USE OF TEMPERATURE TELEMETRY TO MONITOR INGESTION BY A HARBOR SEAL MOTHER AND HER PUP THROUGHOUT LACTATION

The applicability of using stomach temperature telemetry to detect and estimate milk intake throughout lactation was investigated in harbour seals (Phoca vitulina). Observations of a mother-pup pair were conduc ted daily while stomach temperature was concurrently logged. Milk inta ke caused a decrease in the pup's stomach temperature. The duration of stomach temperature change was related to the length of the nursing b out (r(2) = 0.82, P < 0.001). Laboratory stomach simulations suggested a strong relationship between milk volume and duration of temperature change r(2) = 0.98, P < 0.001). This relationship was used to estimat e the volume of milk consumed by the pup. Suckling bout length and the estimated milk intake per bout increased, as a weekly average, with p up age (one-way ANOVA; F-3.67 = 11.66, P < 0.001) over the 5-week lact ation period. A diel change in nursing time was noted, with a transiti on from largely nocturnal to daytime feedings. Although not visually c onfirmed, stomach temperature data collected from the mother provided evidence of seawater ingestion. Methods that could improve estimates o f milk intake are discussed. Stomach temperature telemetry proved to b e a useful technique for detecting ingestion events in harbour seals, and may provide a valuable tool for investigating lactation energetics and aspects of maternal investment in a variety of nursing species.