Showing papers in "Journal of Animal Ecology in 1969"

The Regulation of Wood Mouse (Apodemus sylvaticus) Numbers in Wytham Woods, Berkshire

Abstract: The wood mouse (Apodemus sylvaticus (L.)) is one of the commonest small mammals in English woodland and has been frequently studied. But, apart from the early study of Elton et al. (1931), little attention has been given to the problems of whether and how its numbers are regulated. This paper is an attempt to answer these questions using data collected from one woodland area over 18 years by workers at the Bureau of Animal Population, Oxford.

A Study of the Hibernation of Bumblebees (Hymenoptera:Bombidae) in Southern England

Abstract: In temperate parts of the world such as the British Isles, bumblebee colonies are annual, since only the young queens are able to survive the winter, while the old queens, workers and males all die. The young, fertilized queens produced during the summer months enter hibernation, and it is these bumblebees which reappear in the following spring and later form colonies of their own. In southern England the period of hibernation may last anything from 6 to 9 months, depending on the species and to some extent on spring temperatures. Hibernation is, therefore, an important yet neglected aspect of bumblebee biology. Previous workers (Sladen 1912; Bols 1937, 1939) have indicated that well-drained banks or slopes with a north or north-west exposure are favourite sites for hibernating bumblebees, and both Wagner (1907) and Sladen (1912) have stated that bumblebees hibernate under trees, but do not give precise details. Bumblebees have also been recorded hibernating in rotten tree stumps (Frison 1926; Tkalcu 1960, 1961), under moss, leaves and piles or rubbish (Verrill, in Putnam 1864; Sladen 1912; and others), and in various other miscellaneous places. Plath (1927, 1934), Frison (1929) and Townsend (1951) have all reported the occurrence of many queens of the New World species Bombus impatiens (Cresson) hibernating in very close proximity to one another, and presumably in all these cases the queens were hibernating about the entrance to their maternal nest. However, much of the information on the hibernation of bumblebees so far published has accumulated from casual observations which have not been followed up by more critical data, and apparently only Sladen has investigated the subject of the natural hibernation of bumblebees in this country. In the present studies an attempt has been made to obtain data on various aspects of the natural hibernation of bumblebees and where possible differences between species or groups of species have been investigated.

A population study of house-mice temporarily inhabiting a south australian wheatfield

Abstract: shelter. When the study first began it was assumed that mice lived all year round in the wheatfields. But after a few months I began to suspect that the fields might be temporarily inhabited only and invaded each year. Trapping in a nearby reed-bed indicated that it might hold permanent populations that could provide the wheatfield's colonists; so another intensive population study began there. Though related, these two studies have been presented separately (see Newsome (1969) for the study in the reed-bed) because the ways mice lived in the two habitats were so different. In the wheatfield, population control was extrinsic whereas in the reed-bed intrinsic factors played a part in it. As MacArthur & Connell (1966) have suggested, the kind of population control depended on the harshness of the environment. Descriptions of climate, soils, and vegetation of the study-area, which is the area dominated by red-brown earths shown in Fig. 1, follow.

The Distribution of Benthic Invertebrates on Substrata in Fast-Flowing Streams

Abstract: The highland and moorland reaches of rivers and streams can usually be divided into riffles, with shallow fast-flowing water, and pools, with deeper slow-flowing water. The invertebrate communities living in such distinct habitats are very different and the biological reasons for this have received considerable attention. Only a limited amount of work, however, has been carried out on the spatial distributions of populations of invertebrates and their relationships to environmental factors within these, or any other relatively more homogeneous stream habitat. Scott (1958) and Ambiuhl (1959) have related the distributions of several species to current speeds, and Egglishaw (1964) showed that, even in what was apparently a fairly uniform stretch of riffle, the quantities of several benthic species at different sites varied greatly and were correlated with the distribution of disintegrating plant detritus. Several studies of the effects of certain factors on the distribution of selected species in experimental conditions have, however, been carried out (see Macan 1963). The sampling difficulties imposed by the non-random distribution of most animals apply to stream riffles in the same way as they do to other habitats. The present paper sets out to explore the spatial distributions of benthic organisms (of length greater than 0 5 mm) and their relationships to certain environmental factors in riffles, as riffles usually make up by far the larger proportion of the areas of fast-flowing streams. Within riffles the greatest weight of invertebrates is found among and under stones, and so most of the observations were made on that habitat. Other habitats in riffles in which invertebrates are found, and on which observations were made, include the algal coverings on the upper surface of stones and clumps of moss.

