New classes of conditionally integrable systems of nonlinear reaction–diffusion equations are introduced. They are obtained by extending a well-known nonclassical symmetry of a scalar partial differential equation to a vector equation. New exact solutions of nonlinear predator–prey systems with cross-diffusion are constructed. Infinite dimensional classes of exact solutions are made available for such nonlinear systems. Some of these solutions decay towards extinction and some oscillate or spiral around an interior fixed point. It is shown that the conditionally integrable systems are closely related to the standard diffusive Lotka–Volterra system, but they have additional features.

Despite increasing support for conservation efforts, humans exert strong negative forces on nature and disagree over the management of these effects. Conflicts over conservation policy may reflect evolving opinions about how people ought to conserve species and whether to intervene in various processes. To understand public preferences for conservation in the USA, we measured support for various strategies in five case studies, where we pitted one species against another in simplified but realistic scenarios. Among our online convenience sample of 1040 participants, we found the majority of participants favoured habitat protection in all but one case, and there was little acceptance of lethal control across all cases. The results reveal that habitat protection preferences positively relate to considerations of moral principles and ecosystems and negatively relate to economic and practical considerations. Older, conservative and male participants were less likely to support habitat protection and more likely to support no action. The results suggest broad support for holistic nature conservation that benefits both people and nature and highlight areas where current wildlife management may not align with public preferences. Controversy may continue until wildlife management policies are consistent with societal values and address moral and ecosystem considerations at multiple levels.

In this paper we derive sufficient conditions for the permanence and ergodicity of a stochastic predator–prey model with a Beddington–DeAngelis functional response. The conditions obtained are in fact very close to the necessary conditions. Both nondegenerate and degenerate diffusions are considered. One of the distinctive features of our results is that they enable the characterization of the support of a unique invariant probability measure. It proves the convergence in total variation norm of the transition probability to the invariant measure. Comparisons to the existing literature and matters related to other stochastic predator–prey models are also given.

Specialization is an important attribute of a biological control agent. The maritime pine bast scale, Matsucoccus feytaudi Ducasse (Hemiptera Matsucoccidae), is an invasive species in Southeast France and the North of Italy. Iberorhyzobius rondensis Eizaguirre (Coleoptera: Coccinellidae), is a recently described ladybird species. Both adults and larvae are predaceous, feeding on egg masses of M. feytaudi, and are strongly attracted to M. feytaudi’s sex pheromone. To evaluate the potential of I. rondensis as a biocontrol agent of the scale, we studied its niche breadth and prey range with emphasis on pine forests and hemipterans as tested prey. In this study, I. rondensis was found to achieve complete development only when fed on M. feytaudi egg masses (92.9% survival) and an artificial prey: eggs of Ephestia kuehniella Zeller (27.6% survival). From the 2nd instar onwards, complete development could be achieved using other prey species, although larvae had significantly higher mortality and slower development. In choice tests, M. feytaudi was the preferred prey. Surveys of the ladybird populations in the Iberian Peninsula revealed that it was found exclusively on Pinus pinaster Aiton, the sole host of M. feytaudi. The unusual specialization of I. rondensis, among other predaceous ladybirds, makes it an appropriate candidate for classical biological control of M. feytaudi.

Studies in the Pacific have identified distinct killer whale ecotypes that are either specialized mammal- or fish-eaters. The different types have developed hunting strategies that would suggest specialization could be more advantageous than generalism. However, it has been suggested, based on long-term dietary markers of tooth wear and stable isotope values, that lineages in the North Atlantic are generalist, but with individual variation in the proportion of prey types consumed. Here, we present the results of ten years of observational and photo-identification data of a population of killer whales that follows the Norwegian spring-spawning stock of Atlantic herring. Although the whales were predominantly observed while feeding upon herring, one pod of herring-eating whales was also observed interacting with seals. This supports the hypothesis based on the long-term markers, of a degree of specialization, with a small number of groups persistently feeding upon mammals, but switching between herring and seals. We further investigated this prey switching by conducting playbacks of herring-eating killer whale sounds to harbour seals at haul-out sites on the herring spawning grounds. We recorded changes in behaviour consistent with an anti-predator response, suggesting the seals perceived the herring-eating killer whales as a potential predatory threat and had not habituated to their calls. This could be due to the risk of herring-eating killer whales switching to mammalian prey, or the difficulty of discriminating between killer whale pods due to the large population size and number of killer whale call dialects in this population, or a combination of both.

