Does an Increase of Boats Cause Decreased Vocalization Rates in Killer

Whales (Orcinus orca)?

Matthew J. WilliamsBeam Reach Marine Science and Sustainability

SchoolJune 4, 2009

Bioenergetics

• Every action requires energy

• Energy is a limiting factor

• Do orcas limit vocalizations if they are unlikely to be heard?

Methods• Recorded:

– Vocalizations

– Behavioral state

– Number of boats within 1000 m

– Ambient noise levels

Key Questions

• Does an increase in boats correlate with an increase in ambient noise?

• Do call rates decline with an increase in ambient noise?

Does an increase in boats correlate with an increase in ambient noise?

Boat Noise in Relation to Ambient Noise Levels

y = 0.3201x + 124.7

R2 = 0.0447

0

20

40

60

80

100

120

140

160

0 2 4 6 8 10 12 14 16

Number of Boats

Am

bie

nt

No

ise

(dB

re

1 m

icro

Pa)

Linear (Boat Numbers in Relation toAmbient Noise)

P < .001

Sample Size: 1016

Do call rates decline with an increase in ambient noise?

Ambient Noise in Relation to Call Rates

y = -0.1464x + 19.686

R2 = 0.051

-5

0

5

10

15

20

25

30

100 105 110 115 120 125 130 135 140 145 150

Ambient Noise (dB re 1 micro Pa)

Cal

l Rat

e (C

alls

per

Min

)

Linear (Series1)

P < .001Sample Size: 1016

Call Rates

• Min: 0

• Max: 26

• Mean: 1.22

• Mode: 0

• Sample Size: 1016

• Very large proportion of data is 0 calls/min!

Supplementary Question

• Does the behavioral state influence the call rates?

• Important to limit a source of variance

Call Rates

Behavioral State

Min Max Mean Sample Size

Foraging 0 9 .53 134

Milling 0 1 .02 58

Playing 0 26 11.47 15

Resting 0 0 0 78

Traveling 0 18 1.37 731

Changes in Call Rates: ForagingForaging: Ambient Noise in Relation with Call Rate

y = -0.101x + 13.359

R2 = 0.0853

-2

0

2

4

6

8

10

115 120 125 130 135 140 145

Ambient Noise (dB re 1 micro Pa)

Cal

l Rat

e (C

alls

per

Min

)

Ambient Noise Level in Relation to Call Rate

Linear (Ambient Noise Level in Relation to CallRate)

P < .001Sample Size: 134

Changes in Call Rates: Traveling

Traveling: Ambient Noise Levels in Relation to Call Rates

y = -0.1148x + 15.78

R2 = 0.0349

-5

0

5

10

15

20

100 105 110 115 120 125 130 135 140 145 150

Ambient Noise (dB re 1 micro Pa)

Cal

l Rat

e (C

alls

per

Min

)

Series1

Linear (Series1)

P < .001Sample Size: 731

Questions?

• Acknowledgements:– Jason Wood– Scott Veirs– Val Veirs– Todd Shuster– Mike Kramer– Classmates