In 2011, together with collaborators at London's Institute of Zoology, Phil published a paper showing that the abundance of small carnivores seemed to be less affected by food availability than that of large carnivores. Specifically, when looking across systems at the relationship between carnivore numbers and the biomass of their food, there was a strong effect of carnivore body mass on that relationship: for a given proportional change in food availability, the largest carnivores showed a change in abundance about 5 times larger than the change experienced by the smallest carnivores. Intriguingly, the slope of those relationships seemed very strongly determined by the predators' body masses (see Figure 1).

This finding vexed us because, although we could think of a variety of possible explanations, we couldn't find empirical or theoretical support for any of them. A new paper by Rory Wilson and colleagues presents a possible explanation. Specifically, for a variety of animals with different diets, they present empirical data on the time taken to find and ingest food items. Perhaps unsurprisingly, they find that foragers focusing on low value but highly abundant food (such as grazers eating grass), the time taken to find and ingest food is low and, as a result, the variation in that time between different individuals is also low. By contrast, when foragers focus on high value but low availability foods (like large carnivores preying on large herbivores), the time taken to find and ingest food can be very high; moreover, the variance in time taken by different individuals - simply as a consequence of luck in finding food - can be huge. As Wilson & co. show, this can have very important implications for population dynamics. This is because, as long as food is suitably abundant, low value / high availability foragers will all acquire enough energy to survive and reproduce (and there will be limited variation between individuals in their capacity to do so). However, for high value / low availability foragers, there will be high variation between individuals; simply by chance, many individuals may fail to acquire sufficient energy to survive and reproduce.

In an overview of the importance of Wilson et al.'s new paper, now published in the journal Current Biology, Phil argues that it could influence our thinking about a wide variety of phenomena in ecology and behaviour. These range from the role of diet and luck in determining the evolution of lactation and capital breeding, to food-sharing and alloparenting (with profound implications for the origins of sociality). Importantly, as a result of the link between diet and body size, the modulating effect of body size on luck and population dynamics might thus be expected to explain the strong influence of carnivore body size on the strength of the relationship between food availability and carnivore abundance (see Figure 2).

With further information on the search times of a wider range of species, it might become possible to establish the body-mass scaling of these phenomena. Integrating them with other allometric relations, such as time to starvation, will enable broader, macroecological predictions regarding their implications. It might also be possible to identify sources of autocorrelation in the measured search times of specific individuals, and to identify how much of inter-individual variation is due to luck and how much is due to variation in competence. There is a need to consider the role of handling time which, itself, will induce negative correlations between luck and time available for foraging. These considerations all highlight that further consideration of the inter-related roles of diet and luck could be an active and productive field, which could yield important further insights for a range of disciplines within population and evolutionary ecology.

​To protect biodiversity effectively, we need to identify where to focus conservation actions and what those actions should be. This requires an understanding of the distribution and drivers of threatened species richness. We have a fairly good idea of where threatened species currently occur, but we don’t necessarily know why some areas are home to larger numbers of threatened species than others.  Are these areas subject to the pressures of extensive human activities? Or, conversely, might they be providing refuges for species away from human activities? Are the species present in an area more prone to extinction than species elsewhere? Or is it purely a question of numbers; do areas with large numbers of threatened species simply have more species overall?
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Our new paper in Conservation Letter addresses these questions, identifying the features of an area that influence how many threatened species occur there.  To do this, we collaborated with Curt Flather from the USDA Forest service to examine the distribution of threatened birds and mammals across the contiguous United States (Fig.1). We found that environmental factors, such as temperature and precipitation, are of far greater importance in determining threatened species richness than either the effects of human activities or the biological characteristics of the species present (e.g. their body mass, life span etc.).

​Significantly, we found that the effects of a number of variables on the richness of threatened species differed substantially from their effects on species richness as a whole (Fig. 2). For example, we found that whilst the number of threatened birds and mammals increases with the amount of land dedicated to anthropogenic activities (i.e. agriculture, urban development), the total number of species decreases. 

By identifying the factors that drive the distribution of threatened species, we are better able to establish the costs and benefits of different conservation actions. So for example, we now have a better understanding of where new protected areas should be established in order to maximise their benefits for nature conservation. Our findings can also yield recommendations for the management of existing protected lands. In particular, some protected areas in the US operate under multiple-use mandates, allowing for timber harvesting, livestock grazing and mining. We can use our results to identify how much of an area needs to be dedicated to the protection of at-risk species, and how much could contribute to the provisioning of ecosystem services.

​Finally, and importantly, the results of our study can be used to help the USDA forest service with their scenario planning. By pairing these results with information on possible environmental change, we can now identify where threatened species may occur in future. This information can then feed into conservation planning to ensure that planned interventions are future-proof, maximising the benefits for nature conservation.