Research with children: methodological issues and innovative techniques

In the past few decades, a growing body of literature examining children’s perspectives on their own lives has developed within a variety of disciplines, such as sociology, psychology, anthropology and geography. This article provides a brief up-to-date examination of methodological and ethical issues that researchers may need to consider when designing research studies involving children; and a review of some of the methods and techniques used to elicit their views. The article aims to encourage researchers to critically reflect on these methodological issues and the techniques they choose to use, since they will have implications for the data produced.

The replacement of a native freshwater amphipod by an invader: roles for environmental degradation and intraguild predation

We assessed the extent to which an invader, Gammarus pulex (Crustacea: Amphipoda), has replaced a native, Gammarus duebeni celticus, over a 13-year period in a European river system and some of the abiotic and biotic factors that could account for this. Between 1988 and 2001, 56% of mixed-species sites had become invader-only sites, whereas no mixed sites had become native only again. The native dominated areas of higher dissolved oxygen and water quality, with the reciprocal true for the invader. Field transplant experiments revealed that native survivorship was lower in areas where it had been replaced than in areas where the invader does not yet occur. In invader-only areas, native survivorship was lower than that of the invader when kept separately and lowest when both species were kept together. We also observed predation of the native by the invader. Laboratory oxygen manipulation experiments revealed that at 30% saturation, the native's survivorship was two thirds that of the invader. We conclude that decreasing water quality favours replacement of the native by the invader.

Intraguild predation may explain an amphipod replacement: evidence from laboratory populations

In a laboratory experiment that permitted both observations of the behaviour of individuals and the monitoring of small populations, the role of 'intraguild predation' in the elimination of the freshwater amphipod Gammarus duebeni celticus by the introduced G. pulex was examined. Over 18 weeks, deaths in single and mixed species replicates were monitored. Rates of 'mortality' (deaths not due to cannibalism or predation) did not differ between the species. Gammarus cl. celticus, however, was more cannibalistic than G. pulex and, in both species, males were more often cannibalized than females. In mixed species replicates, the mean proportions of animals preyed upon did not differ among replicates with differing starting proportions of the two species, nor was there a difference between the sexes in numbers preyed upon. G. pulex, however, preyed more frequently on G. d celticus than vice versa, and this became more pronounced over time. In 87% of mixed species replicates, G. pulex eliminated G. d. celticus. The results support the proposition that intraguild predation may be the primary mechanism whereby G. pulex rapidly replaces G. d. celticus in freshwater. Integrating behavioural observations with population level monitoring may thus link pattern and process in behaviour and ecology.

Influence of replacement rate on the welfare of sows introduced to a large dynamic group

This experiment investigated the effects of replacing 10, 20, 30 or 40% of a dynamic group of forty sows on the welfare of newly-introduced animals. The experiment was replicated five times, using a total of 200 multiparous sows. Replacements took place at 3 week intervals, and 3 days prior to sows being added to the group the same number of animals were removed from the group. Sows were added to the dynamic group as pre-formed groups of four animals which had resided together for a period of 5 weeks beginning directly after their piglets were weaned. Replacement rate did not appear to influence overall levels of aggression to which newly-introduced animals were exposed on the day of mixing, however aggression among newly-introduced animals increased significantly as replacement rate increased between 20 and 40% (P