Winter Fat Deposition and Overnight Survival of Yellow Buntings (Emberiza citrinella L.)

Abstract: In a recent review of the adaptive role and regulation of winter fattening in birds, King & Farner (1966) concluded that information available at present does not permit a decision to be made as to the role of temperature in the regulation of fat depositionwhether a proximate or ultimate factor, or both. The present paper reports a study of yellow buntings (Emberiza citrinella L.) caught at a roost at Wytham, near Oxford, in the winter of 1966-67. Carcass analyses of samples of birds showed the levels of fat and other energy reserves carried by the birds on different dates, and in this paper these reserves are related to the calculated energy requirements for each night to determine the proportion of birds which should survive each roosting period (from dusk to dawn). The results arecontrasted with studies on bullfinches (Pyrrhula pyrrhula (L.)) made in the same locality by Newton (1969). Yellow buntings are mainly granivorous birds, which may feed up to several miles away from their communal roosts. However, recoveries of ringed birds (Spencer 1966) indicate that they move only short distances during their lifetimes, seldom as much as 10 miles. The same individuals may be caught at any one roost throughout a winter and in successive winters. Thus a given roosting population may be considered practically 'closed' for purposes of estimating survival.

A population study of house-mice permanently inhabiting a reed-bed in South Australia.

Abstract: Wheatfields in South Australia are inhabited by house-mice (Mus musculus L.) for only part of each year, and not in late winter and early spring (Newsome 1969). So there must be permanently inhabited places which provide colonists for the fields. At Turretfield, 30 miles (48 km) north-east of Adelaide, the site of a population study in a wheatfield (Newsome 1969), a reed-bed along Salt Creek which runs through the fields looked a likely habitat and preliminary trapping supported this view. Reed-beds, if permanently inhabited, would provide ready spring-boards for the fields' re-invasion each year, since they commonly line streams throughout the 4000 square miles (10 360 km2) of wheatlands that Turretfield represents. So a second intensive population study began at Turretfield in the reed-bed.

The Ecology of the Partridge

Abstract: Most studies of game bird populations have led to the conclusion that the numbers available at the end of the breeding season are largely determined by the severity of the mortality suffered by the young chicks (Jenkins 1961; Jenkins, Watson & Miller 1963; Blank, Southwood & Cross 1967). Studies on the red grouse (Lagopus lagopus scoticus (Lath.)) (Jenkins et al. 1963; Jenkins, Watson & Picozzi 1965; Jenkins, Watson & Miller 1967) and on other Tetraonidae (Siivonen 1957; Watson 1965) have suggested that in most years the extent to which the chicks survived was determined before the eggs hatched. Jenkins and his co-workers have been able to show in the red grouse a correlation between chick survival in the wild and in captivity, and also between the former, hatching success, clutch size and adult sex ratio. Variations in these pre-hatching

The Occurrence and Distribution of Crabs in a Jamaican Mangrove Swamp

Abstract: The zonation of animals and plants in mangrove swamps is often greatly complicated by the structure of the swamps. Developing in sheltered areas, often around river mouths, extensive mangrove swamps are interlaced with drainage and tidal channels, and contain semi-stagnant lagoons, deep mud banks, thickets of mangrove and the occasional island of hot, dry land. The diversity of these features depends on the size of the swamp which, in its turn, depends on the proximity of rivers and the tidal range. A further complication introduced by the proximity of rivers is variable salinity which may also be caused by heavy rain and poor drainage. Workers in mangrove environments (Verwey 1930; Dansereau 1947; Macnae & Kalk 1962; Berry 1963; Macnae 1963, 1966, 1967), while recognizing the existence of faunal zonation, have described this zonation only in a qualitative fashion. Rodriguez (1959, 1963) did not describe zonation within mangrove environments but, in common with Berry (1963), recognized several habitats, each with its characteristic fauna. The only workers who collected quantitative data in mangrove environments (Golley, Odum & Wilson 1962; Rodriguez 1963) did not relate these data to tidal levels. These apparent difficulties were probably due to the complexity of the swamps involved. The swamp chosen for the present investigation avoids many of these difficulties. It is situated some distance from river mouths and is not, therefore, liable to regular salinity change. It is not particularly extensive, the intertidal zone rarely exceeds 150 m in width. The complicating features listed above are almost entirely absent and it is possible to take a straight line transect from low tide level to high tide level without encountering channels, mud banks, lagoons, etc. The zonation of the swamp crabs was, therefore, studied in the conventional way, with transect and quadrat. This investigation showed that the distributions of most of the crab species are related to tidal levels in a way that is similar to the zonation of other types of shore. The investigation also provided information on the microhabitats of the crab species and on the size distributions of the populations of three common species.

