Showing papers in "Journal of Animal Ecology in 1968"

Habitat preferences in net-spinning caddis larvae with special reference to the influence of water velocity

Abstract: enough to allow most of the British species to be identified with certainty. This has made the group available for ecological studies and the present work has been concerned with some of the habitat preferences shown by the larvae. Biologists have long maintained that some stream animals are 'fast flow' specialists and others are 'slow flow' specialists. This is also the impression gained from a study of net-spinning caddis larvae, in which different species predominate in rapids and in pools. It has always been difficult to confirm that water velocity is the important factor because of the problems of measuring it in sites where the animals live. This difficulty has been partly overcome in the present study by the use of a new type of miniature water velocity meter. It has been possible to establish beyond question that high velocity and low velocity species can be distinguished in this group of caddis larvae. It has also been possible to interpret these limitations of distribution in terms of the specializations shown by the various species. Net-spinning caddis show another type of distribution pattern, one which entails a sequential replacement of species down the length of a stream. Such sequences are found in many groups of stream animals. In caddis the sequences appear to be unrelated to water velocity and a complete explanation for them cannot be offered at present.

Experiments on Population Control by Territorial Behaviour in Red Grouse

Abstract: Male red grouse (Lagopus lagopus scoticus (Lath.)) contest for territory each autumn, and some males are successful while others fail to secure territories. This paper describes experiments undertaken to test whether males which were not occupying territories could become territorial if the established territory owners were removed; that is to say, whether the number of breeding males was being limited simply by the territorial accommodation available or by some deficiency in the unsuccessful birds. Previous research consisted of counts of the grouse on 100-120 ha study areas on heather (Calluna vulgaris L. (Hull)) moorland in north-east Scotland, with more detailed studies of the behaviour of individually marked birds on smaller parts of these areas (Jenkins, Watson & Miller 1963, 1967). Territorial behaviour, courtship and pair formation are described by Watson & Jenkins (1964). The population studies showed that there were many more grouse in autumn, even after the grouse shooting was over, than in the following spring. The behaviour studies showed that grouse populations from October to May consisted of (a) cocks which courted hens and defended territories, plus hens paired with them (territorial birds), and (b) non-territorial birds which did not defend territories, show courtship, pair up, or breed. Classes (a) and (b) both included birds less than 1 year old (called 'young' in this paper) and older birds. On average, 52%0 of the August population later became non-territorial over the autumn and winter and died before the next April-May (Jenkins et al. 1967), whereas both young and old territorial grouse survived the winter well and bred next summer. Consequently we postulated (Jenkins et al. 1967) that possession of territory was essential for breeding, and that territorial behaviour in autumn greatly limited the size of the next spring's breeding stock. These hypotheses were open to the criticism that although territorial behaviour was associated with the population changes, it might not really be preventing the non-territorial grouse from taking territories. The crux was to find if they would take territories and breed when vacant ground was made available. If they did not, the hypotheses would be refuted. One might then explain the presence of non-territorial birds simply by suggesting that they were immature individuals, as in many other species where some individuals do not breed till 2 years old or more.

Aspects of the relationship between burying beetles, necrophorus spp. and the mite, poecilochirus necrophori vitz.

Abstract: The various types of association between mites and other invertebrates, particularly insects, have been discussed by Vitzthum (1941) and Tragardh (1943), and more recently by Evans, Sheals & Macfarlane (1961). The associations fall into five broad categories, the parasitic and predacious mites being the best defined and studied. The other categories are commensals, phoretic species and exudate feeders, and detailed information on the relationships between the mites and other animals involved in these apparently harmless associations is lacking. During a study of the biology of the carrion beetles, Necrophorus humator 01. and N. investigator Zett. on the Fame Islands, Northumberland, in 1963 and 1964, it was found that all of these beetles carried large numbers of mesostigmatid mites, the commonest species of mite being Poecilochirus necrophori Vitz. The life history of these mites, associated with Necrophorus humator, has previously been studied by Neumann (1943), who indicated that the relationship is a loose one, the mite being a paraphage and symphorist, using the beetle for transport and feeding on the fly maggots and the carrion encountered by the host. Neumann obtained all stages of the life cycle of Poecilochirus necrophori from the host, and he found that a single generation lasted 8-9 days. The present investigation aims at elucidating the interaction of P. necrophori with Necrophorus and demonstrates the complex interrelationship between these two animals as well as their interdependence.

