Journal of Animal Ecology

1. Life history theoreticians have traditionally assumed that juvenile growth rates are maximized and that variation in this trait is due to the quality of the environment. In contrast to this assumption there is a large body of evidence showing that juvenile growth rates may vary adaptively both within and between populations. This adaptive variation implies that high growth rates may be associated with costs.

2. Here, I explicitly evaluate the often‐proposed trade‐off between growth rate and predation risk, in a study of the temperate butterfly, Pararge aegeria (L).

3. By rearing larvae with a common genetic background in different photoperiods it was possible to experimentally manipulate larval growth rates, which vary in response to photoperiod. Predation risk was assessed by exposing larvae that were freely moving on their host plants to the predatory heteropteran, Picromerus bidens (L.).

4. The rate of predation was significantly higher in the fast‐growing larvae. An approximately four times higher relative growth rate was associated with a 30% higher daily predation risk.

5. The main result demonstrates a trade‐off between growth rate and predation risk, and there are reasons to believe that this trade‐off is of general significance in free‐living animals. The results also suggest that juvenile development of P. aegeria is governed by a strategic decision process within individuals.

Movement behaviour has become increasingly important in dispersal ecology and dispersal is central to the development of spatially explicit population ecology. The ways in which the elements have been brought together are reviewed with particular emphasis on dispersal distance distributions and the value of mechanistic models.

1.We examined published studies relating resting oxygen consumption to body mass and temperature in post‐larval teleost fish. The resulting database comprised 138 studies of 69 species (representing 28 families and 12 orders) living over a temperature range ofc.40 °C.

2. Resting metabolic rate (R_b; mmol oxygen gas h^–1) was related to body mass (M;wet mass, g) byR_b = aM^b, where a is a constant and b the scaling exponent. The model was fitted by least squares linear regression after logarithmic transformation of both variables. The mean value of scaling exponent, b, for the 69 individual species was 0·79 (SE 0·11). The general equation for all teleost fish was 1nR_b = 0·80(1nM) – 5·43.

3. The relationship between resting oxygen consumption and environmental temperature for a 50‐g fish was curvilinear. A typical tropical fish at 30°C requires approximately six times as much oxygen for resting metabolism as does a polar fish at 0°C. This relationship could be fitted by several statistical models, of which the Arrhenius model is probably the most appropriate. The Arrhenius model for the resting metabolism of 69 species of teleost fish, corrected to a standard body mass of 50 g, was 1nR_b = 15·7 – 5·02.T^–1, whereTis absolute temperature (10³ × K).

4.The Arrhenius model fitted to all 69 species exhibited a lower thermal sensitivity of resting metabolism (mean Q₁₀ = 1·83 over the range 0–30 °C) than typical within‐species acclimation studies (median Q₁₀ = 2·40,n = 14). This suggests that evolutionary adaptation has reduced the overall thermal sensitivity of resting metabolism across species. Analysis of covariance indicated that the relationships between resting metabolic rate and temperature for various taxa (orders) showed similar slopes but significantly different mean rates.

5. Analysis of the data for perciform fish provided no support for metabolic cold adaptation (the hypothesis that polar fish show a resting metabolic rate higher than predicted from the overall rate/temperature relationship established for temperate and tropical species).

6. Taxonomic variation in mean resting metabolic rate showed no relationship to phylogeny, although the robustness of this conclusion is constrained by our limited knowledge of fish evolutionary history.