Population regulation in Magellanic penguins: what determines changes in colony size?

Seabirds are often studied at individual colonies, but the confounding effects of emigration and mortality processes in open populations may lead to inappropriate conclusions on the mechanisms underlying population changes. Magellanic penguin (Spheniscus magellanicus) colonies of variable population sizes are distributed along the Argentine coastline. In recent decades, several population and distributional changes have occurred, with some colonies declining and others newly established or increasing. We integrated data of eight colonies scattered along ∼600 km in Northern Patagonia (from 41°26´S, 65°01´W to 45°11´S, 66°30´W, Rio Negro and Chubut provinces) and conducted analysis in terms of their growth rates, production of young and of the dependence of those vital rates on colony age, size, and location. We contrasted population trends estimated from abundance data with those derived from population modeling to understand if observed growth rates were attainable under closed population scenarios. Population trends were inversely related to colony size, suggesting a density dependent growth pattern. All colonies located in the north--which were established during the last decades--increased at high rates, with the smallest, recently established colonies growing at the fastest rate. In central-southern Chubut, where colonies are the oldest, the largest breeding aggregations declined, but smaller colonies remained relatively stable. Results provided strong evidence that dispersal played a major role in driving local trends. Breeding success was higher in northern colonies, likely mediated by favorable oceanographic conditions. However, mean foraging distance and body condition of chicks at fledging were influenced by colony size. Recruitment of penguins in the northern area may have been triggered by a combination of density dependence, likely exacerbated by less favorable oceanographic conditions in the southern sector. Our results reaffirm the idea that individual colony trends do not provide confident indicators of population health, highlighting the need to redefine the scale for the study of population changes.

Ultrastructural aspects of the tongue in Magellanic Penguins Spheniscus magellanicus (Forster, 1781) / Aspectos ultraestruturais da língua de Pinguim-de-Magalhães Spheniscus magellanicus (Forster, 1781)

The tongue of birds presents diversified morphologic characteristics, related directly their feeding habits and may be adapted to food capture. Penguins of the Spheniscidae family are pelagic birds that are totally adapted to the marine environment.  The objective of this study was to describe the morphology of the tongue in Magellanic penguins (Spheniscus magellanicus). In order to investigate these characteristics, six tongues of juvenile S. magellanicus were collected and their morphology analyzed macroscopically and microscopically.  The tongue of the Magellanic penguin has a fusiform shape with a round apex that is narrower than the root, following the shape of the beak.  The epithelium of the tongue of the Magellanic penguin showed to be stratified and very keratinized, with the presence of lingual papillae that showed a caudally inclined apex. The neighboring connective tissue showed absence of mucous glands. The cartilaginous skeleton was observed in the medial region of the tongue, extending from the base to the apex. The structure of the tongue of the Magellanic penguin showed to be similar to that of other penguin species, but also showed peculiar characteristics that were not observed in other bird families.(AU)

A língua das aves apresenta características morfológicas diversificadas, relacionados diretamente com seus hábitos alimentares e pode ser adaptado para a captura de alimentos. Os pinguins da família Spheniscidae são aves pelágicas totalmente adaptadas ao ambiente marinho. O objetivo deste estudo foi descrever a morfologia da língua de pinguins de Magalhães (Spheniscus magellanicus). Para investigar tais características, seis línguas de S. magellanicus juvenis foram coletados e sua morfologia analisada macro e microscopicamente. A língua do pinguim de Magalhães tem formato fusiforme com ápice arredondado e mais estreito em relação à raiz, acompanhando o formato do bico. O epitélio da língua do pinguim-de-Magalhães mostrou-se estratificado e muito queratinizado, com a presença de papilas linguais, com ápices voltados caudalmente. O tecido conjuntivo adjacente mostrou ausência de glândulas mucosas. Um esqueleto cartilaginoso, formado por cartilagem hialina, foi observado na região mediana da língua se estendendo da base até ápice. A estrutura da língua do pinguim Magellanic mostrou ser semelhante ao de outras espécies de pinguins, mas também apresentou características peculiares que não foram observados em outras famílias de aves.(AU)

