| Summary: | Three juvenile narwhals captured during August 1998 in the northeast of Svalbard, Norway, were equipped with satellite-relayed data loggers (SRDLs) that transmitted diving and swim-speed data, in addition to location, for up to 46 days. A total of 1,354 complete dive cycles were recorded. Location data was filtered to exclude unreliable position data due to satellite transmission errors or positions that would have involved impossibly fast swimming from a reliable position (using a maximum horizontal swimming speed between consecutive positions of 2 m/s). Dive data consisted of depth readings (+/- 1 m) recorded at intervals of 60 s that were transmitted in batches of 29–32 readings. Batches were later concatenated to provide longer time series of data where possible. Swim speed was measured with a turbine odometer that had a stall speed of 0.3 m per s. Swim-speed information for the first and last complete inter-depth readings in a dive were used to calculate vertical descent speed, descent angle, and vertical ascent speed and ascent angle respectively for all dives where these data were available.Most of the diving was shallow and of short duration. Maximum recorded dive depth was 546 m, maximum recorded dive duration was 24.8 min, and maximum recorded swim-speed was 4.7 ms-1. Ascent speed, vertical ascent speed, descent speed and vertical descent speed were all significantly higher during deep dives (>200 m) than for shallow dives (<200 m). In addition both ascent and descent angles were much steeper for deep dives than during shallow dives. Most of the shallow diving seemed to be associated with travelling, with the animal shifting between various locations, while the deep diving (often to the bottom) for extended periods in some specific areas might have been associated with foraging. Even though the sample size in this study is small, the data are the first information available for movements and diving behaviour of narwhals near Svalbard.
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