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2014-01-01T00:00:00 |
Satellite transmitters were attached to the body of gray whales using a pneumatic
delivery system. Whales were tagged with the implantable configuration of the SPOT
5 and MK10A transmitters produced by Wildlife Computers (Redmond, WA). Transmitters
were duty-cycled to optimize data collection in the feeding grounds and for maximizing
tag longevity. Location-only tags (SPOT5) were programmed to transmit every day for
6 hours during daytime and 6 hours during night time. One archival tag (Mk10A) was
programmed to sample and transmitter between 1 and 22hs every day from 1 September
to 1 November and every second day afterwards. Histogram data sampling was enabled
to sample maximum dive depth and time at depth in 14 bins (10, 20, 30, 40, 50, 75,
100, 125, 150, 200, 250, 300, 350 and >350m), and dive duration in 9 bins (2, 3, 5,
10, 15, 20, 25, 30 and >35 minutes). Time series messages were enabled with sampling
intervals of 75 seconds every day for the first 30 days and every second day afterwards).
Satellite tags were monitored by Argos Data Collection and Location Service receivers
on NOAA TIROS-N weather satellites in sun-synchronous polar orbits. Locations were
calculated by Argos from Doppler-shift data when multiple messages were received during
a satellites passage overhead. Argos codes locations in quality classes (LQ) labeled
B, A, 0, 1, 2, 3, in order of increasing accuracy. Argos locations were processed
using the software R. The SDA Argos filter (Freitas et al., 2008) was applied to all
location qualities in software R in order to remove locations that implied unlikely
deviations from the tracks path as well as unrealistic travel rates. This filter requires
two main parameters: turning angles and maximum speed of travel. The default value
of turning angles (Freitas et al., 2008) was used and the maximum speed was assumed
to be 18km/h. Distances between filtered locations were calculated assuming a great
circle route.
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