Relationship between VeDBA, behaviour, ODBA and power from Long necks enhance and constrain foraging capacity in aquatic vertebrates

Highly specialized diving birds display substantial dichotomy in neck length with, for example, cormorants and anhingas having extreme necks, while penguins and auks have minimized necks. We attached acceleration loggers to Imperial cormorants <i>Phalacrocorax atriceps</i> and Magellanic penguins <i>Spheniscus magellanicus</i>, both foraging in waters over the Patagonian Shelf, to examine the difference in movement between their respective heads and bodies in an attempt to explain this dichotomy. The penguins had head and body attitudes and movements that broadly concurred throughout all phases of their dives. By contrast, although the cormorants followed this pattern during the descent and ascent phases of dives, during the bottom (foraging) phase of the dive, the head angle differed widely from that of the body and its dynamism (measured using vectorial dynamic acceleration) was over four times greater. A simple model indicated that having the head on an extended neck would allow these cormorants to half the energy expenditure that they would expend if their body moved in the way their heads did. This apparently energy-saving solution is likely to lead to greater heat loss though and would seem tenable in slow-swimming species because the loss of streamlining that it engenders would make it detrimental for fast-swimming taxa such as penguins

Additional file 1: of A spherical-plot solution to linking acceleration metrics with animal performance, state, behaviour and lifestyle

Methods. Changing shapes for frequency distributions. Figure S1. A 3-d scatter plot (g-sphere) of static (orthogonal) tri-axial acceleration data. Figure S2. A spherical coordinate’s visualization of (a) postural state plotted onto the surface of a sphere in three-dimensional space, (b) points joined together in chronological order, (c) projecting the data outwards from the sphere according to other parameters. Figure S3. A spherical histogram (Dubai plot) visualization to depict frequent postural states. Figure S4. Histogram, Frequency shape (stacked), fixed shape (skittle) from urchin plots. Figure S5. G-urchin of skittle shape and stacked frequency urchins emitted from the centre of each facet of the sphere. Figure S6. Overview of user interface for a program in which spherical plots can be created. Figure S7. G-spheres and comparable g-urchins derived from a rod-mounted tri-axial accelerometer showing fly-fishing visualisations. (DOCX 5289 kb