Diurnal Acoustic Activity of Southern Resident Killer Whales

in the Salish Sea

Looking for daily patterns in vocal activity

Laura ChristofersonEnergy Labs, Inc.

Billings, MTPhoto by Laura Christoferson

IntroductionMotivation for night/day study• Potential listing as threatened species = need to

understand habitat usage• Boat noise difference between day and night and

potential effects on behavior, specifically foraging• Relatively new study focus

Questions • How active are the Southern Residents at night? • Is there a pattern in how often acoustic behavior is

detected throughout a 24-hour period? • Can association with

acoustic activity reliably describe physical activity?

Photo by Laura Christoferson

How do I study this? • My original plan:

follow the same pod/subgroup continuously for 72 hours while recording underwater sounds and surface behaviors

• What we actually did

– Attempted three night follows, extending our recording and observation time into the evening hours

– Left anchorage at first light or before to extend our recording and observation time into the morning hours

• What held us back

– Maintaining contact at night was difficult, especially in windy conditions

– We depended heavily on the pager network to locate the whales and are grateful to Orca Spirit for lending us a pager

Recording Methods• Hydrophones

– Single stationary hydrophone– “ears” stationary localizing two-hydrophone array

Potentially a valuable tool for night study when real-time localization becomes possible

– “toad” towed single hydrophone• Flow noise • Boat noise• Whale-sail event

• Recording– Marantz recorder created continuous time stamped one

minute files– Collected nearly 300 minutes of sound files in one 12-hour

period

Observing Orcas

• What I looked for– Originally planned to use a numeric system to

describe surface activity• Synchronous breathing• Spread of individuals• Directional / nondirectional movement• Percussive Behaviors

• What I saw– Most often there were 20-30 whales present, with

many small groups doing different activities– Difficult to use value system– Could identify overall group activity as one of the

following: Traveling, milling, resting

Analyzing the sound files

• Audacity Sound editing program• Finding the percent of time spent vocal

– Within a minute file– Within an observation

• Too many files to process them all– Chose one hour observation that was interesting and

processed every file– Used that observation to develop a method for

sampling files by processing every fifth file within an observation

Results

• Overall, we made recordings 8:30 am to 1:00 am.• Recordings with vocals, 9:30 am to 10pm• Followed for thirteen hours consecutively• Recorded members of L pod in each of twelve

continuous hours on October 21.• Examined every minute for approximately one hour (48

minutes) during high level of vocal and physical activity• Noticed distinct difference in acoustic levels during

traveling and resting behaviors• Compared the same hour on each of three evenings

Daily Patterndiurnal pattern of vocal activity

0

5

10

15

20

25

30

9 10 12 13 14 15 16 17 18 19 20 21

hour of day

average percent vocal

Standard Deviation = 7.4Mean Value = 11.9

Comparing three nights/behaviors

Six o'clock on October 11, 21, 22

02468

10121416

11-Oct 21-Oct 22-Oct

Surface Active SlowTravel/Foraging

Resting

date and behavior

% time vocally active

Mean Value = 5.8 - Standard Deviation = 7.0

Vocal Activity over one HourVocal Activity: 1 min samples, 12:00 to 1:00 p.m. on 10/21/05

0

10

20

30

40

50

60

70

80

90

100

12:2412:2712:3012:3312:3612:3912:4212:4512:4812:5112:5412:5713:0013:0313:0613:09

Time of day

% time vocal

Mean Value = 23.0Standard Deviation = 24.4

Conclusions

• Resting = quiet– Two hours with J pod close by, no sound– Confirmed expected

• Traveling = lots of vocals– High physical activity (speed >5 knots, many

breaches and tail slaps)

• Suggests that acoustic activity level is related to physical activity state

Here Comes the Sun…• What were the benefits and drawbacks of

night observation?– Difficulty maintaining contact– Weather and whale constraints– Wear and tear on crew

• Future Studies– More detailed study of acoustic and physical

activity relationship during the day– Daily patterns in behavior and range– Utilize real-time acoustic bearings and night

vision technology to track orca movement and enhance following ability in the dark

AcknowledgementsThanks to the many people who added their time and

knowledge to developing this project, especially:– Ken Balcomb and Dave Bain for their interest,

encouragement and input– Bob McLaughlin and BE Meyers company for

providing night vision technology and guidance (wish we’d had whales!)

– The staff of Friday Harbor Labs for making us feel at home when we were a long way from it

– Scott and Val Veirs and their family for their vision in creating this program and their enthusiasm, patience, and inspiration both academically and personally throughout this incredible experience

– My little pirate family: Celia, Brett, Freddie, Courtney, and Nicole for making this a fun and exciting adventure. Arr!

– Captain Todd for introducing me to the joy of sailing and life on a boat. I won't forget it.

– My family, friends, and coworkers at home for their encouragement and support

– Most of all, to my husband Pat for making a huge personal sacrifice to allow me to follow my dreams.