Zipfs Slope Investigating the southern residents repertoire with Information Theory Kenna Lehmann Beam Reach Marine Science and Sustainability School - beamreach.org/071

Communication The passing of information from one individual (the sender) to another (the receiver) Sender Receiver Information

Communication Channels Different senses (i.e. sight, sound, smell) Different environments (i.e. the ocean, the forest, the savanna)

Background Orcas are highly social and vocal –Communication is key in maintaining social interactions Call meanings have never been determined –No correlation between behavior and call-type

Questions What information do orcas send in their calls? How much information do orcas send in their calls? How is that information organized?

Information Theory Quantitative way to analyze a communication system As designed by Shannon and Weaver (1949) –Determines how a communication system is internally organized Zipfs slope: indication of a repertoires potential to contain information

Calculating Zipfs slope Tally, Rank, Log10 of each, Graph, Calculate the slope

Zipfs Slope

Balance between Diversity Unification

Too diverse Y=-.5+B

Too unified Y=-1.5x+B

Methods Additional recordings

Call Types

Ford (1991)

What? The southern residents repertoire has a Zipfs slope that is steeper than optimum Decreased from to Repertoire is too unified (i.e. repetition)

Why? Too much background noise in the communication channel? Contact calls? Have Soundwatch guidelines decreased boat noise in recent years?

Further Research Comparing different populations and species Use Shannon and Weavers Information Theory to evaluate the internal organization of the repertoire

Acknowledgments John Burt for Syrinx, Scott and Val Veirs for Call Tutor and guidance, FHL computer team for helping with the many computer glitches, team VaTo, Leslie Veirs for the goodies, Mike for not crashing the boat (oh wait), my parents for obvious reasons, Shannon Fowler for the excellent feedback on my papers and life, Jason Wood for the support, feedback, brainstorming and putting up with us And to my favorite whales: Liz, Heather, Elise, and Wes For the good times