Impact of wind on crash-landing mortality in grey-headed albatrosses Thalassarche chrysostoma breeding on Marion Island

Albatrosses exploit winds to travel vast distances across the ocean. Their morphology is adapted for low-cost dynamic soaring flight, but these adaptations confer low manoeuvrability, which may be risky when flying over land. This study investigates how wind conditions influence Endangered grey-headed albatross Thalassarche chrysostoma crashes in the valley below an inland sub-colony on Marion Island. Carcass surveys were conducted in a 1 km2 area spanning the length of this sub-colony (ca. 4000 breeding pairs) from October 2017 to June 2021. Hundreds of adult and fledgling albatross carcasses were discovered, some with evidence of fatal crash-landings in the form of broken bones. Wind data measured on the cliff-top above the colony were supplemented by computational fluid dynamics simulations of wind vectors over Marion Island. Most crashes occurred below the centre of the colony, where there are strong gradients in wind speed and direction under the dominant westerly wind conditions. Observations of albatrosses in flight indicate that most birds are killed when attempting to leave the colony, specifically when flying low above ground in strong wind. An average of at least 41 adults and 40 fledglings died after crashing into the valley annually. This represents an estimated 2% of the annual production of fledglings, 0.5% of the estimated annual breeding adult population and 11% of the adult annual mortality, suggesting a substantial cost to breeding at this inland site. For these long-lived seabirds, even low levels of adult mortality can have potential demographic consequences. This is the first study to document persistent wind-driven, land-based mortalities in albatrosses.The South African National Antarctic Programme and the Department of Forestry, Fisheries and the Environment.http://www.int-res.com/journals/meps/meps-homehj2024Mechanical and Aeronautical EngineeringNon

Discrete Multiscale Analysis: A Biatomic Lattice System

We discuss a discrete approach to the multiscale reductive perturbative method and apply it to a biatomic chain with a nonlinear interaction between the atoms. This system is important to describe the time evolution of localized solitonic excitations. We require that also the reduced equation be discrete. To do so coherently we need to discretize the time variable to be able to get asymptotic discrete waves and carry out a discrete multiscale expansion around them. Our resulting nonlinear equation will be a kind of discrete Nonlinear Schr\"odinger equation. If we make its continuum limit, we obtain the standard Nonlinear Schr\"odinger differential equation

Habitat preferences of Phoebetria albatrosses in sympatry and allopatry

Competition is often proposed to drive niche segregation along multiple axes in speciose communities. Understanding spatial partitioning of foraging areas is particu�larly important in species that are constrained to a central place. We present a natural experiment examining variation in habitat preferences of congeneric Southern Ocean predators in sympatry and allopatry. Our aim was to ascertain consistency of habitat preferences within species, and to test whether preferences changed in the presence of the congener

Classification of discrete systems on a square lattice

We consider the classification up to a Möbius transformation of real linearizable and integrable partial difference equations with dispersion defined on a square lattice by the multiscale reduction around their harmonic solution. We show that the A1, A2, and A3 linearizability and integrability conditions constrain the number of parameters in the equation, but these conditions are insufficient for a complete characterization of the subclass of multilinear equations on a square lattice

Spurious Resonance in SemiDiscrete Methods for the Korteweg--de Vries Equation

A multiple scales analysis of semidiscrete methods for the Korteweg--de Vries equation is conducted. Methods that approximate the spatial derivatives by finite differences with arbitrary order accuracy and the limiting method, the Fourier pseudospectral method, are considered. The analysis reveals that a resonance effect can occur in the semidiscrete solution but not in the solution of the continuous equation. It is shown for the Fourier pseudospectral discretization that resonance can only be caused by aliased modes. The spurious semidiscrete solutions are investigated in numerical experiments and we suggest methods for avoiding spurious resonance

Avian pox in seabirds on Marion Island, southern Indian Ocean

Albatrosses are among the most threatened groups of seabirds with the main land-based threats being alien invasive species, human disturbance and habitat degradation. Disease outbreaks in Antarctic and sub-Antarctic seabird populations are uncommon, but in the past few decades there has been an increase in reported cases. The sub-Antarctic Prince Edward Islands (46°S, 37°E) in the south-western Indian Ocean provide breeding grounds for many seabird species, including 44% of all wandering albatrosses (Diomedea exulans L.). In 2015, five wandering albatrosses and two penguins (Eudyptes chrysocome Forster and Aptenodytes patagonicus Miller) with pox-like lesions were observed on Marion Island, the larger of the two Prince Edward Islands. Despite intensive study of the wandering albatross population since the 1980s, the only previous records of such lesions are one case in 2006 and another in 2009 in white-chinned petrels (Procellaria aequinoctialis L.). Molecular and phylogenetic analysis of tissue samples from two albatross chicks confirmed the presence of avian pox virus (Avipoxvirus). This highlights the need for research into the diseases present on sub-Antarctic islands, for strict controls to limit the risk of accidental introduction of diseases through human activities and the need for effective conservation measures in the event of an outbreak.The South African Department of Environmental Affairs, through the South African National Antarctic Programme (SANAP), the National Research Foundation and the University of Cape Town.http://journals.cambridge.org/action/displayJournal?jid=ANS2018-08-30hj2018Mammal Research InstituteZoology and Entomolog

