[MARMAM] New paper " Continuous Focal Group Follows Operated by a Drone Enable Analysis of the Relation Between Sociality and Position in a Group of Male Risso’s Dolphins (Grampus griseus)"

Nova Atlantis oceanwatch at gmail.com
Mon May 11 03:19:33 PDT 2020

Dear colleagues,

My co-authors and I are pleased to share our recent publication in
Frontiers in Marine Science/ Marine Mageafauna

Hartman K, van der Harst P and Vilela R (2020) Continuous Focal Group
Follows Operated by a Drone Enable Analysis of the Relation Between
Sociality and Position in a Group of Male Risso’s Dolphins (Grampus
griseus). Front. Mar. Sci. 7:283. doi: 10.3389/fmars.2020.00283

Link to paper (full open-access): https://doi.org/10.3389/fmars.2020.00283


Relationships between social status and relative position of group-living
animals have been described in a variety of species. For wild cetaceans,
who spend most of their time underwater, collecting detailed, continuous
data to assess such relationships depends highly on group size, formation,
shyness of animals and observation platform. We test a new method for focal
group sampling using an Unmanned Aerial Vehicle (UAV), focusing on one
long-term followed group of 13 male Risso’s dolphins (*Grampus griseus*) in
the Azores, Portugal. We aim to assess the usefulness of a UAV in
delivering robust data to evaluate sociality in relation to relative
position. Our analysis is based on recordings of synchronous breathing
events, which are taken as an indicator of association strength. Twenty-one
separate UAV flights were performed during seven surveys in July–August
2017, recording 2,886 breathing events and 571 synchronous dyads. Results
showed strong differences in sociality between individuals and identified
two strongly associated pairs, one strongly associated trio and six less
associated individuals within the group. We subsequently created continuous
time series of relative positions by interpolation of the positions
recorded with the UAV at breathing events, and applied the Dynamic Time
Warping method to assess associations based on relative position. This
analysis identified more detailed association patterns than the synchrony
analysis, and revealed a correlation between measures of sociality and
relative position, at an individual and sub-cluster level, which may
indicate dominant relationships. We compared results with those obtained
with Photo-ID to assess any observation bias related to using a UAV. We
found that 37% more breathing events were recorded with the UAV, and 21%
more synchronous dyads detected, compared with Photo-ID, collected over the
same observation periods, but, based on synchrony data, both methods
yielded very similar results. We conclude that using a UAV for focal group
follows of Risso’s dolphins enables a more granular study of association
patterns than Photo-ID, by taking into account the relative position of
individuals. The correlation found between measures of sociality and
relative position holds promise for using UAVs in future studies of
dominant relationships in Risso’s dolphins and other cetacean species.

Keywords: UAV, focal group follow, Risso’s dolphins, male associations,
synchrony, relative position, dynamic time warping, levels of association

Please contact me if you have any questions.


Karin Hartman

Nova Atlantis Foundation
oceanwatch at gmail.com
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