Javier Negrete

ANNUAL DIET OF THE LITTLE HAIRY ARMADILLO, CHAETOPHRACTUS VELLEROSUS (MAMMALIA, DASYPODIDAE), IN BUENOS AIRES PROVINCE, ARGENTINA

Abstract Analysis of the stomach contents of 28 little hairy armadillos (Chaetophractus vellerosus), collected during a 14-month period at Pipinas, Argentina, showed that about 63.6% of the weight of prey items was composed of animal remains, 18% was plant material, and the remaining 18.4% was undetermined organic remains. Insects were the most frequent diet item, followed by plant material, amphibians, reptiles, and lastly birds and mammals in similar proportion. During autumn, plant material was the most abundant item, followed by vertebrates and invertebrates. During winter invertebrates prevailed, followed by a lower percentage of vertebrates and scarce plant remains. Invertebrates also were predominant during spring, whereas plant material and vertebrates composed very low percentages.

Further evidence of king penguins’ breeding range extension at the South Shetland Islands?

Short Note Further evidence of king penguins’ breeding range extension at the South Shetland Islands? MARIANA A. JUÁRES, JAVIER NEGRETE, JORGE A. MENNUCCI, PABLO J. PERCHIVALE, MERCEDES SANTOS, EUGENIA MOREIRA and NÉSTOR R. CORIA Departamento Biologı́a de Predadores Tope, Instituto Antártico Argentino, Balcarce 290, C1064AAF, Buenos Aires, Argentina Consejo Nacional de Investigaciones Cientı́ficas y Técnicas, Av. Rivadavia 1917, C1033AAJ, Buenos Aires, Argentina marianajuares@hotmail.com

Adélie penguin population changes at Stranger Point: 19 years of monitoring

Abstract The Adélie penguin (Pygoscelis adeliae) breeding population at Stranger Point, King George Island (25 de Mayo), increased in number from 1965/66 until 1980/81 after which it started to decrease almost continuously up to the present. A significant decrease in the number of breeding pairs and chicks crèched was observed between 1995/96 and 2013/14 (75% and 78%, respectively), although the rate of this decrease has slowed since 2006/07. Over the last seven years, larger interannual fluctuations were recorded in the number of breeding pairs and chicks in crèches, as well in the breeding success. The values for the index of breeding success during 2007/08, 2009/10 and 2012/13 were low and this parameter showed higher temporal fluctuation in the period 2007/08 to 2013/14. The reduction in breeding success and the number of chicks reared to crèche will unfavourably impact on future population size at Stranger Point through the reduction of new recruits. Although Adélie penguin population trends on the Antarctic Peninsula are linked to the marine environment variability (i.e. reduction in sea ice affecting the availability of prey), breeding success is also influenced by the amount of snow fall which has increased in recent years.

Better late than never? Interannual and seasonal variability in breeding chronology of gentoo penguins at Stranger Point, Antarctica

Rapid climate change recorded in the western Antarctic Peninsula confronts species with less predictable conditions in the marine and terrestrial environments. We analysed the breeding chronology and nesting site selection of gentoo penguins (Pygoscelis papua) at King George Island (Isla 25 de Mayo), Antarctica, during four seasons in which differences in snow presence and persistence on the ground were observed. We recorded an overall delay as well as seasonal asynchrony at the beginning of reproduction for those years with higher snow deposition. A redistribution of breeding groups was also observed. Nevertheless, the population breeding success and chicks’ weight at fledging remained relatively constant, despite the delay in breeding chronology, the increased duration of foraging trips during the guard stage and the decreased weight of stomach contents during the crèche stage. We suggest that the plasticity of their trophic biology, along with the flexibility of their breeding phenology and relocation of breeding groups, may be complementary reasons why gentoo penguin populations in the region have remained stable in spite of the changing conditions currently registered.

Morphology of the tympanic‐basicranial region in Mirounga leonina (Phocidae, Carnivora), postnatal ontogeny and sexual dimorphism

The auditory region of pinnipeds has seldom been described. Here we describe and analyze the ontogenetic trajectory of the tympanic bulla of the southern elephant seal, Mirounga leonina (Phocidae, Mammalia). This species is extremely sexually dimorphic and highly polygynous (organized in harems). We examined 118 specimens, arranged in three age classes (CI, CII, and CIII), ranging from newborn to adults (males and females). To analyze the overall size and shape of the tympanic bulla we performed a geometric morphometric analysis including 87 skulls. Females reach definitive shape and size of the bulla at earlier ontogenetic stages than males, in agreement with their earlier involvement in reproductive activities. The internal anatomy of the tympanic region (e.g. form and extension of the paries) does not show remarkable differences between sexes or age classes. The greatest differences between age classes are related to bone thickness, resulting from the apposition of new annual layers. An examination of possible sex‐related external differences among age classes shows significant shape differences between males and females in CIII. The morphology observed in neonates is conserved across all individuals from CI, which included specimens up to 1 year old. Clear morphological differences were observed between CI individuals, on one hand, and CII individuals plus CIII females on the other. During cranial development of both male and females, the glenoid cavity expands and compresses the bulla; this condition reaches its maximum expression in CIII males. CIII males showed the greatest morphological differences, with respect to both CI and CII individuals, and CIII females.

