Responses to intra and interspecific predation risks in Triops newberryi
Predation is a common interaction among members of ecological communities and it shapes both the population dynamics and many adaptations of both prey and predators. Not only does a predator lower the fecundity and survivorship of prey, predators can kill enough prey that they cause population cycles in the prey. For example, lynx have long been associated with population cycling in hares, which they prey upon (Korpimaki and Krebs 1996). Furthermore, under some conditions, individuals of a species may prey upon other individuals of the same species, called cannibalism. This is one type of a larger phenomenon, called intraguild predation, where individuals of the same trophic level feed on other individuals of the same trophic level, including their own species resulting in cannibalism. This phenomenon complicates our understanding of how predators interact with other members of the biological community. Because cannibalism can profoundly impact communities, there has been reconsideration of prey and predator interactions such as stability and diversity of communities, trophic cascades, niche shifts and species exclusion (Gagnon et. al 2011).
In order to measure the responses of Triops, we will be staggering generations to raise larger triops, while also have a younger generation of Triops available. To test responses to predation risk, we will expose young triops, in a controlled environment, to stimuli produced by intraspecific predators and interspecific predators, older Triops and birds, respectively. To test interspecific responses, we will expose adult Triops to bird silhouettes of species that are known to prey on larger triops at the water surface (as described in Davis and Madison 2000). We will create silhouettes of birds and display them above the Triops in their controlled environment as it has been observed that tadpole shrimp can have light-dark responses, especially adult tadpole shrimp (Davis and Madison 2001). Triops’ responses to predator cues will be digitally recorded and using animal behavior software (such as BORIS - Behavioral Observation Research Interactive Software), each Triops in the sample will be observed for their behavior and data analysis will be performed. We will be looking for behaviors such as digging, hunkering down or hiding, and other active trying to avoidance behaviors. Trials will be repeated through multiple generations to give insight on correlation between biological fitness via defense mechanism and life history.