Recent population trends of sooty and light-mantled albatrosses breeding on Marion Island

Sub-Antarctic Marion Island is one of the few islands where both species of Phoebetria albatrosses breed sympatrically. The last published assessment of their population trends, which reported counts up to 2008, concluded that the numbers of breeding pairs of sooty albatross P. fusca (Endangered) were decreasing, whereas numbers of light-mantled albatross P. palpebrata (Near Threatened) were increasing. Extending the counts to 2014 reversed these trends, with numbers of sooty albatrosses increasing from 2006 to 2014, and numbers of light-mantled albatrosses decreasing from 2007 to 2014. Confidence in island-wide counts is low due to the cryptic nature of the albatrosses on their largely inaccessible cliff-side nest sites, as well as counts for sooty albatrosses taking place late in the incubation period when 10−20% of nests have already failed. Given the greater conservation concern for the sooty albatross, we recommend that dedicated annual counts be conducted during the early incubation period, and be repeated shortly after the chicks hatch (late December), mid-way through the nestling period (late February) and prior to fledging (late April), to give a better idea of breeding success. Count zones also should be revised to facilitate more accurate counts, ensuring more reliable estimates of sooty albatross population trends at Marion Island.Keywords: count technique, phenology, Phoebetria, population size, Prince Edward Island

High metabolic and water-loss rates in caterpillar aggregations : evidence against the resource-conservation hypothesis

CITATION: Schoombie, R. E. et al. 2013. High metabolic and water-loss rates in caterpillar aggregations : evidence against the resource-conservation hypothesis. Journal of Experimental Biology, 216: 4321-4325; doi: 10.1242/jeb.095554.The original publication is available at http://jeb.biologists.orgSeveral hypotheses have been proposed for explaining animal aggregation, including energy or water conservation. However, these physiological hypotheses have not been well investigated. Here, we report the effects of aggregation on metabolic (Embedded Image) and evaporative water-loss rates (Embedded Image) of the gregarious caterpillar Eutricha capensis, by comparing individuals and groups of individuals (N=10–100). Contrary to findings from previous physiological studies, we did not find an advantage to aggregation: unexpectedly, Embedded Image and Embedded Image did not decrease with increasing group size. Embedded Image and Embedded Image generally remained constant or increased in larger groups relative to individuals. The amount of water lost per unit of CO2 exchanged (Embedded Image: Embedded Image ratio) showed a marked increase in grouped caterpillars, particularly in larger groups. Other benefits of aggregation (e.g. reduced predation or increased growth rates) likely outweigh these potential costs, because individuals of E. capensis aggregate voluntarily despite no obvious energetic or hygric advantage, and other potentially confounding group effects (e.g. increased thermoregulatory advantage or whole-animal activity) are inconsequential. The results of this study provide an important exception to physiological studies reporting enhanced energy or water conservation in animal groups.http://jeb.biologists.org/content/216/23/4321Publisher's versio

Effects of within-generation thermal history on the flight performance of Ceratitis capitata : colder is better

CITATION: Esterhuizen, N. et al. 2014. Effects of within-generation thermal history on the flight performance of Ceratitis capitata : colder is better. Journal of Experimental Biology,217:3545-3556, doi:10.1242/jeb.106526.The original publication is available at http://jeb.biologists.orgThe influence of thermal history on temperature-dependent flight performance was investigated in an invasive agricultural pest insect, Ceratitis capitata (Diptera: Tephritidae). Flies were exposed to one of four developmental acclimation temperatures (Tacc: 15, 20, 25, 30°C) during their pupal stage and tested at these temperatures (Ttest) as adults using a full-factorial study design. Major factors influencing flight performance included sex, body mass, Ttest and the interaction between Ttest and Tacc. Successful flight performance increased with increasing Ttest across all acclimation groups (from 10% at 15°C to 77% at 30°C). Although Tacc did not affect flight performance independently, it did have a significant interaction effect with Ttest. Multiple comparisons showed that flies which had been acclimated to 15°C and 20°C performed better than those acclimated to 25°C and 30°C when tested at cold temperatures, but warm-acclimated flies did not outperform cold-acclimated flies at warmer temperatures. This provides partial support for the ‘colder is better’ hypothesis. To explain these results, several flight-related traits were examined to determine whether Tacc influenced flight performance as a consequence of changes in body or wing morphology, whole-animal metabolic rate or cytochrome c oxidase enzyme activity. Although significant effects of Tacc could be detected in several of the traits examined, with an emphasis on sex-related differences, increased flight performance could not be explained solely on the basis of changes in any of these traits. Overall, these results are important for understanding dispersal physiology despite the fact that the mechanisms of acclimation-related changes in flight performance remain unresolved.http://jeb.biologists.org/content/217/19/3545Publisher's versio