The Food of the Grey Field Slug, Agriolimax reticulatus (Muller), on Grassland

Abstract: The grey field slug, Agriolimax reticulatus (Muller), widely distributed in a variety of habitats (Quick 1960), is probably the most numerous species and the most important slug pest (Runham & Hunter 1970), although its status as a pest of permanent grassland is not known. South (1965) found average populations on pasture in Northumberland of over 60 per m2, aggregated in association with tufts of Dactylis glomerata L. No detailed investigation has been made of basic food requirements of this species and feeding in natural habitats has only so far been investigated in woodland (Pallant 1967, 1969, 1970). The diet of Agriolimax reticulatus, on grassland neighbouring on the woodland previously studied, was investigated by the analysis of crop contents. Prat (1932), Davies (1959) and Metcalfe (1960) used epidermal characteristics in the taxonomic study of grasses but Davies concludes that the distribution of differentiated cells over the leaf is of limited value for identifying a single leaf of a vegetative shoot and could only provide a 'broad analysis' of grass constituents of animal food. However, with a limited number of grass species available, it has been found possible to distinguish between them (Martin 1955, 1964; Croker 1959; Stewart 1967; Pollard & WaltersDavies 1968; Watts 1968; Bernays & Chapman 1970).

Organization of Communities of Frogs Along Small Rain Forest Streams in Sarawak

Abstract: It is commonly assumed that faunal diversity reaches a maximum in tropical rain forest. At this end of the diversity scale, we expect an increase in the number of interactions between ecologically similar species, which should increase the pressure for ecological segregation. Arguing from a different basis, Margalef (1963) suggests that the relationships between species become more specialized, that stenophagy and other precise relationships increase in these rich and complex communities. A consequence of these suggested relations is that niches should tend to be discrete and to overlap only slightly in rain forest communities. In contrast, Klopfer & MacArthur (1961) maintain that the niches of sympatric species of tropical birds overlap more than do niches of temperate zone birds. Their conclusion is based on the ratios of culmen lengths*, which in turn are used as a measure of feeding behaviour. At best this can be considered only a very limited characterization of the niches occupied by the birds in question. Furthermore, the kinds of tropical environments studied by Klopfer and MacArthur were not specified. Consequently, we still do not know the extent to which the niches of related, coexisting species overlap in tropical rain forest. If niches were completely separated, occasional restriction of certain resources or occasional fluctuation in the physical qualities of an environment might result in the elimination of some niches. Overlapping niches, on the other hand, might provide the system with the flexibility needed to resist such perturbations. The degree of overlap of niches of related species is, therefore, ecologically significant. Observations made by our field party in Sarawak, Borneo in 1962 and 1963 provide information bearing on this matter of niche overlap. The hilly tropical rain forest of our work area is laced with numerous small, permanent streams. Many species of frogs and toads live along or in these streams and are easily collected or observed in numbers by persons wading up the streams at night. Frogs have another advantage as subjects for ecological study: they can be caught by hand and their positions recorded with precision. There are three serious limitations in dealing with niches. The first is that niches cannot be completely defined; there will always remain some unknown dimensions. Secondly, we still lack a satisfactory, rigorous way of measuring niche dimensions. Thirdly, what is true of one group of animals may not be true of another; the kinds of specializations open to insects apparently are not available to most vertebrates. In this analysis, characterization of niches depends on eight main attributes: size of animal; position on stream (along course of stream, distance from stream bed and height