Study of bacteria isolated from the foot pad of Spheniscus magellanicus with and without bumblefoot / Estudo de bactérias isoladas de coxins plantares de Spheniscus magellanicus com e sem bumblefoot

The bumblefoot or pododermatitis is among the diseases with the highest morbidity in Magellanic penguins, sometimes evolving to septicemia and death. Therefore, this study aimed to relate the main species involved in the disorder, as well as the in vitro susceptibility profile of the microorganisms against routine antimicrobial usage in Veterinary Medicine. During two years in vivo material was harvested from 200 footpads (n=100 animals) for microbiological analysis and in vitro susceptibility tests against the Antibiotic enrofloxacin, streptomycin, penicillin and cephalosporin. Bacteria have been identified both as part of permanent and transient microbiota, also being associated to 100% of the pododermatitis cases. The most prevalent genus were Staphylococcus and Corynebacterium. The antibiograms of all the isolated bacteria resulted in greater susceptibility of the strains facing cephalosporin, followed by enrofloxacin, streptomycin and penicillin.

O bumblefoot ou pododermatite está entre as afecções de maior morbidade em pinguins-de-magalhães, podendo evoluir para septicemia e óbito. Portanto, o presente estudo objetivou relacionar as principais espécies bacterianas envolvidas na afecção, bem como o perfil de susceptibilidade in vitro destes microrganismos frente a antimicrobianos de uso rotineiro em medicina veterinária. Durante o período de dois anos, foi realizada colheita de material in vivo de 200 coxins plantares (n=100 animais) para análise microbiológica e testes de susceptibilidade in vitro frente aos antibióticos enrofloxacina, estreptomicina, penicilina e cefalosporina. Bactérias foram identificadas tanto como parte da microbiota permanente quanto da transitória, bem como estiveram associadas a 100% dos casos de pododermatite. Os gêneros mais prevalentes foram Staphylococcus e Corynebacterium. Os antibiogramas de todas as bactérias isoladas resultaram em maior sensibilidade das cepas frente à cefalosporina, seguida de enrofloxacina, estreptomicina e penicilina.

Study of bacteria isolated from the foot pad of Spheniscus magellanicus with and without bumblefoot / Estudo de bactérias isoladas de coxins plantares de Spheniscus magellanicus com e sem bumblefoot

The bumblefoot or pododermatitis is among the diseases with the highest morbidity in Magellanic penguins, sometimes evolving to septicemia and death. Therefore, this study aimed to relate the main species involved in the disorder, as well as the in vitro susceptibility profile of the microorganisms against routine antimicrobial usage in Veterinary Medicine. During two years in vivo material was harvested from 200 footpads (n=100 animals) for microbiological analysis and in vitro susceptibility tests against the Antibiotic enrofloxacin, streptomycin, penicillin and cephalosporin. Bacteria have been identified both as part of permanent and transient microbiota, also being associated to 100% of the pododermatitis cases. The most prevalent genus were Staphylococcus and Corynebacterium. The antibiograms of all the isolated bacteria resulted in greater susceptibility of the strains facing cephalosporin, followed by enrofloxacin, streptomycin and penicillin.(AU)

O bumblefoot ou pododermatite está entre as afecções de maior morbidade em pinguins-de-magalhães, podendo evoluir para septicemia e óbito. Portanto, o presente estudo objetivou relacionar as principais espécies bacterianas envolvidas na afecção, bem como o perfil de susceptibilidade in vitro destes microrganismos frente a antimicrobianos de uso rotineiro em medicina veterinária. Durante o período de dois anos, foi realizada colheita de material in vivo de 200 coxins plantares (n=100 animais) para análise microbiológica e testes de susceptibilidade in vitro frente aos antibióticos enrofloxacina, estreptomicina, penicilina e cefalosporina. Bactérias foram identificadas tanto como parte da microbiota permanente quanto da transitória, bem como estiveram associadas a 100% dos casos de pododermatite. Os gêneros mais prevalentes foram Staphylococcus e Corynebacterium. Os antibiogramas de todas as bactérias isoladas resultaram em maior sensibilidade das cepas frente à cefalosporina, seguida de enrofloxacina, estreptomicina e penicilina.(AU)