Diving heart rate development in postnatal harbour seals, Phoca vitulina

Area of Science:

• Marine Mammal Physiology
• Behavioral Ecology
• Physiological Adaptations

Background:

• Harbour seals (Phoca vitulina) exhibit diving behaviors from birth.
• Understanding the development of the diving response is crucial for assessing physiological adaptations in marine mammals.
• Postpartum development of diving bradycardia in seals has not been extensively documented.

Purpose of the Study:

• To investigate the postpartum developmental changes in diving bradycardia in harbour seal pups.
• To map the maturation of the diving response in relation to age and dive characteristics.
• To determine if pups are born with the full diving bradycardia capacity.

Main Methods:

• Remote recording of dive depth and heart rate (HR) in harbour seal pups (n=20) over 60 days.
• Analysis of 86,931 recorded dives, with additional depth-only data for 20,300 dives.
• Observation period conducted in the St. Lawrence River Estuary during May-July 2000 and 2001.

Main Results:

• Mean dive depth and duration were conservative during the nursing period (2.1 m and 0.57 min).
• Neonatal pups displayed a bimodal heart rate during dives, with one rate disappearing by 15 days of age.
• By 15 days, most dive time was spent at the lower, more developed bradycardia rate.
• Pups demonstrated the ability to maintain lower bradycardia during focused dives but not shorter, routine dives.

Conclusions:

• Harbour seal pups are born with the capacity for diving bradycardia.
• The diving bradycardia response matures significantly within the first 15 days postpartum.
• Dive behavior and physiological responses adapt as pups age and develop their diving skills.