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The article reflects on the pet population explosion of dogs and cats in the United States. The study aims to call the attention of the scientific community, which has hardly received the attention of the pet population explosion of dogs and cats. The section also offers several tables showing a summary of different surveys of the United States dog and cat population, showing a range of 90 but not less 20 million animals. Data gathered from countries like Japan, West Germany, Canada and the United Kingdom are also summarized in a table and compared in terms of owned pet ratios with U. S. figures.

Recently there has been an increasing awareness of the need to study the genus Drosophila in the wild, to assess the various ecological and behavioral parameters determining its distribution. It must be stressed that the classic work of Dobzhansky and his collaborators has over the years provided much information especially in D. pseudoobscura and closely related species such as D. persimilis. It is one of the curiosities of this sort of scientific endeavor, that the species D. melanogaster, perhaps best known genetically of all species in the genus, has been studied extensively under laboratory conditions for over 60 years, with little thought given to the situation in the wild. In this review, some environmental stresses, natural and artificial, for which genetic variability has been found within and between species of Drosophila will be examined, as they are important in determining the distribution of species of the genus in the wild. Stresses to be considered are temperature extremes, desiccation, anoxia as assessed by resistance to long-term exposure to CO2, 60Co γ-radiation, various chemical stresses (some of importance in nature because of the activities of man), and ethyl alcohol. [ABSTRACT FROM AUTHOR]

The population density, growth, biomass, fecundity and production of fish were estimated with the Tees River, England and different streams of the proposed reservoir basin. The fish species present were brown trout, bullhead and minnow. Trout were widespread throughout the study area, whereas bullhead and minnow were confined to the main river of the proposed reservoir. Trout growth was slow and compared with published estimates from other waters, whereas the minnow showed god growth. The range in numbers of O group fish was considered to be a reflection of variation in survival between time of oviposition and the period when the fry first became vulnerable to capture by electro-fishing.

A general type of mathematical model based on the matrix representation of first order difference equation is considered in the light of harvesting animal population. Simplifications in the model that occur if harvesting keeps the population level constant are noted and are used to investigate optimum age and sex specific harvesting strategies. A general result is obtained for cropping to be optimal. In the light of these results, the problem of optimal size for the population itself is considered.

The establishment and course of a benign enteric infection with Escherichia coli O127 was studied in adult mice specifically immunized by the parenteral and oral routes, and in infant animals born and suckling of mothers immunized with E. coli O127 antigens. Although parenteral injection of living, formalinized, or heat-killed E. coli resulted in the production of intestinal as well as circulating antibody, it had no effect on the establishment, course, or duration of colonization in adult mice. Neither active oral immunization with 0 antigen nor passive oral immunization with specific immune sera had any effect; oral infection with E. coli O127 did not reduce susceptibility to reinfection two to three months later. Enteric colonization of infant animals born and suckling of immune mothers was not inhibited, as judged by the 50% infectious dose or rates of natural colonization with E. coli O127 from their mother's stools. Although bacteremia with E. coli O127 was less frequent in infants of immunized mothers, these infants acquired E. coli in liver and spleen as did nonimmune infants. Findings suggest that colonization of the intestine with certain strains of E. coli is not significantly affected by local or circulating antibody. [ABSTRACT FROM PUBLISHER]

Primary production, production of and energy flow through small mammal populations, as well as their consumption, was measured by IBP methods. In a mature spruce forest with mainly granivorous species the impact by small rodents was not appreciable. In a reforestation on a clear felled area there were large annual variations in productivity with 0.5-2% total and 1-3% "useful" primary production being consumed by small rodents. The main snail mammal consumer in this habitat was Mictotus agrestis (14. Production varied between 05 and 5% of the assimilated energy; the differences being due mainly to species and physiological properties. [ABSTRACT FROM AUTHOR]