Parasites typically have low reproductive fitness on paratenic hosts. Such hosts offer other significant inclusive fitness benefits to parasites, however, such as increased mobility and migration potential. The parasite fauna of the guppy (Poecilia reticulata) is dominated by the directly transmitted ectoparasites Gyrodactylus bullatarudis and Gyrodactylus turnbulli. In the wild, close predatory and competitive interactions occur between the guppy and the killifish Rivulus hartii. Previous observations suggest that these fish can share gyrodactylids, so we tested experimentally whether these parasites can use R. hartii as an alternative host. In aquaria, G. bullatarudis was the only species able to transmit from prey to predator. Both parasite species transferred equally well to prey when the predator was experimentally infected. However, in semi-natural conditions, G. bullatarudis transmitted more successfully to the prey fish. Importantly, G. bullatarudis also survived significantly longer on R. hartii out of water. As R. hartii can migrate overland between isolated guppy populations, G. bullatarudis may have an enhanced ability to disperse and colonize new host populations, consistent with its wider distribution in the wild. To our knowledge, this is the first empirical study demonstrating a predator acting as a paratenic host for the parasites of its prey.

Habitat modelling requires incorporation of both biotic and abiotic information. For juvenile flatfish the factors that most influence growth are water temperature, food abundance and predatory pressure. This study focuses on the impact the predator, the shore crab, Carcinus maenas, has on the foraging activity of sole, Solea senegalensis. The results show that in the presence of both prey (ragworm, Nereis diversicolor) and predator, ≃10% decrease in foraging activity is observed when compared to the sole in the presence of only food. This suggests that when the shore crab is present, Senegalese soles are not only affected by direct predation but sub-optimal foraging is also found. Behaviours most correlated with foraging were crawling and tapping and these activities were also affected by the presence of the predator. This study also provides further support for visual recognition of predators and olfactory prey recognition in the Senegalese sole. Predator–prey encounters shape species behaviours profoundly and have to be looked at from different levels of ecology, behaviour and modelling.

Little information is available regarding predator-prey interactions in High-Antarctic coastal systems. In this study, the predation of Trematomus bernacchii (Pisces: Nototheniidae) on Adamussium colbecki (Mollusca: Pectinidae) is described and the related impact on the population structure of the mollusc is hypothesized. Fishes and scallops were collected during several expeditions between 1990/91 and 1997/98 summers, in nearshore waters at Terra Nova Bay (Antarctica). Adamussium colbecki was the main food item of T. bernacchii and an ontogenetic prey-size selection was observed. The predation was mainly on medium size classes of the scallop. These were lacking in the A. colbecki population sampled in the same period suggesting that the impact of fish-feeding on the size structure of the natural population of the mollusc may be substantial. Two size classes of the Adamussium population were not preyed on. Large adults avoid predation either because of the limits for mouth gape in the fish or by swimming avoidance capability, while smaller scallops may not be preyed upon because they are attached through byssus threads to very mobile large adults.

The diet of 789 stoats Mustela erminea and 458 weasels M. nivalis collected in Great Britain between 1995 and 1997 is described from analyses of their gut contents. As a percentage frequency of occurrence, stoat diet consisted of 65% lagomorphs, 16% small rodents and 17% birds and birds' eggs. Weasel diet consisted of 25% lagomorphs, 68% small rodents, mainly Microtus agrestis, and 5% birds and birds' eggs. Male stoats ate a greater proportion of lagomorphs than females, which ate more small rodents. No differences in diet between the sexes of the weasels were detected. The proportion of lagomorphs in the diet of both species was greatest in the spring. Both species ate more lagomorphs in the 1990s than in the 1960s as a result of increasing rabbit populations following recovery from myxomatosis. The importance of small rodents had decreased for stoats and increased for weasels. Both species had a dietary niche that was more specialized than in the 1960s. The implications of these findings for stoat and weasel conservation are discussed.