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Maximum diving depth and diving patterns of the Gentoo penguin Pygoscelis papua at the Crozet Islands
Abstract
Results from 15 birds showed that the individual maximum dive depths ranged from 40-210 m. The accumulated time spent shallow and flat bottomed diving was 24.5 and 75.4% of the total time spent under water, respectively. Dive duration was positively related to maximum depth. There was a positive relationship between the time spent at the bottom and depth. Stomach flushing indicated that the prey was exclusively Euphausia vallentini. -from Authors
... Authors did suggest that larger bill and body size in males (Valenzuela-Guerra et al. 2013) may be driving this difference. However, other studies have also found no sex related differences in diet or diving behaviour (Croxall et al. 1988, Bost et al. 1994, and rather suggest that differing results across studies might be expected due to temporal and/or spatial variation in prey and foraging habitat availability . ...
... Roads, but far less accessible to those birds at Steeple Jason where the 100m isobath is in close proximity to the island. Although gentoo penguins have been recorded to dive as deep as 210 m (Bost et al. 1994), their typical depth range of 30-50 m , Miller et al. 2009, Kokubun et al. 2010) makes them far more suited to the consumption of benthic prey around the eastern part of the Falkland Islands. ...
Marine top predators often occupy broad geographical ranges that encompass varied habitats. Therefore, a pre-requisite towards conserving these animals is to determine the components of their realized niche, and investigate whether a species is a specialist or a generalist. For generalist species, it is also necessary to understand if local specialisation occurs. Uncovering these components can allow us to build models of a species realized niche that may then be used to infer habitat use in unsampled locations. However, fully understanding the components of a marine top predators realized niche is challenging owing to the limited opportunity for in situ observations. Overcoming these limitations is a key step in marine top predator research. It will enhance our understanding of trophic coupling in marine systems, and aid in the development of tools to better study these predators in their dynamic environment.
Seabirds, penguins (Spheniscids) in particular, are a group of animals for which investigating their realized niche is of vital importance. This is because numerous species face growing uncertainty in the Anthropocene, and in a time of rapid environmental change there is furthermore a need to better understand the potential use of these birds as indicators of ecosystem health. The aim of this thesis, therefore, is to investigate the foraging ecology of gentoo penguins (Pygoscelis papua) at the Falkland Islands. At the Falkland Islands, limited historical information exists regarding this species foraging ecology, with most information coming from a single location at the Falklands. As the Falkland Islands have the world’s largest population of gentoo penguins, elucidating factors influencing this population will have global relevance. Furthermore, historical information indicated potential competition with fisheries, and with prospecting for hydrocarbons and an inshore fishery, there is a need to understand the distribution of these birds across the islands. Penguins are also well suited to carry biologging devices allowing for in situ observations of inter and intraspecific interactions, as well as habitat specific interactions.
In this study, I sampled birds over three breeding seasons, from four breeding colonies - chosen for their varied surrounding at sea habitat - across the Falkland Islands. I investigated the diet with stomach content and stable isotope analysis, the at-sea distribution with GPS and time depth recorders, and how these birds behaved at sea using custom made animal-borne camera loggers. Furthermore, I developed a method to recognise prey encounter events from back mounted accelerometers, using a supervised machine learning approach.
As part of the first species specific description of diet at this scale for the Falklands, I revealed six key prey items for the birds: rock cod (Patagonotothen spp.), lobster krill (Munida spp.), Falkland herring (Sprattus fuegensis), Patagonian squid (Doryteuthis gahi), juvenile fish (likely all nototheniids), and southern blue whiting (Micromesistius australis). The use of animal-borne camera loggers verified that not only do gentoo penguins consume a diverse array of prey items, but they adopted various methods to capture and pursue prey, with evidence of birds following optimal foraging theory.
Prey composition varied significantly between study sites with the at-sea distribution and habitat use of penguins reflecting that of local prey. Birds from colonies close to gently sloping, shallow waters, foraged primarily in a benthic manner and had larger niche widths. However, those at a colony surrounded by steeply sloping, deeper waters, typically foraged in a pelagic manner. Contrasting diet patterns were also prevalent from stable isotope data, and the niche widths of birds relating to both stomach content and stable isotope data were larger at colonies where benthic foraging was prevalent. Therefore, it was clear that surrounding bathymetry played a key role in shaping this species’ foraging ecology, and that at the population level at the Falkland Islands birds are generalists. However, at individual colonies some specialisation occurs to take advantage of locally available prey.
