Agriculture, Ecosystems and Environment 78 2000 249–259
Can plant palatability trials be used to predict the effect of rabbit grazing on the flora of ex-arable land?
A. Diaz
∗
Farmland Ecology Unit, Scottish Agricultural College, Mill of Craibstone, Bucksburn, Aberdeen, AB21 9TS, UK Received 10 May 1999; received in revised form 10 May 1999; accepted 28 September 1999
Abstract
Surplus food production has led to increased interest in taking land out of arable farming, notably under set-aside regulations, and converting it into grasslands that resemble semi-natural plant communities. Despite the value of being able to predict the
long-term success of such habitat creation projects, there is little ecological data available on which to base such predictions. This study tests whether plant palatability trials can be a useful method to predict the effect of grazing by rabbits on the
success of individual species growing in grasslands. The palatability of 22 common, grassland species was tested by offering wild rabbits pot-grown plants of each species in a variety of grassland vegetation backgrounds in NE Scotland. Plants were
inserted into plots consisting of a regular grid of holes cut into rabbit-grazed grasslands. The palatability of each species was tested in 10 such plots, on 20 occasions each. Plots varied in their vegetation composition and were each grazed by
rabbits from a different warren. Plant species were found to differ greatly in their palatability to rabbits. Palatability was found to be unaffected by the composition of the surrounding vegetation. A survey was also carried out to determine the
floristic composition of ungrazed and rabbit grazed swards of 8-year old set-aside. A strong relationship was found between the palatability of most plant species and their comparative abundance in ungrazed and grazed swards. Possible reasons for
the few exceptions are discussed. In general, these findings indicate that palatability trials can be a useful and robust method of predicting the effect of rabbits on the success of individual plant species growing in grasslands. A method such as this,
that allows the impact of rabbits on floristic composition to be predicted, can be used to inform grassland recreation and management decisions. ©2000 Published by Elsevier Science B.V. All rights reserved.
Keywords: Palatability; Rabbits; Grazing; Set-aside; Herbivory
1. Introduction
There is much current interest in the potential for converting arable land into grasslands that resemble
long established, semi-natural vegetation types. How-
∗
Present address: School of Conservation Sciences, Bournemouth University,
Dorset House,
Talbot Campus,
Fern Barrow,
Poole, Dorset, BH12 5BB, UK; Tel.: +44-1202-595178; fax: +
44-1202-595255.
ever, arable systems and semi-natural vegetation types characteristically have a very different soil chem-
istry, flora and fauna. Consequently, many ecological changes need to occur during the transition from an
arable system to a re-created semi-natural vegetation and these need to be well understood. Rabbits, which
can be common on farmland, are known to influence the floristic composition of many types of vegetation
Farrow, 1917; Fenton, 1940; Gillham, 1955; Ran- well, 1960; Thomas, 1960, 1963; Watt, 1981; Bishop
0167-880900 – see front matter ©2000 Published by Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 8 8 0 9 9 9 0 0 1 3 1 - 0
250 A. Diaz Agriculture, Ecosystems and Environment 78 2000 249–259
and Davy, 1984; Foran, 1986. Rabbits have a range of direct and indirect effects on plant community
composition. Direct effects can be caused by factors such as herbivory, scrapes, middens, trampling and
seed dispersal in faeces. All of these factors may also produce indirect effects such as changes in the
activity of other herbivores or changes in plant–plant competitive interactions. The effects of rabbit activity
occur at different scales — for example, scrapes and middens can result in dramatic but localised impacts
on vegetation composition Thomas, 1963; Dixon and Hambler, 1993, while the effects of herbivory may
be more diffuse and so affect a greater proportion of the vegetation at a locality. Recent investigations into
the influence of rabbits on vegetation have sought to distinguish the impact of the various effects Crawley,
1990; Prins and Nell, 1990; Hambler et al., 1995. Achieving this is difficult as many of the effects may
be impossible to separate experimentally Hambler et al., 1995 or may significantly interact, so impeding
interpretation. Direct measurement of the extent of herbivory on different plant species is very difficult
to obtain for free-living rabbits with open access to feeding areas. An index of relative herbivory can
be obtained by scoring the proportion of stems and leaves that have been nibbled Zeevalking and Fresco,
1977, but this gives no information on the amount of each stem or leaf that has been consumed unless
fenced controls are used. However, the use of fenced controls has two important weaknesses; i the cages
may cause micro-environmental changes Williams, 1951; Watt, 1957, 1960, 1962, and ii they may not
produce an accurate measure of herbivory as the rel- ative growth of different species may not be the same
under grazed and ungrazed conditions. Alternative techniques such as the analysis of rabbit stomach con-
tents Myers and Bults, 1977 or rabbit faeces e.g., Williams et al., 1974; Bhadresa, 1977 can establish
the proportion of different species consumed but not where they were consumed. Direct observation of
grazing can establish where species were consumed but not the proportion, unless combined with an anal-
ysis of gut contents immediately after the feeding event. Such data would be difficult to obtain for wild
rabbits in field conditions.
This study examines the potential for a non-invasive and non-destructive approach to estimating relative
herbivory by wild rabbits in the field. It investigates the relative palatability of a range of grasses and
forbs to wild rabbits and then examines the extent to which such data can be used to predict the difference
in abundance cover of these species in grazed and ungrazed swards. Included is an examination of
whether relative palatabilities are consistent when tested against a range of vegetation types.
2. Methods
