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... The P. harroweri southern distribution limit is around the coast of Rio Grande do Sul, about 30°S (Di Dario et al., 2017). This species distribution was reflected in the absence of P. harroweri among the main prey items in FMAs III and IV (Paso-Viola et al., 2014;Denuncio et al., 2017;Franco-Trecu et al., 2017;Tellechea et al., 2017). Pellona harroweri is pelagic, contrasting with the demersal habits of I. parvipinnis and Stellifer sp.; the latter two are typically found close to unconsolidated substrates and usually found in coastal and estuarine waters in at least one stage of their life cycle (Fischer et al., 2011). ...
... The average size of consumed fish was 5.25 cm (see Table 2), smaller than the average length (up to 11 cm) observed in other FMAs (e.g. Di Beneditto & Ramos, 2001;Rodriguez et al., 2002;Bittar & Di Beneditto, 2009;Cremer et al., 2012;Denuncio et al., 2017;Tellechea et al., 2017). The observed small prey sizes are often associated with younger development stages of the prey species (Cousseau & Perrota, 2000;Fischer et al., 2011). ...
... Therefore, juvenile and adult individuals may also be important for the feeding habits of franciscana dolphins, especially due to their contribution to the ingested biomass. The consumed cephalopods were generally larger than fish (mean = 8.6 cm) as observed in previous studies (Rodriguez et al., 2002;Paso-Viola et al., 2014;Denuncio et al., 2017). ...
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This study evaluated the feeding habits of the franciscana dolphin ( Pontoporia blainvillei ) in south-eastern Brazil. Stomach contents were collected from a total of 145 dead specimens found incidentally caught by fishing vessels or stranded between 2005 and 2015. Fish otoliths, cephalopod beaks and whole non-digested prey were used for prey species identification. A total of 9337 prey items were identified, including 26 species of teleost fishes and three species of cephalopods. The most important prey families were Sciaenidae among fish and Loliginidae among cephalopods. Franciscana dolphins tended to feed on small fish (mean = 5.25 cm) and cephalopods (mean = 8.57 cm). The index of relative importance (IRI) showed that Pellona harroweri and Doryteuthis plei were the most important prey for both males and females. The PERMANOVA test confirmed that there is no significant difference between the feeding habits of different sexes, but detected a significant difference among seasons. Overall, our results show that franciscana dolphins are predominantly ichthyophagous and non-selective in relation to the type of prey, feeding on pelagic, demersal and pelagic-demersal prey.
... One tool within the NGF, the right-angled mixture triangle (RMT, Box 1, Fig. 1), models foods and diets as their proportional compositions, and thus overcomes the complexities of collecting accurate data on absolute amounts of foods consumed by wild animals in the field (Raubenheimer, 2011). Proportional data modelled in RMTs can be gathered from a wide range of sources including gut content analysis (Tait et al., 2014;Denuncio et al., 2017), regurgitations (Hyslop, 1980;Machovsky-Capuska et al., 2016a, fecal analysis (Panthi et al., 2012) and biologging devices (Machovsky-Capuska et al., 2016b, 2016d. Detailed discussion of the relative strengths and weaknesses of these techniques is beyond the scope of this paper (reviewed in Box 1 Right-angled-mixture models (RMT) user's guide. ...
... RMTs have been increasingly used to address questions in fieldbased nutritional ecology from individuals to populations and species (Tait et al., 2014;Raubenheimer et al., 2015), applied to micro-and macronutrients, and pollutants Nie et al., 2014) within marine (Tait et al., 2014;Machovsky-Capuska et al., 2016b) and terrestrial environments (Rothman et al., 2011;Raubenheimer et al., 2015). This approach has contributed significantly to the study of animal nutrition in the wild across several research disciplines including wildlife conservation (Rothman et al., 2011;Raubenheimer et al., 2015;Denuncio et al., 2017), movement ecology (Nie et al., 2014), human-wildlife interactions (Coogan and Raubenheimer, 2016) and urban ecology Coogan et al., 2017Coogan et al., , 2018, as well as to human nutrition (Raubenheimer and Simpson, 2016). ...
... Given the large range of feeding strategies and forms of plastic that occur within the environment, work is needed to explore whether plastic types shape the nutritional niche breadths of species and populations. To illustrate (Fig. 2), following Machovsky-Capuska et al. (2018), we combined MNNF with standard ellipse areas corrected for small sample sizes (SEAc) on stomach content data extracted from Denuncio et al. (2011Denuncio et al. ( , 2017. We compare the minimal range of dietary compositions that contributes to the nutritional niche breadths of 26 Table 1 Outstanding research questions that emerge from integrating plastic ingestion to nutritional ecology. ...
Article
Although the perils of plastics to living organisms including humans have been neglected for decades, they have recently been recognized as a major environmental problem worldwide. Little progress has been made on understanding the factors that drive species' and populations' susceptibilities to the ingestion of plastic. Here, we propose using nutritional ecology as a multidisciplinary framework for bridging the gaps that link nutrition, behavior, plastics, physiology and ecology. We show that nutritional niches are tightly linked to plastic ingestion, illustrating the application of our framework in the context of nutritional niche theory, habitat-specific foraging from species to populations, and transfer patterns in food webs.
... Viewing dietary niche through this nutritional lens showed that the range of foods eaten represents the food composition niche, whereas the range of diets through feeding on different foods is defined as the realized nutritional niches. Recent studies showed the importance of multidimensional niches to understand the nutritional requirements of endangered wildlife and support effective conservation and management strategies (Machovsky-Capuska et al., 2016b;Denuncio et al., 2017;Nie et al., 2019). For example, Denuncio et al. (2017) showed that sub-populations of endangered Franciscana dolphins (Pontoporia blainvillei) occupied different habitats that are likely related to the nutritional composition of their foods (i.e. ...
... Recent studies showed the importance of multidimensional niches to understand the nutritional requirements of endangered wildlife and support effective conservation and management strategies (Machovsky-Capuska et al., 2016b;Denuncio et al., 2017;Nie et al., 2019). For example, Denuncio et al. (2017) showed that sub-populations of endangered Franciscana dolphins (Pontoporia blainvillei) occupied different habitats that are likely related to the nutritional composition of their foods (i.e. 'food composition niche', Machovsky-Capuska et al., 2016a). ...
... It seems likely to assume that green turtles are dietary generalists, based on the foods they are capable of exploit, as a response to complex nutritionally heterogeneous estuarine environments. Emphasis should thus be placed on establishing the extent to which a species may be considered dietary generalist to identify potential threats and improve conservation strategies for them and their natural habitats (Machovsky-Capuska et al., 2016a;Denuncio et al., 2017). ...