Aves, Charadriiformes, Scolopacidae, Limosa haemastica (Linnaeus, 1758): first record from South Shetland Islands and Antarctic Peninsula, Antarctica

We report herein the southernmost record of the Hudsonian Godwit ( Limosa haemastica ), at two localities in the Antarctic: Esperanza/Hope Bay (January 2005) and 25 de Mayo/King George Island (October 2008). On both occasions a pair of specimens with winter plumage was observed.

The tympanic region of Otaria byronia (Otariidae, Carnivora) – morphology, ontogeny, age classes and dimorphism

Here we describe and explore for the first time the ontogeny and sexual dimorphism of the auditory region of Otaria byronia. We studied the tympanic region of skulls of 237 specimens of different ages and sexes. Geometric morphometric methods were used to analyze the tympanic bulla. In addition, 3D reconstructions of the tympanic bulla were performed using computed tomography analysis scans and a serial wearing technique. We provide a description of the external and internal morphology of the tympanic bulla in both sexes and across different stages (bioclasses). The average shape of the bulla in O. byronia has a subtriangular contour, with variations between sexes and ages. Each stage (bioclasses I, II, and III) is characterized by the respective mean shape of the tympanic bulla and designated as a morphoclass (1, 2, and 3). In all cases, the ectotympanic shows greater surface area than the endotympanic, as in other otariids, in contrast to Phocidae. During ontogeny, the relative size of the ectotympanic increases, growing in all directions and covering the endotympanic. This pattern is seen to the greatest extent in adult males, in which the ectotympanic forms an extremely well‐developed apophysis jugulare. No differences in internal morphology of the tympanic cavity were recorded between ages and sexes. The bulla does not increase in thickness in successive age classes; in fact, the walls are extremely thin in the adult stages, despite the extensive development of its processes. This pattern is opposite that observed in Phocidae. In morphoclass 3, adult males older than 7 years undergo hypermorphic change that results in a peramorphic condition when compared to adult females. These changes probably follow the same pattern shown by the rest of the skull and contribute to the marked sexual dimorphism of the species.

Cephalopoda as prey of juvenile Southern elephant seals at Isla 25 de Mayo/King George, South Shetland Islands

The aim of the present study was to enhance the knowledge of the feeding habits of the juvenile component of the population of Southern elephant seals [Mirounga leonina (Linnaeus, 1758)] from Isla 25 de Mayo, South Shetland Islands, age class whose diet information is scarce. A total of 60 individuals were stomach lavaged in the spring - summer seasons of three consecutive years (2003, 2004 and 2005) of which 53.3 % (n = 32) presented food remnants. The Antarctic glacial squid Psychroteuthis glacialis Thiele, 1921 was the dominant prey taxon in terms of frequency of occurrence (68.7%), numerical abundance (60.1%) and biomass (51.5%), contributing 84.1% to the total relative importance index. Other squid prey species of importance were Slosarczykovia circumantartica Lipinski, 2001 in terms of occurrence (37.5%) and numerical abundance (14%) and Moroteuthis knipovitchi Filippova, 1972 in terms of biomass (16%). All identified cephalopod prey taxa are distributed south of the Antarctic Polar Front, except for the squid Martialia hyadesi Rochebrune & Mabille, 1889 which has a circumpolar distribution associated to the Polar Frontal Zone. No significant differences in the sizes of P. glacialis preyed upon by elephant seals were found between sexes and years. However, significant interannual differences were found in the taxonomical composition of their diet. This would be associated with temporal changes in food availability at the foraging areas of seals, which in turn may have been influenced by changes in oceanographic conditions as a result of the El Nino Southern Oscillation (ENSO) phenomenon that occurred during part of the study period. Furthermore, a differential response of males and females to this temporal variation was observed, with the former being also associated to a predation on octopods. This would suggest a sexual segregation in foraging habits of this species from the early stages of its life cycle.

Aggregation of mummified adult crabeater seals (Pinnipedia: Phocidae) in the eastern Antarctic Peninsula: age and sex structure, taphonomy and cause of death

Abstract In Antarctica, crabeater seals tend to strand as immature animals with disorientation, due to their inexperience, given as the probable cause. In 2012 and 2013, we examined a group of 80 mummified crabeater seals on Seymour Island (Marambio). The age and gender of 28 seals was determined, and virology and stomach content analyses were performed in order to determine the cause of stranding. Around 82% of the seals examined were adults and 79% were females, some of which were pregnant. All of the seals sampled tested negative for Morbillivirus, suggesting that the stranding was not related to the mass mortality event reported in the 1950s in the region. Most seals had empty stomachs and thin blubber suggesting that they died from starvation. The state of the carcasses suggests multiple stranding events. Most of the seals were located along an ice-covered stream, suggesting that this may act as a ‘natural trap’, isolating the seals from the open ocean. This is exceptional as it is the first report of mostly adult female seals to strand in Antarctica and refutes the theory that only young animals are prone to stranding.