Do penguins dare to walk at night? Visual cues influence king penguin colony arrivals and departures

Characterisation of cataracts and other ophthalmic findings in various species of captive penguins

BACKGROUND

The identification of ophthalmic diseases that affect vision and/or cause discomfort should be a priority in captive penguins to improve their overall health and quality of life.

METHODS

A routine ophthalmological examination was performed on 80 clinically normal penguins (160 eyes), and any lesions observed were recorded.

RESULTS

Ocular lesions were frequent (56% of penguins), with cataracts being the most common (48.8% of penguins). Cortical cataracts (63% of eyes) and posterior subcapsular cataracts (27.4%) were the most commonly occurring. All maturation stages were found; incipient cataracts (52.1% of eyes with cataracts) were predominant, while Morgagnian cataracts (8.2%) were the least frequent. A correlation existed between lenticular changes and increasing age. Uveitis was present in 43.8% of eyes with cataracts, and ectropion uveae was the predominant clinical sign. Other ocular findings included blepharitis (3.8% of all eyes), corneal leukoma (5.6%) and posterior lens subluxation (7.5%).

LIMITATIONS

The small number of birds of some species prevented the comparison of ophthalmic findings between species.

CONCLUSION

This study corroborates the high prevalence of ocular lesions in captive penguins. Cataracts were frequent and age related. Most cataracts were cortical, and the predominant maturation stage was incipient. Lens-induced uveitis was a common finding. Lowered intraocular pressure was related to cataract formation.

Determination of reference values for tear production and intraocular pressure in Pygoscelis penguins of the Antarctic Peninsula

BACKGROUND

According to the literature review, this is the first study investigating tear production (TP) and intraocular pressure (IOP) in the Pygoscelis penguins living in their natural habitat. The study aimed to establish normal values for standard ocular tests in the genus Pygoscelis, namely, the Adélie (Pygoscelis adeliae), gentoo (Pygoscelis papua), and chinstrap (Pygoscelis antarctica) penguins, in four different islands of Antarctica. Sampling was made by specifically using the left eye of the penguins. The Schirmer's tear test type I (STT-I) and the Tonovet® (rebound tonometer) were used to measure the TP and the IOP, respectively.

RESULTS

The mean TP and IOP values of 129 Adélie, chinstrap, gentoo, and 120 adult Adélie, gentoo penguins were determined as 10.2 ± 4.0 mm/min and 38.9 ± 13.2 mmHg, respectively. No statistical difference was detected between the penguin species for the mean IOP values, while the difference was determined in all the locations. However, statistical differences in the mean TP values were determined between all locations.

CONCLUSION

The results of this study provide a reference range of Schirmer's tear test (STT) and IOP values in Pygoscelis penguins and show that the IOP is significantly affected by locations. This result can be attributed to the harsh climatic conditions of the Antarctic Peninsula that change very quickly. The described data may help diagnose clinical pathological findings in Pygoscelis penguins. The STT and rebound tonometry appears to be safe and reproducible methods in Pygoscelis penguins, as the results were obtained quickly and were well tolerated by the birds. Based on our results, we propose that similar studies can be initiated in crowded colonies of three penguin species of this genus on the Antarctic Peninsula, the southern Shetland Islands, and other frequently visited islands in Antarctica.

Long walk home: Magellanic penguins have strategies that lead them to areas where they can navigate most efficiently

Understanding how animals move in dense environments where vision is compromised is a major challenge. We used GPS and dead-reckoning to examine the movement of Magellanic penguins commuting through vegetation that precluded long-distance vision. Birds leaving the nest followed the shortest, quickest route to the sea (the 'ideal path', or 'I-path') but return tracks depended where the birds left the water. Penguins arriving at the beach departure spot mirrored the departure. Most of those landing at a distance from the departure spot travelled slowly, obliquely to the coast at a more acute angle than a beeline trajectory to the nest. On crossing their I-path, these birds then followed this route quickly to their nests. This movement strategy saves birds distance, time and energy compared to a route along the beach and the into the colony on the I-track and saves time and energy compared to a beeline trajectory which necessitates slow travel in unfamiliar areas. This suggests that some animals adopt tactics that take them to an area where their navigational capacities are enhanced for efficient travel in challenging environments.

