Showing papers in "Journal of Animal Ecology in 1975"

Mutual interference between parasites or predators and its effect on searching efficiency

Abstract: A number of experiments (Burnett 1956; Hassell & Huffaker 1969; Holling 1959; Ullyett 1949a,b, 1950) indicate that a basic assumption implicit in early population models of predator-prey and parasite-host interactions (Lotka 1925; Yolterra 1926; Nicholson & Bailey 1935) is false. This assumption requires the number of hosts parasitized (or prey attacked) to be proportional to the density of hosts and the density of parasites*. It is possible to formalize this assumption in terms of searching efflciency (E) where E is deSned by E Na (1)

The Growth Rate of Brown Trout (Salmo trutta L.) Fed on Maximum Rations

Abstract: The many factors affecting the growth and feeding of fishes have been reviewed by Brown (1957), Ivlev (1961), Paloheimo & Dickie (1965, 1966a, b) and Phillips (1969). These reviews include the relevant work on salmonids and the only important addition is the work on sockeye salmon (Oncorhynchus nerka Walbaum) by Brett, Shelbourn & Shoop (1969) and Brett (1971). The present paper is one of a series dealing with feeding and growth in brown trout (Salmo trutta L.). From the results of previous work, it is now possible to estimate the rate and time for the gastric evacuation of different meals (Elliott 1972), the maximum weight of food consumed in a meal (satiation amount) and the time taken to eat this meal (Elliott 1975a), the maximum weight of food consumed in a day and the maximum rate of feeding (Elliott 1975b). These estimates are applicable to trout of different weights (approximate range 10-350 g live weight) at different water temperatures (range 3-821-6? C). The next stage was to examine the growth rates of trout fed on maximum rations. These experiments are described in the present paper and a mathematical model is developed to estimate maximum growth rates of different sized trout at different temperatures.

The Resource Limitation of Trophic Levels in Tropical Grassland Ecosystems

Abstract: One feature of terrestrial ecosystems that is becoming widely recognized is the small proportion of primary production, measured on an annual basis, that is consumed by herbivores.t In grassland systems Wiegert & Evans (1967) found that consumption rarely exceeded 10% of the primary production and the only exceptions appeared to be in the East African tropical grasslands supporting large ungulate populations, where it was roughly estimated that between 30 and 60% of the primary production was consumed. But with further information Phillipson (1973) put forward a tentative model for the Serengeti ecosystem in Tanzania, and in this model only 18% of the net primary production was utilized by the herbivores. In woodland systems similar results have emerged: herbivores consumed less than 70 of the tree production in a deciduous woodland (Varley 1970), and Reichle et al. (1973) found that insects consumed only 2-6% of the primary production in a forest canopy. The more restricted studies of the energy flow in small mammal communities have all found that less than 20% and sometimes only 2% of the primary production is utilized (Grodzinski 1963, 1971; Grodzinski et al. 1970; Ryszkowski 1970). Slobodkin, Smith & Hairston (1967) have summarized other similar results all of which show that less than 10% of the primary production is consumed.

The Growth Rate of Brown Trout (Salmo trutta L.) Fed on Reduced Rations

Abstract: The growth rate of brown trout (Salmo trutta L.) is affected by many factors including the size and metabolic requirements of the fish, the water temperature, and the amount of food eaten by the fish. As a result of previous work on feeding and growth, it is now possible to estimate the maximum weight of food eaten in a day and the maximum growth rate of trout in the weight range 5-300 g at both constant and fluctuating temperatures in the range 3.8-19.5? C (Elliott 1975a, b). The chief purpose of the present paper is to investigate the relationship between the growth rate of brown trout and the amount of food eaten in a day. A mathematical model is developed to estimate the daily ration required for different levels of growth ranging from zero to maximum growth rate.