I developed habitat distribution models - via boosted regression trees – which transferred well in time but poorly across space. Reasons for poor model transfer might relate to the generalist foraging nature of these birds and the reduced availability of environmental predictors owing to the limited range of these birds. I furthermore developed a method to identify prey encounter events that can also, to a degree, distinguish between prey items. This method will be a promising approach to refine habitat distribution models in future. These habitat distribution models could potentially contribute to marine spatial planning at the Falkland Islands.
Footage from animal-borne camera loggers clearly showed that prey behaviour can significantly influence trophic coupling in marine systems and should be accounted for in studies using marine top predators as samplers of mid to lower trophic level species. Ultimately, flexibility in foraging strategies and inter-colony variation will play a critical role when assessing factors such as inter-specific competition or overlap with anthropogenic activities.
... It has been demonstrated that African penguins Spheniscus demersus (closely related to Magellanic penguins) and chinstrap penguins Pygoscelis Antarctica (closely related to Gentoo penguins) are attracted to the odour of dimethyl sulphide DMS generated by some prey species in the water at a distance of up to 23 km, therefore scent may be an important cue for penguins to find prey patches (Wright et al. 2011;Amo et al. 2013). In addition, Gentoo penguins are able to dive to depths of 200 m (Bost et al. 1994) which is the threshold of light penetrance in sea water. Individuals may choose to hunt at the limit of visibility either as a mechanism to reduce prey awareness or adjusting to behaviour of prey that has vertical migrations, such as sprat, and reaches shallower depths at night (Diez et al. 2017). ...
Seabirds coexist within colonies yet the role of conspecifics, whilst foraging is still poorly understood. In the 2019/20 and 2020/21 breeding seasons Magellanic penguins Spheniscus magellanicus and Gentoo penguins Pygoscelis papua were equipped with video loggers and GPS devices (n = 3 and n = 2, respectively) or only GPS devices (n = 11 and n = 2) at Martillo Island (54°54′ S, 67°23′ W), Argentina and compared with GPS tracks from previous seasons (2014, 2015 and 2017). Magellanic penguins transited in groups with conspecifics to the feeding grounds (up to 13 individuals were recorded simultaneously) in search of pelagic Fuegian sprat Sprattus fuegensis, but then were not filmed in close company of conspecifics during prey capture. Gentoo penguins generally fed on Nototheniid sp. at the seafloor. Contrary to predictions, Gentoo penguins foraged with conspecifics in small groups of 2–4 individuals, they coordinated to dive down, search and ambush prey. Gentoo penguins were also recorded foraging pelagically on Fuegian sprat. Conspecifics play an important role either during the initial search for prey patches, particularly when searching for elusive pelagic prey or during the small-scale search and hunt for benthic prey hidden in the seafloor substrate. The presence of conspecifics seems to be important during foraging for Magellanic and Gentoo penguins and this may be reflecting a positive aspect of coloniality.
... Total krill biomass encountered on a given survey day (only considering our 20 nautical mile survey line) ranged from 27.2 to 1075.4 tons WW in the Adélie region and from 18.9 to 1266.6 tons WW in the gentoo region, indicating no shortage of krill for penguins within each foraging region, and plenty of prey left over for other krill predators foraging in the region such as whales, seals, fishes, and flying seabirds. In addition, Palmer region penguins forage relatively close to colonies ($ 8-25 km) compared to penguins in other locations where foraging trips can reach 100 km (Williams 1995), and both species are capable of much deeper dives than are seen in the Palmer region (Bost et al. 1994;Watanuki et al. 1997), further supporting that penguins do not appear to be limited by krill in this area. ...
The Palmer Deep canyon along the West Antarctic Peninsula is a biological hotspot with abundant phytoplankton and krill supporting Adélie and gentoo penguin rookeries at the canyon head. Nearshore studies have focused on physical mechanisms driving primary production and penguin foraging, but less is known about finer‐scale krill distribution and density. We designed two acoustic survey grids paired with conductivity–temperature–depth profiles within adjacent Adélie and gentoo penguin foraging regions near Palmer Station, Antarctica. The grids were sampled from January to March 2019 to assess variability in krill availability and associations with oceanographic properties. Krill density was similar in the two regions, but krill swarms were longer and larger in the gentoo foraging region, which was also less stratified and had lower chlorophyll concentrations. In the inshore zone near penguin colonies, depth‐integrated krill density increased from summer to autumn (January–March) independent of chlorophyll concentration, suggesting a life history‐driven adult krill migration rather than a resource‐driven biomass increase. The daytime depth of krill biomass deepened through the summer and became decoupled from the chlorophyll maximum in March as diel vertical migration magnitude likely increased. Penguins near Palmer Station did not appear to be limited by krill availability during our study, and regional differences in krill depth match the foraging behaviors of the two penguin species. Understanding fine‐scale physical forcing and ecological interactions in coastal Antarctic hotspots is critical for predicting how environmental change will impact these ecosystems.