Samples of dace were taken from the Afon Llynfi and the River Lugg each month for 13 consecutive months. Male dace grew faster than females and rates were comparable with those described for several other populations. Variations in year-class strengths were observed and these differed between the populations although 1959 was strongly represented in both. The sex ratio varied throughout life and disturbances in the expected ratio were attributed to the attainment of sexual maturity at the end of the fourth year of life (3+). Observation of the seasonal gonad cycles indicated that spawning occurred in March or April. Fecundity was estimated at about forty eggs per gram of total weight. A seasonal cycle of feeding activity was established with highest food consumption during summer. There was evidence of a fast during the spawning period. No correlation between temperature and feeding activity could be established. Dace were omnivorous, but aquatic insects and algae were the main components of the diet. Seasonal variations generally followed availability. The importance of aerial insects declined with age. Many differences in feeding habits were detected between the populations. [ABSTRACT FROM AUTHOR]

This paper, on aquatic snails at Malham Tarn (Grid. ref. 34897666), is concerned with the dispersion patterns of two species-populations of littoral, stone-dwelling gastropods (Ancylus fluviatilis Müll. and Planorbis contortus Linn.) and forms part of a sequence involved with the ecology of this group. It will consider the nature of the patterns observed, and will infer causes, a-posteriori, from correlated distributions in independent environmental variables. This type of information is generally lacking for freshwater, bottom-dwelling invertebrates (Elliott, 1971) and previous reports on the Mollusca have been based on extensive rather than intensive surveys (e.g. Boycott, 1936). The habitat of an organism and consequently its dispersion pattern may be defined at various observational levels, e.g. in the case of the snails in question as: bodies of freshwater; littoral regions; submerged stones; submerged stones of a particular type; a particular part of submerged stones. Clearly the habitat definition chosen will depend on the degree of precision associated with the observations made, and on the type of ecological question being posed. The data presented below are extracted from different levels on such an observational sequence. They begin with a consideration of the overall vertical and lateral patterns of dispersion in the total sampling area and then focus attention on the between- and on-stone patterns respectively. Information on whole-Tarn dispersion patterns has been published elsewhere (Calow, 1973a). [ABSTRACT FROM AUTHOR]

(1) The vertical distribution of the benthic fauna of the Speed River, Ontario, was studied over a 13-month period from October 1970 to October 1971. Various physical and chemical parameters of this interstitial environment were also measured. (2) Several new techniques for sampling the interstitial environment of rivers wert devised. These methods and their relative efficiencies are considered. (3) The validity of the terms ‘hyporheal’ and ‘hyporheic’ are discussed and the term ‘hyporheos’ is offered to replace the former. (4) A brief résumé of interstitial sampling methods is given with comments on their limitations for sampling deep heterogeneous substrates. (5) Chemical parameters are thought to be more important in the control and distribution of the fauna than physical parameters. (6) It is suggested that many larvae of stream-dwelling chironomids have overwintering stages when they penetrate deep into the substrate to: (a) actively feed on the trapped organic detritus; (b) follow an optimum temperature for development. (7) It is suggested that the shape of an organism determines its success as a hyporheic form and examples are given. (8) The numbers of animals occurring in the sub-benthic populations are shown to be very large indeed. For the Speed River, estimates of between 184,760 and 797,960 animals/m³ are made for different times of the year. Dry weight biomass is estimated to vary between 30.9 g and 253.2 g/m³ throughout the year. (9) Sub-benthic or hyporheic populations are shown to exist in at least three other Canadian rivers. Some of the animals found are shown to be common to two or more of these rivers. (10) The inefficiencies of many conventional benthic samplers in sampling the total biomass of certain streams with hyporheic populations is discussed. [ABSTRACT FROM AUTHOR]

Evaluates the relative importance of physical and biological factors in determining the pattern of species composition in the marine rocky intertidal. Correlations between the increasing degree of exposure to air from low to high-tide levels and the pattern of distribution of organisms in narrow horizontal zones; Causes of limits in vertical zonation in natural populations; Importance of biological interactions.

Focuses on the factors that influence chromosomal arrangements and speciation in animal populations exemplified by the studies carried out on Drosophila. Nature of the genetic and cytogenetic processes involved in speciation; .

Presents a review of literature on experimental population genetics. Magnitude of the genetic variation in a population; Experimentation with genotypes in populations; Environmental factors and selective precision; Genetic assimilation or genetic recruitment; Disruptive or diversifying selection.

Presents a computer simulation study estimating animal populations through the use of the capture-recapture method. Survival rates that are independent of animal age; Expected age-specific mortality rates so that all animals of all ages were subject to the same probability of death at the end of each day in the simulations with the life tables; Animals in the simulations with life tables that were subject to high infant mortality.

