The bowhead whale is the only baleen whale endemic to the Arctic and is well adapted to this environment. Bowheads live near the polar ice edge for much of the year and although sea ice dynamics are not the only driver of their annual migratory movements, it likely plays a key role. Given the intrinsic variability of open water and ice, one might expect bowhead migratory plasticity to be high and linked to this proximate environmental factor. Here, through a network of underwater passive acoustic recorders, we document the first known occurrence of bowheads overwintering in what is normally their summer foraging grounds in the Amundsen Gulf and eastern Beaufort Sea. The underlying question is whether this is the leading edge of a phenological shift in a species’ migratory behaviour in an environment undergoing dramatic shifts due to climate change.   

File: Daily_Bowhead_Presence.csv

Methods:

Passive acoustic data were recorded at four sites in NWT, Canada: Ulukhaktok (70°42.857’N, 117°48.020’W), Cape Bathurst at 50 m depth (70°34.5469’N, 127°39.6319’W), Cape Bathurst at 300 m depth (70°40.8732’N, 126°52.2977’W), and near Pearce Point (70°12.055’N, 123°09.470’W). Data from Ulukhaktok were recorded using a Wildlife Acoustics SM3M acoustic recorder, and all other data were recorded using a SoundTrap ST500 acoustic recorder. All recorders were set to record 5 minutes of audio data every hour at a 48 kHz sampling rate, and data included in this study are from October 2018 to April 2019. The recorder at Ulukhatoky used a gain setting of +12 dB. Data were processed using an automated detector and classifier for bowhead whale vocalizations, and all detections in the autumn and winter were manually verified for the presence of bowhead whale vocalizations, as well as 10% of the data without any automated detections.

Metadata:

Date: The date in Mountain Standard Time.

Ulu_Pres: The presence of manually verified bowhead whale vocalizations within audio data from that day recorded at the Ulukhaktok site.

CB50_Pres: The presence of manually verified bowhead whale vocalizations within audio data from that day recorded at the Cape Bathurst 50 m site.

CB300_Pres: The presence of manually verified bowhead whale vocalizations within audio data from that day recorded at the Cape Bathurst 300 m site.

PP_Pres: The presence of manually verified bowhead whale vocalizations within audio data from that day recorded at the Pearce Point site.

NA value: no data available for that day.

 

File: Ulukhaktok_Ice_Comparison.csv

Methods:

Remotely-sensed daily sea ice concentration data in 6.25 × 6.25 km grid cells from the AMSR-2 satellite array (Spreen et al. 2008) were obtained from 2013-2019, and then the average value per day between 15 November and 15 April of each year within a 100 km radius of the Ulukhaktok acoustic recorder (70°42.857’N, 117°48.020’W) was calculated.

Metadata:

Month-Day: Month and day for observation

2013-2014: Average daily ice concentration in 2013-2014 within 100 km radius of the Ulukhaktok recorder site.

2014-2015: Average daily ice concentration in 2014-2015 within 100 km radius of the Ulukhaktok recorder site.

2015-2016: Average daily ice concentration in 2015-2016 within 100 km radius of the Ulukhaktok recorder site.

2016-2017: Average daily ice concentration in 2016-2017 within 100 km radius of the Ulukhaktok recorder site.

2017-2018: Average daily ice concentration in 2017-2018 within 100 km radius of the Ulukhaktok recorder site.

2018-2019: Average daily ice concentration in 2018-2019 within 100 km radius of the Ulukhaktok recorder site.

 

File: Cape_Bathurst_Ice_Comparison.csv

Methods:

Remotely-sensed daily sea ice concentration data in 6.25 × 6.25 km grid cells from the AMSR-2 satellite array (Spreen et al. 2008) were obtained from 2013-2019, and then the average value per day between 15 November and 15 April of each year within a 100 km radius of the Cape Bathurst 50 m acoustic recorder (70°34.5469’N, 127°39.6319’W) was calculated.

Metadata:

Month-Day: Month and day for observation

2013-2014: Average daily ice concentration in 2013-2014 within 100 km radius of the Cape Bathurst 50 m recorder site.

2014-2015: Average daily ice concentration in 2014-2015 within 100 km radius of the Cape Bathurst 50 m recorder site.

2015-2016: Average daily ice concentration in 2015-2016 within 100 km radius of the Cape Bathurst 50 m recorder site.

2016-2017: Average daily ice concentration in 2016-2017 within 100 km radius of the Cape Bathurst 50 m recorder site.

2017-2018: Average daily ice concentration in 2017-2018 within 100 km radius of the Cape Bathurst 50 m recorder site.

2018-2019: Average daily ice concentration in 2018-2019 within 100 km radius of the Cape Bathurst 50 m recorder site.

 

File: Pearce_Point_Ice_Comparison.csv

Methods:

Remotely-sensed daily sea ice concentration data in 6.25 × 6.25 km grid cells from the AMSR-2 satellite array (Spreen et al. 2008) were obtained from 2013-2019, and then the average value per day between 15 November and 15 April of each year within a 100 km radius of the Pearce Point acoustic recorder (70°12.055’N, 123°09.470’W) was calculated.

Metadata:

Month-Day: Month and day for observation

2013-2014: Average daily ice concentration in 2013-2014 within 100 km radius of the Pearce Point recorder site.

2014-2015: Average daily ice concentration in 2014-2015 within 100 km radius of the Pearce Point recorder site.

2015-2016: Average daily ice concentration in 2015-2016 within 100 km radius of the Pearce Point recorder site.

2016-2017: Average daily ice concentration in 2016-2017 within 100 km radius of the Pearce Point recorder site.

2017-2018: Average daily ice concentration in 2017-2018 within 100 km radius of the Pearce Point recorder site.

2018-2019: Average daily ice concentration in 2018-2019 within 100 km radius of the Pearce Point recorder site.