... In P. papua, the recess was completely air-filled, no soft tissue was detectable. Assuming that the tissue found in this study is a corpus cavernosum, its distribution in the different taxa is possibly correlated with varying diving depth of the three species with S. demersus reaching around 130 m (Wilson 1985) and P. papua reaching 210 m (Bost et al. 1994). ...
Ear morphology of three penguin species (Aptenodytes forsteri, Pygoscelis papua and Spheniscus demersus) was analyzed using diffusible iodine-based contrast-enhanced computed tomography (diceCT). Main aural structures were visualized and the results were animated in 3D videos as open educational resources to facilitate UNESCOs mandate for a free use of these digital models for scholars and teachers. Based on the annotated segmentations, the morphology of main structures of the penguin ear is described. In general, the penguin ear can be regarded as an organ for the reception of air sound with adaptations to the semiaquatic lifestyle of the animals. No alternative pathways for the reception of sound in water, as are known in aquatic vertebrates, were detected by the used methods so far. The significance of missing contralateral connections between the air-filled spaces of the middle ear needs further evaluation in that respect. The low relation of the area of the tympanic membrane to the columella footplate and a potential venous corpus cavernosum in the middle ear are discussed as important factors for pressure regulation and for the protection of the sensitive tympanic membrane. Our results indicate that penguins have at least basic abilities to hear underwater even under high ambient pressures.
... The king penguin (KP) is a large oceanic species that feed on mesopelagic fish (myctophids) at deep depths (100-300 m) in distant southern foraging grounds located in the vicinity of the Polar Front [20][21][22] . In contrast, the medium-sized gentoo penguin (GP) is a coastal neritic species that dive both pelagically and benthically to feed opportunistically on a large diversity of prey, including swarming crustaceans and benthic fish 23,24 . The smaller and closely-related macaroni (MP) and rockhopper (RP) penguins forage in offshore waters where they primarily target swarming crustaceans (euphausiids and hyperiids) in the top 70 m of the water column 21,[24][25][26] . ...
Seabirds are widely used as bioindicators of mercury (Hg) contamination in marine ecosystems and the investigation of their foraging strategies is of key importance to better understand methylmercury (MeHg) exposure pathways and environmental sources within the different ecosystems. Here we report stable isotopic composition for both Hg mass-dependent (e.g. δ202Hg) and mass-independent (e.g. Δ199Hg) fractionation (proxies of Hg sources and transformations), carbon (δ13C, proxy of foraging habitat) and nitrogen (δ15N, proxy of trophic position) in blood of four species of sympatric penguins breeding at the subantarctic Crozet Islands (Southern Indian Ocean). Penguins have species-specific foraging strategies, from coastal to oceanic waters and from benthic to pelagic dives, and feed on different prey. A progressive increase to heavier Hg isotopic composition (δ202Hg and Δ199Hg, respectively) was observed from benthic (1.45 ± 0.12 and 1.41 ± 0.06‰) to epipelagic (1.93 ± 0.18 and 1.77 ± 0.13‰) penguins, indicating a benthic-pelagic gradient of MeHg sources close to Crozet Islands. The relative variations of MeHg concentration, δ202Hg and Δ199Hg with pelagic penguins feeding in Polar Front circumpolar waters (1.66 ± 0.11 and 1.54 ± 0.06‰) support that different MeHg sources occur at large scales in Southern Ocean deep waters.
... The king penguins (KP) is a large oceanic species that feed on mesopelagic fish (myctophids) at deep depths (100-300 m) in distant southern foraging grounds located in the vicinity of the Polar Front (Kooyman et al., 1992;Bost et al., 2015). In contrast, the medium-sized gentoo penguin (GP) is a coastal neritic species that dive both pelagically and benthically to feed opportunistically on a large diversity of prey, including swarming crustaceans and benthic fish (Bost et al., 1994;Ridoux, 1994). The smaller and closely-related macaroni (MP) and rockhopper (RP) penguins forage in offshore waters where they primarily target swarming crustaceans (euphausiids and hyperiids) in the top 70 m of the water column (Ridoux 1994;Y. ...
