In order to understand how whales are using Geographe Bay, GMR researchers tracked animals’ movements visually using a theodolite in 2011-2014.  A theodolite is traditionally a surveying instrument:  it measures angles in the horizontal and vertical planes, and is typically used to reproduce scale models of the landscape.  However, it can also be used to observe and measure the direction, distance and position of objects out at sea.

The theodolite was placed at a high vantage point overlooking the survey area: in this case, the hill behind Pt Picquet is the perfect location to look for whales travelling through Geographe Bay.  From this position, the theodolite was used to measure angles from the theodolite to a whale.  At the start of each shift, the position of the reference point was recorded (located at the slipway in Eagle Bay).  When a whale was seen, the theodolite measured the horizontal angle from the location of the theodolite to the whale , which told us which direction the whale was in.  The upwards or downwards tilt of the theodolite telescope gave us the vertical angle – since we knew the height of the hill the theodolite was on, we used the vertical angle to calculate the distance to the whale .  Because the theodolite angles are so precise, we were able to calculate whale positions in the bay with accuracy. This work has already led to the publication of several papers and reports, and it is possible more will emerge as new theodolite-based research questions are addressed..

Marley, S.A., Salgado Kent, C.P., Recalde-Salas, A. and Burton, C. (2013) Pygmy blue whale responses to vessel traffic during migration through Geographe Bay, southwestern Australia.  20th Biennial Conference on the Biology of Marine Mammals; Dunedin, New Zealand.

Salgado Kent, C., Marley, S.A., Bouchet, P. and Nagy, J. (2011) A theodolite tracking study of baleen whales in Geographe Bay, Western Australia48th Australian Marine Sciences Association Annual Conference; Fremantle, Western Australia.

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