Towards a Predator-Prey Model Incorporating Age Structure: The Effects of Predator and Prey Size on the Predation of Daphnia magna by Ischnura elegans

Abstract: The functional response of a predator relates the change in the number of prey consumed per predator to changes in prey density (Solomon 1949). Holling (1959a, 1961) has described three types of functional responses, all of which have now been observed experimentally. Not all results fit conveniently into this scheme (see Mori & Chant 1966; Sandness & McMurtry 1970). The most frequently described curve, particularly for invertebrate predators, is Holling's type 2 response, in which the curve rises at a decreasing rate to a plateau (for example, Burnett 1951, 1954; Morris 1963; Tostowaryk 1972; Fox 1973). Holling (1959b) proposed an equation which incorporated what he considered to be the basic components of predation, namely the total time prey were exposed to predation, the rate of successful search (attack coefficient) and the handling time:

Succession, Diversity and Trophic Relationships of Some Soil Animals in Decomposing Leaf Litter

Abstract: Soil systems contain some of the most species-rich communities in existence. Well developed temperate woodland soils may contain up to a thousand species of soil animals alone, including several hundred species of mites and Collembola, in populations exceeding 1 to 2 millions per square metre. Investigations of the interand intra-specific relationships within these immensely complex communities has proved to be one of the most intractable ecological problems. The study of microhabitat development and successional changes in soil organism communities during the breakdown and decomposition of organic materials in the soil could provide useful information towards an understanding of the larger system. Unfortunately few studies of this kind have been carried out. Succession of the soil microflora on leaves has been demonstrated in a number of studies (notably, Hogg & Hudson 1966; Frankland 1966; Hudson 1968, Parkinson & Balasooriya 1969; Jensen 1971) but there have been few investigations of the soil fauna associated with decomposing leaf litter. One major problem in studies of this type is in maintaining the identity of the experimental material without altering the soil environment. Crossley & Hoglund (1962) suggested that the use of litter bags would overcome this difficulty and this method has been used by Stevanovic (1968) to study general arthropod succession and by Metz & Farrier (1969) to study succession of the Mesotigmata (Acari) in leaf litter. Anderson (1973a, b) investigated the breakdown and decomposition of beech (Fagus sylvatica L.) and sweet chestnut (Castenea sativa Mill) litter using litter bags and found that beech leaves were less palatable to soil animals and more resistant to microbial decomposition than chestnut leaves. The present study is an analysis of the soil animal populations extracted from these litter bags over a 20-month period to investigate the successional development, structure and trophic relationships of soil organism communities in beech and chestnut leaves.

The Role of Algae in the Diet of Asellus aquaticus L. and Gammarus pulex L.

Abstract: The food of Asellus aquaticus L: and Gammarus pulex L. consists of decaying vegetation, microscopic algae and invertebrate animals. Several workers have examined the gut contents of these and related species, and have concluded that allochthonous leaf material is the most important food in the diet (Haempel 1908; Willer 1922; Steusloff 1943; Levanidov 1949; Hynes 1954, 1963; Minckley 1963; Minshall 1967). Other workers have reared Asellus or Gammarus on a diet of decaying leaves and have concluded that the animals were feeding to a large extent on the epiphytic fungi and bacteria on the leaves (Hynes & Williams 1965; Kaushik & Hynes 1971; Prus 1971, 1972; Barlocher & Kendrick 1973a, b; Nilsson 1974). The other components of the diet have usually been ignored by most workers, but Margalef (1948) reported that G. pulex fed chiefly on insects and copepods, and Deksbakh & Sokolova (1965) stated that G. lacustris Sars fed chiefly on algae, macrophytes and invertebrate animals. Hynes (1970) notes that most of the information on invertebrate feeding is qualitative and thus serious errors may exist in the estimation of the relative importance of the different dietary components. As the algal component of the diet has been neglected by most workers and is relatively easy to quantify, a detailed study was made of their role in the diet of Asellus aquaticus and Gammarus pulex. Samples were collected from rocks and growths of Cladophora glomerata (L.) Kz. in three rivers of south-western England between June 1973 and May 1974.