The ocular pyogranulomatous lesion in a Gentoo penguin (Pygoscelis papua) from the Antarctic Peninsula: evaluation of microbiological and histopathological analysis outcomes

In this study, it was aimed to present the results of microbiological, cytological, histopathological, and immunohistochemical analyses of ocular samples from an Antarctic (Ardley Island, King George Island) Gentoo penguin chick (Pygoscelis papua) with a pyogranulomatous lesion in the right eye. Samples were taken from both the healthy left eye and the lesion in the right eye. Conventional culture methods and phenotypic and molecular tests were used for bacterial isolation and identification, respectively. None of the isolates could be identified phenotypically. As a result, four of the five isolates obtained from the right eye were considered to belong to putative novel bacterial species and taxa as their similarity to GenBank data was below 98.75%. The isolates were considered to be Pasteurellaceae bacterium, Corynebacterium ciconiae, Cardiobacteriaceae bacterium, Actinomyces sp., and Dermabacteraceae bacterium. The only isolate from the left eye was identified as Psychrobacter pygoscelis. The cytological analysis demonstrated cell infiltrates composed mostly of degenerate heterophils, reactive macrophages, plasma cells, lymphocytes, and eosinophils. Based on histopathological findings, the lesion was defined as a typical pyogranulomatous lesion. Immunohistochemistry demonstrated that the granuloma was positive for TNF-α, IL-4, MMP-9, IL-1β, and IL-6. This is the first documented report of the unilateral pyogranulomatous ocular lesion in a Gentoo penguin chick, living in its natural habitat in Antarctica. This report also describes the isolation of four bacteria from the infected eye, which are considered to belong to novel Genus, species, or taxa. The primary bacterial pathogen that caused the ocular lesion was not able to be detected and remains unclear.

Inter-Annual Variability of Fledgling Sex Ratio in King Penguins

As the number of breeding pairs depends on the adult sex ratio in a monogamous species with biparental care, investigating sex-ratio variability in natural populations is essential to understand population dynamics. Using 10 years of data (2000–2009) in a seasonally monogamous seabird, the king penguin (Aptenodytes patagonicus), we investigated the annual sex ratio at fledging, and the potential environmental causes for its variation. Over more than 4000 birds, the annual sex ratio at fledging was highly variable (ranging from 44.4% to 58.3% of males), and on average slightly biased towards males (51.6%). Yearly variation in sex-ratio bias was neither related to density within the colony, nor to global or local oceanographic conditions known to affect both the productivity and accessibility of penguin foraging areas. However, rising sea surface temperature coincided with an increase in fledging sex-ratio variability. Fledging sex ratio was also correlated with difference in body condition between male and female fledglings. When more males were produced in a given year, their body condition was higher (and reciprocally), suggesting that parents might adopt a sex-biased allocation strategy depending on yearly environmental conditions and/or that the effect of environmental parameters on chick condition and survival may be sex-dependent. The initial bias in sex ratio observed at the juvenile stage tended to return to 1∶1 equilibrium upon first breeding attempts, as would be expected from Fisher’s classic theory of offspring sex-ratio variation.

The invisible cues that guide king penguin chicks home. The use of magnetic and acoustic cues during orientation and short-range navigation

King penguins (Aptenodytes patagonicus) live in large and densely populated colonies, where navigation can be challenging due to the presence of many conspecifics that could obstruct locally available cues. Our previous experiments demonstrated that visual cues were important but not essential for king penguin chicks' homing. The main objective of this study was to investigate the importance of non-visual cues, such as magnetic and acoustic cues, for chicks' orientation and short-range navigation. In a series of experiments, the chicks were individually displaced from the colony to an experimental arena where they were released under different conditions. In the magnetic experiments, a strong magnet was attached to the chicks' heads. Trials were conducted in daylight and at night to test the relative importance of visual and magnetic cues. Our results showed that when the geomagnetic field around chicks was modified, their orientation in the arena and the overall ability to home was not affected. In the low sound experiment we limited the acoustic cues available to the chicks by putting ear pads over their ears, and in the loud sound experiment we provided additional acoustic cues by broadcasting colony sounds on the opposite side of the arena to the real colony. In the low sound experiment, the behavior of the chicks was not affected by the limited sound input. In the loud sound experiment, the chicks reacted strongly to the colony sound. These results suggest that king penguin chicks may use the sound of the colony while orienting towards their home.