Predator prey interactions are a key part of ecosystem function, and non-consumptive effects fall under the landscape of fear theory. Under the landscape of fear, the antipredator responses of prey are based on the spatial and temporal distribution of predatory cues in the environment. However, the aversive stimuli (fear) are not the only stimuli prey can utilize when making behavioral decisions. Prey might also be using attractive stimuli that represent safety to guide decision making. Using a novel, orthogonal design, we were able to spatially separate aversive and attractive stimuli to determine if prey are utilizing safety cues to navigate their environment. Crayfish Faxonius rusticus were placed in the center of a behavioral arena. Aversive stimuli of either predatory bass Micropterus salmoides cues or conspecific alarm cues increased along the x-axis of the behavioral arena. Safety cues (shelters) increased along the y-axis by decreasing the number of shelter openings in this direction. Crayfish were allowed two phases to explore the arena: one without the fearful stimuli and one with the stimuli. Linear mixed models were conducted to determine if movement behaviors and habitat utilization were affected by the phase of the trial and the type of aversive stimuli. Crayfish responded more strongly to alarm cues than fear cues, with only alarm cues significantly impacting habitat utilization. When responding to alarm cues, crayfish used safety cues as well as fear cues to relocate themselves within the arena. Based on these results, we argue that crayfish are utilizing a landscape of safety in conjunction with a landscape of fear when navigating their environment.

The expression of an individual animal’s behaviour can be placed along many different personality spectra. Parasite load can alter animal behaviour and, thus, fitness. The personality traits of rusty crayfish, Faxonius rusticus, were analysed in three different behavioural contexts: foraging, exploration, and threatened. Each crayfish was tested in each context 3 times, giving a total of 9 assays per crayfish. After assays were completed, crayfish were dissected, and the hepatopancreas of each crayfish was photo analysed to determine the parasite load of the trematode, Microphallus spp. A composite personality score for each assay and parasite load was loaded into a PCA. The PCA model showed that as parasite load increased, crayfish became bolder in threatening contexts and less exploratory in novel environments, whether or not a food stimulus was present. Thus, parasite load alters the placement of crayfish on different personality spectra, but this change is context specific.

Parasites can alter a wide range of host behaviors resulting in changes in organismal interactions and ecosystem processes. One of the most important behaviors that controls food web dynamics is herbivore grazing because an alteration in grazing behavior leads to changes in trophic dynamics and ecosystem processes by changing the abundance and diversity of primary producers. To test whether parasite load can alter host grazing levels and choices, feeding trials were conducted using the keystone species, the rusty crayfish Faxonius rusticus (Girard, 1852), grazing on a selection of macrophyte species. The rusty crayfish is a keystone species because its grazing significantly alters the abundance of macrophytes in freshwater ecosystems. We used a total of 165 wild-caught, naturally-infected crayfish individuals with a wide range of parasite loads by species of the digenetic trematode Microphallus Ward, 1901. Crayfish were presented with 1 g each of the macrophytes Elodea canadensis (Michaux), Ceratophyllum demersum (L), Chara sp., and Potamogeton richardsonii (A. Benn.) in a 23-hr foraging assay. Subsequently, crayfish were dissected, and parasite loads were calculated. Mixed models were then utilized to determine how parasite load affected consumption. As infection of Microphallus increased in the crayfish hepatopancreas, consumption of all four macrophytes significantly decreased. Melanization of Microphallus spp. within the hepatopancreas, the immune response to. infection, did not significantly reduce crayfish macrophyte consumption. These results indicate that macrophyte consumption in the crayfish was affected by Microphallus. This impact on crayfish grazing could alter macrophyte abundances in aquatic ecosystems. Because of the many ecosystem functions macrophytes play, an alteration in their abundances could lead to community-level ramifications by impacting nutrient flow and organismal abundances in aquatic ecosystems.