The Community of Invertebrates in Decaying Oak Wood

Abstract: This paper reports a study of the invertebrate fauna of pieces of decaying oak wood taken from the floor of a mixed deciduous woodland in the Wytham Woods Estate, Berkshire, a property used for field studies by Oxford University (Elton 1966). In order to reduce variability due to differences between localities, all samples were taken from a small area in Marleywood Plantation-approximately 100 m wide by 150 m long. Emphasis has been placed on information obtained from four types of synthetic logs (boxes of compressed oak sawdust) that were placed on the forest floor in this area for various lengths of time. As the initial differences between the types of logs were controlled and there were exact replicates for each of two seasons and at each of three locations, it has been possible to examine the effects of log characteristics, season and locality separately and also to obtain some idea of the interaction between these environmental factors. Interspecific relationships have been looked at using the concept of recurrent groups outlined in a previous paper (Fager 1957). A total of 182 species were found in the fifty-one samples that were examined completely (thirty-six synthetic logs and fifteen natural logs taken for comparison). The distribution of these species among major taxonomic groups is shown in Table 1. This does not, of course, represent a complete list of the fauna of decaying oak wood; approximately fifty additional species were found in a small number of logs that were examined during preliminary work, and records inthe survey of Wytham, beingdone by Elton (Elton M Elton 1966) and others would add more. It does, however, appear to give a satisfactory representation of the organisms that were abundant in this habitat at this locality. The analyses in this paper are based solely on the 108 species that occurred in five or more samples (middle three columns in Table 1). This division is arbitrary but seems justified because what is wanted is a knowledge of the processes that affect the numerically more important species. The full names of these species and details of determinations are given in the Summary List of Species (Appendix A). The animals found in small pieces of decaying oak wood have been treated as an ecological unit, the components of which influence each other directly and indirectly and are variously affected by the environment. A complete, detailed picture of the workings of this unit will require much more study, but it has been possible to make a start at untangling the complex of factors and processes that operate in this habitat and determine the composition and structure of the animal groupings found in it.

Ecological Association of Bird Species and Habitats in Eastern Australia; Similarity Analysis

Abstract: Ornithologists have long recognized the fact that bird species tend to be associated with particular habitats. The terrestrial habitats are generally described in terms of vegetation or land use (Palmgren 1930; Moreau 1934; Lack & Venables 1939; Kendeigh 1944), and the species-habitat associations are analysed in terms of ecological and behavioural habitat selection of birds (Lack 1933; Svardson 1949; Klopfer & Hailman 1965). The basis for classification of bird habitats is usually provided by the structural forms of vegetation, which are reflected by the ecological distribution of bird species, However, patterns of resource utilization by birds are complex and are never completely matched by hierarchical arrangements of plant communities. Thus, recognized assemblages of bird species for a given habitat may not share the boundaries with plant communities within major formation types (Kendeigh 1948, 1954), nor is it possible to predict precisely the distribution and abundance of species in relation to any particular features of vegetation (MacArthur 1964). Bond (1957) studied the ecological distribution of birds from the viewpoint of the continuum concept (Curtis & McIntosh 1951) and demonstrated a high correlation between the order of avifaunal similarity and the phytosociological order within the upland deciduous forests of southern Wisconsin. However, several species showed little or no quantitative response to the vegetational differences along the gradient of xeric to mesic sites and the response of each species to this gradient was unique. These classificatory problems are viewed dynamically by Elton (1966) who has proposed a system of habitat inventory which extends beyond the physiognomic and structural characters normally used in the classification of vegetation. It is aimed at a synthesis that will describe not only the parts of a complex system but also the interaction and balance between them, as well as the dynamic properties of the system as a whole (Elton & Miller 1954). Such a classification demands a long-term study of habitats with their varying features and of animal populations in them. On the one hand major requirements of the species must be studied in relation to the principal limiting factors of the environment and the characteristic features or structures of the habitat. On the other hand the dynamic aspect of a species network must be followed through the utilization of resources by various key species. This kind of approach in animal ecology is largely neglected in Australia. This is partly because ecological problems demanding practical solutions are identified in terms of human exploitation of resources in semi-arid environments where physical factors fluctuate violently (Andrewartha & Birch 1954). However, the coastal fringe of the Australian continent supports relatively stable environments of what are often called the zoogeographical 'refuge' areas in which a number of species of birds are considered to have evolved simultaneously (Gentilli 1949; Serventy 1953; Keast 1961). Here the

The food of the common shrew Sorex araneus L. (Insectivora: Soricidae) in Britain.

Abstract: Mainland Britain has three species of shrew; Sorex araneus L. the common shrew, S. minutus L. the pigmy shrew and Neomysfodiens (Pennant) the water shrew. This paper concerns the common shrew only, a species whose almost unceasing activity and voracity have attracted the attention of natural historians from the ancients to the present day. Crowcroft (1957) summarizes present information on the biology of the common shrew. Further information on ecology may be found in Shillito (1960) and on metabolism in Hawkins & Jewell (1962). Notable in these works is the almost total lack of information on the feeding of wild shrews. The common shrew spends much of its life tunnelling through the loose accumulation of plant detritus in woods, hedgerows and rank grassland. From this material it must each day glean a mass of food in the form of invertebrates equal to its own body weight (about 8-0 g) (Rorig 1905; Adams 1912; Tupikova 1949; Crowcroft 1957; Hawkins & Jewell 1962). Present qualitative information on the diet of British shrews comes mainly from experiments in which captive animals have been fed as wide a range of prey as was available (English 1908; Adams 1912; Cranbrook 1959 (on Neomysfodiens)). Greater meaning was given to these species lists by the more sophisticated foraging trials of Shillito (1960) and the preference experiments of Crowcroft (1957). The more direct method, of gut analysis, has been advocated (Hamilton 1930; Crowcroft 1963) but so far it has been used in Britain only for a small sample (n = 4) of Sorex minutus (Newstead 1947). In the present study, analysis of the gut contents of 444 wild-trapped comm;on shrews is described. These analyses are preceded by an account of laboratory feeding trials whose object was to aid the interpretation of the analysis results.