RESUMO

Although extinct sloths exhibited a wide range of dietary habits, modes of locomotion, and occupied various niches across the Americas, modern sloths are considered quite similar in their habits. The dietary habits of living sloths can be directly observed in the wild, and understanding the mechanical behavior of their jaws during chewing through finite element analysis (FEA) provides a valuable validation tool for comparative analysis with their extinct counterparts. In this study, we used FEA to simulate the mechanical behavior of sloth mandibles under lateral mastication loads, using it as a proxy for oral processing. Our research focused on the six extant sloth species to better understand their diets and validate the use of FEA for studying their extinct relatives. We found that all living sloths have the predominancy of low-stress areas in their mandibles but with significant differences. Choloepus didactylus had larger high-stress areas, which could be linked to a reduced need for processing tougher foods as an opportunistic generalist. Bradypus variegatus and Choloepus hoffmanni are shown to be similar, displaying large low-stress areas, indicating greater oral processing capacity in a seasonal and more competitive environment. Bradypus torquatus, Bradypus pygmaeus, and Bradypus tridactylus exhibited intermediary processing patterns, which can be linked to a stable food supply in more stable environments and a reduced requirement for extensive oral processing capacity. This study sheds light on extant sloths' dietary adaptations and has implications for understanding the ecological roles and evolutionary history of their extinct counterparts.

RESUMO

Many primatological studies do not assess direct indexes of food availability to make inferences about behavioral strategies. We related the diet and behavior of a group of Callicebus coimbrai in northeastern Brazil to fruit availability indexes and compared this pattern between seasons (direct and indirect assessment of food availability) to assess whether direct and indirect approaches detect similar ecological patterns. We monitored the study group for 33 months (5 days/month) via scan sampling. The monthly availability of fruits and new leaves was recorded in phenological transects. Fruit availability varied across years based on fruit prevalence, and timing and duration of the abundant seasons. We did not find evidence of a time-minimizing strategy, since C. coimbrai did not change its activity levels according to food availability. However, the negative relationship between foraging and fruit availability indicates that C. coimbrai can compensate for the lower fruit availability by increasing the search for alternative food sources. Monthly fruit consumption was positively correlated to fruit availability and negatively related to the consumption of other food items. However, the behavioral and feeding profiles did not vary between seasons and were not related to rainfall levels. Primate studies should directly relate behavioral and feeding profiles to fruit availability indices, thus avoiding using seasons as proxies of food availability.

Assuntos

RESUMO

Shape ontogenetic changes of the lower jaw in crocodylians are poorly understood. In order to answer some questions related to the inter- and intraspecific morphological variation of the mandible of two extant Caiman species, we performed a three-dimensional geometric morphometric approach. For this purpose, we used landmarks and semilandmarks on two ontogenetic mandibular series of 48 and 15 post-hatching specimens of C. yacare and C. latirostris, respectively. We have also examined the relationship between these anatomical transformations and ontogenetic shifts in diet. We performed a principal component analysis (PCA) for the two species, and regression and partial least squares (PLS) analyses for each species, separately. As a result, species were segregated along the PC1 with specimens of C. yacare showing more gracile mandibles, and specimens of C. latirostris more robust ones. The PC2 and regression analyses showed an age gradient and represented ontogenetic shape changes. Adult caiman mandibles are higher and wider than juvenile ones, and shape changes are more conspicuous in C. latirostris. The PLS analyses showed a significant relationship between shape and diet. Morphological changes of the PLS1 of block-1 match with those of the regression analysis for both species. We have detected morphological transformations in areas where the musculature in charge of mandibular movements is attached. Common morphological changes occurring during ontogeny seem to reflect the same mechanical properties required for crushing and killing in both species, driven by an ontogenetic shift in the diet from invertebrates to vertebrates. Additionally, interspecific differences were also found to be correlated to ontogenetic changes in diet and could be related to dissimilar feeding mechanical requirements (e.g., stiffness and toughness of the item consumed), and to different habitat preferences. Robust mandibles would be more suitable for shallow and fully vegetated environments, as it can be seen in C. latirostris, whereas slender jaws seem to be more suitable for more aquatic species such as C. yacare.