The article examines the behavioral defects and mental deficiency in a population of animals. The animal subjects were analyzed for differences in behavior, especially of learned behavior. As indicated, the changing emphasis regarding the etiological factors in mental deficiency for animals is discussed. Research has been conducted relating heredity to adaptive behavior in animal models using psychometrics represented by the mental test movement and prevailing methodologies in plant and animal husbandry.

The article describes the effects of hippopotamus grazing on vegetation zones in the Queen Elizabeth National Park, Uganda. The three vegetation zones studied were mosaic grassland, sporobolus pyramidalis grassland and Themeda triandra grassland. According to the author, the hippopotamus population of the area probably increased greatly after the removal of the human population and with the formation of the National Park. The author adds that the mosaic grassland appears to be the preferred habitat of hippopotamuses.

The article discusses the main principles of evolutionary ecology. The first principle is that one must be clear from the start as to which features of an animal species or population are evolutionary adaptations and which are merely consequences of population dynamics. The second principle is that adaptive features are to be interpreted on two levels, proximately in terms of the physiological and behavioral factors. The third principle is to stress that the overriding agent of evolution is natural selection. The fourth principle is that it is important to study evolutionary ecology in the natural habitats of a species.

The article presents a study which examines the distribution of some common plants and animals of the littoral and shallow sublittoral regions in relation to wave action in the Lough Ine area. Thirty-three accurately defined stations have been used for the study of the distribution and population density of common plants and animals of the littoral and sublittoral regions in the Lough Ine area. According to the study, littoral species treat the Rapids as sheltered, probably because there is little splash.

The article presents a study which assesses the factors that affect the periodicity and population density of diatoms situated in bogs. It shows that the higher summer temperature influenced the reduction of water volume and population density, while temperature increase tend to spend growth and multiplication. The study reveals considers rainfall as the most important factor of growth and multiplication relative to the correlated conditions of maximal wetness. It concludes that population density is influenced by the mineral concentrations of mineral nutrients in their habitat.

Information about the papers discussed at the Spring meeting of the British Ecological Society on March 27-28, 1956 is presented. Topics include forest production management, production of some forest birds and their prey, and effect of artificial ecological conditions on plant and animal production. The conference features several ecology experts including Nature Conservancy director general E. M. Nicholson, Dr. J. D. Ovington and J. A. Gibb.

The article describes a cold-temperature region farther north on the same coast. The field work on which it is based was done between June 28, 1948 and September 1948. A general ecological account of the intertidal plant and animal populations of the Nova Scotia region is provided. A stretch of rocky coast adjacent to the harbor in Nova Scotia is described. It emphasizes the difficulties in distinguishing well-marked zones above the infralittoral fringe. The zonation between tide-marks shows very marked variations in the region.

The article presents a study that asserts the ecological condition of central Iceland. The study was conducted at Snaefell area, an extinct glacial volcano with outstanding topographical features, by comparing its animal and plant populations from the surrounding highlands to observe the different problems and association with northern elements of British fauna and flora. The study reveals that Snaefell manifest similar condition and specie populations from the semi-glaciated areas of Great Britain, however, the scarcity in the area is not the cause of the absence pf more than 30 species and does not provide any difference in vegetation. It also described climactic, physiographic condition of the area, principal plant communities succession interrelationships.

The article presents notes on the ecological and natural history of Pabbay and other islands in Sound of Harris, Scotland. Information regarding the island of Pabbay in Sound of Harris, Scotland is provided. It emphasizes that sand drift and grazing dominates much of the vegetation. It examines the tension zone between open dune and inland sandy pasture at one spot near the croft. A discussion of the origin of the present fauna of the Outer Hebrides, which has a pronounced woodland character, especially in the birds and mammals is provided.

The article examines the population of birds living in Lundy Island that is situated in the mouth of the Bristol Channel. The island, accordingly, is divided into four distinct vegetation. From June 7-11, 1930, the island has become the subject of bird census because it was perceived that the area could provide a more reliable information about the bird's various species. Results reveal that the island nurtures a number of birds including raven, carrion crow, magpie, house sparrow, skylark, rock pipit, yellow wagtail, and willow warbler. The total number of pairs of land birds has also found to be about 630. The number of larger birds like raven, peregrine, kestrel and buzzard, has likewise allegedly remained constant.