Article
Little attention has been drawn toward the effects of marine debris ingestion in relation to nutrient acquisition and fitness consequences. We tested whether anthropogenic debris ingestion influence the nutritional niches of endangered green turtles (Chelonia mydas) in estuarine and reef habitats on the Brazilian coast. Our results showed that estuarine turtles consumed diets with lower proportional wet mass composition of protein (P) and water (W) than their reef conspecifics. The amounts of debris, mostly plastics, retrieved from the digestive tracts of estuarine turtles were higher compared with those individuals from reefs. The realized nutritional niche from estuarine turtles was subject to the debris density in the environment, lack of benthic food resources available and the surface foraging behavior, likely preventing them from reaching their nutritional goals and resulting in lower fitness. The study provides critical information for the management and conservation of ecologically threatened individuals, populations, and their natural habitats. To access pdf: https://authors.elsevier.com/a/1aX9t,ashxl5A
... Several studies suggest that P. blainvillei has a generalist and opportunistic feeding behaviour, most commonly preying upon demersal fish, cephalopods and crustaceans (Bassoi 2005). At the same time, in Argentina, there is evidence of differences in the trophic habits between P. blainvillei from the estuary and those from oceanic areas (Denuncio et al. 2017;Rodríguez et al. 2002). Indeed, prey species and the frequency of occurrence of some species in the diet of marine and estuarine P. blainvillei differed: Cynosicion guatucupa and cephalopods were the dominant species in the former, and Micropogonias furnieri was the key component of the latter (Rodríguez et al. 2002). ...
... Differences in the trophic habits between P. blainvillei residing in estuaries and those from oceanic areas have been reported (Rodríguez et al. 2002), and this difference has been present prior to the development of fisheries. In addition, Denuncio et al. (2017) recently reported differences in consumed prey and macronutrient composition in the diets of P. blainvillei from three different habitats (estuarine and two marine areas) in Argentina, suggesting a trophic subdivision in the corresponding management area (FMA IV). This subdivision into three populations has already been proposed based on genetic evidence, and supported with behavioural, ecological and environmental information (Mendez et al. 2008). ...
Article
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Context: As top predators, marine mammals play a key role consuming in different trophic levels and the trophic niche characterization may help to understand how species utilize and share resources. On the coast of the Río de la Plata and the South-west Atlantic, the South American sea lion (Otaria flavescens) and the franciscana dolphin (Pontoporia blainvillei) are two important predators. Aims: The present study investigated potential trophic overlap of both species by measuring stable carbon (δ ¹³ C) and nitrogen (δ ¹⁵ N) isotopes over two periods: historical (1959-79) and recent (2002-15) on the Uruguayan coast. Methods: Bone samples of P. blainvillei and O. flavescens were used to determine the isotopic niche using the Stable Isotope Bayesian Ellipses in R (SIBER) analysis. Key results: The isotopic niche did not overlap between species in any period. δ ¹⁵ N was higher in O. flavescens in both periods (20.29‰ ± 0.73 in the historical and 19.95‰ ± 1.0 in the recent period), indicating that it feeds at a higher trophic level than P. blainvillei. The δ ¹³ C was also significantly higher in O. flavescens than in P. blainvillei during the two periods (O. flavescens: -11.43 ± 0.6‰ historic, -12.72 ± 0.4‰ recent, and P. blainvillei: -12.69 ± 1.1‰ historic, -13.84 ± 1.3‰ recent). The isotopic niche areas of P. blainvillei in recent and historic periods confirmed they forage in 2 distinct environments, marine and estuarine, with low isotopic overlap. This overlap was higher in the recent period. Conclusions and Implications: O. flavescens and both P. blainvillei groups were segregated in both periods, with a higher overlap in the recent. These species appear to reduce competition by using different resources in the same coastal habitat. O. flavescens preferentially feeds on benthic fish and showed wider trophic amplitude in both periods, whereas P. blainvillei has a more coastal-pelagic diet and included a greater variability of resources in its diet. The differences between species trophic niches can still be detected after both marine mammals species abundance has declined and after the development of fisheries.
... This nutritionally explicit framework is particularly relevant to marine apex predators known to forage in complex and fluctuating marine environments (Machovsky-Capuska et al., 2016a;Machovsky-Capuska and Raubenheimer, 2020). While the characterization of nutritional niche breadths of marine predators has shown to be critical to trophic interactions, marine pollution, aquaculture, captivity and rehabilitation, climate change, and conservation and management of endangered species (Machovsky-Capuska and , yet the field remains poorly characterized to few species of seabirds (Machovsky-Capuska et al., 2016c, 2016dMiller et al., 2018;Tait et al., 2014), sharks (Grainger et al., 2020;Machovsky-Capuska and Raubenheimer, 2020), turtles , cetaceans (Denuncio et al., 2017;Machovsky-Capuska et al., 2019) and pinnipeds . ...
... It has been suggested that the abundance of small size demersal fishes, as consequence of overfishing, combined with the historical reduction of the SASL population have modified SAFS diet to focus on demersal/pelagic prey over time (Drago et al., 2017;Szteren et al., 2018). Overall, these findings support previous suggestions that marine predators in the wild explore very dynamic marine nutritional environments (Machovsky-Capuska et al., 2016aDenuncio et al., 2017;Machovsky-Capuska and Raubenheimer, 2020). While we recognized the potential uncertainties in the inherent variability of scats and stomach contents combined with spatiotemporal differences in the proximate compositions of prey, the proposed multimethodological approach is likely to overcome these limitations (Majdi et al., 2018;Tait et al., 2014), and provide a unique opportunity to better understand how sympatric marine mammal species coexist in the wild. ...
Article
Niche segregation has been recognized as a valuable mechanism for sympatric species to reduce interspecific competition and facilitate coexistence. The differential use of habitats is one of the behavioural mechanisms that may shape coexistence among marine predators. In this study, we provide a dietary and nutritional assessment of two pinnipeds, the South American sea lion (SASL) and the South American fur seal (SAFS) and explore their sympatric coexistence within the Warm Temperate Southwestern Atlantic biogeographic province (WTSA province). Pelagic prey species within the WTSA province showed significantly higher proportional composition of lipids than demersal counterparts, evidencing a nutritional variability in a vertical dimension accessible to marine predators. By modelling the dietary niches of these pinnipeds through a nutritional lens, we showed high overlapping prey composition niche breadths suggesting that both species consumed prey with similar nutritional composition; however, distinct realized nutritional niches showed that diets are likely shaped by differences in foraging behaviours. The SAFS combined pelagic and demersal prey, whereas SASL mostly preyed upon demersal species. This paper provides crucial information on how nutritional variability in the water column likely drives the feeding strategies of both pinnipeds in the WTSA province. Given that this variation can influence the stability of the contrasting population trends shown by these two pinnipeds, nutritional dynamics must be taken into consideration when defining conservation strategies.
... In contrast to amounts-based geometry, the proportions-based approach offers opportunities for constructing models using data that are routinely collected in marine field studies, including compositional analysis of different food categories, gut content analysis (Croll et al. 1998, Bunce 2001, Majdi et al. 2018, and analysis of predator body compositions (Stansby 1969, Donnelly et al. 1994, Spitz et al. 2010, Denuncio et al. 2017). An important advantage of proportions models is that they plot three nutritional dimensions in a single two-dimensional plot (Figure 4). ...
... Not least among these is the collection and standardization of reliable data for proximate composition analysis of prey that reflect spatiotemporal and species variation and can be linked to foraging behavior and environmental variables (e.g., sea surface temperature), as has been implemented recently in marine environments . A second priority is increased multidisciplinary collaboration to enhance cross-field communication, improve the conservation and management of apex predator populations, and predict how they will respond to impacts on their marine environments (Denuncio et al. 2017). ...
