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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