This article discusses three different uses of ratio variables in aggregate data analysis: (1) as measures of theoretical concepts, (2) as a means to control an extraneous factor, and (3) as a correction for heteroscedasticity. In the use of ratios as indices of concepts, a problem can arise if...

Many aposematic prey combine their visual warning signals with additional signals. Together, these signals constitute a multimodal or multicomponent warning display. The additional signals are thought to increase the effects of the visual signals on predators. Olfactory signals are much...

Females are predicted to adjust their reproductive investment in relation to resource quality. In zebra finches (Taeniopygia guttata), diet quality has been found to influence egg mass both between and within clutches. We tested the prediction that diet quality also affects the quantity of...