Absolute Population Estimates Using Capture–Recapture Experiments

The main methods used to estimate population size using capture–recapture for both closed and open populations are described, including the Peterson–Lincoln estimator, the Schabel census, Bailey’s triple catch, the Jolly–Seber stochastic method, and Cormack’s log-linear method. The robust design approach is described. R code listings for commonly used packages are presented. The assumptions common to capture–recapture methods are reviewed, and tests for assumptions such as equal catchability described. The use of programs to select model assumptions are described. The main methods for marking different animal groups are described, together with the use of natural marks and parasites and DNA. Marking methods include paint marks, dyes, tagging, protein marking, DNA, natural marks, tattooing, and mutilation. Methods for handling and release are described.

‘Stray appetites’: a socio-ecological analysis of free-ranging dogs living alongside human communities in Bangalore, India

Across the developing world, humans and free-ranging domestic dogs share common spaces. The relationship between these dogs and humans can range from one of dependence, to apathy, to conflict. Given the high number of humans attacked by dogs every year in India, and the lack of an effective population control strategy, we seek to provide insights into the conflict and propose alternative population management options based on reducing the carrying capacity of the environment. We used a mixed methods approach to understand both ecological and sociological underpinnings of free-ranging dog-human relationships in Bangalore, India. We conducted a photographic capture-recapture survey of free-ranging dogs to estimate population size and linked it to the availability of potential food sources. We also conducted a qualitative survey to assess attitudes of residents towards the dog population. We found that dog population varied from 192 to 1888 per square kilometre across a gradient of housing densities. The density of houses, bakeries and garbage piles were significant predictors of dog population size. Crucially, as low as 10 to 18% of houses supported the large population of dogs, highlighting the need for residents to act responsibly towards the dogs. Further, we found that garbage, although significant, is a secondary food source to household-maintained dogs. Since on the whole, respondents expressed the desire for a reduction in dog population, we suggest decreasing the carrying capacity of the environment by targeting these three food sources.

Rangeland loss and population decline of the critically endangered Liben Lark Heteromirafra archeri in southern Ethiopia

Summary Liben Lark Heteromirafra archeri is a ‘Critically Endangered’ species threatened by the loss and degradation of grassland at the Liben Plain, southern Ethiopia, one of only two known sites for the species. We use field data from nine visits between 2007 and 2019 and satellite imagery to quantify changes over time in the species’ abundance and in the extent and quality of its habitat. We estimate that the population fell from around 279 singing males (95% CL: 182–436) in 2007 to around 51 (14–144) in 2013, after which too few birds were recorded to estimate population size. Arable cultivation first appeared on the plain in the early 1990s and by 2019 more than a third of the plain had been converted to crops. Cultivation was initially confined to the fertile black soils but from 2008 began to spread into the less fertile red soils that cover most of the plain. Liben Larks strongly avoided areas with extensive bare ground or trees and bushes, but the extent of these did not change significantly over the survey period. A plausible explanation for the species’ decline is that grassland degradation, caused before 2007 by continuous high-pressure grazing by livestock, reduced its rates of reproduction or survival to a level that could not support its previous population. Since 2015, communal kalos (grazing exclosures) have been established to generate forage and other resources in the hope of also providing breeding habitat for Liben Larks. Grass height and density within four grassland kalos in 2018 greatly exceeded that in the surrounding grassland, indicating that the plain retains the potential to recover rapidly if appropriately managed. Improvement of grassland structure through the restitution of traditional and sustainable rangeland management regimes and the reversion of cereal agriculture to grassland are urgently needed to avert the species’ extinction.

Demography and Networks

Demographers have incorporated social network concepts and measures into contemporary demographic research as determinants of demographic behaviors; they have invoked structural properties of networks to improve descriptions of hard-to-survey populations; they have relied on network data and measures to estimate population size and parameters under conditions of sparse information. This chapter illustrates how social network concepts and models are integral to the development of explanations of fertility and migration behaviors and of population-level characterizations of demographic systems. It highlights productive ways for advancing demographic research that rely on the adoption of a wider array of network data and tools to link structural characteristics of networks to the mechanisms involved in shaping demographic behavior, understand how demographic behaviors structure networks, and map social network structures in data collection for more efficient and cost-effective population enumeration and parameter estimation.

‘Stray Appetites’: A Socio-Ecological Analysis of Free-Ranging Dogs Living Alongside Human Communities in Bangalore, India

Across the developing world, humans and free-ranging domestic dogs share common spaces. The relationship between these dogs and humans can range from one of dependence, to apathy, to conflict. Given the high number of humans attacked by dogs every year in India, and the lack of an effective population control strategy, we seek to provide insights into the conflict and propose alternative population management options based on reducing the carrying capacity of the environment. We used a mixed methods approach to understand both ecological and sociological underpinnings of free-ranging dog-human relationships in Bangalore, India. We conducted a photographic capture-recapture survey of free-ranging dogs to estimate population size and linked it to the availability of potential food sources. We also conducted a qualitative survey to assess attitudes of residents towards the dog population. We found that dog population varied from 192 to 1888 per square kilometre across a gradient of housing densities. The density of houses, bakeries and garbage piles were significant predictors of dog population size. Crucially, as low as 10 to 18.3% of houses supported the large population of dogs, highlighting the need for residents to act responsibly towards the dogs. Further, we found that garbage, although significant, is a secondary food source to household-maintained dogs. Since on the whole, respondents expressed the desire for a reduction in dog population, we suggest decreasing the carrying capacity of the environment by targeting these three food sources.

Removal modelling in ecology

Removal models were proposed over 80 years ago as a tool to estimate unknown population size. Although the models have evolved over time, in essence, the protocol for data collection has remained similar: at each sampling occasion attempts are made to capture and remove individuals from the study area. Within this paper we review the literature of removal modelling and highlight the methodological developments for the analysis of removal data, in order to provide a unified resource for ecologists wishing to implement these approaches. Models for removal data have developed to better accommodate important feature of the data and we discuss the shift in the required assumption for the implementation of the models. The relative simplicity of this type of data and associated models mean that the method remains attractive and we discuss the potential future role of this technique.Author summarySince the introduction of the removal in 1939, the method has being extensively used by ecologists to estimate population size. Although the models have evolved over time, in essence, the protocol for data collection has remained similar: at each sampling occasion attempts are made to capture and remove individuals from the study area. Here, we introduce the method and how it has been applied and how it has evolved over time. Our study provides a literature review of the methods and applications followed by a review of available software. We conclude with a discussion about the opportunities of this model in the future.

Estimating population sizes and demographic trends in Ipswich c. 1570-1620: re-evaluations and new approaches

This article explores the characteristics and experiences of the population of the town of Ipswich, Suffolk, between 1570 and 1620. It reassesses current estimates of the total number of inhabitants in the town at specific points throughout this period. This provides a basic framework for the subsequent analysis of the parish registers, which enables a better understanding of the town's demographic trends in this period. In addition, it puts forward new methods to estimate population size. These methods combine data from the town's communicant returns, parish poor rates, poor relief payments, and similar sources in order to determine the social structure of the town, the relative wealth of the town's parishes, and the approximate population sizes of the town's main socio-economic groups.