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Bourget, 1989 and littorinds Chapman and Underwood, 1996 was influenced by local environmental heterogeneity, time of emersion and the weather. The decision to forage
by the whelk Thais lapillus L. was influenced by local environmental conditions and the state of hunger of the animals Burrows and Hughes, 1989, 1991.
Much evidence now suggests that behaviour of intertidal invertebrates is very flexible. It changes in response to broad-scale and localized environmental and physiological cues
and, therefore, would be expected to vary spatially and temporally. Nevertheless, many studies of behaviour are done once in one area and the results presented as if they
demonstrate fixed patterns of behaviour.
3. The change in focus from broad to small scales of spatial patterns
Along with the change of emphasis from fixed to variable patterns of behaviour, there has been a change in focus from broad-scale patterns of distribution and abundance to
patterns of abundance which vary at an hierarchy of different spatial scales, which themselves can vary from place to place Underwood and Chapman, 1996. Many
factors cause patchiness, but this change in focus has been strongly influenced by the recognition of the importance that natural disturbances play in ecological interactions
Pickett and White, 1985 and that, on intertidal shores, many disturbances are relatively localized and patchy e.g. Dayton, 1971; Sousa, 1979, 1984; Archambault and Bourget,
1996; Benedetti-Cecchi and Cinelli, 1996; Underwood, 1999.
Distribution and abundance of animals on intertidal shores were originally thought to be governed primarily by large-scale physical factors, particularly the height above sea
level, or the degree of exposure to waves Lewis, 1964; Stephenson and Stephenson, 1972. These theories were often supported by laboratory tests on physiological
tolerances of different species to desiccation or heat, which often showed a greater tolerance in those species which lived higher on the shore Brown, 1960. In many
cases, tolerances were, however, far in excess of what might normally be encountered and their ecological importance has been debated McMahon, 1990. In other studies,
there has been little relationship between vertical zonation and physiological tolerances McMahon and Britton, 1985, or animals have behaviours that cause them to avoid
potential lethal conditions Wolcott, 1973. Subsequent experimental work on responses of organisms to physical stress in the field Connell, 1972; Menge, 1978a,b; Underwood,
1991a, among many others and detailed quantification of patterns of abundance at a hierarchy of scales Archambault and Bourget, 1996; Benedetti-Cecchi and Cinelli,
1996; Thompson et al., 1996; Underwood and Chapman, 1996 have suggested that physical stresses associated with these two broad-scale gradients are not adequate to
describe patterns of abundance for many intertidal organisms.
While attention was focussed on broad-scale patterns, researchers assumed that behaviour was influenced by large-scale variables, such as amounts of emersion or
wave-exposure. Therefore, it was expected that behaviour could differ among heights on a shore Chelazzi et al., 1983, or among shores of different exposure Cook and Cook,
1978. There was little attempt to document variability in behaviour from site to site at
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.G. Chapman J. Exp. Mar. Biol. Ecol. 250 2000 77 –95
the same level of a single shore. Behaviour was compared among shores which differed in wave-exposure or tidal inundation, as if there was little variability within a shore,
using a single site per shore and thereby replicating the wrong units of focus pseudoreplication sensu Hurlbert, 1984. For example, Cook and Cook 1978
examined patterns of activity in two species of siphonarian limpets in three sites in the Marshall Islands and two sites in Bermuda. The sites were selected to vary according to
wave-exposure, slope, drainage and exposure to sun, but, within each site, the activity of the limpets was measured in as small an area as possible, to minimise local environmen-
tal variability. Nevertheless, the activity in these small patches of habitat was assumed to represent activity in the site as a whole. Comparisons among different environmental
conditions were thus made without comparable data from replicate sites within each set of environmental conditions.
Similarly, many early experiments that examined changes in behaviour when animals were transplanted from one height on the shore to another, did not examine replicate
sites at each height McQuaid, 1981; McCormack, 1982, assuming that the only factor that might influence movement was height on the shore. Without measures of variability
from site to site within each height, it is not possible to interpret any difference between one site at one height and one site at a different height to be due to the heights of the two
sites. Studies that have examined similar transplant experiments in multiple sites and in multiple experiments, incorporating all necessary controls for disturbing and transplant-
ing the animals Underwood, 1988; Chapman and Underwood, 1992 have shown considerable small-scale spatial variability in the responses of intertidal animals to
experimental treatments Chapman and Underwood, 1994; Crowe, 1996; Chapman, 1999a.
Measuring variation among sites does not mean that general patterns of behaviour cannot be identified because similar trends can be shown in different sites, even if
detailed differences among treatments vary from place to place Chapman, 1999a. In this case, what is important is the general pattern of behaviour and the spatial and
temporal scales at which it varies, thereby focussing attention of causation at the relevant scales. Of course, if patterns of behaviour do vary significantly in different ways among
replicate sites in what was expected to be a homogeneous habitat, then the results indicate that we are focussing on the wrong variables to measure the habitat. The
animals must be responding to some environmental condition or feature of habitat which was not considered in the general model, i.e. there may be no generality of behaviour at
the scales we are investigating. Many behaviours appear to be very plastic traits, changing rapidly and differently to varying environmental conditions.
Recent research has also expanded the focus to include broad-scale processes, particularly oceanographic upwellings and currents, in determining patterns of recruit-
ment and other ecological patterns reviewed by Menge, 2000. The interaction of such processes with local, smaller-scale biological and physical heterogeneity in regulating
assemblages and interactions among species is of increasing importance. It will be necessary to examine variability of behaviour at many spatial scales before the role of
behaviour in determining such complex patterns will be elucidated. As yet, these contributions of behavioural ecology to larger-scale patterns have been little explored.
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4. The change in focus from laboratory to field experiments
