Low Mate Encounter Rate Increases Male Risk Taking in a Sexually Cannibalistic Praying Mantis

Male praying mantises are forced into the ultimate trade-off of mating versus complete loss of future reproduction if they fall prey to a female. The balance of this trade-off will depend both on (1) the level of predatory risk imposed by females and (2) the frequency of mating opportunities for males. We report the results of a set of experiments that examine the effects of these two variables on male risk-taking behavior and the frequency of sexual cannibalism in the praying mantis Tenodera sinensis. We experimentally altered the rate at which males encountered females and measured male approach and courtship behavior under conditions of high and low risk of being attacked by females. We show that male risk taking depends on prior access to females. Males with restricted access to females showed greater risk-taking behavior. When males were given daily female encounters, they responded to greater female-imposed risk by slowing their rate of approach and remained a greater distance from a potential mate. In contrast, males without recent access to mates were greater risk-takers; they approached females more rapidly and to closer proximity, regardless of risk. In a second experiment, we altered male encounter rate with females and measured rates of sexual cannibalism when paired with hungry or well-fed females. Greater risk-taking behavior by males with low mate encounter rates resulted in high rates of sexual cannibalism when these males were paired with hungry females

From dividend yield to discounted cash flow: a history of UK and US equity valuation techniques

This article explores how, as capital markets developed, equity valuation methods changed. The history of equity valuation is described, from its early origins during the South Sea Bubble, through the new issue boom of the nineteenth century and the stock market booms of the 1920s and 1950s. The moves from dividend yield and asset backing, to earnings yield and then P/E ratios are chronicled. The article compares developments in the UK and the US, in particular the relative slowness of the UK market to adopt US-pioneered techniques such as the P/E ratio, the concept of value versus growth stocks, and using intrinsic value to determine whether shares are cheap or dear. The article concludes with a discussion of the relatively slow introduction of the dividend discount model and of discounted cash flow as equity valuation tools on both sides of the Atlantic.history of valuation, dividend yield, P/E ratio, intrinsic value, discounted cash flow,