Harbor seals (Phoca vitulina) can be an elusive species, especially concerning the weaning process (going from milk to prey) in pups. Using stomach temperature telemetry (sensor that can detect changes in stomach temperature), researchers could detect patterns of food ingestion in pups. The results showed that 63.7% of milk ingestions occurred while the pups were in the water and these ingestions were mixed in with solid food ingestion. This indicates that unlike other phocid species, harbor seals may have a more gradual weaning process where pups are learning to forage on their own while also gaining nutrition from their mom.

[Photo by Nick Chudeau and caption by Karli Chudeau]

Sauve, C. C., Walle, J. Van De, Hammill, M. O., Arnould, J. P. Y., & Beauplet, G. (2014). Stomach Temperature Records Reveal Nursing Behaviour and Transition to Solid Food Consumption in an Unweaned Mammal , the Harbour Seal Pup ( Phoca vitulina ). PLOS One, 9(2). https://doi.org/10.1371/journal.pone.0090329