Article
Apex predators play pivotal roles in marine ecosystems, mediated principally through diet and nutrition. Yet, compared with terrestrial animals, the nutritional ecology of marine predators is poorly understood. One reason is that the field has adhered to an approach that evaluates diet principally in terms of energy gain. Studies in terrestrial systems, by contrast, increasingly adopt a multidimensional approach, the nutritional geometry framework, that distinguishes specific nutrients and calories. We provide evidence that a nutritional approach is likewise relevant to marine apex predators, then demonstrate how nutritional geometry can characterize the nutrient and energy content of marine prey. Next, we show how this framework can be used to reconceptualize ecological interactions via the ecological niche concept, and close with a consideration of its application to problems in marine predator research.
... Certainly, knowledge of predator nutritional niche breadths and requirements could assist in understanding their responses to variations in prey availability and composition (Machovsky-Capuska et al., 2016d). Several studies on marine predators, including seabirds (Tait et al., 2014;Machovsky-Capuska et al., 2016b,c;Miller et al., 2017), cetaceans (Denuncio et al., 2017), fish, sharks and pinnipeds (Machovsky-Capuska and Raubenheimer, 2020) have now drawn from the MNNF to provide fresh insights into their nutritional ecology. Machovsky-Capuska et al. (2018) incorporated a standardised metric (standard ellipse area, SEA) and statistical framework utilising Bayesian multivariate ellipses (sensu Jackson et al., 2011) to quantify and compare nutritional niche breadths. ...
... Therefore, initial models with predictors sex + PCL and either a logit or clog-log link were fitted for each prey group and the link giving the lowest AIC c was favoured. Following Denuncio et al. (2017), several candidate binomial GLMs were then fitted within each prey functional group using the predictors sex, PCL, sex + PCL, and a null model with no predictors (intercept only) to investigate whether sex and PCL did not influence prey occurrences. The model with the lowest AIC c was selected for each prey functional group. ...
Article
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Establishing diets and dietary generalism in marine top predators is critical for understanding their ecological roles and responses to environmental fluctuations. Nutrition plays a key mediatory role in species-environment interactions, yet descriptions of marine predators’ diets are usually limited to the combinations of prey species consumed. Here we combined stomach contents analysis (n = 40), literature prey nutritional data and a multidimensional nutritional niche framework to establish the diet and niche breadths of white sharks (Carcharodon carcharias; mean ± SD precaudal length = 187.9 ± 46.4 cm, range = 123.8–369.0 cm) caught incidentally off New South Wales (NSW), Australia. Our nutritional framework also facilitated the incorporation of existing literature diet information for South African white sharks to further evaluate nutritional niches across populations and sizes. Although teleosts including pelagic eastern Australian salmon (Arripis trutta) were the predominant prey for juvenile white sharks in NSW, the diversity of benthic and reef-associated species and batoids suggests regular benthic foraging. Despite a small sample size (n = 18 and 19 males and females, respectively), there was evidence of increased batoid consumption by males relative to females, and a potential size-based increase in shark and mammal prey consumption, corroborating established ontogenetic increases in trophic level documented elsewhere for white sharks. Estimated nutritional intakes and niche breadths did not differ among sexes. Niche breadths were also similar between juvenile white sharks from Australia and South Africa. An increase in nutritional niche breadth with shark size was detected, associated with lipid consumption, which we suggest may relate to shifting nutritional goals linked with expanding migratory ranges.
... Several studies on seabirds (Machovsky-Capuska et al., 2018;Machovsky-Capuska and Raubenheimer, 2020), preda-tory fish , turtles (Machovsky-Capuska et al., 2020a;Santos et al., 2020), cetaceans (Denuncio et al., 2017;Machovsky-Capuska and Raubenheimer, 2020;Machovsky-Capuska et al., 2020b), pinnipeds (Machovsky-Capuska and Denuncio et al., 2021), and sharks (Machovsky-Capuska and Grainger et al., 2020), have increasingly applied the MNNF to (i) understand how marine predators adjust their foraging behaviour and nutritional goals to environmental fluctuations (Machovsky-Capuska et al., 2018); (ii) explore the nutritional consequences of consuming plastics and anthropogenic pollutants (Machovsky-Capuska et al., 2019, 2020aSantos et al., 2020Santos et al., , 2021Stockin et al., 2021a, b); and (iii) disentangle the dynamics that facilitates coexistence with other sympatric species (Denuncio et al., 2021), and examine how they are likely to interact with humans (Grainger et al., 2020). ...
Article
Prey detection and subsequent capture is considered a major hypothesis to explain feeding associations between common dolphins and Australasian gannets. However, a current lack of insight on nutritional strategies with respect to foraging behaviours of both species has until now, prevented any detailed understanding of this conspecific relationship. Here we combine stomach content analysis (SCA), nutritional composition of prey, a multidimensional nutritional niche framework (MNNF) and videography to provide a holistic dietary, nutritional, and behavioural assessment of the feeding association between dolphins and gannets in the Hauraki Gulf, New Zealand. Dolphins consumed ten prey species, including grey mullet (Mugil cephalus) as the most representative by wet mass (33.4%). Gannets preyed upon six species, with pilchards (Sardinops pilchardus) contributing most of the diet by wet mass (32.4%) to their diet. Both predators jointly preyed upon pilchard, jack mackerel (Trachurus spp.), arrow squid (genus Nototodarus), and anchovy (Engraulis australis). Accordingly, the MNNF revealed a moderate overlap in the prey composition niche (0.42) and realized nutritional niche (0.52) between dolphins and gannets. This suggests that both predators coexist in a similar nutritional space, while simultaneously reducing interspecific competition and maximizing the success of both encountering and exploiting patchily distributed prey. Behavioural analysis further indicated that dolphin and gannets feeding associations are likely to be mutually beneficial, with a carouselling foraging strategy and larger pod sizes of dolphins, influencing the diving altitude of gannets. Our approach provides a new, more holistic understanding of this iconic foraging relationship, which until now has been poorly understood.
... Marine apex predators are long-lived species that forage in complex three-dimensional environments and therefore represent an ideal group to better understand dietary generalism in the wild (Denuncio et al., 2017;Machovsky-Capuska, Priddel et al., 2016;Malinowski & Herzing, 2015;Österblom, Olsson, Blenckner, & Furness, 2008;Spitz et al., 2011Spitz et al., , 2012. Understanding the foraging goals of marine predators is pivotal in predicting how they will respond to environmental changes in prey availability and composition (Tait, Raubenheimer, Stockin, Merriman, & Machovsky-Capuska, 2014). ...
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1.Our understanding of the niche concept will remain limited while the quantity and range of different food types eaten remains a dominant proxy for niche breadth, as this does not account for the broad ecological context that governs diet. Linking nutrition, physiology and behaviour are critical to predict the extent to which a species adjusts its nutritional niche breadth at the levels of prey (“prey composition niche”, defined as the range of prey compositions eaten), and diet (“realized nutritional niche” is the range of diets composed through feeding on the prey). 2.Here we studied adult‐chick rearing Australasian gannets (Morus serrator) to propose an integrative approach using sea surface temperature anomalies (SSTa), geographic location and bathymetry over different years, to explore their relationship with the nutritional composition of prey and diets (i.e., prey composition and nutritional niche breadth), habitat use and foraging behavior. 3.We found that gannets feed on prey that varied widely in their nutritional composition (have a broad prey composition niche), and composed diets from these prey that likewise varied in composition (have a broad realized nutritional niche), suggesting generalism at two levels of macronutrient selection. 4.Across seasons, we established “nutritional landscapes” (hereafter nutriscapes), linking the nutritional content of prey (wet mass protein to‐lipid ratio ‐P:L‐) to the most likely geographic area of capture and bathymetry. Nutriscapes varied in their P:L from 6.06 to 15.28, over time, space and bathymetry (0 to 150 m). 5.During warm water events (strong positive SSTa), gannets expanded their foraging habitat, increased their foraging trip duration and consumed prey and diets with low macronutrient content (wet mass proportions of P and L). They were also constrained to the smallest prey composition and realized nutritional niche breadths. 6.Our findings are consistent with previous suggestions that dietary generalism evolves in heterogeneous environments, and provide a framework for understanding the nutritional goals in wild marine predators and how these goals drive ecological interactions and are, in turn, ultimately shaped by environmental fluctuations.
