Spatial Distribution and Exploitation of Trees Gouged by Common Marmosets (Callithrix jacchus)

Detection of conspicuous and cryptic food by common marmosets (Callithrix jacchus): An evaluation of the importance of color and shape cues

In primates, the advantage of trichromacy (i.e., color vision expressed by most humans) over dichromacy (i.e., color vision expressed by many colorblind humans) has been linked to the detection of yellowish/reddish targets against a background of mature green leaves. Nevertheless, mostly because of studies conducted in humans, we know that achromatic cues might also play an important role in object identification, particularly when camouflage is involved. For instance, dichromacy favors the detection of camouflaged targets by exploitation of shape cues. The present study sought to evaluate the relative importance of color and shape cues on the detection of food targets by female and male marmosets (Callithrix jacchus). Animals were observed with respect to their foraging behavior and the number of food targets captured. We confirmed that females are advantageous in detecting conspicuous food against a green background and revealed that females and males rely on shape cues to segregate cryptic food. Unexpectedly, males outperformed females in cryptic food foraging, while camouflage improved males' (but not females') performance. Here we show that dichromats could potentially benefit from a better segregation of green natural targets (e.g., immature fruits, green insects, and gum trees) when viewed against a green dappled background.

Captive Common Marmosets (Callithrix jacchus) Are Colonized throughout Their Lives by a Community of Bifidobacterium Species with Species-Specific Genomic Content That Can Support Adaptation to Distinct Metabolic Niches

The common marmoset (Callithrix jacchus) is an omnivorous New World primate whose diet in the wild includes large amounts of fruit, seeds, flowers, and a variety of lizards and invertebrates. Marmosets also feed heavily on tree gums and exudates, and they have evolved unique morphological and anatomical characteristics to facilitate gum feeding (gummivory). In this study, we characterized the fecal microbiomes of adult and infant animals from a captive population of common marmosets at the Callitrichid Research Center at the University of Nebraska at Omaha under their normal dietary and environmental conditions. The microbiomes of adult animals were dominated by species of Bifidobacterium, Bacteroides, Prevotella, Phascolarctobacterium, Megamonas, and Megasphaera. Culturing and genomic analysis of the Bifidobacterium populations from adult animals identified four known marmoset-associated species (B. reuteri, B. aesculapii, B. myosotis, and B. hapali) and three unclassified taxa of Bifidobacterium that are phylogenetically distinct. Species-specific quantitative PCR (qPCR) confirmed that these same species of Bifidobacterium are abundant members of the microbiome throughout the lives of the animals. Genomic loci in each Bifidobacterium species encode enzymes to support growth and major marmoset milk oligosaccharides during breastfeeding; however, metabolic islands that can support growth on complex polysaccharide substrates in the diets of captive adults (pectin, xyloglucan, and xylan), including loci in B. aesculapii that can support its unique ability to grow on arabinogalactan-rich tree gums, were species-specific.

Navigating in a challenging semiarid environment: the use of a route-based mental map by a small-bodied neotropical primate

To increase efficiency in the search for resources, many animals rely on their spatial abilities. Specifically, primates have been reported to use mostly topological and rarely Euclidean maps when navigating in large-scale space. Here, we aimed to investigate if the navigation of wild common marmosets inhabiting a semiarid environment is consistent with a topological representation and how environmental factors affect navigation. We collected 497 h of direct behavioral and GPS information on a group of marmosets using a 2-min instantaneous focal animal sampling technique. We found that our study group reused not only long-route segments (mean of 1007 m) but entire daily routes, a pattern that is not commonly seen in primates. The most frequently reused route segments were the ones closer to feeding sites, distant to resting sites, and in areas sparse in tree vegetation. We also identified a total of 56 clustered direction change points indicating that the group modified their direction of travel. These changes in direction were influenced by their close proximity to resting and feeding sites. Despite our small sample size, the obtained results are important and consistent with the contention that common marmosets navigate using a topological map that seems to benefit these animals in response to the exploitation of clustered exudate trees. Based on our findings, we hypothesize that the Caatinga landscape imposes physical restrictions in our group's navigation such as gaps in vegetation, small trees and xerophytic plants. This study, based on preliminary evidence, raises the question of whether navigation patterns are an intrinsic characteristic of a species or are ecologically dependent and change according to the environment.