Rodents in desert environments

Abstract: I. The Desert as a Habitat.- Distribution.- Soils.- Climate.- Vegetation.- References.- II. The Ecology of Rodents in the northern Sudan.- Desert Species.- Jebel Species.- Riverine Species.- Commensal Species.- Reproduction.- Other Adaptations for Life in the Desert.- Discussion.- Acknowledgements.- References.- III. The Rodents of the Iranian Deserts.- The Rodents: northern and southern Types.- Annual Rhythm.- Population Densities.- Some Peculiarities.- References.- IV. Comparative Ecological Notes on Afghan Rodents.- Results.- Discussion.- Summary.- References.- V. The Population Ecology of the Rodents of the Rajasthan Desert, India.- Population Structure.- Ranges of Movements.- Food.- Predator-Prey Relationship.- Breeding Season and Litter Size.- References.- VI. Outbreaks of Rodents in Semi-Arid and Arid Australia: Causes, Preventions, and Evolutionary Considerations.- Climates in Central Australia.- The Study-Area: Habitats and Rodents.- Populations.- Conclusions and Discussion.- Acknowledgements.- References.- VII Observations of Argentine Desert Rodent Ecology, with Emphasis on Water Relations of Eligmodontia typus.- The Argentine Monte and some of its Rodents.- Methods and Materials.- Results and Discussion.- Acknowledgements.- References.- VIII. La diversite des Gerbillides.- IX. Some Observations on Ecological Adaptations of Desert Rodents and Suggestions for further Research work.- The Desert Environment.- Ecological Adaptations.- Need for further Research.- References.- X. The Behavior Patterns of Desert Rodents.- The Evolution of Desert Adaptations.- A Comparison of Behavior Patterns.- A Comparison of Behavior Patterns in : Meriones, Gerbillus and Perognathus.- Spacing and Communication.- Acknowledgements.- References.- XI Activity Patterns of a Desert Rodent.- Methods.- The Microdosimeter and the Index of Activity.- Variation in Activity.- Climatological Variables and Animal Activity.- Analysis.- Discussion.- Summary.- References.- XII. Patterns of Food, Space and Diversity.- Resource Allocation by Seed Selection.- Habitat Selection in Space.- The Pattern of Local Species Diversity.- Acknowledgements.- References.- XIII. Desert Coloration in Rodents.- Desert Coloration.- Acknowledgements.- References.- XIV. The Biology of some Desert-Dwelling Ground Squirrels.- Reproduction.- Food Habits.- Population Characteristics.- Habitat Factors.- References.- XV. Reproductive Biology of North American Desert Rodents.- Reproductive Biology: Species Summaries.- References.- XVI. Rodent Faunas and Environmental Changes in the Pleistocene of Israel.- The Main Biogeographical Changes in the Near-East since the Miocene.- The Composition of the Rodents Faunas in the Pleistocene of Israel.- The Main Ecological Changes in the Quarternary of Israel.- Analysis of the Main Habitats Occupied by the Pleistocene Rodents of Israel.- Note on the Origin of the Israeli Desert Rodents.- References.- XVII. Prehistoric Rodents of the Middle East.- Prehistoric Rodents.- Discussion.- Acknowledgements.- References.- Addenda.- XVIII. Desert Rodents : Physiological Problems of Desert Life.- Problems of Temperature Regulation.- Water Balance, Intake and Loss.- References.- XIX. Ecophysiology of Water and Energy in Desert Marsupials and Rodents.- Methods.- Ecophysiology of Water and Energy.- Discussion.- References.- XX. Thermo-Regulation and Water Economy in Indian Desert Rodents.- Methods.- Thermo-Regulation.- Water Economy.- Conclusion.- References.- XXI. The Physiological Adaptations of Desert Rodents.- Water Conservation in Desert Rodents.- Structure and Concentrating Mechanisms in the Desert Rodent Kidney.- Tolerance to Heat and Thermo-Regulation of Desert Rodents.- Reproduction in Desert Rodents.- References.- XXII. Nematode Parasites of the Indian Desert Rodents.- Material and Methods.- Nematode Parasites of the Indian Desert Rodents.- Discussion.- References.- XXIII. Ecology of the Desert Rodents of the U.S.S.R. (Jerboas and Gerbils).- Jerboas.- Gerbils.- References.- Author Index.- Genus and Species Index.

