92
history of Antarctic krill Euphausia superba, their preferred
prey (Nachtsheim et al. 2017).
Oceanographic and environmental data are readily available online, with the NOAA and the Copernicus program
being the largest providers (Copernicus 2017; NOAA 2017),
or from the animal-borne devices themselves. The latter
sometimes provide physical oceanographic data from areas
that cannot be sampled using other conventional approaches
(Fig. 4) (Årthun et al. 2012; Roquet et al. 2013). Following
this further, detailed oceanographic data could provide
information about how marine top predators will probably
respond to climatic change (Costa et al. 2010a; McIntyre
et al. 2011). For instance, CTD satellite tags deployed on
southern elephant seals Mirounga leonina, crabeater seals,
and Weddell seals in the Western Antarctic Peninsula have
shown that these three species occupy very different habitat
types, hence trophic niches, within this region, and will
therefore be affected differently by climate change (Costa
et al. 2010a). Additionally, many marine top predators feed
at depth and several studies have demonstrated the association between oceanographic features of the water column
and predator’s diving behavior (Fig. 5) (Biuw et al. 2010;
Heerah et al. 2013; Guinet et al. 2014). Quantifying foraging effort at depth, based on the detection of changes in diving behavior, can relate the actual behavior of the predator
in three dimensions to the heterogeneous environment they
respond to (Heerah et al. 2016). For southern elephant seals,
the switch from transit to hunting mode was associated with
colder water temperatures, relatively short dive bottom time
and rapid descent rates (Bestley et al. 2013). As mentioned
before, foraging efficiency should be investigated by looking at both horizontal and vertical movements, as this can
reveal interesting inter-specific behavioral differences, for
example, resource partitioning through different dive behavior in closely related predator species (Wilson 2010;
Villegas- Amtmann et al. 2013; Bestley et al. 2015).
Information on foraging effort, which is, among others and
depending on the species, determined by the number of
dives, dive duration, vertical and horizontal travel distance,
and the time a foraging trip takes, can be readily derived
from conventional tracking data (Boyd et al. 2014).
However, the study of movement ecology is lifted to another
level by using tri-axial accelerometers combined with GPS
loggers, which are able to provide high-resolution behavioral data on the level of decision-making (Wilson et al.
2008; Watanabe and Takahashi 2013; Bidder et al. 2014).
For example, by linking GPS and accelerometer data of
lesser black-backed gulls, a recent study was able to provide
insight into how a flight generalist (i.e., a bird who has the
ability to radically alter its flight mode in response to external conditions) can reduce the energetic cost of movement
(Shamoun-Baranes et al. 2016).
Fig. 4 Number of temperature-salinity profiles of (a) seal-derived data
from the Marine mammal Exploring the Oceans Pole to Pole (MEOP)
program, and (b) Argo float profiles (see Gould et al. (2004) for more
details). Superimposed in pink are the Antarctic Circumpolar Current
borders. This figure shows clearly how animal-borne devices can complement traditional observations, particularly at places where access is
limited (e.g., due to sea ice). (Reproduced from Roquet et al. (2013)
(CC-BY 4.0))
B. C. Heylen and D. A. Nachtsheim
history of Antarctic krill Euphausia superba, their preferred
prey (Nachtsheim et al. 2017).
Oceanographic and environmental data are readily available online, with the NOAA and the Copernicus program
being the largest providers (Copernicus 2017; NOAA 2017),
or from the animal-borne devices themselves. The latter
sometimes provide physical oceanographic data from areas
that cannot be sampled using other conventional approaches
(Fig. 4) (Årthun et al. 2012; Roquet et al. 2013). Following
this further, detailed oceanographic data could provide
information about how marine top predators will probably
respond to climatic change (Costa et al. 2010a; McIntyre
et al. 2011). For instance, CTD satellite tags deployed on
southern elephant seals Mirounga leonina, crabeater seals,
and Weddell seals in the Western Antarctic Peninsula have
shown that these three species occupy very different habitat
types, hence trophic niches, within this region, and will
therefore be affected differently by climate change (Costa
et al. 2010a). Additionally, many marine top predators feed
at depth and several studies have demonstrated the association between oceanographic features of the water column
and predator’s diving behavior (Fig. 5) (Biuw et al. 2010;
Heerah et al. 2013; Guinet et al. 2014). Quantifying foraging effort at depth, based on the detection of changes in diving behavior, can relate the actual behavior of the predator
in three dimensions to the heterogeneous environment they
respond to (Heerah et al. 2016). For southern elephant seals,
the switch from transit to hunting mode was associated with
colder water temperatures, relatively short dive bottom time
and rapid descent rates (Bestley et al. 2013). As mentioned
before, foraging efficiency should be investigated by looking at both horizontal and vertical movements, as this can
reveal interesting inter-specific behavioral differences, for
example, resource partitioning through different dive behavior in closely related predator species (Wilson 2010;
Villegas- Amtmann et al. 2013; Bestley et al. 2015).
Information on foraging effort, which is, among others and
depending on the species, determined by the number of
dives, dive duration, vertical and horizontal travel distance,
and the time a foraging trip takes, can be readily derived
from conventional tracking data (Boyd et al. 2014).
However, the study of movement ecology is lifted to another
level by using tri-axial accelerometers combined with GPS
loggers, which are able to provide high-resolution behavioral data on the level of decision-making (Wilson et al.
2008; Watanabe and Takahashi 2013; Bidder et al. 2014).
For example, by linking GPS and accelerometer data of
lesser black-backed gulls, a recent study was able to provide
insight into how a flight generalist (i.e., a bird who has the
ability to radically alter its flight mode in response to external conditions) can reduce the energetic cost of movement
(Shamoun-Baranes et al. 2016).
Fig. 4 Number of temperature-salinity profiles of (a) seal-derived data
from the Marine mammal Exploring the Oceans Pole to Pole (MEOP)
program, and (b) Argo float profiles (see Gould et al. (2004) for more
details). Superimposed in pink are the Antarctic Circumpolar Current
borders. This figure shows clearly how animal-borne devices can complement traditional observations, particularly at places where access is
limited (e.g., due to sea ice). (Reproduced from Roquet et al. (2013)
(CC-BY 4.0))
B. C. Heylen and D. A. Nachtsheim