Download Do penguins play leap-frog? Niche partitioning in Adélie and

ORAL ABSTRACT
Do penguins play leap-frog? Niche partitioning in Adélie and Chinstrap penguins:
the roles of allochrony and phase-dependent foraging ranges
Harriet Clewlow1, Norman Ratcliffe1, Mike Dunn1, Stacey Adlard1, Steve Votier2, Rod Downie3, Akinori
Takahashi4
1
British Antarctic Survey, 2University of Exeter, 3WWF, 4National Institute of Polar Research Japan
Ecological theory states that closely related species with similar ecological requirements, occupying the
same fundamental niche will display niche partitioning in areas of overlap to reduce competition.
Sympatrically breeding congeneric seabirds commonly display allochrony (differences in timing of breeding)
and this, in combination with phase-dependant variability in foraging trip duration, can lead to spatiotemporal segregation of species by foraging areas. This causes birds to “leap-frog” one another in time and
space to exploit distinct spatial niches as the season progresses. Seabird phenology is sensitive to
temperature change but species do not always respond to the same degree. Therefore, if the timing of
breeding of one species advances at a different rate to that of its competitor niche overlap may increase,
leading to synchronous breeding, increased inter-specific competition and population declines in one or
both species. Alternatively if both species advance their phenology at similar rates, thus preserving
allochrony, then niche partitioning and the level of competition experienced will be unaffected.
Adélie and Chinstrap penguins have similar foraging ecology in terms of diet, dive depths and phasedependent foraging ranges. Allochrony is therefore likely to be important in reducing competition between
these species. This leads us to formulate the following hypotheses:
a. Adélie and Chinstrap penguins show phase-dependent foraging distributions
b. Allochrony causes “leap-frogging” of foraging areas
c. Breeding synchronisation would substantially increase niche overlap
d. Phenology of the two species will advance in parallel due to climate change as competition will
be an important selective force in preserving allochrony
Data was collected at Signy Island, South Orkneys during breeding seasons from 1999 to 2015. Penguins
were fitted with rapid-acquisition GPS, (43 Adélie and 52 Chinstrap), or PTT tags, (50 Adélie and 75
Chinstrap; tag type year dependant). Phases were defined as incubation (~33days), guard (~22 days) and
crèche (~25 days).
Foraging paths will be modelled in the ‘R’ package CRAWL, which accounts for ARGOS errors and
uncertainty in the path the bird followed between fixes. Species- and phase-specific foraging areas will be
determined and overlaps assessed, both on the basis of the observed level of allochrony and on the
assumption of complete synchrony due to climate change, to quantify the degree of niche partitioning that
allochrony induces. ANCOVA will be used to model species-specific relationships between hatching dates
and temperature to determine whether their phenology advances in parallel or interactively and quantify
the change in competition future warming scenarios may produce.
9th International Penguin Congress, Cape Town, South Africa, 5th – 9th September 2016