This study reports the first quantitative data on nursing behaviour of hooded seals which have a four-day nursing period, the shortest known for any mammal. Twenty mother pup-pairs were observed at a whelping patch off the coast of Newfoundland, Canada during March, 1990. A total of 38 nursing sessions were recorded in 19 hours of observations. Pups nursed for an average duration of 5.5 min and at a frequency of approximately 2.4 bouts/ hour. Morning and afternoon rates were similar (x = 2.5 bouts/hr and x = 2.4 bouts/hr, respectively) and nocturnal nursing was witnessed. Pups were nursing for 18% of the total observation time which, assuming no diurnal pattern, would total 4.3 hr per day, the highest daily nursing duration reported for any phocid. We concluded that hooded seal nursing behaviour is another important factor in the unique lactation strategy attributed to a particularly unstable environment. It helps to ensure that pups attain sufficient weaning mass, double their birth weights, in the four-day nursing period.