A simplified method of determining the sex of Pygoscelis penguins using bill measurements

We examined sexual dimorphism in bill size in adult Adelie Penguins Pygoscelis adeliae, adult Chinstrap Penguins P. antarctica and adult and juvenile Gentoo Penguins P. papua at King George Island, Antarctica, using a DNA-based molecular sexing technique. Bill length and depth were the most consistent dimorphic character examined, with measurements 5.4%–11.5% larger in males than in females, on average. Within breeding pairs sampled, male Chinstrap and Gentoo Penguins had consistently longer and deeper bills than their mates, although bill measurement overlapped between sexes at the population level. We used bill measurements to calculate species- and age-specificdiscriminant functions that correctly classified 83.2%–96.7% of the individuals in our study following cross-validation. The discriminant functions derived from this analysis provide a practical method of sex determination for all three Pygoscelis penguin species in the South Shetland Islands where they breed sympatrically. Posterior probability analysis can also be used to identify individuals that are likely to be incorrectly classified using discriminant function analysis, allowing DNA-based tests for gender to be reserved for targeted use. Furthermore, we report raw morphometric data to facilitate future analysis and discriminant function improvemen

Skuas at penguin carcass: patch use and state-dependent leaving decisions in a top-predator

Foraging decisions depend not only on simple maximization of energy intake but also on parallel fitness-relevant activities that change the forager's ‘state’. We characterized patch use and patch leaving rules of a top-predatory seabird, the Brown Skua (Catharacta antarctica lonnbergi), which during its reproductive period in the Antarctic establishes feeding territories in penguin colonies. In feeding trials, we observed how skuas foraged at penguin carcass patches and analysed patch leaving decisions by incorporating the estimated state of foraging birds and patch availability. Patches were exploited in a characteristic temporal pattern with exponentially decreasing remaining patch sizes (RPSs) and intake rates. Patch size decreased particularly fast in small compared to large patches and exploitation ended at a mean RPS of 47.6% irrespective of initial size. We failed to identify a measure which those birds equalized upon patch departure from raw data. However, when accounting for the birds' state, we ascertained remaining patch size and intake rates to have the lowest variance at departure whereas food amount and feeding time remained variable. Statistical correction for territory size only and combined with state had lower effects, but remaining patch size remained the measure with lowest coefficient of variation. Thus, we could clearly reject a fixed-time or fixed-amount strategy for territorial skuas and rather suggest a state-dependent strategy that equalizes remaining patch size. Thus our results provide evidence that under natural conditions, territorial skuas adjust their foraging decision on actual energy requirements, i.e. offspring number and age

Options for allocating the precautionary catch limit of krill among small-scale management units in the Scotia Sea

Following an assessment of Antarctic krill (Euphausia superba) in the Scotia Sea, CCAMLR established a precautionary catch limit of 4 million tonnes and further adopted 15 small-scale management units (SSMUs). The intent was to subdivide the precautionary catch limit for krill among the SSMUs so as to preclude the inadvertent concentration of catches in a small portion of the surveyed area. Five options for allocating the catch limit among the SSMUs in the Scotia Sea are presented in this paper. The first four are static allocations where the allotment of catch to an SSMU is proportional to: (i) the historical catch within the SSMU; (ii) estimated predator demand in the SSMU; (iii) estimated standing stock of krill in the SSMU; and (iv) standing stock less predator demand in the SSMU. The fifth option is a dynamic allocation based on land-based predator monitoring conducted just prior to, or early in, the fishing season. For the purposes of illustration and comparison between the options, parameter estimates are made using available data, although it is recognised that considerable refinement of these estimates is possible. Qualitative conclusions are that: under the first two options a substantial portion (>65%) of the catch limit would be allocated to three or less of the SSMUs adjacent to large concentrations of land-breeding predators; under options (iii) and (iv) a similar portion of the catch limit would be directed to pelagic SSMUs beyond the foraging range of these predators but into areas where krill fishing has not regularly occurred; and under option (v), an example of an adjustable catch limit dependent on the results of ecosystem monitoring, the fishery would be restricted in some of its traditional fishing grounds during years of low krill availability. Under all five options there would be little effect on the existing fishery However, as catches increase, a trade-off may be drawn between options that displace the fishery from its current operating area, but reduce the potential for contravening the terms of the Convention, and options that do not displace the fishery, but are likely to contravene the terms of the CCAMLR Convention

Gastrointestinal helminths of Adélie penguins (Pygoscelis adeliae) from Antarctica

Knowledge about parasitic organisms in Antarctica is scarce and fragmentary. The study reported here adds to the knowledge of gastrointestinal parasites of the Adélie penguin (Pygoscelis adeliae) (Sphenisciformes), from 25 de Mayo/King George Island (South Shetlands), Bahia Esperanza (Hope Bay) and Avian Island (Antarctica). Thirty-five freshly dead specimens (20 chicks and 15 adults) were collected from December 2007 to December 2014 and examined for internal macroparasites. Three adult parasite species were found: one Cestoda, Parorchites zederi, and two Nematoda, Stegophorus macronectes and Tetrameres sp. Immature Tetrabothrius sp. were found in hosts from Avian Island. Helminth communities are known to be related to host feeding behaviours. Low parasite richness observed in Adélie penguins could be related to the stenophagic and pelagic diet of this host species, which feeds almost exclusively on krill.Keywords: Parorchites zederi; Stegophorus macronectes; Tetrameres sp.; parasites; ecosystem health.(Published: 16 June 2016)Citation: Polar Research 2016, 35, 28516,http://dx.doi.org/10.3402/polar.v35.2851