Despite their distance from industrial pressure, marine southern and Antarctic environments are contaminated by worldwide distributed pollutants, such as mercury (Hg), through atmospheric transport and oceanic currents. So far, Hg contamination pathways in the Southern Ocean remains poorly understood, particularly in the Indian sector, and new studies are required to elucidate its fate and impact in these regions. Seabirds, as top predators of marine food webs, are exposed to elevated concentrations of biomagnified methylmercury (MeHg) via dietary intake and moreover, they forage in the different marine compartments both in spatial and depth terms. Therefore, they are considered as effective bioindicators of Hg environmental contamination and the good knowledge of their ecological characteristics permits their application for tracing Hg in such remote environments otherwise of difficult access. The main objective of this doctoral work is the characterization of the exposure pathways of the MeHg accumulated in model seabirds and the identification of the processes involved in the Hg biogeochemical cycle in the Southern Ocean (from Antarctic to subtropical waters). The proposed methodological approach consisted on the combination of Hg isotopic composition and Hg speciation in tissues of a precise selection of seabirds of the Southern Ocean. In a first step, the evaluation of tissue-specific Hg isotopic signatures was accomplished notably in blood and feathers, as they can be non-lethally sampled. In chicks, both tissues can be effectively and indifferently used for biomonitoring of local contamination using Hg isotopes, whereas in adults each tissue provides access to different temporal exposure : blood at recent scale (i.e. exposure during the breeding period) and feathers at annual scale, thus providing complementary isotopic information at the different stages of seabird annual cycle. A second part was focused on the exploration of MeHg sources in four penguin species within a same subantarctic location, the Crozet Islands. Hg isotopes effectively discriminated the four populations and species-specific foraging habitats and latitudinal movements were found the main factors determining their exposure to distinct environmental MeHg sources. In a third part, Hg isotopes were investigated in two ubiquitous seabird models (skua chicks and penguins) over a large a latitudinal scale from Antarctica to the subtropics. Latitudinal variations of Hg isotopic values (δ202Hg, Δ199Hg) appeared to be influenced by different extent of photochemical processes and other biogeochemical pathways such as Hg reduction, and methylation/demethylation processes, as well as trophic or metabolic processes.
... Lepidonotothen larseni, Parachaenichthys georgianus [96,97]) than females, which tend to be limited to shallower pelagic waters. However, Croxall et al. [89] and Bost et al. [98] found no significant differences in the diving parameters of male and female Gentoo penguins. With such flexibility in their diet and in foraging habitat, male Gentoo penguins may be more resilient, especially in years when pelagic prey (i.e. ...
Knowledge about sexual segregation and gender-specific, or indeed individual specialization , in marine organisms has improved considerably in the past decade. In this context, we tested the " Intersexual Competition Hypothesis " for penguins by investigating the feeding ecology of Gentoo penguins during their austral winter non-breeding season. We considered this during unusual environmental conditions (i.e. the year 2009 had observations of high sea surface and air temperatures) in comparison with the long term average at Bird Island, South Georgia. Through conventional (i.e. stomach contents) and stable isotopic values from red blood cells, plasma and feathers of both male and female Gentoo penguins, we showed that there were significant differences between sexes, with males feeding mainly on fish (54% by mass) followed by crustaceans (38%) whereas females fed mainly on crustaceans (89% by mass) followed by fish (4%). Themisto gaudichaudii was the most important crustacean prey for males (64% by mass; 82% by number; 53% by frequency of occurrence) and females (63% by mass; 77% by number; 89% by frequency of occurrence), contrasting with all previous studies that found Antarctic krill Euphausia superba were generally the main prey. Stable isotopic data showed that, in terms of habitat use (based on δ 13 C), there were significant differences in short-term carbon signatures between males and females (based on plasma and red blood cells), suggesting that both sexes explored different habitats, with females exploring more offshore pelagic waters and males feeding more in coastal benthic waters. Based on δ 15 N, males fed on significantly higher trophic level than females (based on plasma and red blood cells), in agreement with our diet results., Thus, Gentoo penguins behave in a similar manner to other non-breeding penguins species (e.g. king, macaroni and rockhopper penguins)
... The data re-iterate the great flexibility in foraging strategies in gentoo penguins which are largely driven by local conditions. This probably to a large extent explains the resilience to environmental change observed in this species (with an increasing global population as opposed to its congeners which are dietary specialists across their range; see Borboroglu and Boersma (2012)). Furthermore, the study highlights how gentoo penguins would require a multi-faceted approach towards their conservation and management owing to spatial variability in prey consumption. ...
