Mammalian Biology最新文献

The scaling relationship between digestive system and body mass shapes foraging strategies in herbivores. The Jarman–Bell principle and the forage maturation hypothesis (FMH), two of the most important predictions formulated in herbivore foraging ecology, have been used to explain this relationship.We aimed to test these predictions for the largest European herbivore—the European bison-which is highly sexually dimorphic and recognised as a refugee species in non-optimal forest habitats. We conducted our study in the Białowieża Primeval Forest, where the European bison has been recognized as a refugee species. We estimated vegetation quality and biomass along the foraging paths of male and female European bison, and the vegetation biomass at random points in different habitats and months. We found no support for the Jarmann-Bell principle at the intraspecific level in European bison, as males and females foraged on patches of similar crude protein and fibre content. However, females selected for higher biomass. The quality of vegetation on the bison foraging patches showed a significant spatio-temporal variation. It increased from May to July and then gradually decreased. It also increased with the fertility and wetness of the habitats being the highest in wet forests. Mean biomass on European bison foraging patches (131.5 g/m²), was significantly lower than on random plots (210.5 g/m²), which supported the FMH. Our study suggests that in rich forest habitats, the abundant food resources available in summer may not constrain the metabolic rate/gut capacity ratio of either sex, potentially leading to dietary segregation. In contrast to open habitats, where vegetation maturation is less temporally variable, European bison in rich forest habitats may optimise patch selection and energy intake by tracking a habitat- and species-specific changes in the plant phenology. Understanding the relationship between European bison forage selection and forage nutritional constraints in forest habitats may be critical for conservation programmes, as European bison are better adapted to more open habitats and are recognised as refugee species in suboptimal forest habitats.

Giraffes exhibit a large sexual dimorphism in body size. Whether sexual dimorphisms also exist in body proportions of the axial and appendicular skeleton has been debated, particularly regarding the giraffe’s iconic long neck. We examined the anatomical proportions of the neck, forelegs, hindlegs, and body trunk of the Masai giraffe (G. tippelskirchi) in captive and wild populations. We found that female Masai giraffes have proportionally longer necks relative to their forelegs than males in contradiction to the original necks-for-sex hypothesis that proposed that the evolution of the giraffe’s long neck was driven by male-male competition. However, male neck width and apparent mass are proportionally larger than females’, supporting a modification of the necks-for-sex hypothesis. Moreover, male foreleg length is proportionally longer whereas female trunk length is proportionally longer. These sexual dimorphisms were found in both captive and wild Masai giraffes. We speculate that the initial evolution of the giraffe’s long neck and legs was driven by interspecific competition and the maternal nutritional demands of gestation and lactation through natural selection to gain a competitive advantage in browsing, and then later the neck mass was further increased as a consequence of male-male competition and sexual selection. Differences in the proportions of major body components define sex phenotypes, but several giraffes display opposite-sex phenotypes with a significantly higher level of discordancy seen in captive males. We speculate that body proportion sexual dimorphisms are maintained in the wild by natural and/or sexual selection, but in captivity selection is relaxed resulting in a higher occurrence of discordances in sexual phenotypes.

Paca (Cuniculus paca) is a medium-sized caviomorph rodent that plays an important role in the dynamics of plant and animal diversity in Neotropical forests. Despite being a generalist species, habitat use can be influenced by the availability of resources, cover, and shelter, but also by the landscape of fear. We investigated whether paca habitat use is mainly driven by resource availability and/or the landscape of fear in a spatiotemporal context in the Atlantic Forest montane of Brazil. We used camera traps and generalized least squares models to investigate the influence of lunar phases on the modulation of environmental factors in paca habitat use and the effects on the prey–predator activity pattern. The availability of food resources, specifically Juçara palm (Euterpe edulis) and Paraná pine (Araucaria angustifolia), was the best predictor to explain paca habitat use, regardless of moonlight. These threatened and dominant trees provide keystone resources for paca safely and efficiently in the study area. However, we found that moonlight can alter the importance of the effect of its main predator (Puma concolor), on the spatiotemporal use of the paca. The risk of predation has a greater impact on the paca's habitat use during phases of intense moonlight, and as an anti-predation strategy, the paca changes its activity pattern precisely during these periods. Although the conservation status of the paca is of least concern, our results have highlighted its important ecosystem role in Neotropical forests, interacting strongly with key and threatened species of the Atlantic Forest.

Sound management of coastal resources is based on science-based decisions. Bottlenose dolphins are found around Puerto Rico; however, limited information exists on the ecology, behavior, sex ratio, distribution patterns, and population structure presenting, challenges in managing the bottlenose dolphin as defined in the Marine Mammal Protection Act of 1972. We sequenced the mitochondrial control region (mtDNA-CR) of 27 live and 11 stranded dolphins from Puerto Rico, five stranded dolphins from Guadeloupe and included sequences from the North Atlantic and the Pacific Ocean. Our genetic data from the new samples indicates the presence of distinct genetic lineages (inshore—represented by coastal individuals) and worldwide-distributed form (represented by both coastal and offshore individuals) in Puerto Rico. DNA divergence between inshore/coastal and offshore haplotypes ranged from 4.34 to 6.58%. All haplotypes from Puerto Rico have been previously reported from the Caribbean and North Atlantic. Genetic analysis yielded a complex population structure without a clear geographic signal; an expected result from a highly mobile marine mammal. A clade consisting exclusively of coastal dolphins of the Caribbean and the western North Atlantic was recovered. Offshore haplotypes from the eastern and western North Atlantic were generally clustered with offshore haplotypes of the Caribbean. Coastal and offshore haplotypes from the Pacific differed from those from the Atlantic. When we partitioned the data by form (coastal vs. offshore) and ocean (Atlantic vs. Pacific), we detected significant population differentiation (F_ST = 0.4089), indicating limited gene flow between forms and across oceans.

The capybara, Hydrochoerus hydrochaeris, is a rodent that inhabits the wetlands of South America. Despite being widely distributed and having the nuclear genomes available, there has been a lack of information regarding the mitochondrial genome. To address this, we conducted the assembly and annotation of the capybara’s mitochondrial genome and reconstructed the phylogeny of Parvorder Caviomorpha. The assembly was conducted under the de novo method with GetOrganelle, while the annotation was performed with MitoZ. Analysis of relative codon synonymous usage was conducted in the mitochondrial genomes of the capybara and two other Caviidae species: Cavia porcellus and Cavia aperea. The phylogenetic inference was conducted under the Maximum Likelihood method, using the 13 protein-coding genes, including the capybara as well as other 42 Caviomorpha mitochondrial genomes. The resulting capybara mitochondrial genome consisted of 16,681 bp, 37 genes (22 tRNAs, 2 rRNAs, and 13 protein-coding genes) and a control region. The number of genes and their arrangement corresponds to the pattern observed in most mammalian species. The capybara was recovered as a sister group of Cavia. Caviidae was reconstructed as a monophyletic group that is closely related to Cuniculidae. Overall, this study provides valuable insights into the mitochondrial evolution and evolutionary relationships of the capybara.