An insect fauna of late bronze age date from wilsford, wiltshire

Abstract: The Wilsford shaft, discovered at Normanton Gorse, Wiltshire, was first described by Ashbee (1963). It is one of the earlier of a series of artificial shafts or ritual wells which are a feature of later prehistoric Europe (Schwarz 1962; Piggott 1965). They are either associated with ceremonial structures and burials, or else are in isolation. Cults centring upon them were current in Roman times. The English examples, their associations and usages, have recently been discussed by Ross (1967 s.v.). Before excavation, the Wilsford shaft was a 'pond-barrow', i.e. a circular dish-like depression surrounded by a bank which had been destroyed by total agriculture. Such 'barrows', some of considerable size, are a regular feature of the barrow cemeteries about Stonehenge (Piggott 1951, Fig. 1) and are found elsewhere in Wiltshire. Excavation of this pond-barrow disclosed an inverted conical cavity which proved to be the weathering cone of a vertical, cylindrical shaft 6 ft in diameter and almost 100 ft (30 m ) deep (Fig. 1). At this depth a fault in the chalk through which water could enter the shaft was encountered and this may have been the reason that the original excavators stopped digging. The shaft had been dug in vertical stages, and checked by plumbing and a template. Deep antler pick marks showed where deviations from the vertical had been corrected and the sides had been dressed with a broad-bladed metal axe. Seams of flint had been broken through. Near the top of the shaft artifacts of Recent, Roman and Iron Age cultures were recovered while at about 60 ft the greater part of a late Bronze Age pot was found. The bottom of the shaft contained a considerable quantity of organic material. This included much wood, both the remains of fabricated containers and also timber, broken branches, twigs and other pieces. Also present were seeds, leaves, cereal straw, moss, possibly fungi and pollen as well as pieces of rope and hide. Artifacts included a shale ring, bone pins and amber beads. Until the time of its excavation by Mr Ashbee and his colleagues the lowest part of the shaft's contents appears to have been more or less continuously waterlogged, thus being preserved in conditions normally only met with in bogs and lakes. This would account for the remarkably fine state of preservation of the insect remains. A sample consisting of pieces of wood collected at depths between 96 ft 6 in. and 97 ft 6 in. (29.4 m and 29*8 m) was submitted to the National Physical Laboratory for radiocarbon dating and an age of 3330 + 90 B.P. was obtained (N.P.L. 74) (Ashbee 1966). It was from this layer that the insect remains described here were obtained. The material examined, which was all recovered from the bottom 6 ft (1 8 m) of the shaft, filled eighteen jars and consisted of a mixture of silt, small fragments of chalk and a mass of comminuted wood and other vegetable matter. It had been mixed with water, alcohol and glycerine to preserve it. It was estimated that the volume of this sludge examined for insects was about 23 1.

A Study of the Mortality Factors Acting upon Cyzenis albicans (Fall.), a Tachinid Parasite of the Winter Moth (Operophtera brumata (L.))

Abstract: In an earlier paper (Hassell 1968) the behavioural responses of the adult population of Cyzenis albicans (Fall.) at Wytham Woods, Berkshire towards uneven spatial distributions of hosts were considered. To explain the part played by Cyzenis in the natural control of the winter moth population it is the intergeneration relationships that are most important. Only from these can firm conclusions be drawn about the ability of natural enemies to regulate their hosts or prey. An intergeneration relationship is detected when a plot of the yearly mean percentage host mortality (or k-values) caused by the enemy population against the yearly mean host density (or its logarithm) reveals a linear, curvilinear or some form of spiral relationship. Each of these has, of course, very different implications. A curvilinear or rectilinear relationship indicates a superproportional or subproportional relationship depending on whether the slope is positive or negative. Such relationships imply a relatively constant parasite or predator density. A tendency for 'spiralling' to occur when the points are joined serially implies some form of delayed relationship, resulting from changes in the parasite or predator density, which can be caused only by changes in their reproductive rate and/or survival (Hassell 1966). Cyzenis is a specific parasite of the winter moth with a single annual emergence moreor-less synchronized with the availability of host larvae, and so may be expected to play an important part in the control of the winter moth population at Wytham. However, the intergeneration relationship between Cyzenis and the winter moth (Varley & Gradwell 1968) reveals no sign of delayed density-dependency, and the variation in the winter moth mortality due to Cyzenis is clearly insignificant when compared with the variation in generation mortality of the winter moth. The mean density of adult Cyzenis in the area of oak studied at Wytham since 1950 is 0 96/m2 (having varied between 7-2 and 0 1/Im2). In only three of these years has there been more than 700 parasitism of winter moth larvae. In contrast, in Nova Scotia, Canada, where Cyzenis was first introduced in 1954 (Graham 1958), adult parasite densities rapidly increased and in 1960 were causing a mean of 58% parasitism (Embree 1965, 1966). Clearly some unfavourable factor(s) are operating at Wytham and cause Cyzenis to be less effective than in Canada. This paper is concerned with the mortality factors acting upon the Cyzenis population, and a subsequent paper will deal with the construction of a population model describing the fluctuations in parasite density observed in the field.