Patterns of distribution of the tick Ixodes trianguliceps Birula on its hosts

Abstract: The survival of a single parasite is dependent on individual adaptations in relation to its specialized situation, while the evolution and survival of the parasite species is the product of an ecological relationship with its hosts at the population level. The patterns of distribution of the parasite on its hosts reflect the biological factors working within the host-parasite interaction (Crofton 1971a, b; Schmid & Robinson 1972), thus providing insight into the nature of the adaptive mechanisms permitting the survival of the parasite species. During a three-year study of the ecological relationship between the tick, Ixodes trianguliceps Birula 1895, and its small mammal hosts (Randolph 1973b) the tick infestation patterns were analysed with respect to the distribution of the ticks on the host population as a whole, and with respect to the variation in tick infestation levels on the different species of hosts and the intraspecific groups of hosts. This latter factor is very important to the understanding of the tick-host relationship, not only because the disparity reflects the importance of each small mammal species as hosts to this parasite, but also because the basis of its cause must lie in the mechanics of how the ticks are picked up and allowed to attach successfully.

Bird community dynamics and energetics in a northern hardwoods ecosystem

Abstract: One of the central goals of ecology is to understand the organization and functional relationships among natural assemblages of organisms and their complex interaction within ecological systems. Although the structures and productivities of terrestrial plant communities and their role as primary producers have been frequently studied (Whittaker 1970), there is little comprehensive information on whole communities of consumer organisms, especially those such as birds living above ground and often high in forest canopies. This is due in large part to the methodological difficulties of obtaining quantitative data simultaneously on the seasonal and annual fluxes in numbers and energy expenditures of a large number of populations. Recent work has demonstrated, however, that with intensive field investigations, bird community structures can be determined quantitatively (Emlen 1971, 1972; this paper) and that the energy expenditure of freeliving birds can be realistically estimated, using information on avian bioenergetics that has recently become available (Holmes & Sturges 1973). Several studies provide information on the structure and energy flow of individual bird populations, e.g. old field sparrows in winter (Odum, Connell & Davenport 1962), breeding red-winged blackbirds, AgelaEus phoeniceus* (Brenner 1968), and marsh wrens, Telmatodytes palustris (Kale 19653, and tree sparrows Passer montanus (Pinowski 1968) on an annual basis. At the community level, Uramoto (1961) and Karr (1968, 1971) have estimated the populations sizes and energy expenditure of birds breeding in deciduous forest in Japan and in Illinois and Panama, respectively, but their results were not discussed in an ecosystem context. Varley (19703 and Phillipson (19733 have modelled energy pathways through a temperate oak woodland, with emphasis on consumer organisms, although their data on the avian community were very incomplete. The most thorough and comprehensive analysis of avian community structure and energetic role is that of Wiens (1973) for grassland bird communities in summer. Inthis paper, we report some results from 51 continuous months of intensive and quantitative studies of bird community dynamics and energetics in the northern hardwoods ecosystems of the Hubbard Brook Experimental Forest in West Thornton, New Hampshire, U.S.A. The major objectives of this paper are to examine the seasonal and annual Ruxes in bird community composition, absolute population densities, biomass, productivities, and energy expenditures, and to consider the place of birds in the energy flow pathways of northern hardwood forests. A report with procedures for estimating

The Role of Environmental Factors in the Growth of Tern Chicks

Abstract: Seabirds have to forage under conditions of exceptionally large and rapid environmental fluctuations. In particular, those that plunge from air to water in search of prey are exposed to complex interactions between weather and sea surface conditions, and those that dive close inshore are further subjected to changes in their feeding sites caused by the daily tidal movements. We might therefore anticipate considerable day-to-day variation in the amount of food that such birds can obtain, and this should be most evident in the breeding season when adult birds are feeding chicks. A number of studies on the daily growth rates of chicks have suggested that this is the case for certain plunge-diving terns. Hawksley (1950, 1957) showed that chicks of Arctic terns (Sterna paradisaea Pont.) gained weight on clear days but generally lost weight on foggy days and Lemmetyinen (1972) has produced some supporting evidence. Langham (1968) has shown that daily weight changes in chicks of Arctic terns, common terns (S. hirundo L.) and roseate terns (S. dougallii Montagu) were affected by windspeed, duration of sunshine and amount of rainfall. Some of these relationships obtained by Langham and others have been briefly summarized by Anon. (1968). In these studies, observations at the nest-site were not accompanied by observations at sea, and consequently interpretation of results has been speculative. To gain a fuller understanding of variation in growth rates of tern chicks, it is desirable to know (a) whether the factors correlating with growth rates are also determinants of fishing ability in the adults, and (b) the nature of any relationship between environmental factors and fishing ability. In an attempt to fulfil these requirements, a study was therefore designed to interrelate environmental factors, fishing ability and growth of chicks. The work was carried out from 1968 to 1970 at Coquet Island (55?20'N,1?32'W) in Northumberland. The island supports breeding populations of Arctic terns, common terns, roseate terns and Sandwich terns (S. sandvicensis Latham); this study is concerned with the last three of these. Observations near the colony showed that fishing ability of common and Sandwich terns was influenced by windspeed and sea surface conditions (Dunn 1973) and also by tide (Dunn 1972; see also Boecker 1967). To determine whether these factors also affected chick development, they were included in a multivariate analysis of growth in chicks of the three species. In the present paper the results of this analysis are presented and examined in the context of parental fishing ability.

