Circulating nutrient concentrations in free-ranging Humboldt penguins (Spheniscus humboldti) in Punta San Juan, Peru.

Free-ranging Humboldt penguin (HP, Spheniscus humboldti) populations are under pressure from resource competition with industrial fisheries, habitat loss, and El Niño Southern Oscillation events. Foraging patterns for this top marine predator change during periods of aberrant oceanographic conditions and scarce fish stock numbers. These radical dietary fluctuations can lead to poor fertility, early embryonic death, poor hatchability, suppressed immune function, high chick mortality, and illness. To understand the variability of nutrient status in reproductive seasons, we measured select circulating nutrient concentrations (fat-soluble vitamins A, D, E, and carotenoids, fatty acids, amino acids, minerals, and electrolytes) of 105 HP at Punta San Juan, Peru during the first reproductive seasons of 2007 and 2008. We determined significant differences in nutrient status between sexes, years of sampling, and reproductive stages. Males (4.5 ± 0.38 kg) weighed more than females (4.0 ± 0.29 kg) and exhibited higher concentrations of vitamin A (0.71 ± 0.11 vs. 0.61 ± 0.12 µg/ml) and docosahexaenoic acid (6.70 ± 1.61 vs. 5.65 ± 1.59%). Males also displayed lower concentrations of ß-carotene (0.01 ± 0.01 vs. 0.012 ± 0.001 µg/ml) and phosphorus (3.43 ± 0.83 vs. 4.40 ± 1.66 mg/dl). Comparison between the 2 years showed most circulating amino acid concentrations were higher in 2007. Significant differences in circulating amino acids and vitamins were also noted between different reproductive stages. These results demonstrate concentrations of nutrients can vary due to the physiological state of the animal, as well as the overall dynamics of their marine ecosystem habitat.

Uncovering population structure in the Humboldt penguin (Spheniscus humboldti) along the Pacific coast at South America.

The upwelling hypothesis has been proposed to explain reduced or lack of population structure in seabird species specialized in food resources available at cold-water upwellings. However, population genetic structure may be challenging to detect in species with large population sizes, since variation in allele frequencies are more robust under genetic drift. High gene flow among populations, that can be constant or pulses of migration in a short period, may also decrease power of algorithms to detect genetic structure. Penguin species usually have large population sizes, high migratory ability but philopatric behavior, and recent investigations debate the existence of subtle population structure for some species not detected before. Previous study on Humboldt penguins found lack of population genetic structure for colonies of Punta San Juan and from South Chile. Here, we used mtDNA and nuclear markers (10 microsatellites and RAG1 intron) to evaluate population structure for 11 main breeding colonies of Humboldt penguins, covering the whole spatial distribution of this species. Although mtDNA failed to detect population structure, microsatellite loci and nuclear intron detected population structure along its latitudinal distribution. Microsatellite showed significant Rst values between most of pairwise locations (44 of 56 locations, Rst = 0.003 to 0.081) and 86% of individuals were assigned to their sampled colony, suggesting philopatry. STRUCTURE detected three main genetic clusters according to geographical locations: i) Peru; ii) North of Chile; and iii) Central-South of Chile. The Humboldt penguin shows signal population expansion after the Last Glacial Maximum (LGM), suggesting that the genetic structure of the species is a result of population dynamics and foraging colder water upwelling that favor gene flow and phylopatric rate. Our findings thus highlight that variable markers and wide sampling along the species distribution are crucial to better understand genetic population structure in animals with high dispersal ability.

Determination of Tear Production and Intraocular Pressure With Rebound Tonometry in Wild Humboldt Penguins ( Spheniscus humboldti ).

Tear production and intraocular pressures (IOPs) were determined in 38 and 102 wild Humboldt penguins (Spheniscus humboldti), respectively, from the Punta San Juan Marine Protected Area in Ica, Peru. Tear production was measured by Schirmer tear test, and IOP was measured with a TonoVet rebound tonometer. Adult (n = 90) and chick (n = 12) penguins were sampled from 2 different beaches (north and south facing) during 2 sampling years (2010 and 2011). Results showed a mean ± SD (range) of 9 ± 4 (2-20) mm/min for tear production and 28 ± 9 (3-49) mm Hg for IOP. Tear production in penguins differed between beach and sex, whereas IOP differed between age, year, and beach. The IOPs were negatively correlated with packed cell volume. Tear production and IOP values had greater variation in this population than it has in other avian species. Previous investigations of IOP and tear production in Spheniscus species were conducted with birds housed under professional care in artificial marine and freshwater environments. This is the first study, to our knowledge, investigating tear production and IOP in wild penguins and establishes valuable reference intervals for this species.