Acoustic Signals in Mammals

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AMSA Navigational Services in Australian Waters 2010-2025 .... http://www.ctgclean.com/tech-blog/2011/10/ultrasonics-sound-wave-length-vs-frequency/ ...
Why does a dolphin whistle and a dog bark? Drivers behind the evolution of acoustic behaviour in mammals. Kobé Martin, Marlee Tucker, Tracey Rogers

Conservation • Increased levels of anthropogenic noise. • Shipping lanes in Australia means additional levels of water traffic, pollution etc.

AMSA Navigational Services in Australian Waters 2010-2025

Australia’s Treasures • Acoustic signaling is important for communication, breeding, navigation, feeding. • Limited data available on marine mammals. • 56+ species of marine mammals in Australian waters. • Focus of knowledge on these important species.

Macroecology

Acoustic Signal Design • Important for inter- and intra-species communication. • Different vocalisation types for specific contexts. • Focus on intra-species derived vocalisations. • High and low-frequency vocalisations.

http://www.scienceinthenews.org.uk/contents/?article=4

Acoustic Signal Detection • Ability to detect signals in the environment. • Overcoming ‘noise’.

• Collected using multiple methods – Click-evoked potential, Auditory-brainstem response, behavioural. • High and low-frequency hearing thresholds.

http://www.planetjune.com/blog/category/south-africa/page/2/

http://www.openideo.com/open/usaid-humanity-united/inspiration/elephant-distresssignals-you-have-probably-never-heard-it...

Properties of Sound • Low-frequency has a longer wavelength. • Longer wavelengths travel further.

http://droualb.faculty.mjc.edu/Course%20Materials/Physiology%20101/Chapter%20Notes/Fall%202011/chapter_10%20Fall%202011.htm

Acoustic Signals • Evolutionary driving factors • Environment

• Body Mass • Sociality

• Diet • Phylogeny

Environment vs. Body Mass Acoustic Adaptation Hypothesis

Allometry

Morton (1975)

Shwartzkopff (1955); Ryan & Brenowitz (1979)

http://www.chrissonksen.com/environmental-disasters/

Brudzynski (2009)

Frequency (kHz)

Frequency (kHz)

Hypotheses - - - Terrestrial Aquatic

- - - Social Solitary

Frequency (kHz)

Frequency (kHz)

Body Mass (kg)

Herbivore - - Omnivore Carnivore

Methods • Collected data from the literature. • Compiled phylogenetic trees. • Phylogenetic Generalised Least-Squares analysis. • Akaike’s Information Criterion. • Best-model approach.

Model Selection ∆ AICc

∆ AICc 95% CI (Lower, Upper)

PGLS l

Effect size (r)

b 0+bmass+benvironment

0.0

-

0.28

0.49

b 0+bmass*benvironment

1.9

1.55, 2.28

0.75

0.50

b0+bmass+benvironment+b so ciality+bdiet

3.4

3.26, 3.58

0.79

0.49

b 0+bmass+bdiet

8.4

7.57, 10.11

0.80

0.44

b 0+bmass

9.3

8.49, 10.93

0.80

0.43

b 0+bmass+bsociality

11.4

10.52, 13.26

0.83

0.41

b 0+bmass*bsociality

12.0

11.27, 13.31

0.80

0.42

b 0+bmass*bdiet

12.2

11.38, 13.96

0.80

0.44

b0

39.6

38.22, 40.83

0.80

-

Model

Low-Frequency Vocalisations Mass + Environment accounts for 24% of variance

1000

Frequency (kHz)

100

Env=5% Mass=18%

10

1

Terrestrial Aquatic

0.1

0.01

0.001 0.001

0.01

0.1

1

10

100

Body Mass (kg)

1000

10000

100000

1000000

Propagation Efficiency

• Sound travels 3-5 times faster in water than air.

• A sound wave will travel further and faster in water than air.

http://www.ctgclean.com/tech-blog/2011/10/ultrasonics-sound-wave-length-vs-frequency/

High-Frequency Vocalisations Mass x Environment accounts for 27% of variance

1000

Frequency (kHz)

100

Env=15% Mass=4%

10 Terrestrial Terrestrial Echolocators

1

Aquatic

0.1

0.01 0.001

0.01

0.1

1

10

100

Body Mass (kg)

1000

10000

100000 1000000

Low-Frequency Hearing Threshold Mass x Environment accounts for 35% of variance

100

Env=30% Mass=