Geography Reference
In-Depth Information
3 Geovisual Analytics and Possum Movement Visualisation
3.1 The Nature of the Possum Lifestyle
In spite of the considerable common ground between species in their drivers, it is
relatively unusual to see cross citation of studies of analysis or visualisation of
human viz a viz animal movement data sets. This mutual isolation may seem
logical to some and regrettable to others. Free of major ethical issues animal
behaviourists and ecologists have created strong currents of interest with their
innovation in capturing movement data (Hebblewhite and Haydon
2010
; Dennis
et al.
2010
). Eroded control of privacy may see a similar surge in scientific rather
than commercial exploration of human movement. In the meantime the Ringmap
project has been fortunate in collaborating with local NZ research in high reso-
lution animal data capture and visualising ongoing sample data sets. The albatross
flights illustrate that the basic aquarium model can be just as effective for
extracting rapid insights in the animal kingdom as it is with human data. However,
soaring sea birds live in a different geometry and geography than Halifax com-
muters and for a more even comparison of species we switch to a small group of
strictly terrestrial animals, the common brushtail possum.
The common brushtail possum is a semi-arboreal, nocturnal marsupial native to
mainland Australia and Tasmania but introduced to and recognised as a major pest
in New Zealand. Brushtail possums are commonly located in tree cavities or
perching epiphytes. They usually sleep in their dens during day time, awake and
emerge from the dens about half an hour after sunset, and cease active behaviour
before dawn. Their nightly activities can be grouped into feeding, grooming,
resting, and travelling. Males move further than females but females have more
philopatric dens. However peak periods of activity and how activity changes over
time, by sex and among seasons have not yet been characterised at fine temporal
scales (Koefoed
2009
; Dennis et al.
2010
). Therefore, the next two sections
explore the possum movement data collected at fine temporal scale.
3.2 Viewing Possums Movement and Activity as Timelines
Absolute time was displayed in the albatross timelines (Fig.
3
); however, time also
can be represented in relative terms for different purposes. For example, Fig.
5
shows
time relative to sunset in hours, depicting the timelines of an adult female common
brushtail possum (#6012) over a period of 8 consecutive nights. Segments of time-
lines are colour-coded to represent habitat (Fig.
5
a) and behavioural modes (defined
by two classes of step lengths and turning angles) that were inferred by a segmen-
tation model (Dennis et al.
2010
; Dennis and Shah
2012
; Koefoed
2009
) (Fig.
5
b).
When comparing both images, one sees a regular periodicity of behaviour both
within and between nights, with rapid movements over grassland during the early