A list of publications on animal ecology is presented, including the papers "The Collembola of Ireland," by H. Womersley, "Birds the North Atlantic," by V. C. Wynne-Edwards and "Animal Life in the Marsh Ditches of the Thames Estuary," by F. J. Lambert.

The article focuses on further investigations concerning the study of cycles in British voles or microtus. To obtain evidence concerning future fluctuations, several methods have been used including an annual trapping census carried out on a number of areas in Great Britain and a system of reports from observers throughout the country. Sponsored by the Empire Marketing Board, the research was conducted under the direction of Charles Elton in the Department of Zoology and Comparative Anatomy at Oxford. One factor affecting the cycles of British voles is the effect of weather conditions on trapping in the exposed areas.

The article discusses findings of a study which examined the bird population of a settled valley in the West Usambaras, Tanganyika Territory. Tilted down towards the south, Kongei Valley's point is about 4000 feet above sea level. The color of the valley's soil range from brightest red through a variety of red and browns to almost black in the most heavily cultivated land. The farms found at the valley have formed like a hedge that acts as a natural boundary to birds, and present itself as a highway and a base of operations for birds.

The article offers information on an investigation carried out under the direction of researcher Charles Elton regarding the existence of a cycle in the numbers of the short-tailed field mouse, or vole, in Great Britain. It states that the vole maximum is not necessarily a plague, as the numbers may increase and fall again without doing any noticeable damage. It offers information on the cycles in the numbers of voles and the occurrence of vole maxima from 1890 to 1929. It also offers information on the results of the 1929 census for voles, Microtus hirtus and Microtus agrestis, and mentions that the study shows that past maximum years for field voles show a periodicity of nearly four years, and there is evidence that disease and the climatic factors are the controlling mechanism.

The article discusses various observations made by Charles S. Elton, author of the book "Animal Ecology," regarding the population of fresh-water Calanoids, Diaptomus gracilis and Eurytemora, in the filter-tanks of the Oxford Corporation Waterworks. It offers information on a series of breeding experiments carried out in the waterworks during the period of September to November 1929 to present various facts with regard to the Elton's statements such as that Diaptomus gracilis does not live in the filter-tanks because its eggs cannot withstand being dried up and the Eurytemora population was derived from resting eggs that had survived the drying process. It is inferred that contrary to the Elton's statement, the resting eggs of Eurytemora play no part in the population of the filter beds.

The article presents several publications that relate to the topic of animal ecology. General papers on particular animal groups include "A List of the Harvest-Spiders of Ireland," by D. R. Pack-Beresford, "The Eisenias of North Wales," by H. Friend, and "A Further List of Species of Coleoptera new to the County of Hertfordshire," by B. S. Williams. Several publications on action of environmental factors are also mentioned including "Local Changes in Distribution," by T. G. Longstaff, "Studies of some Lanarkshire Birds," by W. Stewart, and "The Fauna of Brackish Pools of the Sussex Coast," by W. H. Thorpe.

This article offers information regarding the tern colony. The study was carried out in 1913 on Blakeney Point, Norfolk. It aims to determine some of the laws that control the choice of site, the nesting materials, and the pigmentation of eggs by using a census. Previous studies provides the basis for the methods employed and the improvements in method suggest themselves, and the future work should prove of decided value. The study is a systematic attempt at such a census and publishes the results mainly as a suggestion to ornithologists and workers in Animal Ecology.

Animal bites are considered as a significant urban public health problem, and the situation in Baltimore, Maryland is discussed. The need for more lay and professional education and interest is presented, and specific forms of action are indicated. [ABSTRACT FROM AUTHOR]

This paper considers natural animal populations whose members are harvested for their own value, either esthetic or monetary. At the time of the harvest, population members are assumed to be indistinguishable as to sex. Revenue and cost structures are defined for these populations as they relate to the ecosystem. A stochastic description of population growth is used in which a change in the distribution at the growth parameter is described by an associated Markovian distribution process. This associated process describes the changes in environmental conditions. A harvesting policy is described in terms of an optimal population size. This policy maximizes the expected economic gain to be realized for the duration of time over which management of the system is anticipated. [ABSTRACT FROM AUTHOR]

