DRILL or NO DRILL? How Stramonita haemastoma finds its ideal prey

Eastern oysters (Crassostrea virginica) are an economically and ecologically important species that is plagued by high mortality from predators at early life stages, particularly by the southern oyster drill (Stramonita haemastoma) in the Gulf of Mexico. Oysters can detect predator cues and respond by reallocating energy from growth to increasing shell strength, significantly increasing survivorship. While there is extensive research on how oysters respond to predators, relatively little is known on how drills select the ideal oyster for consumption. We investigated how drills locate oysters and discern prey profitability between oysters reared with predator cues (induced-stronger shells) and without cues (control-weaker shells) through a series of predator choice experiments and behavioral assays. We found that drills would perform a series of inspective behaviors to select prey, first with their siphon and then by physically manipulating the oysters with their foot for an extended period before attempting consumption. Although there was no difference in the number of control and induced oysters drills would choose to handle, drills successfully consumed control oysters twice as frequently as induced oysters. Furthermore, soft tissue mass per shell length did not differ between treatments, indicating that the larger control oysters offered more reward, making them a more profitable prey. Our results match expectations from optimal foraging theory and demonstrate that drills maintain a complex suite of behaviors to select prey. Additionally, these findings indicate that early predator exposure may be a viable strategy to reduce oyster mortality, potentially improving industry yield and restoration efforts.

Presentation Preference: Poster

Primary Presenter: Jonathan Mai, Gonzaga University (jmai@zagmail.gonzaga.edu)

Authors:

Jonathan Mai, Gonzaga University  (jmai@zagmail.gonzaga.edu)

Ben Belgrad, Dauphin Island Sea Lab  (babelgra@eckerd.edu)

Randi Cannon, Dauphin Island Sea Lab  (rcannon@disl.org)

Christa Russell, Dauphin Island Sea Lab  (crussell@disl.org)

Delbert Smee, Dauphin Island Sea Lab  (lsmee@disl.org)