A. Diaz Agriculture, Ecosystems and Environment 78 2000 249–259 253
Fig. 1. The range in faecal pellet counts per site in the three regions studied. Closed squares represent Fintray sites. Open circles represent Oyne sites. Closed triangles represent Dalcross sites.
adjustments to quadrat positions. The quadrats were revisited 7 days after having been cleared and a count
was made of all faecal pellets present. The differ- ences between the sites found by this method were in
agreement with those found using two other indices of rabbit incidence, night counts and the removal of
carrot bait Diaz, 1998.
3. Results
3.1. Assessment of relative plant palatability Plant species varied greatly in their observed palata-
bility to rabbits Table 3 Chi square for species grouped across plots = 2016.73, d.f. = 21, P 0.001.
Most palatable were many of the grass species such as Elymus repens and Arrhenatherum elatius, while
Senecio jacobaea and Cirsium vulgare were least palatable. Species’ differences in palatability were
generally consistent across plots even for many species of intermediate palatability, such as Poa annua
and Holcus lanatus Chi square for plot × species’ ef- fects Mather, 1966 = 100.63, d.f. = 168, P 0.995.
However, all of the most variable palatability scores were recorded for species of intermediate palatabil-
ity; results for Festuca rubra were by far the most variable Table 3.
3.2. Survey of sites to determine floristic composition and incidence of rabbits
Rabbit incidence, as estimated from counts of fae- cal pellets deposited, varied greatly between sites
in all three study regions Fig. 1. Large differ- ences were also found in plant species’ abundance
between sites in all three regions Table 4. The abundance of many plant species was significantly
254 A. Diaz Agriculture, Ecosystems and Environment 78 2000 249–259
A. Diaz Agriculture, Ecosystems and Environment 78 2000 249–259 255
Table 5 Spearman Rank correlations r between species’ abundance cover and levels of rabbit incidence number of faecal pellets in 625 m
2
sites in each region
a
Fintray n = 40 sites Oyne n = 40 sites
Dalcross n = 30 sites Species
r P
Species r
P Species
r P
Aphanes arvensis +
0.66 0.001
Myosotis discolor +
0.73 0.001
Poa annua +
0.80 0.001
Bellis perennis +
0.66 0.001
Holcus lanatus +
0.67 0.001
Veronica officinalis +
0.76 0.001
Poa annua +
0.66 0.001
Cerastium fontanum +
0.67 0.001
Myosotis discolor +
0.75 0.001
Agrostis capillaris +
0.54 0.001
Trifolium repens +
0.62 0.001
Erophila verna +
0.70 0.001
Myosotis discolor +
0.54 0.001
Lolium perenne +
0.58 0.001
Aphanes arvensis +
0.69 0.001
Cerastium fontanum +
0.50 0.001
Cirsium arvense +
0.50 0.001
Capsella bursa-pastoris +
0.64 0.001
Trifolium dubium +
0.50 0.001
Veronica serpyllifolia +
0.47 0.002
Myosotis arvensis +
0.64 0.001
Senecio jacobaea +
0.48 0.002
Ranunculus repens +
0.45 0.004
Viola arvensis +
0.58 0.001
Sagina procumbens +
0.48 0.002
Bellis perennis +
0.36 0.024
Agrostis capillaris +
0.53 0.003
Veronica officinalis +
0.48 0.002
Cirsium vulgare +
0.33 0.037
Vicia sativa +
0.52 0.003
Viola tricolor +
0.41 0.009
Papaver rhoeas +
0.50 0.005
Trifolium repens +
0.38 0.015
Trifolium dubium +
0.49 0.005
Cirsium vulgare +
0.35 0.025
Geranium molle +
0.44 0.015
Rumex acetosa +
0.37 0.044
Senecio vulgaris +
0.36 0.049
Dactylis glomerata −
0.54 0.001
Elymus repens −
0.52 0.001
Dacylis glomerata −
0.76 0.001
Poa trivialis −
0.48 0.002
Holcus mollis −
0.48 0.002
Taraxacum officinale group −
0.72 0.001
Arrhenatherum elatius −
0.42 0.007
Poa trivialis −
0.56 0.001
Epilobium obscurum −
0.32 0.048
Chamaenerion angustifolium −
0.53 0.003
Ranunculus repens −
0.47 0.009
Geranium dissectum −
0.46 0.010
a
Only species that occurred in at least 20 of the sites per region are shown. Only correlations of P 0.05 are shown.
correlated to levels of rabbit incidence Table 5. Species that were significantly more abundant
where rabbit incidence was higher tended to be low-growing forbs, e.g., Bellis perennis and Myoso-
tis discolor, or species of disturbed ground, e.g., Papaver rhoeas and P. annua. By contrast, species
whose abundance was negatively related to the inci- dence of rabbits were often taller-growing grasses
e.g., Dactylis glomerata and Poa trivialis.
3.3. The relationship between plant palatability and sward composition
The extent to which differences in sward compo- sition between grazed and ungrazed sites could be
related to differences in plant palatability was inves- tigated for the 22 species in the palatability trials.
Although the sites showed a range of incidence of rabbits and plant abundance Fig. 2, they were for
the purpose of this analysis categorised as ‘grazed’ or ‘ungrazed’ based on whether they had more than 125
faecal pellets per 100 m
2
per week recorded on the site. The mean relative abundance of each plant species on
‘ungrazed’ and ‘grazed’ sites was calculated. A clear relationship emerged when the percent palatability of
each plant species were plotted against the ratio of its mean relative abundance on ungrazed and grazed sites
Fig. 3. Most very palatable species were seen to be far more abundant on ungrazed sites and most un-
palatable species were more abundant on grazed sites.
4. Discussion