Callitrichid responses to dead and dying infants: the effects of paternal bonding and cause of death

Many primates show responses to dead infants, yet testing explanations for these behaviors has been difficult. Callitrichids present a unique opportunity to delineate between hypotheses, since unlike most species, male caretakers form closer social bonds with infants than mothers. Callitrichids are also known to commit infanticide, leaving obvious wounds that may enable them to more readily recognize death. We present: (1) a case study of a wild common marmoset (Callithrix jacchus) group responding to an infant's natural death, and (2) a review of published infant deaths across callitrichids (N = 16), testing for trends in the sex of reacting individuals and cause of death. In our case study, several group members frequently interacted with the dead infant, attempting to carry it. However, the strongest response was from a male that remained with the corpse for ~ 3 h, despite his group leaving the area. Across callitrichid species, corpse interactions were significantly sex-biased: 100% (N = 6) of accidental deaths involved corpse interaction by males (p = 0.007), compared to 60% (N = 3 of 5) by females (p = 0.095). Cause of death also played a significant role, with individuals attempting to carry dead infants in 100% (N = 6) of accidental deaths, but only 11.1% (N = 1 of 9) of infanticides (p = 0.001). Although the available literature is small and potentially subject to publication biases, these data support the idea that visually obvious wounds may influence callitrichids' perception of dead conspecifics. Additionally, male-biased patterns of corpse interaction in callitrichids indicate that social bonds likely shape reactions to the dead, in addition to kinship. While published data on primate thanatology are limited, this study demonstrates quantitative approaches that can provide empirical insights into primates' responses to dead conspecifics.

The Endless Challenges of Arboviral Diseases in Brazil

In this Editorial, we list and discuss some of the main challenges faced by the population and public health authorities in Brazil concerning arbovirus infections, including the occurrence of concurrent epidemics like the ongoing SARS-CoV-2/COVID-19 pandemic.

Habitat selection by the black-tufted marmoset Callithrix penicillata in human-disturbed landscapes

There are several primate species with high risk of extinction in small forest fragments disturbed by human activities. However, some species exhibit high ecological plasticity, which allows them to persist in human-modified landscapes. The main goal of this study is to examine the relative roles of vegetation (mean distance among trees and mean canopy cover), human disturbance (distance to the road, distance to the fragment edge and edge type), and habitat spatial configuration (spatial autocorrelation index, category of quadrat – position within the fragment/fragment type) on the habitat selection of the black-tufted marmoset Callithrix penicillata in forest patches. We selected forest patches near and away from roads/urban areas, in southern Minas Gerais state, south-eastern Brazil. We used generalized linear mixed models to explain the presence of black-tufted marmoset in those patches. Our results show that black-tufted marmoset tend to occupy forest fragments closer to roads/urban areas, and consequently are under the influence of anthropic disturbance. In addition to the area delimited by these fragments, there is a preference for edge environments, where disturbances are exacerbated and the ecological conditions are suitable for exploitation by the black-tufted marmoset (supply of gum trees and reduced risk of competition). We suggest that a cross-habitat spillover by marmoset occur from forests to small habitat patches close to human-modified areas, such as those in proximity to roads and urban zones.

