Can stomach temperature telemetry be used to quantify prey consumption by seals? A re-examination

To further determine the efficacy of stomach temperature probes in quantifying harp seal (Phoca groenlandica) feeding behaviour, captive seals were fed stomach temperature sensors and given pre-weighed meals of herring (Clupea harengus) and crushed ice. Ingestion of either substance caused a decrease in stomach temperature. Results suggested that the magnitude of the stomach temperature change could indicate whether an ingested substance was a prey item or ice. The duration of stomach temperature change was significantly related to the quantity of fish consumed, but it accounted for just 27% of the overall variation. This percentage was considerably less than previously reported, perhaps due to the more extensive sampling regime of this study. Both the magnitude and duration of temperature change were related to the quantity of ice consumed, accounting for 69% of the mass variation. However, subsequent modelling revealed that the relationship was not robust. Despite problems with quantification, combining the use of stomach temperature telemetry with time-depth and satellite recordings could provide valuable information on the location, timing and frequency of prey consumption by seals. Results indicate that, with sufficient samples, this technique may provide a valuable tool for investigating the feeding ecology of seals and other marine endotherms.