... Nutritional ecology focuses on exploring the relationships between nutrition, behavior, pollutants, ecology and physiology (Martinez del Rio and Cork, 1997;Raubenheimer et al., 2009). The proportions-based nutritional geometry was designed to deal with the complexities of understanding how wild animals meet their nutritional requirements in environments where multiple foods of differing nutritional composition are available (Raubenheimer, 2011;Raubenheimer et al., 2015;Machovsky-Capuska et al., 2016a, Machovsky-Capuska et al., 2016bDenuncio et al., 2017). Being multidimensional, proportions-based nutritional geometry provides an opportunity to integrate micro- (Nie et al., 2014) and macro-nutrients (reviewed in Simpson and Raubenheimer, 2012;Machovsky-Capuska et al., 2018), secondary metabolites and toxins , and plastics (Machovsky-Capuska et al., 2019 into a broader ecological context. ...
Article
Bioaccumulation of Hg and Cd from food is a complex ecological process that has been oversimplified in the past. Common dolphins (Delphinus delphis) provide a powerful model to biomonitor metal concentrations in marine environments worldwide. We combined proportions-based nutritional geometry with metal analysis, stomach content analysis and the proximate composition of prey, to yield novel insights into the accumulation of Hg and Cd. Our analysis showed an age-related accumulation trend for Cd and Hg in kidney and liver, with highest concentrations found at 18 years of age. When view through the lens of nutritional ecology, Argentine anchovy (58.1 Mass %) and South American long-finned squid (22.7 Mass %), provided most of the dietary intake of protein (P) and lipids (L) (P:L ratio = 2.6:1.0) and also represented the main source for Cd and Hg levels accumulated in their bodies. This study presents unprecedented evidence on metal accumulation in relation to age and nutritional intake in a marine predator.
... After A. australis, P. blainvillei was the marine mammal species with the second lowest trophic relationship with fisheries, mainly due to its preference for smaller prey than those targeted by fisheries and the high importance of squid (Doryteuthis sanpaulensis) in its diet, as revealed in many studies across its distribution (e.g. Troina et al. 2016, Denuncio et al. 2017. In this context, it is worth mentioning that D. sanpaulensis is not an important commercial fishing resource in southern Brazil, and excessive pressure on its stock does not seem likely in the coming years. ...
Article
Marine mammals and humans are apex predators and both may compete for fish in ecosystems under continuous fishing pressure. We assessed the degree of trophic overlap between prey species found in the diet of 5 marine mammals (39 specimens of sea lion Otaria flavescens, 61 fur seals Arctocephalus australis, 76 franciscana dolphins Pontoporia blainvillei, 25 bottlenose dolphins Tursiops truncatus and 28 Lahille’s bottlenose dolphins T. gephyreus) and the catches of the 6 main commercial fishing gears used in southern Brazil (coastal gillnets, oceanic gillnets, purse seine, demersal pair trawling, bottom [single] trawl and double-rig trawling) between 1993 and 2016. An adjusted general overlap index indicated an overall moderate to high overlap. Specific overlap analysis showed that O. flavescens and T. truncatus presented high trophic relationships with fisheries, followed by T. gephyreus. Smaller interactions were observed for A. australis and P. blainvillei, even though they also exploit commercial fishing resources. Coastal gillnet and pair bottom trawling are the fisheries that most target the fish species favoured by O. flavescens, T. gephyreus and T. truncatus. The information presented in this study on trophic interactions may assist decision making for both fishery management and conservation measures for these apex predators. Commercial fishing activities are a major threat to marine mammals both regionally and globally. Current levels of fishing or its intensification may lead to dramatic changes in the coastal marine food web, including additional threats to coastal marine mammal populations in southern Brazil.
... An important feature of the BMC is that its position oscillates seasonally and geographically along the study area, affecting the north and south coastal regions differently, which in turn influences the distribution and abundance of many franciscana dolphin prey species (Haimovici, 1997a(Haimovici, , 1997b. Consequently, the most important prey of franciscana dolphin differed between the northern and southern regions of the study area, which was also reported in other studies comparing neighbourhood sites and franciscana sub-populations distributed in marine and estuarine areas in Argentina (Rodrígues et al., 2002;Denuncio et al., 2017). Despite the fact that these are adjacent areas and some diet differences also include cephalopod beak presence and absence (and these structures can remain months in the stomach), it seems that the animals are not swimming to distant areas. ...
Article
The franciscana dolphin ( Pontoporia blainvillei ) is a coastal dolphin endemic to the western South Atlantic Ocean. The dolphin is listed as vulnerable in the IUCN Red List, with incidental catches in gillnet fisheries the greatest conservation concern for this species. Insights into the feeding habits of this dolphin are essential to understand its distribution, movements and use of habitat, which are fundamental for effective management of the species. The feeding habits of franciscana dolphins were investigated from analyses of stomach contents of animals incidentally caught by two fishing operations from southern and northern regions of the southern Brazilian coast. In this study we investigate the existence of intrapopulation (sexual maturity and sex-related) variation in the diet of the franciscana dolphin, evaluating the spatial (northern and southern geographic areas) and seasonal influences. The analyses were based on Linear and Generalized Linear Models (LM and GLM). The majority of identified prey species were bottom-dwelling teleosts and the squid Doryteuthis sanpaulensis . The most important prey differed spatially and seasonally between northern and southern regions of the study area, and our results revealed significant differences between sexes and sexual maturity stages, mainly related to prey species sizes. This variation might indicate differences in prey selection, availability or habitat use patterns among these groups. In any case, these dietary differences are likely to minimize intraspecific competition for food resources, and/or indicate spatio-temporal variation in prey availability.
... With regard to trace elements, Seixas et al. (2008) found that the concentrations of selenium (Se), total mercury (Hg), and organic mercury (OrgHg) were higher in the livers and kidneys of franciscanas from Rio Grande do Sul State than Rio de Janeiro State, Brazil. For both areas, the values were of the same order of magnitude as those reported in earlier studies with the same species from Brazil (Lailson-Brito et al., 2002;Kunito et al., 2004;Seixas et al., 2007) and Argentina (Marcovecchio et al., 1994;Gerpe et al., 2002;Denuncio et al., 2017;Romero et al., 2017). Franciscana livers showed higher concentrations of mercury, zinc, and copper relative to concentrations in other organs, whereas their highest cadmium concentrations were mostly found in kidneys (Marcovecchio et al., 1990;Gerpe et al., 2002;Lailson-Brito et al., 2002;Kajiwara et al., 2004;Seixas et al., 2008). ...
