42
Activity Patterns
scorpions Buthotus judaicus and Nebo hierochonticus seem to determine
habitat selection. The former inhabits stone terraces and surface rocks,
whereas the latter prefers burrows dug under large stones (Warburg and Ben
Horin 1979).
In all previous cases, changes in abiotic factors are considered of primary
importance for the daily activity of arthropods. However, no general agreement exists on the factors controlling daily activity patterns. In specific cases
biotic factors such as avoidance of predators may be equally involved. For
example, Cloudsley-Thompson (1981) stated that nocturnality in desert
arthropods may be correlated either with avoidance of climatic extremes, or
with avoidance of predators or even both phenomena, and analogous explanations might be suggested for the daytime activity of arthropods from Mediterranean habitats.
4.2
Seasonal Patterns
Seasonal activity patterns in Mediterranean areas have frequently been discussed in relation to the climate (Hornung and Warburg 1996). For example,
Karamaouna and Geoffroy (1985) reported that surface activity of five diplopod species in an insular Mediterranean formation was confined to the wet
period from November to April. Analogous observations were also reported
by Baker (1979a) for the millipede Ommatoiulus moreletii, in which activity
peaks were recorded during the breeding period in autumn/early winter. In
summer, most animals displayed little activity - due to their high moisture
and moderate temperature preferences - and formed aggregations in favourable microsites (Baker 1980). In the isopod Schizidium tiberianum surface
activity in early winter is conditioned by the first rains and ceases by late
spring. During summer and autumn, animals hide deep in the ground (Warburg et al. 1993). In general, activity peaks in winter characterise arthropods
from arid ecosystems, while peaks in autumn and spring characterise fauna
from semi-arid ecosystems (Di Castri and Vitali-Di Castri 1981; Magioris and
Tsiourlis 1992).
Apart from climatic factors, the effect of grazing and frequent fires can
also be recognised in the activity patterns of Mediterranean arthropods. Pantis et al. (1988) analysed pitfall data from an asphodel semi-desert, using the
reciprocal average (RA) technique (Fig. 4.1). The seasonal gradient is depicted on the first axis of the graph. Samples from summer and spring are ordinated towards the right end point of the gradient, while samples from
autumn and winter are ordinated towards the left side of the graph. Samples
from winter and summer occupy the endpoints of the seasonal gradient
along with Staphylinidae, Lithobiomorpha (winter samples), scorpions and
Scarabeidae (summer samples). Activity peaks of most taxa occur in autumn.
Activity Patterns
scorpions Buthotus judaicus and Nebo hierochonticus seem to determine
habitat selection. The former inhabits stone terraces and surface rocks,
whereas the latter prefers burrows dug under large stones (Warburg and Ben
Horin 1979).
In all previous cases, changes in abiotic factors are considered of primary
importance for the daily activity of arthropods. However, no general agreement exists on the factors controlling daily activity patterns. In specific cases
biotic factors such as avoidance of predators may be equally involved. For
example, Cloudsley-Thompson (1981) stated that nocturnality in desert
arthropods may be correlated either with avoidance of climatic extremes, or
with avoidance of predators or even both phenomena, and analogous explanations might be suggested for the daytime activity of arthropods from Mediterranean habitats.
4.2
Seasonal Patterns
Seasonal activity patterns in Mediterranean areas have frequently been discussed in relation to the climate (Hornung and Warburg 1996). For example,
Karamaouna and Geoffroy (1985) reported that surface activity of five diplopod species in an insular Mediterranean formation was confined to the wet
period from November to April. Analogous observations were also reported
by Baker (1979a) for the millipede Ommatoiulus moreletii, in which activity
peaks were recorded during the breeding period in autumn/early winter. In
summer, most animals displayed little activity - due to their high moisture
and moderate temperature preferences - and formed aggregations in favourable microsites (Baker 1980). In the isopod Schizidium tiberianum surface
activity in early winter is conditioned by the first rains and ceases by late
spring. During summer and autumn, animals hide deep in the ground (Warburg et al. 1993). In general, activity peaks in winter characterise arthropods
from arid ecosystems, while peaks in autumn and spring characterise fauna
from semi-arid ecosystems (Di Castri and Vitali-Di Castri 1981; Magioris and
Tsiourlis 1992).
Apart from climatic factors, the effect of grazing and frequent fires can
also be recognised in the activity patterns of Mediterranean arthropods. Pantis et al. (1988) analysed pitfall data from an asphodel semi-desert, using the
reciprocal average (RA) technique (Fig. 4.1). The seasonal gradient is depicted on the first axis of the graph. Samples from summer and spring are ordinated towards the right end point of the gradient, while samples from
autumn and winter are ordinated towards the left side of the graph. Samples
from winter and summer occupy the endpoints of the seasonal gradient
along with Staphylinidae, Lithobiomorpha (winter samples), scorpions and
Scarabeidae (summer samples). Activity peaks of most taxa occur in autumn.