A study of the relationship between The Southern Resident Killer Whale echolocation click production

and depth: A Beam Reach first

Anne Harmann

27 October 2007

Beam Reach Marine Science and Sustainability Schoolbeamreach.org/071

Salmon!

Why Echolocation clicks?

The SRKW are listed as an endangered species.• prey availability• environmental contaminants• vessel effects• oil spills• disease•cumulative effects of multiple chronic stressors

I wanted to study fish.

We only had the equipment to study killer whales.

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Echolocation Click Production

Cranford et al. 1996

Melon

Blowhole

Phonic Lips

A beluga whale (Delphinapterus leucas)

Echolocation clicks are typically emitted at a rate that allows the echoes to return to the animal before next click is emitted.

Foraging

http://www.teara.govt.nz/EarthSeaAndSky/en

Foraging

http://www.cascadiaresearch.org

Foraging

www.wildriversoutfitters.com/ rivers.htm

My Research Chain of Logic

•The SRKW forage on fish.

•These fish swim at various depths in the water column.

•The SRKW use echolocation clicks to find these fish.

So…

Is there a relationship between the pattern of SRKW echolocation click production and depth?

Remember, this is a novel study.

It’s all very simple…

Data Collection

A

B

C

D

E

Hph 1 at 5 m

Hph 2 at 15 m

Hph 3 at 25 m

Hph 4 at 35 m

• Data collected October 7-13, 2007

• Positioned ahead of whales when possible

• Array deployed vertically

• Minor movements of Gato Verde to maintain vertical orientation

• Stopped recording if calls or clicks became difficult to hear above background noise

A. Starboard hull of GVB. OutriggerC. 2 m bungee cordD. Hydrophone arrayE. 12 lb weight attached to rope

Diagram not to scale

Data Analysis

Audacity (Version 1.2.5, Sourceforge.net)

Data Analysis: Time of Arrival Differences

Data Analysis: Time of Arrival Differences

Data Analysis: Time of Arrival Differences

Data Analysis: Time of Arrival Differences

Data Analysis: Time of Arrival Differences

Data Analysis: Time of Arrival Differences

Data Analysis: Time of Arrival Differences

Data Analysis: Time of Arrival Differences

Data Analysis: Time of Arrival Differences

Data Analysis: Time of Arrival Differences

Data Analysis: Time of Arrival Differences

Data Analysis: Time of Arrival Differences

Classification of Clicks

Shallow Middle Deep

77 15 73

n = 165

Foraging Model 1: Repeated Dives for Chinook

5 m

35 m

44.5 m

67.4%

11.2%

21.3%

Null hypothesis: Observed distribution of clicks will match distribution predicted by model.

•Dives made to 44.5 m, average daytime traveling depth for chinook salmon (Candy and Quinn 1999)

•Swimming at a constant speed

•Echolocating constantly

•Diving repeatedly, no lingering at surface or at depth

GroupObserved # of Clicks

Expected # of Clicks 2 p < d.f

Shallow 77 18.54 184.35 0.001 2

Middle 15 111.24 83.26 0.001 2

Deep 73 35.22 40.51 0.001 2Total 165 165

Observed distribution of clicks was significantly different from expected distribution (p < .001, d.f. 2)

Null hypothesis: rejected

Foraging Model 2: Repeated Deep Dives

35 m

5 m

Deep 62.5%

Shallow 14.6% Middle 22.9%

Null hypothesis: Observed distribution of clicks will match distribution predicted by model.

• Model based on dive profile from one dive made by L87 (Baird et al. 2003)

• Echolocating constantly

• Diving repeatedly

• No lingering at surface

GroupObserved # of Clicks

Expected # of Clicks 2 p < d.f.

Shallow 77 24.06 116.46 0.001 2

Middle 15 37.81 13.76 0.02 2

Deep 73 103.13 8.80 0.0025 2Total 165 165

Observed distribution of clicks was significantly different from expected distribution (p < .02, d.f. 2)

Null hypothesis: rejected

Click Trains and Clicking Rate

Click Train Length (sec) Clicking Rate (clicks/sec)Sample size (n) Mean

Standard Deviation

Sample size (n) Mean

Standard Deviation

Shallow 40 5.66 7.06 Shallow 40 8.8 7.41Deep 37 6.53 6.72 Deep 37 8.18 9.7t = -0.5508, p (2 tail) = 0.58, d.f. = 74.9 t = 0.3098, p (2 tail) = 0.76, d.f. = 67.2

No significant difference between deep and shallow groups for either click train length or clicking rate

Slow Fast

Clicks with Surface Reflections

Clicks with Surface Reflections

*

**

**

*

Clicks with Surface Reflections

DR

Summary

n= 165 shallow = 77 middle = 15 deep = 73

Do not fit simple dive profile models•Array geometry?•Directional characteristic of clicks?•Deep diving year?

Click train length and clicking rate: No significant difference between shallow and deep

•Foraging at surface for deeper fish?•Navigating around boats?

Acknowledgements

I would like to extend the warmest thank you to Val, Shannon, Todd, Jason, Scott, Team VATO, Team JAMI, Marla Holt, and the good folks at the Whale Museum. This has been an amazing experience. And a special thank you goes to Gilda and Vernon Harmann and to B.

Literature CitedAu, W.W.L. 2004. Echolocation signals of wild dolphins. Acoustical Physics, 50:454-462.

Au, W.W.L., Ford, J.K.B., Horne, J.K., Newman Allman, K.A. 2004. Echolocation signal of free-ranging killer whales (Orcinus orca) and modeling of foraging for Chinook salmon (Oncorhynchus tshawyscha). Journal of the Acoustical Society of America, 77:726-730.

Baird, R.W., Hanson, M.B., Dill, L.M. 2005. Factors influencing the diving behaviour of fish-eating killer whales: sex differences and diel and interannual variation in diving rates. Canadian Journal of Zoology, 83:257-267.

Barrett-Lennard, L.G., Ford, J.K.B., Heise, K.A. 1996. The mixed blessing of echolocation: differences in sonar use by fish-eating and mamma-eating killer whales. Animal Behavior, 51:553-565.

Candy, J.R. and Quinn, T.P. 1999. Behavior of adult chinook salmon (Oncorhynchus tshawytscha) in British Columbia coastal waters determined from ultrasonic telemetry. Canadian Journal of Zoology, 77(7):1161-1169.

Cranford, T.W., Amundin, M., Norris, K.S. 1996. Functional morphology and homology in the odontocete nasal complex: implications for sound generation. Journal of Morphology, 228:223-285.

Ford, J.K.B. and Ellis, G.M. 2006. Selective foraging by fish-eating killer whales Orcinus orca in British Columbia. Marine Ecology Progress Series, 316:185-199

Tieman, C.O., Thode, A.M., Straley, J., O’Connell, V., Folkert, K. 2006. Three-dimensional localization of sperm whales using a single hydrophone. Journal of the Acoustical Society of America, 120(4):2355-2365.

Questions?

Overlapping Click Trains