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Date of Award


Document Type

Thesis - Pacific Access Restricted

Degree Name

Master of Science (M.S.)


Biological Sciences

First Advisor

Richard Tenaza

First Committee Member

Lee Christianson

Second Committee Member

Alice S. Hunter

Third Committee Member

Eric Thomas


Between 15 March and 29 July 1998 we quantified aggressive movements (AMs) in a breeding colony of 44 adult magellanic penguins (MPs) during their nesting season at San Francisco Zoo (SFZ). We sampled their behavior for a total of 149.5 hrs in 46 sessions of 195 min each, all starting at 0945 hrs and stopping at 1300 hrs. We recognized 4 types of AMs, of which 2 (eye-pointing and charging) were threat signals, I (bill-fencing) was a ritualized contest of strength and agility, and I (biting) was physical attack. MPs only performed AMs within 2-3 m of nest entrances. Males performed 83% of all AMs, females 17%. The eye-pointing threat signal accounted for 92% of all AMs, and the 3 non-attack AMs combined accounted for 99% of all AMs; only I% involved physical assault. Both sexes performed eye-pointing and bill-fencing, but only males charged or bit their adversaries.



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