The principles of evaluating relative estimates is described on the basis of a study of Clethrionomys glareolus (Schreber) and Apodemus flavicollis (Melchior). The frequency distribution of the trappability of the two species conforms to a Poisson distribution with added zeros. These surplus zeros are considered to be inversely proportional to the habitat penetration. If unrestricted trapping capacity (or a good approximation of it) is applied at each trap site, the mean of the catches at the trap sites constitutes a rectified population density index. ‘Rectified’ means that a doubled index value always implies a doubled population density. The properties of the Poisson distribution makes it possible, however, to sketch a theoretical model of relative estimates in which only one single-catching trap is set at each trap site. The known relation between the mean and the zero class of the Poisson distribution (a non-linear asymptotic regression) may be used to calculate a rectified population density index from such presence/absence data. In this case the surplus zeros must be formulated as a population parameter. [ABSTRACT FROM AUTHOR]

Quantitative sampling of the fauna was made in 1971 and 1972 to complement previous data about the faunal recovery after the cessation of the sulphite pulp mill in 1966. In 1972 the succession had approached a final phase in which the fauna had regained a composition similar to that found forty years earlier. The benthic faunal increment, expressed as dry weight, in Saltkällefjord over the period 1968–71 was roughly estimated to 20 per cent and the yearly production to 70–80 tonnes on this 4.4 km² area. Different indices have been used to describe the communities and the diversity. The succession showed a logistic pattern similar to population growth curves. [ABSTRACT FROM AUTHOR]

In Iceland, the polymorphic land snail Cepaea hortensis Müll. is confined to a relatively small area in the extreme south. Sampling 19 populations revealed the presence of a considerable range of phenotypes, the occurrence and frequency of which varies from population to population, A method of expressing the total genetic diversity of the phenotypes in different populations is suggested. The effective absence of the song thrush Turdus philomelos Brehm, a bird that is known to prey selectively on Cepaea elsewhere, suggests that other factors promote and maintain the polymorphism. In one area rodents were found to be feeding upon hibernating snails, and it is possible that they exert a considerable selection pressure. [ABSTRACT FROM AUTHOR]

Breeding populations of Anas platyrhynchos, A. strepera, A. crecca, A. penelope, Aythya marila, A. fuligula, Bucephala islandica, Clangula hyemalis, Melanitta nigra, and Mergus serrator were studied at Lake Mɓvatn in northeast Iceland (65°35'N, l7°00'W) during 1960 through 1970. Reproductive success and fluctuations in the size of the populations were studied in relation to the available resources. The variations and effects of certain breeding parameters, such as breeding frequency, hatching success, and duckling mortality, determining the reproductive success (full-grown young per female) were investigated. Relative scarcity of chironomid larvae (chief food item of the diving ducks and young) in 1970 was associated with reduced breeding frequency and a high rate of nest desertion (low hatching success). The survival of ducklings was mainly determined by the prevailing weather conditions during the week following hatching; therefore the total number of full-grown young was not closely correlated with the size of the breeding population. The reproductive success did not have an appreciable effect on the size of the population in subsequent years. [ABSTRACT FROM AUTHOR]

The rotatory-flow technique has been applied to roach Leuciscus rutilus L. from the mercury-contaminated Lake Övre Hillen and from Lake Snösjön, which, as it chiefly receives spring-water, is supposed to contain water that is comparatively pure. A highly significant difference in the mean critical rate of rotation (in r.p.m.) was found between the two samples of fish which also differed but in a reverse way with respect to the amount of methylmercury hydroxide found in their muscles. For the combined samples of fish, the critical rate of rotation showed a highly significant negative correlation to the amount of mercurial per unit muscle. The appearance of the same relationship for the fish from Lake Snösjön indicates that also in "pure" natural waters the coordination of a proportion of the fish is significantly decreased by the presence of methylmercury hydroxide in their bodies. [ABSTRACT FROM AUTHOR]

