Data from: Modelling durophagous predation and mortality rates from the fossil record of gastropods

Gastropods often show signs of unsuccessful attacks by durophagous predators in the form of healed scars in their shells. As such, fossil gastropods can be taken as providing a record of predation through geological time. However, interpreting the number of such scars has proved to be problematic - would a low number of scars mean a low rate of attack, or a high rate of success, for example? Here we develop a model of population dynamics amongst individuals exposed to predation, including both lethal and non-lethal attacks. Using this model we calculate the equilibrium distributions of ages and healed scars in the population and amongst fossilised specimens, based on the assumption that predation is independent of age or scar number. Based on these results we formally show that the rates of attack and success cannot be disambiguated without further information about population structure. Nevertheless, by making the assumptions that the non-durophagous predatory death rate is both constant and low, we show that it is possible to use relatively small assemblages of gastropods to produce accurate estimates of both attack and success rates, if the overall death rate can be estimated. We consider likely violations of the assumptions in our model and what sort of information would be required to solve this problem in these more general cases. However, it is not easy to extract the relevant information easily from the fossil record: a variety of important biases are likely to intervene to obscure the data that gastropod assemblages may yield