Marine species occupy broad geographical ranges that encompass varied habitats. Accordingly, resource availability is likely to differ across a species range and, in-turn, this may influence the degree of dietary specialization. Gentoo penguins Pygoscelis papua are generalist predators occupying a range of habitats with a large breeding range extending from Antarctica to temperate environments. Using the most extensive stomach content data set on gentoo penguins this study investigated their feeding ecology at the Falkland Islands (52°S, 59.5°W), the world’s largest population. Sampling occured in consecutive breeding seasons (2011–2013), across multiple foraging habitats utilizing stomach content data and carbon and nitrogen stable isotope values of feathers. The first species specific description of diet at this scale for the Falklands revealed six key prey items for the birds: rock cod (Patagonotothen spp.), lobster krill (Munida spp.), Falkland herring (Sprattus fuegensis), Patagonian squid (Doryteuthis gahi), juvenile fish (likely all nototheniids), and southern blue whiting (Micromesistius australis). Niche width, relating to both stomach content and stable isotope data related to the surrounding bathymetry. Birds from colonies close to gently sloping, shallow waters, fed primarily on benthic prey and had larger niche widths. The opposite was observed at a colony surrounded by steeply sloping, deeper waters. Therefore, gentoo penguins at the population level at the Falklands are indeed generalists, however, at individual colonies some specialization occurred to take advantage of locally available prey, resulting in these birds being classified as Type B generalists. Hence, future studies must account for this intra-colony variation when assessing for factors such as inter-specific competition or overlap with anthropogenic activities.
... Gentoo Penguins take mainly fish (chiefly juvenile Notothenia squamifrons, with lesser amounts of myctophids and Channichthys rhinoceratus) and crustaceans (Euphausia vallentini all year, and Nauticaris marionis mainly in winter) (Adams & Klages 1989). They usually dive to less than 40 m at Marion Island (Adams & Brown 1983), but regularly dive to > 100 m, occasionally > 200 m at the Crozet Islands (Bost et al. 1994). Both Macaroni and Rockhopper Penguins feed their chicks mainly on small crustaceans, E. vallentini and Thyssanoessa vicina, with small amounts of fish and squid, especially in Macaroni Penguins (Brown & Klages 1987; Crawford et al. 2003c). ...
... Pütz (1994), stated that the dispersion of myctophid fish close to the surface at night negatively affects prey capture rates of King Penguins. This is supported by results obtained from Gentoo Penguins where Bost et al. (1994) concluded that dive depths in these birds also reflect the distribution of their prey. ...
The Humboldt Penguin Spheniscus humboldti is an endangered species whose population is decreasing over its whole distributional range. In support of conservation efforts, systematic studies are being conducted on the ecology and behaviour of these birds at sea. Time-depth recorders were used to investigate the foraging behaviour of Humboldt Penguins at Isla Pan de Azúcar (26°S, 72°W), northern Chile, during the breeding seasons of 1994/95 and 1995/96. A four-channel logger (MK6, Wildlife Telemetry) equipped with speed, depth, temperature and light-intensity sensors was used to obtain information from 20 foraging trips of 12 penguins, amounting to a total of 301 hours of swimming consisting of 11 011 dives. Birds departed from the colony between 06h00 and 09h00 and returned mainly between 15h00 and 23h00. Distance travelled was strongly correlated with total time spent at sea. Maximum dive depth was 53 m around mid-day when light intensity was maximal. At night maximum depth attained was 12 m. Maximum dive depth was positively correlated with dive duration (r = 0.80), as well as with descent and ascent angle (r = 0.78), and descent and ascent rate (r = 0.86). Dives to between 0.5 and 3 m were interpreted as travelling dives and had a mean depth of 1.6 m. All dives deeper than 3 m were regarded as foraging dives with a mean depth of 11.5 m. Mean dive durations during travelling and foraging were 18.4 s and 47.9 s, respectively. Mean swim speed during travelling was 1.7 m.s-1. Overall speed during foraging dives (descent, bottom and ascent) was 1.9 m.s-1.
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