Feeding habits of marmosets: A case study of bark anatomy and chemical composition of Anadenanthera peregrina gum

Primates of the genus Callithrix often obtain exudates from plants of the family Fabaceae. This study characterizes the chemical composition of exudates, and the anatomy and hystochemistry of the secretory ducts in the bark of Anadenanthera peregrina (L.) Speg. var. peregrina (Fabaceae). Exudates from this tree species represent an important component of the diet of hybrid marmosets, Callithrix spp. (Primates: Cebidae). A. peregrina was selected as the focal study tree because it is the only gum tree species exploited by Callithrix groups present within five urban forest fragments in the municipality of Viçosa, Minas Gerais State, Brazil. Gum samples were obtained directly from gouges made by the marmosets, while bark samples were obtained from A. peregrina plants, whether or not they were damaged by the marmosets. Constitutive secretory ducts were present in the bark of ungouged A. peregrina, whereas, marmoset damage caused induced secretory duct formation and an increase in the size of these ducts. The gum produced in the gouges made by the marmosets and in ungouged plants reacted positively to tests for polysaccharides, pectin, mucilage, and proteins. The gum from the gouges exhibited high water (41.0%), carbohydrate (38.2%), protein (19.0%), and mineral (Ca 0.4% and K 0.3%) content. We argue that the relatively high calcium content of A. peregrina gum plays an important nutritional role in, balancing a diet that is otherwise rich in phosphorous and poor in calcium.

A review of home-range studies on Australian terrestrial vertebrates: adequacy of studies, testing of hypotheses, and relevance to conservation and international studies

Describing the spatial requirements of animals is central to understanding their ecology and conservation needs. I reviewed 115 studies describing the home ranges of Australian terrestrial vertebrates that were published during 2001–12. Understanding the features that characterise best practice can guide future studies. I aimed to: evaluate the adequacy of these studies, examine the use of current analysis techniques, examine the application of home-range knowledge to species’ management, and examine hypotheses that seek to explain the size and location of home ranges. The reviewed studies were unevenly distributed across taxa with a majority (68%) involving mammals compared with birds (12%), reptiles (19%) and frogs (1%). Many studies had various shortcomings, suggesting that they had not fully described home ranges; many (41%) involved 10 or fewer individuals, ≤50 locations per individual (44%), and spanned periods of ≤3 months (46%). Studies of short duration risk underestimating home-range area and overlooking seasonal habitat use. Global positioning system telemetry was used in 10% of Australian studies. Many were also of short duration. Despite frequent criticism in the literature, the Minimum Convex Polygon was the most frequently used home-range estimator (84% of studies), followed by the Fixed Kernel (45% of studies). Applying knowledge of home ranges appears to be underappreciated, with only 39% of studies explicitly aiming to address management or conservation issues. Only three studies tested hypotheses that may explain home-range characteristics. Resource (food and shelter) distribution and, in one case, its heterogeneity, shaped home-range characteristics. I found that most studies use the term ‘home range’ in an indiscriminate way. Only 11% of studies within the international literature used qualifying terms (e.g. seasonal, annual). Tracking period is shown to influence home-range estimates. Therefore, I recommend that qualifying terms be used more frequently to avoid confusion when referring to animal home ranges.

Vegetable exudates as food for Callithrix spp. (Callitrichidae): exploratory patterns

Marmosets of the genus Callithrix are specialized in the consumption of tree exudates to obtain essential nutritional resource by boring holes into bark with teeth. However, marmoset preferences for particular tree species, location, type, and other suitable factors that aid in exudate acquisition need further research. In the current study, the intensity of exudate use from Anadenanthera peregrina var. peregrina trees by hybrid marmosets Callithrix spp. groups was studied in five forest fragments in Viçosa, in the state of Minas, Brazil. Thirty-nine A. peregrina var. peregrina trees were examined and 8,765 active and non-active holes were analyzed. The trunk of A. peregrina var. peregrina had a lower number of holes than the canopy: 11% were found on the trunk and 89% were found on the canopy. The upper canopy was the preferred area by Callithrix spp. for obtaining exudates. The intensity of tree exploitation by marmosets showed a moderate-to-weak correlation with diameter at breast height (DBH) and total tree height. The overall results indicate that Anadenanthera peregrina var. peregrina provides food resources for hybrid marmosets (Callithrix spp.) and these animals prefer to explore this resource on the apical parts of the plant, where the thickness, location, and age of the branches are the main features involved in the acquisition of exudates.