Cetacean Surveys of the Southern Mariana Islands: Updates from the satellite-tagged short-finned pilot whales and false killer whales (May 29-June 09, 2014)

by Marie Hill, Andrea Bendlin, Allan Ligon, and Adam Ü

Short-finned pilot whales

As of 9 June (local time), all four satellite tags deployed on short-finned pilot whales (Globicephala macrorhynchus) encountered off Guam (19 and 25 May) were still transmitting.  Figure 1 shows the tracks from two of the pilot whales (tag ID#s 128920 and 128914). These two individuals were encountered on different days in separate groups.

Figure 1: Satellite tag locations of two adult male short-finned pilot whales (tag ID#s 128920-pink squares and 128914-white triangles) tagged off of Guam on 19 and 25 May 2014.

Figure 1: Satellite tag locations of two adult male short-finned pilot whales (tag ID#s 128920-pink squares and 128914-white triangles) tagged off of Guam on 19 and 25 May 2014.

The satellite tag with ID# 128920 was deployed on an adult male pilot whale on 19 May (Figure 2).  He was with a group of individuals that had been previously photographed off Guam in 2011, although this was our first encounter with him.  A second satellite tag (ID# 128889) was deployed on another adult male pilot during the 19 May encounter.  These two individuals have been traveling together since then.  On 29 May they were 32km north of Ritidian Pt., Guam.  Over the following 5 days they moved steadily southward along the west side of Guam.  During 4-6 June they spent time at Galvez Banks, southwest of Guam, and then proceeded further south to Santa Rosa Reef where the most recent satellite tag messages were transmitted during 7-9 June.

Figure 2: Adult male short-finned pilot whale with satellite tag #128920 off Orote Pt., Guam on 19 May 2014 (photo credit: Adam Ü).

Figure 2: Adult male short-finned pilot whale with satellite tag #128920 off Orote Pt., Guam on 19 May 2014 (photo credit: Adam Ü).

On 25 May, while our first two tagged short-finned pilot whales were north of Guam near Rota, we encountered another group of short-finned pilot whales just outside of Agat Bay, Guam.  During this encounter we deployed two more satellite tags.  One (tag ID# 128914) was deployed on an adult male (pictured in Figure 3 of our previous blog post; see the following link: https://pifscblog.wordpress.com/2014/06/03/cetacean-surveys-of-the-southern-mariana-islands-guam-may-15-27-2014).  This individual was photographed in July 2013 off Orote Pt., Guam.  Since tag deployment, he has continued to travel with the second individual tagged on 25 May (tag ID# 128910), which was a male or female sub-adult who had also been photographed in 2013. On 29 May these two individuals were also north of Ritidian Pt., Guam.  They met up with the first two tagged indivduals and all four individuals remained together during 30-31 May (Figure 1).  During 1-3 June, the whales with tag ID#s 128910 and 128914 first traveled north toward Rota before turning south again and traveling along the east side of Guam.  All four satellite-tagged whales met up again on 4-6 June at Galvez Banks and moved south to Santa Rosa Reef.  The satellite tag ID# 128889 not only records the location of the individual but also collects data on the depth to which the animal dives, which will provide us with more information on its behavior over time.

False killer whales

On 21 May, we encountered false killer whales (Pseudorca crassidens) off the northwest side of Guam.  We deployed two satellite tags (ID#s 128887 and 128902). Both were deployed on adults of unknown sex.  We collected biopsy samples from both so we will be able to determine sex when the samples are processed.   The tag (ID# 128887) that was deployed on the first individual (pictured in Figure 3) collects both location and dive depth data like the short-finned pilot whale tag ID# 128889.

Figure 3: Adult false killer whale off Guam photographed prior to deployment of satellite tag ID# 128887 (photo credit: Adam Ü).

Figure 3: Adult false killer whale off Guam photographed prior to deployment of satellite tag ID# 128887 (photo credit: Adam Ü).

Since being tagged, these two individuals have continued to travel together.  The satellite track of tag ID# 128887 is pictured in Figure 4.  Except for a circumnavigation of Rota, they have remained off the west side of the islands.

Figure 4: Locations of satellite tag ID# 128887 deployed on an adult false killer whale on 21 May 2014.

Figure 4: Locations of satellite tag ID# 128887 deployed on an adult false killer whale on 21 May 2014.

All survey operations including satellite tagging, photo-id, and biopsy sampling were conducted under NMFS permit 15240 and CNMI Fish and Game License 14-02868.  Funding was provided by the NOAA Fisheries and the U.S. Pacific Fleet. The satellite tag tracks shown are based on raw transmission data and have not been quality checked.  The final products may vary from those shown in the figures above.

 

 

 

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