Insect territoriality and its evolution: population studies of desert grasshoppers on creosote bushes

Abstract: However, territorial defence, a component of site-dependent behaviour is extremely rare in grasshoppers (Acridoidea). The only species now known to defend territories (among more than 150 species studied -Jacobs 1953; Otte 1970) isLigurotettix coquilletti McNeill, a gomphocerine grasshopper living on creosote bushes (Larrea divaricata Cav.) in the Sonoran Desert. Elucidation of factors selecting for territoriality is difficult because other species living on creosote bushes in both North and South America fail to display any territorial defence. Both Ligurotettix and another gomphocerine species, Bootettix argentatus Br., advertise their whereabouts acoustically by stridulating, and both feed on creosote leaves. Bootettix resembles creosote leaves in colour and remains on the foliage day and night, while Ligurotettix resembles the grey stems, resides on stems during the daytime and feeds on the foliage at night. Several Bootettix males commonly inhabit the same bush or even the same branch, whereas Ligurotettix males tend vigorously to defend bushes against other males and may even avoid occupation of adjacent bushes. Such behavioural differences are evidently responsible for the considerable differences in -population density between the two species. Goniatron planum Bruner, a close relative of Ligurotettix, lives on southern blackbrush (Flourensia cernua DC) in the Chihuahuan Desert (Tinkham 1948). This species also does not defend territories but appears to have characteristics which could easily lead to territorial defence, given a change in bush size. In Argentina several species of the proscopiid genus Astroma are host-specific on several Larrea species. They also display no territorial defence system and may reach densities in excess of 15 males per bush. Territorial defence in insects appears to be more common in groups which are capable of recognizing and returning to unique points in their landscape, e.g., Odonata (Jacobs 1955) and certain Hymenoptera (Lin 1963; Wilson 1971). But insects which remain in small, clearly bounded, and defensible places may also be territorial even though they are incapable of distinguishing among similar sites. Our objectives here are to present results of observations and experiments on populations of Larrea-inhabiting grasshoppers occurring in North and South American deserts and to discuss general features of territoriality in relation to distribution and density in insects. Marking experiments and manipulations of population densities were carried out mainly in Ligurotettix coquilletti, but observations on other species allow us to illustrate

The Distribution and Abundance of Woodland Species of British Drosophila (Diptera: Drosophilidae)

Abstract: For seventy years, Drosophila has been used in genetical, cytological and evolutionary studies; in this connection fruit flies are admirable experimental animals. However, in the field of population biology it is increasingly obvious that the solution to many genetical and evolutionary problems must be found within an adequate ecological framework and this area of Drosophila study has received less attention. This paper describes some initial sampling of wild populations and forms part of a series of studies concerned with basic ecological information on the British species of Drosophila. The study was carried out at Adel Dam, an area of mixed deciduous woodland 10 km from the centre of the city of Leeds, which occupies an area of 50 ha surrounding a former mill pond, set in a shallow valley. The Leeds historian, Ralph Thoresby, refers to Adel Mill in 1715 as a corn mill so it is reasonable to suppose that the original dam was built prior to this date. Since that time the area of clear water has gradually been reduced due to extensive silting and the growth of reedmace (Typha latifolia L.). Details of the site with its vegetational zones are shown in Fig. 1.