At-sea behavioural responses of African penguins in relation to
small-scale variability in prey distribution
A fully-funded PhD project, FitzPatrick Institute of African Ornithology, DST/NRF
Centre of Excellence, University of Cape Town
Supervisors: Lorien Pichegru, Peter Ryan, Emilie Tew-Kai
PROJECT OUTLINE
The combined effects of climate change and industrial-scale fishing have affected
marine ecosystems on an unprecedented scale (Jackson 2008, Brierley & Kingsford
2009). Populations of top predators, including seabirds, are declining world-wide
(BirdLife 2004, Lotze & Worm 2009), despite their pivotal roles in the stability and
resilience of ecosystems (Sergio et al. 2006, Baum & Worm 2009). In that context, it
is important to understand the interactions between threatened top predators and their
environment, in order to predict the potential consequences of environmental changes
on their population trends and to take the appropriate conservation measures.
Foraging strategies will determine the amount of energy available for the
animals to survive and reproduce (Boggs 1992). The breeding season is a crucial
energy bottleneck (Stearns 1992), because individuals will require extra energy to
feed their offspring (Bevan et al. 2002). In the marine environment, the distribution
and predictability of resources depend on the spatio-temporal scale considered
(Fauchald et al. 2000). Marine top predators feeding on pelagic prey face high spatial
and temporal variability in their food availability, and how they adapt their behaviour
to such changes during the breeding season is crucial for their population dynamics.
While several studies revealed flexibility in predators’ foraging behaviour between
years and between localities, none investigated the question at a very fine spatiotemporal scale.
We shall study flexibility in the at-sea behaviour of a marine top predator, the
African Penguin Spheniscus demersus, in relation to its prey availability at a very fine
spatio-temporal scale. We shall record simultaneously the penguins’ foraging
behaviour with GPS loggers and their prey distribution with real-time acoustic
surveys. We shall relate the data collected with oceanographic data from the South
African Environmental Observation Network (SAEON) in the study area, as well as
high resolution remote sensing data. The study also builds on four years of existing
data on penguin foraging effort recorded at two sites from 2008 to 2011.
African Penguins are endemic to southern Africa and are listed as globally
Endangered (IUCN 2010). The recent dramatic decline in their population (a loss of
60% of their global population in the last 5 years, Crawford et al. 2011) requires an
understanding of their relationship with their environment, in parallel with active
conservation measures, such as the creation of Marine Protected Areas around their
key breeding localities. African Penguin population dynamics are tightly linked to
small pelagic fish availability (Crawford et al. 2008) and recently both Anchovy
(Engraulis encrasicolus) and Sardine (Sardinops sagax) populations shifted from
being mainly located on the west coast, where most seabird colonies are distributed,
to the south coast, 500 km away, and out of reach of breeding seabirds (van der
Lingen et al. 2006, Roy et al. 2007, Coetzee et al. 2008). This shift might be due to
environmental variability and climate change, but heavy fishing pressure persists in
areas with low fish abundance because of the distribution of land-based processing
plants (Pichegru et al. 2009). Understanding the mechanisms of interaction of the
African Penguin with its environment would thus help for appropriate conservation
measures.
METHODS
African Penguin foraging behaviour
Breeding African Penguins will be studied on St Croix Island (33°48’S, 25°46’E) and
at Bird Island (33°50’S, 26°17’E), Nelson Mandela Bay. Birds will be equipped with
GPS-TD loggers (a GPS recorder combined with a time-depth recorder; 96 x 39 x
26.5 mm; earth&OCEAN Technologies, Germany) that record latitude and longitude
at 1 min-intervals to an accuracy of <10 m, and depth at 1 s intervals to the nearest 0.1
m. The devices weigh <2.5% of adult body mass and are housed in streamlined fibrecomposite containers. They are attached to the penguins’ lower back feathers with
waterproof tape, causing no damage to the plumage. Handling usually lasts <6 min
from capture to release and these methods are approved by University of Cape
Town’s animal ethics committee. After deployment, nest sites of instrumented birds
are monitored until the adult carrying the GPS returns, allowing it to be recaptured
and the logger removed. The data are then downloaded onto a computer and the
device re-deployed on another individual.
Prey distribution
Prey abundance and distribution will be estimated with acoustic surveys from a
dedicated research vessel. The surveys will cover the area within a 20 km radius
around the islands over 1-2 days. Biomass estimation is based on a specific routine,
weighting of transects by length and variance estimation between transects. We shall
compare where penguins forage, and the effort they expend finding food, with the
known distribution of pelagic fish.
Marine habitat
To define the marine habitat of African penguins and their prey, we will use a
combination of oceanographic data (underwater temperature, currents) collected by
the South African Environmental Observation Network (SAEON) in the study area,
data collected by penguins from highly sensitive Temperature-Depth recorders, and
high resolution remote sensing data (Sea Surface Temperature, ocean coulours). They
will be used to describe submesoscale and fine scale physical structures of the areas
used by African penguins and their prey.
APPLICATIONS AND FUNDING
Applicants should have an MSc or excellent BSc Hons in Zoology and some field
experience with seabirds, or equivalent experience. Although they will form part of an
existing research team, they will be required to organize and conduct field work
independently on isolated islands, often under trying conditions and with minimal
comfort. The successful applicant will be awarded a PhD bursary of R100 000 per
year through the Percy FitzPatrick CoE.
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