Article
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The franciscana is endemic to subtropical coastal waters of Brazil, Uruguay, and Argentina, and is the only living species of the family Pontoporiidae. It is regarded as the most endangered cetacean in the western South Atlantic. Five management units are recognized (Franciscana Management Areas, FMAs – sensu Secchi et al., 2003a), with abundance estimates ranging from a few hundred to around 15,000 dolphins. Low reproductive potential and short life span make this species highly susceptible to current non-natural removal rates. Bycatch in gillnet fisheries occurs in high levels since the 1960s in Uruguay and 1980s in Brazil and Argentina. Although other threats exist, such as habitat degradation that includes physical (noise) and chemical pollution, depletion of fish stocks and climate change, incidental mortality in gillnets is currently the greatest threat to franciscanas. Fishing-related mortality ranges from approximately 100, in FMA I, to more than 1,000 in FMA III, and exceed from near two (in FMA IV) to more than five times (in FMA III) the maximum allowed sustainable mortality rate, based on potential biological removal (PBR) approach. These numbers indicate that the species is unlikely to cope with the current levels of bycatch and that urgent and extreme reduction on fishing practice and effort are required to avoid collapse of the franciscana and to lower its risk of extinction. Current mortality levels and projected declines resulted in the listing of the franciscana as “Vulnerable” in the IUCN Red List. Recent fisheries regulations were implemented in areas with extensive bycatch in Brazil and were expected to improve the species’ conservation status. There is evidence, however, that this regulation is insufficient to reduce fishing-related mortality to sustainable levels due to either or both lack of compliance and inadequate regulation strategies. Here we provide a comprehensive review on the franciscana ecology and threats and discuss perspectives for its conservation.
... Di Beneditto and Ramos (2014) suggested that species with demersal-benthic trophic habits might be more impacted than species feeding on pelagic prey. In the RdP estuarine area, P. blainvillei feeds on demersal and small prey -such as juvenile teleost fish and small cephalopods (Denuncio et al., 2017b) -, and A. australis feeds on pelagic fish species (e.g., Franco-Trecu et al., 2014). Consequently, plastic ingestion rate in P. blainvillei is at least 3 times higher than that of A. australis (>30% against 7% for dolphins and fur seals, respectively; Denuncio et al., 2011Denuncio et al., , 2017a. ...
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Marine plastic pollution is projected to increase globally in the next few decades. This holds true for South America where the number of species that interacts with plastics is increasing. In this study, we explore for the first time the potential of certain charismatic species of marine turtles, mammals and seabirds as indicators of plastic pollution in the Río de la Plata (RdP), one of the largest and most important estuarine areas of the Southwest Atlantic. Through a revision of published studies integrated with unpublished data, we summarize studies on the interaction of charismatic marine species with plastics in the region and evaluate their role as indicators of plastic pollution in the RdP based on aspects of their local ecology and key attributes (i.e., biological/ecological, methodological, and conservation attributes) of indicator species. We found that at least 45 charismatic marine species interact –whether by ingestion or entanglement– with plastics in the region. Eight of these species were selected as potential indicators given their occurrence, probability of sampling and interaction with plastics in the RdP, namely: Chelonia mydas , Caretta caretta , Dermochelys coriacea , Pontoporia blainvillei , Arctocephalus australis , Otaria flavescens , Larus dominicanus , and Spheniscus magellanicus . The species shared some key attributes of indicator species, e.g., they are relatively well studied, but differed in critical aspects such as their home range and mobility. We discuss whether the species’ attributes are strengths or weaknesses according to the available knowledge on their ecology in the RdP, and propose a multispecies indicator of plastic pollution given that those strengths and weaknesses can be compensated among species. Monitoring plastic pollution through a combination of species would enable a better understanding of plastic pollution in this relevant area.
... Ecological studies exploring trophic interactions often compare resource use across time and space using published sources. For example, Denuncio et al. (2017) compiled available data on the lipid and protein content of prey across seven geographic locations as a way to estimate the Franciscana dolphin Pontoporia blainvillei prey composition and realized nutritional niches. They used six different data sources published between 1942 and 2014, utilizing different nutrient estimation techniques. ...
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Trophic interactions play a critical role in regulating ecosystem functioning. Advances in trophic ecology have shifted the focus from characterizing resources based on a single ‘currency' such as energy or biomass to more complex multidimensional approaches that consider the resource quality, hence require detailed estimation of different nutrients. For this purpose, ecologists use a wide plethora of extraction and quantification methods that differ substantially in precision and accuracy and vary in efficiency across sample types and taxa. Yet, ecologists seem largely oblivious to these methodological drawbacks and their severe theoretical implications. Focusing on the three main macro-nutrients groups; proteins, lipids and carbohydrates, we provided an overview of the main extraction and quantification methods and their inherent limitations, and discussed possible consequences for ecology research and theory development. We urge ecologists to adopt a standard method for estimating each macronutrient group or to use multiple methods when feasible, until more accurate and precise chromatographic methods become accessible. We hope that our study will raise awareness to the many shortcomings of macro-nutrient estimations to assist in strengthening and further developing the important field of trophic ecology.
... Although feeding habits of FMAs comprising Argentina, Uruguay and southern Brazil are well described (e.g.: Bassoi et al., 2020Bassoi et al., , 2021Denuncio et al., 2017;Danilewicz et al., 2002;Polizzi et al., 2013) For the ES coast, which comprises FMA Ia, Rupil et al. (2019) were the first and only to report feeding habits of franciscanas. Among the prey items identified, fish represented 97.91%, whereas cephalopods comprised only 1.44%. ...
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Trace elements bioaccumulation patterns can be an important tool to assess differences among cetaceans' populations. In this work, their use as potential chemical markers to differentiate franciscanas (Pontoporia blainvillei) populations was evaluated. Franciscanas were collected from three states in southeastern Brazil, which comprise three different Franciscana Management Areas (FMAs): Espírito Santo (FMA Ia), southern Rio de Janeiro (FMA IIa), and central São Paulo (FMA IIb). The concentrations of As, Cd, Cu, Fe, Hg, Mn and Zn were determined in the muscle, liver and kidney of the animals. Cadmium was the most valuable chemical marker to differentiate stocks, separating at least FMA IIa from the others. The higher Cd levels in FMA IIa, along with dietary information, indicate that the predominant consumption of cephalopods by this population is the main reason for the differences found. Additionally, environmental characteristics of the areas should also be considered as divergent sources of trace elements. Our findings suggest that non-essential trace elements, such as Cd, can be successful markers to differentiate populations. The Mn concentrations in FMA Ia raised concern and must be carefully monitored, as well as other elements that compose the iron ore tailings that have impacted the Espírito Santo coastal area. Additionally, this is the first study to report trace element concentration in the franciscanas from FMA IIa (southern Rio de Janeiro). Trace element concentrations found in franciscanas may represent different contamination levels in their preys and environments, which might pose specific threats to distinct populations. Therefore, our findings are important to characterize and differentiate franciscana populations and to guide precise management and conservation actions for the distinct stocks of this endangered species.
