272
P. 5. MEADOWS AND J. I. CAMPBELL
The restriction of a species to localized habitats within its geographical range might be due to one of two reasons; animals might
die if they wandered outside the limits of their habitat, or alternativeIy,
be able to recognize their habitat and to return to it or other similar
ones after having made excursions into less suitable habitats. Almost
all the experimental evidence we shall present supports the latter
hypothesis. Animals find, return to, or stay in their usual habitat
by a process of choice, in which they are continuously assessing and
responding to information received from the environment. Habitat
selection, therefore, is essentially the relationship between behaviour
and environment, and we consider that it largely determines the local
distribution of animal species. On the larger scale of geographical
distribution it is as yet uncertain how important habitat selection is
although it almost certainly plays a significant role. Occasionally, of
course, animal distribution even at the local level w i l l be directly controlled by environmental rather than by behavioural factors. Past
flowing water in rivers, wind-induced water currents in fresh water
and the sea, as well as tides, waves and ocean currents, will carry many
smaller planktonic organisms from place to place in spite of any
behavioural responses they might show. However, these instances
only serve to emphasize the validity of our general thesis that the
distribution of animals is determined by their behaviour, and this will
become evident from the examples we quote.
For the purposes of the present review we shall consider the ways
in which animals react to various parts of their environment. Firstly
we discuss the reactions of invertebrates to their physical and chemical
environment and consider intertidal, marine, freshwater and interstitial
invertebrates, in that order (Verwey, 1949). Then, after commenting
on some problems presented by commensal and parasitic associations,
we outline the response of aquatic invertebrates to their biological
environmentgregariousness and spacing out, larval behaviour and
settlement, reactions to plants and to micro-organisms, and feeding
and oviposition preferences. In the final sections on the general processes
of habitat selection, we outline what is known of physiology and
viability in relation to habitat selection, point out the variability that
can occur between individuals of a species, consider the influence of
learning and previous experience, and lastly discuss the ways that new
environments are colonized and how habitat selection may play a part
in speciation.
We have not discussed the assorted migrations undertaken by
many aquatic invertebrates (e.g. annual, diurnal, vertical) unless they
are relevant to the subject under consideration, as there are a number
P. 5. MEADOWS AND J. I. CAMPBELL
The restriction of a species to localized habitats within its geographical range might be due to one of two reasons; animals might
die if they wandered outside the limits of their habitat, or alternativeIy,
be able to recognize their habitat and to return to it or other similar
ones after having made excursions into less suitable habitats. Almost
all the experimental evidence we shall present supports the latter
hypothesis. Animals find, return to, or stay in their usual habitat
by a process of choice, in which they are continuously assessing and
responding to information received from the environment. Habitat
selection, therefore, is essentially the relationship between behaviour
and environment, and we consider that it largely determines the local
distribution of animal species. On the larger scale of geographical
distribution it is as yet uncertain how important habitat selection is
although it almost certainly plays a significant role. Occasionally, of
course, animal distribution even at the local level w i l l be directly controlled by environmental rather than by behavioural factors. Past
flowing water in rivers, wind-induced water currents in fresh water
and the sea, as well as tides, waves and ocean currents, will carry many
smaller planktonic organisms from place to place in spite of any
behavioural responses they might show. However, these instances
only serve to emphasize the validity of our general thesis that the
distribution of animals is determined by their behaviour, and this will
become evident from the examples we quote.
For the purposes of the present review we shall consider the ways
in which animals react to various parts of their environment. Firstly
we discuss the reactions of invertebrates to their physical and chemical
environment and consider intertidal, marine, freshwater and interstitial
invertebrates, in that order (Verwey, 1949). Then, after commenting
on some problems presented by commensal and parasitic associations,
we outline the response of aquatic invertebrates to their biological
environmentgregariousness and spacing out, larval behaviour and
settlement, reactions to plants and to micro-organisms, and feeding
and oviposition preferences. In the final sections on the general processes
of habitat selection, we outline what is known of physiology and
viability in relation to habitat selection, point out the variability that
can occur between individuals of a species, consider the influence of
learning and previous experience, and lastly discuss the ways that new
environments are colonized and how habitat selection may play a part
in speciation.
We have not discussed the assorted migrations undertaken by
many aquatic invertebrates (e.g. annual, diurnal, vertical) unless they
are relevant to the subject under consideration, as there are a number