Lowe, Wheeler & Twigg: Impact of rabbits 
Table 1 
Analysis (ANOVA) of the differences between the ungrazed (exclosure) and grazed (open) plots over the two year 'experimental' 
period. SS, small shrub cover; SG, sedge and grass cover; OM, other monocotyledonous plant cover; SR-Quadrats, number of quadrats 
with visible seedlings or reshooting rootstocks; SR-Score, seedlings and reshoots score without square root transformation. Significant P 
values are in bold. 
Probability Treatment means Year means 
5% LSD 5% LSD 
Category 
Treatment 
Year 
Treatment 
x Year 
Exclosure 
Open 
critical 
values A 
2000 
2001 
critical 
values A 
SS 
0.460 
0.035 
0.802 
0.177 
0.184 
0.021 
0.189 
0.173 
0.015 
SG 
<0.001 
<0.001 
0.094 
0.428 
0.354 
0.024 
0.435 
0.346 
0.019 
OM 
0.811 
0.440 
0.699 
0.009 
0.008 
0.006 
0.008 
0.009 
0.003 
SR Quadrats 
0.060 
0.004 
0.468 
3.55 
3.03 
0.541 
2.93 
3.65 
0.484 
SR Score 
<0.001 
<0.001 
0.507 
6.05 
4.35 
0.726 
4.45 
5.95 
0.755 
(No transform) 
A The difference between each 'pair' of means for each parameter needs to be greater than the 5% LSD value to be significant at the 5% 
level. 
vegetation with and without rabbit grazing (i.e. the 
treatment). However, the analyses did remove any 
differences between sites (block stratum), and between 
the 20 locations (plots) at each individual site (block.pair 
stratum) before examining the effects of treatment 
(ungrazed vs grazed) and year (2000 vs 2001). The 
covariate (i.e. the 1999 pre-treatment levels) was 
significant (P < 0.05) for all of the plant parameters tested. 
This indicates that the response of the vegetation in 2000 
and 2001 was related to the amount and species diversity 
of the remnant vegetation at the start of the experiment 
in 1999. Thus, the use of the covariate 'compensates' for 
this relationship so that only the treatment effects are 
compared (Zar 1984). 
Rabbit grazing had a significant impact upon the 
sedges and grasses, and on the abundance of seedlings 
and reshoots (treatment effect; Table 1). This effect was 
Figure 5. Changes in the rabbit abundance index (mean dung 
pellets per plot) for the fenced and unfenced areas of remnant 
vegetation during the investigation of the longer-term effects of 
rabbits being confined within this vegetation. Values are mean 
(± se) of the number of pellets per 1 m 2 quadrat (n = 30). Sites 1 
and 2 had been fenced for approximately 4-5 years and 1 year 
respectively, prior to the experimental plots being established 
(i.e. when the twenty 10 m x 10 m exclosures were fenced). 
also greater in Year 2 as the year effect was significant for 
these two vegetation parameters (Table 1). However, 
although the magnitude of this change varied between 
years, the overall trends were the same in both years as 
none of the interactive terms (treatment x year) were 
significant (Table 1). 
Changes in rabbit abundance throughout the long¬ 
term trial, as indicated by the RAI, are given in Fig 5. 
Rabbit numbers on Site 2, the area that had been fenced 
approximately 1 year prior to the experiment, were 
moderate and generally constant throughout apart from 
the higher numbers during the breeding season (spring/ 
November). In contrast, rabbit numbers were lower on 
Site 1, the area that had been fenced for approximately 4- 
5 years. Although rabbit numbers were similar between 
the two sites at the commencement of the trials, the 
seasonal breeding peak in numbers, as determined by 
the RAI, was almost absent on Site 1 in subsequent years 
(Fig 5). 
Figure 6. Changes in the percentage cover of the sedges and 
grasses category as a result of rabbit grazing in the fenced and 
unfenced areas of remnant vegetation at Tomlinson's site. 
Results from rabbit exclosure plots are included for comparison. 
Values are mean (± se) percentage cover of these plants in the 10 
plots at each site. Sites 1 and 2 had been fenced for 
approximately 4-5 years and 1 year, respectively prior to the 
experimental plots being established. 
101 