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We conducted a meta-analysis of the franciscana (Pontoporia blainvillei ) diet based on published data on stomach contents and stable isotopes, from 1867 to 2021. We provide an assessment of the spatial and temporal variation in the occurrence of franciscana prey throughout its distributional range. Pelagic prey was more frequent in the diet of franciscanas from the northern areas, while dominance of demersal characterize the diet of the southern populations. The decreasing latitudinal trend in dietary diversity mirrors the known peak in prey species richness of the northern areas. Carbon and nitrogen stable isotopes in franciscana tissues increase latitudinally reflecting basal isotopic values influenced by distinct oceanographic and biogeochemical conditions. Fisheries over exploitation is an important factor contributing to different dietary proportions for franciscanas overtime but shifts in prey composition due to higher frequency of natural events may also play a role.
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Carnivorous animals are assumed to consume prey to optimise energy intake. Recently, however, studies using Nutritional Geometry (NG) have demonstrated that specific blends of macronutrients (e.g. protein, fat and in some cases carbohydrates), rather than energy per se, drive the food selection and intake of some vertebrate and invertebrate predators in the laboratory. A vital next step is to examine the role of nutrients in the foraging decisions of predators in the wild, but extending NG studies of carnivores from the laboratory to the field presents several challenges. Biologging technology offers a solution for collecting relevant data which when combined with NG will yield new insights into wild predator nutritional ecology.
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We apply a recently established nutritional framework for defining dietary generalism to global populations of wild boar (Sus scrofa). Across its range, wild boar consume a diversity of foods that vary in nutritional composition. The macronutrient (carbohydrate, protein and fat) composition of the diets composed from those foods also varies substantially between countries, particularly in terms of proportion of energy from protein. These results suggest that as a species wild boar have a wide fundamental macronutrient niche, which likely contributes to the success of the species as an invader of novel environments.
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The foraging challenge for predators is to find and capture food with adequate levels of energy and nutrients. Marine predators require particularly sophisticated foraging strategies that enable them to balance self- and offspring-feeding, and also in many circumstances simultaneously consider the nutritional constraints of their partners. Here we combined the use of dietary analysis, proximate composition and nutritional geometry (right-angled mixture triangle nutritional models) to examine the macronutrient preferences of Australasian gannets (Morus serrator) at Farewell Spit gannetry in New Zealand. Our results showed intra- and inter-specific variation in the protein, lipid and water composition of prey captured by our sample of 111 Australasian gannets. In addition, we observed significant differences in the Australasian gannets’ nutritional niche between seasons. We provide evidence of sex-specific macronutrient foraging strategies in a successful marine predator in the wild. We have shown that in spite of fluctuations in the nutritional composition of foods available to Australasian gannets, males consistently capture prey with higher protein-to-lipid ratios and lower lipid-to-water ratios than females. These results aid to better understand the evolutionary relationship between macronutrient selection and sex-specific traits in wild animals. They also suggest an incentive for these predators to combine individually imbalanced but nutritionally complementary foods to achieve dietary balance, further highlighting the likelihood that prey selection is guided by the balance of macronutrients, rather than energy alone.
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Nutritional quality of prey is a significant driver of predator foraging patterns. In mammals, nutritional needs are known to change across ontogeny and reproductive state; however, little is known about nutrition in marine mammals. For this study, we used observational data of diurnal foraging events, collected annually from 1992 to 2009, to investigate nutrition and prey use in Atlantic spotted dolphins (Stenella frontalis) on Little Bahama Bank, Bahamas, between reproductive states (lactating, pregnant, nonreproductively active [NRA]. We also investigated the impact of age class association (various calf age groups [ages 1–6], older “noncalf” juveniles, and adults) on foraging group nutrition and prey use. To obtain representative nutrient values, we measured calories, lipids, proteins, and moisture in common prey. Using nutritional values and observational data, we investigated the influence of nutritional value on prey use. Results indicated that specific nutrients were targeted by different reproductive states and age class groups. Nutritional intake of all nutrients was higher for lactating females than pregnant females, but lower than NRA females. Investigation of age group associations revealed that nutritional intake of all four nutrients was higher for noncalf than calf-associated groups. This study represents one of the first investigations of intraspecific prey use and nutritional differences in cetaceans.
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Nutritional geometry has shown the benefits of viewing nutrition in a multidimensional context, in which foraging is viewed as a process of balancing the intake and use of multiple nutrients. New insights into nutrient regulation have been generated in studies performed in a laboratory context, where accurate measures of amounts (e.g. eaten, converted to body mass, excreted) can be made and analysed using amounts-based nutritional geometry. In most field situations, however, proportional compositions (e.g. of foods, diets, faeces) are the only measures readily available, and in some cases are more relevant to the problem at hand. For this reason, a complementary geometric method was recently introduced for analysing multi-dimensional data on proportional compositions in nutritional studies, called the right-angled mixture triangle (RMT). We use literature data from field studies of primates to demonstrate how the RMT can provide insight into a variety of important concepts in nutritional ecology. We first compare the compositions of foods, using as an example primate milks collected in both the wild and the laboratory. We next compare the diets of different species of primates from the same habitat and of the same species (mountain gorillas) from two distinct forests. Subsequently, we model the relationships between the composition of gorilla diets in these two habitats and the foods that comprise these diets, showing how such analyses can provide evidence for active nutrient-specific regulation in a field context. We provide a framework to relate concepts developed in laboratory studies with field-based studies of nutrition.
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Foraging theory proposes that the nutritional driver of food choice and foraging in carnivores is energy gain. In contrast, recent laboratory experiments have shown that several species of carnivore select prey that provides a diet with a specific balance of macronutrients, rather than the highest energy content. It remains, however, to be determined how nutritionally variable the foods of predators in the wild are, and whether they feed selectively from available prey to balance their diet. Here, we used a geometric method named the right-angled mixture triangle (RMT) for examining nutritional variability in the prey and selected diets of a group of wild carnivores and marine top predators, the gannets (Morus spp.). A prey-level diet analysis was performed on Australasian gannets (M. serrator) from two New Zealand locations, and the macronutrient composition of their chosen prey species was measured. We use RMT to extend the comparison in the compositions of foods and diets from Australasian gannets from Australia as well as Northern gannets (M. bassanus) and Cape gannets (M. capensis). We found nutritional variability at multiple scales: intra- and interspecific variability in the pelagic fish and squid prey themselves; and intra- and interspecific variability in the diets consumed by geographically disparate populations of gannets. This nutritional variability potentially presents these predatory seabirds with both opportunity to select an optimal diet, and constraint if prevented from securing an optimal diet.
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Stomach contents of 110 franciscanas (Pontoporia blainvillei), from northern Argentina were analysed in order to improve our knowledge about the feeding habits of this species and to better characterise the lactation period. The samples included calves, juveniles and adults of both sexes. Evidence of predation by franciscanas is seen at a very young age (2.5-3 months), with a transition diet composed by both milk and solid food, mainly represented by crustaceans. Weaning seems to begin by April, when franciscanas are about 6-7 months old. Franciscanas inhabiting two different habitats were analysed in this study: a brackish water estuary and an adjacent marine coastal system. The diet of Pontoporia blainvillei in northern Argentina was composed by a total of 26 prey species: 20 teleosts, 4 crustaceans and 2 cephalopods. Based on the Index of Relative Importance (IRI) the main prey species were Cynoscion guatucupa, Micropogonias furnieri, Loligo sanpaulensis and Urophycis brasiliensis. Estuarine franciscanas preyed mainly on Micropogonias furnieri (dominant species), Cynoscion guatucupa, Odonthestes argentinensis and Macrodon ancylodon, while dolphins from marine areas preyed mainly on Cynoscion guatucupa (dominant species), Loligo sanpaulensis and Urophycis brasiliensis. Our results confirm that franciscanas prey mainly on juvenile fish (< 8cm) and small loliginid squids, in close agreement with previous results obtained in southern Brazil and Uruguay. Qualitative and quantitative differences observed in the diet of dolphins from each habitat emphasise the need to discriminate between samples from different habitats and environmental parameters.