Home ranges of nine minks Mustela vison in southern Sweden were studied by telemetric techniques during eleven periods in 1968-69. Data obtained allowed accurate determinations of the boundaries of the ranges and quantitative descriptions of the distribution of use-intensity. Information on seasonal movements were obtained by trapping and marking. The adult male occupied the largest home range, twice as large as that of the juvenile male. Adult females kept within smaller ranges than the adult males. In winter the minks tended to concentrate their activity to restricted parts of the home ranges. The great irregularity found in intensity of use of the home range may be due to the availability of food. An adult female may temporarily hold a territory against an adult male. The balance, however, demands more attention from her at the common border. Unlike juvenile females, juvenile males did not seem to be allowed to stay within the ranges of adult males. The dispersal of juveniles started in the beginning of July and most of them left the study area. The extent of male movements during the mating season was greater than during the rest of the year. [ABSTRACT FROM AUTHOR]

A study of the population dynamics of the willow ptarrnigan (Lagopus lagopus alleni L.) was carried out in southeastern Newfoundland from 1955 through 1965. The adult population in spring increased from 1955 to 1961, then decreased in each of the four remaining years, 1962-65. Clutch size varied independently of population trend, being larger in early nesting seasons than in late nesting seasons. Nesting success, by contrast, and chick survival in the first three weeks of life, varied in a non-random sequence, tending to be greater in the years before the peak than in the years immediately after. Changes in population density were associated with changes in the number of young alive per hen in August. Survival after August was about the same each year for all age groups, roughly 28 per cent per year. These observations were consistent with the idea that there was a self-regulatory population process in which the probability of survival of the chicks varied with the stage of population growth. [ABSTRACT FROM AUTHOR]

Specimens of species of the Jaera albifrons group (Isopoda) were collected from 25 stones each month over a period of one year from two different shores. The density was found to be 4-20 per m² undersurface in winter and 2 500-11 400 in summer. The animals usually die within one year. Females always out-number males. Reproduction took place between April and September-November. A strong correlation between size and number of eggs was found. The egg number/brood varied from a mean of 8 up to a mean of 60. A theoretical potential productivity of a hibernating female was estimated to be 9200 descendants in the autumn. Up to 60 % of the females in a sample were carrying dead eggs and young. At one of the localities two species occurred. No evidence of differences in microdistribution was found between these. On exposed sites, however, spatial segregation between the sexes and between different size classes was found. [ABSTRACT FROM AUTHOR]

Data are presented showing patterns of frequency and abundance of soil inhabiting Oribatids associated with a gradient area. This area extends as a strip from the margin of a cultivated field to the edge of a (formerly) ombrogenous Sphagnum bog. Some 113 species of Oribatids belonging to 15 super-families have been taken in the monthly samples on different parts of the nine-point collection line. The mean number of individuals per sample unit shows annual fluctuations and varies with respect to sample site and time. The vertical dispersion of adult Oribatids differs along the gradient as well as seasonally. Some congeneric species studied show a preference for different sections of the strip, which may be caused by intrageneric competition and special autecological requirements. It is possible to group sociologically four isovalent communities of Oribatids with indicator species. The gradient area represents a sequence of associations and of influencing operative factors. [ABSTRACT FROM AUTHOR]

The studies were carried out by observation of tracks and signs in fresh water habitats in southern Sweden in 1958–66. 1. Female otters with cubs and adult males have fairly well-defined home ranges. Other single individuals may keep to restricted home ranges at least for part of the year. 2. The mother-and-young family groups extend their home ranges in the course of a year. They exploit an area of about 7 km in diameter. Topography and access lo open water in winter primarily determine its size and location, while food supply and population density have a secondary influence. 3. Adult dog otters generally cover home ranges with a width of about 15 km. The size varies greatly due to topography, individual qualities and occurrence of other otters, especially adult dog otters. 4. The distance travelled by the family groups is gradually extended as the cubs grow up. 3–4 km is a common length in winter. Dog otters travel large distances all the year round, A mean length was found to be 9–10 km per night, but there is a great variation from one night to another. 5. Home ranges are unevenly frequented. Most time is spent in the centre of the home range. Travels often follow a certain pattern of regular occurrences at places of special importance, viz. dens, rolling places, slides, feeding places, sprainting spots, sign heaps and runways. 6. Spring and autumn are seasons with high activity and great movement, covering the home ranges completely. In summer and winter activity is restricted to favourable haunts. [ABSTRACT FROM AUTHOR]