Assuntos

RESUMO

Knowledge of the feeding habits of primate species is important for an understanding of their natural history and ecological interactions between their groups, and their interactions with their environments. Capuchin monkeys (Sapajus spp.) present significant diet flexibility and are a good model for investigating diet diversity between species. We undertook a systematic literature review of publications on the diet of free-living Sapajus spp. groups by using the Web of Science platform. We performed scientometric analyses of the objectives and hypotheses of the reviewed works, identified knowledge gaps, and evaluated the composition of each group's diet. Our results indicate geographic and taxonomic biases among the 59 published studies that we examined. The studies were focused on Sapajus nigritus, Sapajus libidinosus, and Sapajus apella, and undertaken in long-term study sites. Foraging and behavioral aspects of how food is processed were recurring themes. Capuchin monkeys increase their consumption of anthropogenic food according to its supply. Despite the similar objectives of these studies, standardized data collection protocols were not employed. Although Sapajus spp. are widely distributed and are used for cognitive studies, basic aspects of their natural history, such as their diet, remain unknown. We emphasize the importance of undertaking studies on this genus to fill the identified knowledge gaps, and propose that investigations should be carried out on the effects of dietary changes on individuals and groups. We stress that, as the Neotropical region is one of those most affected by anthropogenic impacts, opportunities to study these primates in their natural environments are diminishing daily.

Assuntos

RESUMO

Some studies have shown that freshwater ecosystems are polluted in a similar proportion to marine ecosystems; however, there are many gaps to be filled in this topic. Here, we investigated whether plastics were consumed by carnivore fishes in a Neotropical floodplain and whether it was connected to seasonality (dry and wet seasons). We also evaluated the association between each type of plastic and the fish species. We analyzed the gastrointestinal contents of 23 species and assessed the occurrence and number of plastic particles. Plastics were obtained through chemical digestion and the spectrum of each sample, using a FT-IR imaging microscope. We performed a correspondence analysis (CA) with plastic data to assess the relationship between each type of plastic and the fish species. We also performed linear regression models to assess the relationships of occurrence and number of plastics ingested with seasonality. Nine species had plastics in their gastrointestinal contents, and they were identified as polyvinyl alcohol (PVA), polyamide (PA), polyethylene (PE), polystyrene (PS), and polypropylene (PP). The number of plastics had a positive relationship with the wet season, while the occurrence did not show a significant relationship with any season. These results are particularly important when considering the socioeconomic relevance and the ecological importance of this trophic guild.

Assuntos

RESUMO

The tiger shark (Galeocerdo cuvier) has been relatively well assessed concerning biology and ecology aspects in both Atlantic and Pacific North America and in Caribbean waters. The amount of data in these regions has led to the species protection under capture quotas and with the creation of sanctuaries. The reality in developing countries, however, is the exact opposite, with scarce information on the species in the southern hemisphere, namely South American and African waters. In these regions, protection measures are insufficient, and studies on tiger shark biology and ecology are scarce, significantly hindering conservation and management efforts. Thus, the aim of this study was to compile scientific literature on the tiger shark in the South Atlantic and discuss the impact of these data (or lack thereof) distributed within a total of ten research categories for guiding management plans. In total, 41 scientific publications on different G. cuvier biology and ecology aspects were obtained. The most studied topics were Feeding Ecology (n = 12), followed by Human Interactions (n = 8), and Movements and Migration (n = 7). Northeastern Brazil (Southwest Atlantic) was the most researched area, probably due to the higher coastal abundance of tiger sharks in this area, alongside a high number of recorded attacks, justifying funding for studies in the region. No studies carried out in other South American or African countries were found. It is important to mention that even though some research topics are relatively well covered, a severe knowledge gap is noted for risk assessments and fisheries management, with a proposition for the implementation of sanctuaries noted. This is, however, particularly worrisome, as the South Atlantic is mostly unexplored in this regard for tiger sharks. It is also important to note how different the attention given to this species is in the North Atlantic when compared to the South region. Lastly, we highlight that the existence of sub-populations, the lack of migratory corridors geographically connecting distinct areas used by the species, and the lack of fisheries statistics on tiger shark landings, all increase the vulnerability of this species in the South Atlantic.

Assuntos

RESUMO

The present study compares the trophic ecology of two guitarfishes (Pseudobatos percellens and Pseudobatos horkelii) from the continental shelf of the São Paulo State, Brazil, caught by the bottom pair trawls between 2007 and 2009. These two sympatric species are under different threat categories, "Vulnerable" and "Critically Endangered," respectively, according to Brazilian agencies. Thus, any study considering trophic ecology parameters is pivotal in understanding the trophic ecology role of such species in the ecosystem. The authors analysed 500 stomachs of P. percellens and 108 of P. horkelii, quantifying with dietary indexes: numerical (%N), gravimetric (%W), frequency of occurrence (%FO) and the prey-specific index of relative importance (%PSIRI). For P. percellens and P. horkelii, 26 and 14 different prey items were found, respectively. Crustacea and Teleostei were the most important prey items for both species, indicating a specialist feeding behaviour due to their low niche amplitude. The results provide evidence related to ontogenetic dietary shift in P. percellens and individual-level diet specialization in both species. These two benthic-demersal elasmobranchs are important mesopredators (3,7 for P. percellens, and 3,5 for P. horkelii) in the study area, with high trophic-level values.

