. Aims Implement a way of monitoring the changes in the grassland Assess the vegetation at each site before and after goat grazing to look at the short term affects. Hypothesis Short term Significant decline in general height and percentage cover in shrub species such as bramble, spindle and ash. Long term A compositional change in species found from shrub and tree species to more typical limestone grassland species such as pyrmidal orchids, autumn ladie s tresses, salad burnet, self heal and st. john s wort. Methods Fenced areas setup. 10 x1m2 permanent quadrats put into the fenced area, using subterrain metallic markers, which could be located again using metal detectors. These were used to prevent goats tampering with them or injuring themselves on them. Vegetation survey before and after goats species identified, % cover and maximum height recorded, (see figure 2.)

Figure 2. Time scale of project Date 27/10/03 Fence installed 50m of fence 28/10/03 Fence enlarged 100m of fence 04/11/03 Goats moved in 06/11/03-11/11/03 Permanent quadrats installed and sampled (site 1) 19/01/04-22/01/03 Re-surveyed quadrats 23/01/04 Installed permanent quadrats into site 2 and sampled 29/01/04 Fence installed and Goats moved into site 2 Results Figure 3 1.4 Mean maximum height of vegetation for before and after goat grazing 1.2 1 Height -m 0.8 0.6 0.4 0.2 0 1 2 3 4 5 6 7 8 9 10 Quadrats Before grazing After grazing Figure 3. indicates a drop in mean maximum heights in all quadrats except 2, from before to after the goats where placed in site one.

The data was tested using Anderson-Darling and found to be normal, a Paired T-test was then carried out on the mean maximum height for all quadrats before and after grazing (see Minitab worksheet 1). Minitab worksheet 1. Paired T-Test and CI: Sampling 1, Sampling 2 Paired T for Sampling 1 - Sampling 2 N Mean StDev SE Mean Sampling 1 10 0.5700 0.3013 0.0953 Sampling 2 10 0.3175 0.2379 0.0752 Difference 10 0.2525 0.2268 0.0717 95% CI for mean difference: (0.0903, 0.4147) T-Test of mean difference = 0 (vs not = 0): T-Value = 3.52 P-Value = 0.007 P < 0.05 reject null hypothesis that difference between sampling 1 and sampling two is zero. Therefore can suggest that there is a significant difference between the heights of sampling one and two, so goat grazing has been effective in decreasing the overall height of the vegetation. Figure 4. Percentage cover for unwanted species Mean Percentage coverover 10 quadrats 45 40 35 30 25 20 15 10 5 0 Spear Thistle Bramble Wild Privet Spindle Wood spurge Buddlea Ash Hawthorn Spurge Laurel Sampling one Species Sampling tw o Figure 4. indicates a decrease in percentage cover for some species such as spear thistle and bramble and spindle. The data was then tested for normality and a Paired T-test carried out, adding all of the undesirable species together, (see minitab worksheet 2.).

Minitab worksheet 2. Paired T for sampling1 - sampling2 N Mean StDev SE Mean sampling1 9 8.23 11.19 3.73 sampling2 9 7.21 10.53 3.51 Difference 9 1.022 2.919 0.973 95% CI for mean difference: (-1.221, 3.266) T-Test of mean difference = 0 (vs not = 0): T-Value = 1.05 P-Value = 0.324 P> 0.05, accept the null hypothesis that there is no significant difference between the average percentage cover values before and after the goats grazed site one for unwanted plant species. Figure 5. average percentage cover 45 40 35 30 25 20 15 10 5 0-5 Grass Ground Ivy Ladies Bed-Straw Figure 5. indicates an increase in grassland species such as wild strawberry and self heal, The data was tested for normality and a Paired T-test carried out ( see minitab worksheet 3.) Percentage cover grassland species Birds Foot-Trefoil Wild Strawberry species Self Heal Speedwell Perforate St. John's Wort Dog Violet Sedge Clover Sampling 1 Sampling 2

Minitab worksheet 3. Paired T for before - after N Mean StDev SE Mean before 13 11.52 13.70 3.80 after 13 11.91 24.10 6.68 Difference 13-0.39 15.32 4.25 95% CI for mean difference: (-9.65, 8.87) T-Test of mean difference = 0 (vs not = 0): T-Value = -0.09 P-Value = 0.929 P>0.05, accept the null hypothesis of no significant difference. Percentage cover of grassland species was not significantly different before and after the goats grazed the area. Conclusions In the short term as expected the mean height was significantly reduced at site one by the goats. However a further two or three years monitoring is needed to tell if the long term aim of compositional change has been met. Over the short term the percentage cover of both unwanted species and grassland species was not significantly changed. This is something that needs to be monitored over the long term. Any short term changes in particular species percentage cover seen could have been due entirely to seasonal variation in plant growth, as the two samplings that were carried out where several months apart. Site two needs to be reassessed to determine if the trend in height reduction is shown at this site as well

References Bowker, D.W, Minitab for biologists, Cardiff School of Biosciences. Devon Wildlife Trust et. Al. (1991) Torbay Wildlife Survey, report on the wildlife resource in Torbay. Rose,F (1991) Wildflower Key- British Isles- N.W.Europe, Penguin Books Ltd. Weeks, S.R (1997-2002) Management plan for Clennon gorge. www.english-nature.org.uk, limestone grasslands