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Age at first reproduction is an important determinant of individual variation in reproductive success in ungulates, but few studies have examined its relationship with later fitness‐related traits in males. We used a long‐term individual based study of a harvested moose population to quantify the individual reproductive performance and survival of males, as well as to examine the determinants of age at first reproduction and consequences of age at first reproduction on lifetime breeding success. The probability that a male successfully reproduced at the age of two was negatively related to the mean age of adult males in the population, but the relationship weakened with increasing population size. Large antlers and large body mass relative to other males in the population increased the number of calves sired at their first successful mating season. In addition, those that successfully reproduced as two year‐olds were more likely to sire calves the next year, making them more productive at a given age compared to those that first reproduced at the age of three or older. We emphasize the importance for males to start reproducing as soon as possible in a harvested population to gain lifetime fitness benefits, as surviving the hunt is a major determinant of reproductive success in this population. We found no costs of early reproduction in males, hence leading to high individual heterogeneity in male reproductive performance. The apparent lack of reproductive costs could partly be explained by the age distribution in the population, individual variation in early‐life body mass and antler size, and differences in probabilities of being hunted of successful and unsuccessful males. Locked until 3 September 2019 due to copyright restrictions. This is the peer reviewed version of an article, which has been published in final form at https://doi.org/10.1111/oik.05494. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

Traditional predation theory assumes that prey density is the primary determinant of kill rate. More recently, the ratio of prey-to-predator has been shown to be a better predictor of kill rate. However, the selective behavior of many predators also suggests that age structure of the prey population should be an important predictor of kill rate. We compared wolf– moose predation dynamics in two sites, south-central Scandinavia (SCA) and Isle Royale, Lake Superior, North America (IR), where prey density was similar, but where prey age structure and prey-to-predator ratio differed. Per capita kill rates of wolves preying on moose in SCA are three times greater than on IR. Because SCA and IR have similar prey densities differences in kill rate cannot be explained by prey density. Instead, differences in kill rate are explained by differences in the ratio of prey-to-predator, pack size and age structure of the prey populations. Although ratio-dependent functional responses was an important variable for explaining differences in kill rates between SCA and IR, kill rates tended to be higher when calves comprised a greater portion of wolves’ diet (p  0.05). Our study is the first to suggest how age structure of the prey population can affect kill rate for a mammalian predator. Differences in age structure of the SCA and IR prey populations are, in large part, the result of moose and forests being exploited in SCA, but not in IR. While predator conservation is largely motivated by restoring trophic cascades and other top–down influences, our results show how human enterprises can also alter predation through bottom–up processes.

Studies of the behaviour of marine birds can, in addition to their direct relevance to the conservation of seabird populations, provide useful information on several aspects of the marine environment in general. Indices of the abundance and of the spatial and temporal distribution of their fish prey can potentially be obtained from studies of seabird numbers, distribution, diet, reproductive performance, adult body condition and adult foraging and reproductive behaviour. The relative usefulness of these parameters is evaluated using data from a study of four seabird species in Shetland over a period when detailed, independent information was available on considerable changes in prey population abundance and structure. The results demonstrate that parameters concerned with foraging behaviour offer the most useful indices of the status of prey populations, moreover, the differences between seabird species in their responses to changes in prey availability can be used to provide information on the abundance, distribution and age structure of the fish far more cheaply than conventional fisheries surveys.

We review the application of spatially explicit models to conservation biology, and discuss several problems regarding the use of these models. First, it is unclear whether increasing the complexity of spatial models to include age structure enhances our ability to predict population growth in temporally varying environments. Second, if simulations of individual behavior are used to identify options for landscape management, predictions about the fate of dispersing organisms are likely to be hugely in error unless dispersal attributes are known to a far greater degree of accuracy than is reasonable to expect. Third, the compelling metaphor of extinction debts resulting from habitat destruction in competitive communities stands firm as a cautionary tale even when the metapopulation models include multiple trophic levels but the question remains of how widespread and tight are the tradeoffs between dispersal capacity and competitive superiority. Given the shakiness of spatial models as a foundation for specific conservation recommendations, we conclude they may be more useful as a tool for exploring the design of spatially-structured monitoring schemes, so that management mistakes might be detected before they become irreversible.

Edmondson, W. T. and Winberg, G. G. (ed.) 1971. A manual on methods for the assessment of secondary productivity in fresh waters. IBP Handbook no. 17, Blackwell, Oxford. Janicki, A. J. and DeCosta, J. 1977. The effect of temperature and age structure on P/B for Bosmina longirostris in a small impoundment. Hydrobiologia 56: 11-16. and DeCosta, J. 1979. The effect of lake trophic status on daily P/B of Bosmina longirostris. Oikos 33: 64-68. Weglenska, T. 1971. The influence of various concentration of natural food on the development, fecundity and production of planktonic crustacean filtrators. Ekol. Pol. 19: 427-473

Age structure, biomass, and productivity in three differently aged Calluna heaths at different distances from the sea were studied in a sand dune area at Sandhammaren, S. Sweden. A method for measuring above ground production, based on only one sampling occasion was used. The phased developmental pattern of Calluna, as originally defined by Watt was not valid in the study area. A continuous rejuvenation of above ground biomass occurred through successive embedding and frequent adventitious rooting of trailing stems, and in spite of age of the heaths, no marked differences in age structure was found between the studied sites. The above ground biomass was assumed to be in a steady state, in conformity with what occurs in certain heaths on peat. The successive accumulation of organic matter is defined in a simple model, based on an assumedly unchanged between-year production.

Density, height, diameter, and age structure of Pinus taeda L. were examined in a 21-year-old abandoned field. A density estimate of 924 trees ha-1 was obtained, a factor of 17 over that found for the area 14 years earlier. Age frequencies resembled an inverse J-shaped depletion model, with 4.3 % of all trees examined being in the 1-year age class. Median ecological longevity was estimated to be 3.2 years. Linear correlations between age, height, and dbh data were also determined.

Good short-cut methods for estimating the production of animal populations through P/B ratios are much sought after among those ecologists who believe that charting the energy flows through an ecosystem is a worthwhile effort. Being one of them, I was attracted to the title of the paper of Janicki and DeCosta (1977): "The effect of temperature and age structure on P/B for Bosmina longirostris". I failed, however, to understand how they had obtained the daily P/B ratios on which their conclusions rested. A later paper by the same authors which recently appeared in Oikos (Janicki and DeCosta 1979) gives more details on the derivation of their P/B ratios. It turns out that their conclusions depend almost entirely on the assumptions they made in calculating the P/B ratios, and are thus mere artifacts of their mathematical manipulations of the data. Since the authors seem to have managed to mislead not only themselves, but also the editors and referees of two reputable scientific journals, it is perhaps worthwhile to examine their method closely. I will first analyse their second, more detailed, paper (Janicki and DeCosta 1979). The input data used consists of biweekly zooplankton net samples from the period May to November, from one to three stations in each of several small lakes. The concentration of Bosmina was determined and the length (1) distribution of the animals measured for each sample. The individual weight (w) was estimated from the regression w = 0.18 X 12.88 (Ivanova, in Edmondson and Winberg 1971: 312-315) for all measured individuals, and mean weights calculated for each of the size groups: I: 0 0.3 mm, II: 0.3 0.4 mm and III: 0.4 0.6 mm, and the total biomass derived from the mean weights of the size groups and their abundance. The next steps are crucial. Production (P) was estimated for each of the three size groups (I-III) from the