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Tesis de doctorado (208 pp.) en Ciencias, Área Biología, defendida el 18 de diciembre de 2012 por Pablo Denuncio <pablodenun@gmail.com>. Lugar: Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Argentina. Director: Diego Rodríguez. Miembros del tribunal: Humberto L. Cappozzo, Juan M. Diaz de Astarloa y Diego Verzi.
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The conservation and sustainable use of marine resources is a highlighted goal in a growing number of national and international policy agendas. Unfortunately, efforts to assess progress, as well as to strategically plan and prioritize new marine conservation measures, have been hampered by the lack of a detailed and comprehensive biogeographic system to classify the oceans. Here we report on a new global system for coast and shelf areas – the Marine Ecoregions of the World (MEOW) – a nested system of 12 realms, 62 provinces and 232 ecoregions. This system provides considerably better spatial resolution than previous global systems, while preserving many common elements, and can be cross-referenced to many regional biogeographic classifications. The designation of terrestrial ecoregions has revolutionized priority setting and planning for land conservation; we anticipate similar benefits from the creation of a coherent and credible marine system.
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Maximum likelihood or restricted maximum likelihood (REML) estimates of the parameters in linear mixed-effects models can be determined using the lmer function in the lme4 package for R. As for most model-fitting functions in R, the model is described in an lmer call by a formula, in this case including both fixed- and random-effects terms. The formula and data together determine a numerical representation of the model from which the profiled deviance or the profiled REML criterion can be evaluated as a function of some of the model parameters. The appropriate criterion is optimized, using one of the constrained optimization functions in R, to provide the parameter estimates. We describe the structure of the model, the steps in evaluating the profiled deviance or REML criterion, and the structure of classes or types that represents such a model. Sufficient detail is included to allow specialization of these structures by users who wish to write functions to fit specialized linear mixed models, such as models incorporating pedigrees or smoothing splines, that are not easily expressible in the formula language used by lmer.
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Nutrient balance is a strong determinant of animal fitness and demography. It is therefore important to understand how the compositions of available foods relate to required balance of nutrients and habitat suitability for animals in the wild. These relationships are, however, complex, particularly for omnivores that often need to compose balanced diets by combining their intake from diverse nutritionally complementary foods. Here we apply geometric models to understand how the nutritional compositions of foods available to an omnivorous member of the order Carnivora, the grizzly bear (Ursus arctos L.), relate to optimal macronutrient intake, and assess the seasonal nutritional constraints on the study population in west-central Alberta, Canada. The models examined the proportion of macronutrients that bears could consume by mixing their diet from food available in each season, and assessed the extent to which bears could consume the ratio of protein to non-protein energy previously demonstrated using captive bears to optimize mass gain. We found that non-selective feeding on ungulate carcasses provided a non-optimal macronutrient balance with surplus protein relative to fat and carbohydrate, reflecting adaptation to an omnivorous lifestyle, and that optimization through feeding selectively on different tissues of ungulate carcasses is unlikely. Bears were, however, able to dilute protein intake to an optimal ratio by mixing their otherwise high-protein diet with carbohydrate-rich fruit. Some individual food items were close to optimally balanced in protein to non-protein energy (e.g. Hedysarum alpinum roots), which may help explain their dietary prevalence. Ants may be consumed particularly as a source of lipids. Overall, our analysis showed that most food available to bears in the study area were high in protein relative to lipid or carbohydrate, suggesting the lack of non-protein energy limits the fitness (e.g. body size and reproduction) and population density of grizzly bears in this ecosystem.
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Franciscanas are the most endangered dolphins in the Southwestern Atlantic. Due to their coastal and estuarine habits, franciscanas suffer from extensive fisheries bycatch, as well as from habitat loss and degradation. Four Franciscana Management Areas (FMA), proposed based on biology, demography, morphology and genetic data, were incorporated into management planning and in the delineation of research efforts. We re-evaluated that proposal through the analysis of control region sequences from franciscanas throughout their distribution range (N = 162), including novel sequences from the northern limit of the species and two other previously unsampled localities in Brazil. A deep evolutionary break was observed between franciscanas from the northern and southern portions of the species distribution, indicating that they must be managed as two Evolutionarily Significant Units (ESU). Furthermore, additional FMAs should be recognised to accommodate the genetic differentiation found in each ESU. These results have immediate consequences for the conservation and management of this endangered species.
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A recent area of progress in nutritional ecology is a growing awareness that nutritional phenotypes are best understood in a multidimensional context, where foraging is viewed as a process of balancing the intake and use of multiple nutrients to satisfy complex and dynamic nutrient needs. Numerous laboratory studies have shown that this view can yield novel insights into unresolved questions and provide a framework for generating new hypotheses. By contrast, progress with this multidimensional view has been slow in the arena of ultimate interest to functional biologists, the field. One reason for this is that the Geometric Framework for nutrition that has been extensively used in laboratory experiments focuses on amounts of nutrients (e.g., required, eaten, or retained), and such data are typically very difficult or impossible to collect for most free-ranging animals. Further, many problems in field-based nutritional ecology involve comparisons of mixtures that are expressed as proportions (e.g., food, diet, body, or fecal compositions), rather than absolute amounts. As yet, however, no geometric framework has been established in nutritional ecology for this. Here I recommend an approach for the geometric analysis of nutritional mixtures, and illustrate its use in a variety of contexts by reanalyzing published data. Despite its simplicity, this approach holds considerable promise for furthering the study of field-based nutritional ecology.
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This study presents new information on feeding habits of Guiana dolphins, Sotalia guianensis, in south-eastern Brazil, together with new regression equations to evaluate the weight and length of fish from otoliths, showing an overview on the knowledge about this species’ diet in this area. Eighteen stomach contents had been analysed and compared to 180 samples collected in another eight feeding studies. The analysed specimens were either incidentally caught in gillnets used in coastal waters by the fleet based in the Cananéia main harbour (25°00′S 47°55′W), south of São Paulo State, or found dead in inner waters of the Cananéia estuary between 2003 and 2009. Based on the index of relative importance analysis, the most important fish species were the banded croaker, Paralonchurus brasiliensis. Doryteuthis plei was the most representative cephalopod species. Stellifer rastrifer was the most important fish species observed in dolphins in inner estuarine waters and P. brasiliensis in recovered dolphins from coastal waters. Loliguncula brevis is the only cephalopod species reported from dolphins found in inner estuarine waters up to date. Doryteuthis plei was the most important cephalopod species observed in coastal dolphins. When considering other feeding studies, the most representative fish family in the diet of S. guianensis was Sciaenidae, which is mainly represented by demersal fishes. The main preys of S. guianensis are abundant in the studied areas, which may indicate an opportunistic feeding habit. The majority of them are not the most important target species by the commercial fishery in south-eastern Brazil.
