Ecological Demography Research Articles

Appearance of chaos and bi-stability in a fear induced delayed predator–prey system: A mathematical modeling study

Since many years ago, it has been only a priori assumption that the diversity of ecological demography is largely influenced by the direct interactions of predator and prey species. But over the years, it has also been recognized that an indirect effect can also affect the system more strongly. The effect of fear on prey species is that it restricts physical activities and feeding times of prey thereby reducing interactions with their predators and leading to an intraspecific competition among predators. By these motives, we investigate a delay-induced model inducing fear of predators on the prey population. Existence of feasible steady points, well posedness of the solutions, local & global stability, subcritical & supercritical bifurcation are well presented. The results show that predator fear reduces both prey and predator populations, but does not affect the steady state of the system. As delay increases within a specific range, it changes the dynamics of the system in a stable–unstable–stable sequences. A small delay shifts an unstable interior equilibrium to a predator-free stable equilibrium. The main result of this study is that a large delay produces chaotic dynamics when cost of fear is high and prey birth is low, whereas a small delay creates bi-stable dynamics when cost of fear is low and prey birth is high. Furthermore, by increasing the competitiveness among the predators, the chaos can be completely controlled. We examine that small fear has a greater effect while relatively large fear has less effect. Delay parameter is responsible for appearing stability switch more than once. Extensive numerical simulations are also carried out for various parameters.

Lichenometric dating of little ice age glacier moraines using explicit demographic models of lichen colonization, growth, and survival

Contemporary variants of the lichenometric dating technique depend upon statistical correlations between surface age and maximum lichen sizes, rather than an understanding of lichen biology. To date three terminal moraines of an Alaskan glacier, we used a new lichenometric technique in which surfaces are dated by comparing lichen population distributions with the predictions of ecological demography models with explicit rules for the biological processes that govern lichen populations: colonization, growth, and survival. These rules were inferred from size–frequency distributions of lichens on calibration surfaces, but could be taken directly from biological studies. Working with two lichen taxa, we used multinomial‐based likelihood functions to compare model predictions with measured lichen populations, using only the thalli in the largest 25% of the size distribution. Joint likelihoods that combine the results of both species estimated moraine ages of ad 1938, 1917, and 1816. Ages predicted by hizocarpon alone were older than those of . pubescens. Predicted ages are geologically plausible, and reveal glacier terminus retreat after a ittle ce ge maximum advance around ad 1816, with accelerated retreat starting in the early to mid twentieth century. Importantly, our technique permits calculation of prediction and model uncertainty. We attribute large confidence intervals for some dates to the use of the biologically variable hizocarpon subgenus, small sample sizes, and high inferred lichen mortality. We also suggest the need for improvement in demographic models. A primary advantage of our technique is that a process‐based approach to lichenometry will allow direct incorporation of ongoing advances in lichen biology.

Predictors of early survival in Soay sheep: cohort-, maternal- and individual-level variation

A demographic understanding of population dynamics requires an appreciation of the processes influencing survival--a demographic rate influenced by parameters varying at the individual, maternal and cohort level. There have been few attempts to partition the variance in demography contributed by each of these parameter types. Here, we use data from a feral population of Soay sheep (Ovis aries), from the island of St Kilda, to explore the relative importance of these parameter types on early survival. We demonstrate that the importance of variation occurring at the level of the individual, and maternally, far outweighs that occurring at the cohort level. The most important variables within the individual and maternal levels were birth weight and maternal age class, respectively. This work underlines the importance of using individual based models in ecological demography and we, therefore, caution against studies that focus solely on population processes.

Health Culture and Health Seeking Behaviour Among The Semi-nomadic Lohar-Gadiyas of Malthon Town of Sagar District, Madhya Pradesh

Health is mans natural condition therefore it is always a major concern of community development and problems of health are the problems of national importance. It is well known fact that health and disease are interrelated and their concept varies from culture to culture and people to people especially in tribal and other backward communities because their concept of health and health seeking behaviour is a part of their culture. Health status and health seeking behaviour of different tribal and backward groups is influenced by their entire way of life like culture including social and economic condition nutrition living conditions housing education food habits taboos and superstition socio-religious beliefs and practices use of indigenous Medicare systerm income communication and transportation ecology demography socio-biological practices genetics attributes and the health service etc. These entire interacting subsystems complex as a whole is termed health culture. Some notable contribution in studying health seeking behaviour are made by Polgar (1962) Saraswati Swain (1992) Chatterjee (1993) Pandey et al. (1996) Sharma and Sharma (2000) and Pandey et al. (2000). Here in this paper an attempt is made to study their health culture and assess health seeking behaviour. (excerpt)

Ecological demography: a synthetic focus in evolutionary anthropology.

"Ecological demography arises from two facts: that the reproductive behavior of humans, like that of other species, is influenced by natural selection and that current fitness is the product of both genotype and environment. Here I review classic atheoretical and recent theoretical studies that contribute to this emerging field, exploring the extent to which human reproductive responses to ecological conditions, considered in their broadest context, follow the same selective rules as other species."

Toward an Ecological Demography

An innovative way of looking at demographic patterns is based on paradigms from the fields of behavioral and evolutionary ecology. Just as the analytic techniques of demography have been important to biological investigations the theoretical advances of the last 25 years in biology may offer important perspectives on central problems in demography and provide paths to fruitful ecologically informed solutions. The authors summarize the pertinent theory in behavioral ecology highlight two important differences in the way biologists and demographers partition problems and illustrate how behavioral ecology might contribute to a new understanding of several important issues in classical demography namely natural versus controlled fertility population regulation and allocation of resources to offspring. (SUMMARY IN FRE AND SPA) (EXCERPT)

Cultural Materialism in the Functionalist Mode

The author critically analyzes Krishnan Namboodiris 1988 defense of ecological demography and adds his own comments on the state and nature of the field. A reply by Namboodiri is included (pp. 660-1). (ANNOTATION)

Ecological Demography: Its Place in Sociology

A partnership between demography and human ecology is argued to be more appropriate to the systematic comprehensive treatment of social systems than any single sociological paradigm. Ecological demography deals with the evolution of societies contemporary societies territorial communities formal organizations interorganizational interdependence interregional interdependence structure and change. It offers a framework for the application of the demographic perspective to the study of both human and organizational populations. The development of subfields such as family and organizational demography has accelerated the rate at which demography has expanded its hold on the core of sociology. Moreover human ecology is becoming more formalized enhancing its capability to address structural and process-related issues of communities and societies. This approach requires a view of the core of sociology as the study of the population-environment-systems-technology complex in its structural and dynamic aspects. Sociologists are urged to compare the power of their favored paradigms with an ecological demographic approach. Such comparative analyses will help clarify the major differences between paradigms and identify lacunae the removal of which makes each paradigm more powerful in addressing the core of the discipline.