Killer Whales Do It In The Dark: Nocturnal Activity By Transients At St. Paul Island Kelly Newman Alan Springer University of Alaska Fairbanks School of Fisheries and Ocean Sciences Hello. I will be talking about the results of a pilot study we did last summer Acknowledge Alan Springer Photo: Bob Pittman

Why Study Killer Whales at St. Paul? Pinniped and sea otter collapses in Alaska Fur seals declining on Pribilofs Predation as a factor in population dynamics St. Paul is a predation hot-spot

Problem of documentation Expensive Time consuming Low probability of observing predation Poor field conditions

Solutions Work in predation hot-spots Use alternative techniques Acoustic monitoring 8x more effective than just visual for detecting marine mammals

FUR SEAL ROOKERIES From NMML website Pribs as a whole support the largest worldwide populations. Pribilofss have over fifty seven % of the worlds pop. Other studies being conducted concurrently show that the NFS at reef will forage to the west. From NMML website

Accepted Theory Transients use stealth to hunt–quieter before kills Transient killer whales are most vocal when feeding Calling behavior can indicate feeding activity

Recording Methods “Pop Up” Autonomous Recording Unit Continuous recording June 22-July 12, 2006 Frequency Range 0.5-16,000 Hz

Analysis Raven 1.3 Sound Analysis Software 512 point spectrograms were visually and aurally inspected for killer whale calls and whistles Sound files were fifteen minutes

Call Detection

Results Number of days recorded 22 Number of 24 days analyzed 20 Number of days killer whales detected 19 Number of hours analyzed 480 Number of 15 minute recording segments killer whales were detected 190 out of 1920 22 days recorded. Two of those were partial days. On Twenty days were the POP UP recorded for 24 hours.

Killer Whale Vocal Frequency Over 24 hours Number of days with calls Killer Whale Vocal Frequency Over 24 hours CT SR ST SS CT Here is a 24 hour break down of the calling activity. Here is Zero and here is 2400. Please note the abundance of calls from zero am throughout the night. Here we have the numThere is a lull mid day, then more activity around 1500. What is about Nocturnal in Alaska? in relation to civil twilight, mid to mid…sunset is at 2300. Note after sunset is when the calls are detected more. TAKE HOME see how much is going on in the middle of the night? Detections CT SR SS CT

More activity from midnight through morning Killer Whale Detections If you break up the day into t, you If three time frames, the number of detections are significantly different throughout the day. With more happening from midnight thru 800 am.The period of 0000 through 0745 0800 through 1545 1600 through 2345 Time of Day P value<.0001

Fur Seal Departure Times This graph demonstrates the movements of NFS throughout the 24 day. The Black bars are the number of seals departing rookeries at St Paul Island. The NFS are departing the rookeries more at sunset. The line indicates pooled sunset times over an entire breeding season, and the dashed lines are Sunset Sunrise From Jeremy Sterling

Known Only transients identified at St. Paul They have only been observed eating fur seals at the islands Considered a “problem” in the past Only transients are confirmed. Not only recent years.. there is some evidence that orcas were considered a nuisance I the past.

Unknown Abundance Persistence Group structure Predation rates So what we do not know is the population structure of killer whales at St Paul. Nor do we know the persistance of the various groups. This type of work can get at these questions because killer whale ecotypes can be identified by their vocalizations. From Heather Vukelic

Conclusions St Paul is frequented by killer whales on a daily basis Only transients have been identified Potential predation rates can be monitored at this hot-spot This is only one feeding area in the Pribilof Islands It is important to recognize that the use of acoustics was the only way t get at this comprehensive picture.

Implications The observation window for killer whale activity needs to be expanded to include nocturnal activity. Quantification of their ecological role is meaningless with limited observation power.

Phase II Identify call types Correlate with visual observations Acoustically “map” the Pribilof Islands for killer whale activity Killer whale groups can be identied by call type. The next step is to correlate with visual observations. There were some but is is noteworthty how much was going on without visuall observations.

Acknowledgements Alaska Sea Grant John Melovidov and Crew of the MarySea Greenpeace Jacob Merculief NPRB (COFFS) AK Sea Grant fo paying for this study. Several boats whoe helped us with deploying and retrieving the pop up, as well as for surveying the area.