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Four distinct Franciscana Management Areas (FMAs) have been proposed based on several lines of evidence including genotype, phenotype, population response and distribution. To determine if differences in external morphology fit this division, a canonical variate analysis was carried out for males and/or females from FMAs I to IV using up to 14 characters. A total of 78 adult specimens were analysed. More than 90% of the differences between groups were summarized by three canonical variates. Females were larger than males in all areas. Females from FMA IV were of intermediate length between those from FMA I and FMA III and individuals from FMA II were smaller than those from all other areas. Position of dorsal fin and morphology of the anterior body region, differentiate individuals from FMA I and FMA III. Morphological differences found in this study give additional support for the proposed FMAs. Since habitat characteristics and franciscana feeding ecology vary regionally, it is possible that observed morphological differences are due to ecological divergence for niche occupation. The indication of a discontinuous distribution, consistency between genetic and morphological evidence, and a short time genetic divergence, might indicate that franciscanas inhabiting FMA I represent a distinct subspecies.
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The red panda (Ailurus fulgens fulgens) is distributed throughout the Himalayas and is found in both protected and unprotected areas of Nepal. Loss and fragmentation of habitat threaten red panda populations throughout its range, and as a consequence, it is listed as vulnerable on the IUCN Red List of Threatened Species. Despite this pressing situation, data on the ecology of the red panda in western Nepal are lacking. Our aim in the current study was to determine the distribution, associated habitats, and summer diet of the red panda in Dhorpatan Hunting Reserve (DHR), Nepal. Evidence of red pandas was found in all 6 blocks (except Dogadi block) of the reserve, spanning an area of 345.8 km2, between elevations of 2800 m and 4000 m and predominantly (> 75%) in forests comprising plant communities dominated by Abies spectabilis, Acer caesium, Tsuga domusa, and Betula utilis, with ground cover of Arundinaria spp. The dominant plant found in scat of the red panda was Arundinaria spp. (81.7%), with Acer spp., B. utilis, and lichen also frequently present. Livestock grazing and human activities were significantly higher in habitats where signs of pandas were recorded than in areas where they were absent. This habitat overlap between the red panda and livestock potentially poses a major threat to the panda's survival in the DHR, a fact that should be taken into account in devising management strategies for this threatened species. http://zoolstud.sinica.edu.tw/Journals/51.5/701.pdf.
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An important goal of primatology is to identify the ecological factors that affect primate abundance, diversity, demography, and social behavior. Understanding the nutritional needs of primates is central to understanding primate ecology because adequate nutrition is a prerequisite for successful reproduction. Here, we review nutritional methods and provide practical guidelines to measure nutrient intake by primates in field settings. We begin with an assessment of how to estimate food intake by primates using behavioral observations. We then describe how to collect, prepare, and preserve food samples. Finally, we suggest appropriate nutritional assays for estimating diet nutritional quality and point to the merits and limitations of each. We hope this review will inspire primatologists to use nutritional ecology to answer many unresolved questions in primatology.
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The occupation pattern of Sotalia guianensis in São Francisco do Sul harbor inlet, in Babitonga bay, Southern Brazil, was studied between September 1996 and June 1998. A total of 200 h of naturalistic observations and 141.2h of estuarine dolphin systematic observations were made using binoculars 7 x 50. At each three minutes interval, data about number of individuals and behavior were registered. The population used the harbor inlet intensively, mainly for fishing activities. Ebb tide was responsible for a higher occupation index. Considering the months analyzed, the higher occupation index occurred in May, and in January the lower occurrence was observed. The mean group size was four individuals.
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This book describes an array of power tools for data analysis that are based on nonparametric regression and smoothing techniques. These methods relax the linear assumption of many standard models and allow analysts to uncover structure in the data that might otherwise have been missed. While McCullagh and Nelder's Generalized Linear Models shows how to extend the usual linear methodology to cover analysis of a range of data types, Generalized Additive Models enhances this methodology even further by incorporating the flexibility of nonparametric regression. Clear prose, exercises in each chapter, and case studies enhance this popular text.
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Todos los mamíferos de los ríos y mares de América del Sur, más todos los mamíferos marinos de la Antártida 74 Especies 500 fotografías color 110 ilustraciones 80 mapas Con espectaculares fotos de los más destacados fotógrafos marinos del mundo, este libro explica claramente las características de cada especie: peso, talla, área de distribución, nombre vulgar y científico, clave de identificación para avistajes y varamientos, biología, ecología, conservación y mucho más. Para conocer y proteger a todos los mamíferos acuáticos de la región, en un libro imprescindible.
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Abstract This is the first study in Argentine waters on the abundance of the threatened Franciscana dolphin, Pontoporia blainvillei. During 2003–2004 we carried out 17 aerial surveys using line transect sampling methodology. We observed 101 Franciscanas in 71 sightings. In northern areas density was estimated at 0.106 individual/km2. Density was lower in southern areas (0.055/km2) and declined with depth beyond 30-m isobaths (0.05/km2). A correction factor for submerged dolphins was applied to density and then extrapolated to the strip between the coastline and the 30-m isobath. Abundance in the northern area was estimated at 8,279 (4,904–13,960) individuals, while in the southern area it was estimated at 5,896 (1,928–17,999) individuals. Considering an annual mortality of about 500–800 individuals, about 3.5%–5.6% of the stock may be removed each year by the fishery and over the 2% recommended by the International Whaling Commission (IWC) and may not be sustainable by the population. Higher densities in coastal areas make Franciscanas more vulnerable to coastal fishing camps, which increased mortality in recent years. A remarkable finding was that while density decreases to the south, values of catch per unit effort (CPUE) increases, indicating different catchability of dolphins between areas.
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Four methods were used to determine the energy content of somatic tissues of Perca fluviatilis. Two forms of direct calorimetry (both adiabatic and non-adiabatic) and wet (dichromate) oxidation gave similar results. When energy contents were calculated from proximate analysis using accepted conversion factors (9.45 cal mg−1 for lipid, 5.65 cal mg−1 for protein) results were higher than those from the other methods. The discrepancy was eliminated when a lower, directly determined energy content for the extracted lipid fraction was used. Some historic and technical aspects of the comparison are discussed.
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The feeding habits of the sand tiger shark Carcharias taurus, one of the most threatened sharks of the world, are poorly known. Sand tiger sharks are critically endangered in the South-west Atlantic. Since 2007, the law requires that all individuals caught in recreational fisheries off Argentina must be released. Using data from a north Patagonian recreational fishery (n=164 stomachs with contents), we analyzed the diet of sand tiger sharks in relation with size, sex, maturity stage and season; assessed prey consumption patterns and hooking location; and estimated diet overlap with fishery landings. Sand tiger sharks consumed mainly teleosts (55.4% of the total prey number, N) and elasmobranchs (41.84%N), and ate more benthic elasmobranchs (batoids and angel sharks) as they become larger. Sharks swallowed prey mostly in one piece (93.7%) and were hooked mainly in internal organs (87.4%, n=175), causing occlusion and perforation of the esophagus and stomach, and lacerations to the pericardium, heart and liver. Sand tiger sharks fed on the most heavily landed species, overlapping almost completely (>90%) with fishery landings. Conservation plans should take into account that releasing hooked sharks could be insufficient to minimize fishing mortality and that competition for food with fisheries is likely to occur.