Distinguishing animal personality and innovation in the guppy - the effect of sex and body size

How individuals within the same population show consistent differences in different behaviours, i.e. animal personalities, and how these correlate into a wider behavioural syndrome has become a hot topic in behavioural research the last 20 years. Lately it has also been suggested that innovative behaviours should be considered as an aspect of animal personalities, since it has become clear that individuals differ in their innovative rate. In this study, guppies (Poecilia reticulata) were tested in four behavioural assays (exploration of an open area and a maze, and investigation of a novel object and a novel food). The individual variation and the co-variance between the measured variables, i.e. syndrome structure, was examined primarily by comparing seven a priori hypotheses using structural equation modelling (SEM). The best model was one that separated variables relating to activity from rates of exploration/investigation (i.e. rather than alternative divisions based on spatial vs. non-spatial or personality vs. innovation variables, etc.). No clear differences in syndrome structure were found when comparing the three different populations. However, there was some effect of individual body size on syndrome structure, because smaller females (but not males) were shown to be more active. Thus, syndrome structure here seems to be driven by individual, and possible sex, differences in developmental state, since size and age are highly correlated in fish. The role of such a syndrome is discussed in the context of guppy life histories, where the reproductive success of females, but not males, is size dependent