Assuntos

RESUMO

Understanding the ecological role of species with overlapping distributions is central to inform ecosystem management. Here we describe the diet, trophic level and habitat use of three sympatric stingrays, Hypanus guttatus, H. marianae and H. berthalutzae, through combined stomach content and stable isotope (δ13 C and δ15 N) analyses. Our integrated approach revealed that H. guttatus is a mesopredator that feeds on a diverse diet of benthic and epibenthic marine and estuarine organisms, principally bivalve molluscs, Alpheus shrimp and teleost fishes. Isotopic data supported movement of this species between marine and estuarine environments. H. berthalutzae is also a marine generalist feeder, but feeds primarily on teleost fishes and cephalopods, and consequently occupies a higher trophic level. In contrast, H. marianae is a mesopredator specialized on shrimps and polychaetas occurring only in the marine environment and occupying a low niche breadth. While niche overlap occurred, the three stingrays utilized the same prey resources at different rates and occupied distinct trophic niches, potentially limiting competition for resources and promoting coexistence. These combined data demonstrate that these three mesopredators perform different ecological roles in the ecosystems they occupy, limiting functional redundancy.

Assuntos

RESUMO

Knowledge of the pattern of exploitation of trees can help us understand the relationship between marmosets and plants, especially in declining forests, such as those in the Brazilian Cerrado. Black-tufted marmosets (Callithrix penicillata) regularly exploit exudates by gouging the bark of trees with their specialized teeth. Determining preferred tree species to exploit exudates is important for forest management aimed at maintaining an essential food source for urban marmosets. We characterized the tree species, dendrometry, and the characteristics of the holes made by marmosets to obtain exudates. Based on these data, we proposed a gouging effort index (Chiseling Suitability Index for Marmosets, ChiSI). We identified 16 species belonging to 10 families of trees with gouging marks made by marmosets. Eleven new tree species used by black-tufted marmosets for exudates were identified in urban forests in the Cerrado. Exudate exploration was predominantly of medium intensity, with round holes concentrated in the canopy. The species Tapirira guianensis and Croton urucarana were preferred. The ChiSI was characterized by a narrow range for both T. guianensis and C. urucarana. Despite the flexibility of obtaining exudates, the black-tufted marmosets concentrate their exploitation to only a few tree species. The T. guianensis and C. urucarana tree species should be considered the most important species for management plans and the preservation of black-tufted marmosets that live in urban forests in the Cerrado.

RESUMO

To examine how precipitation patterns and climate change impact feeding choices made by a population of critically endangered cotton-top tamarins (Saguinus oedipus), we examined 22 years of feeding data (1999-2020) from 21 groups collected at Parque Natural Regional Bosque Seco El Ceibal Mono Tití in Santa Catalina, Colombia. We describe the diet and examine the role of seasonal rainfall and annual variation in rainfall on diet. Rainfall is highly seasonal (mean annual rainfall 1562 mm [range 940-2680 mm]) with a dry, early rainy, and late rainy season in each year. Over 80 species of plants formed part of the fruit, nectar, and exudate components of the diet. Fruits, although available year-round, were more commonly available and consumed during the late rainy seasons (August-November). Exudates were consumed more frequently in the dry season (December-March) and invertebrate consumption was stable across the year. Nectar feeding from a single species (Combretum fruticosum) peaked in November. Rainfall varied over the years, with 13 years exceeding the 99% confidence intervals for mean rainfall. Ten of these extreme years (both drought and extremely wet) occurred in the last 11 years. Fruit consumption did not vary between extreme and average years, but cotton-top tamarins consumed more invertebrates and exudates in wet years. Presently, cotton-top tamarins appear to be able to cope with these extreme variations in rainfall due to their highly varied diet. However, the forests that these primates depend upon for survival are threatened by human exploitation making it critically important to maintain a generalist feeding strategy for survival as many fruiting trees that compose a large proportion of the diet are removed. As conservation efforts continue, plant species consumed by cotton-top tamarins provide useful data when selecting species for habitat restoration programs.

Assuntos