Browsing by Author "Fedigan, Linda Marie"
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- ItemOpen AccessThe Acoustic Structure and Ontogeny of Vervet Monkey Vocalizations(2019-11) Dubreuil, Colin; Notman, Hugh; Pavelka, Mary McDonald; Henzi, Peter; Hare, James; Fedigan, Linda Marie; Barclay, Robert Malcolm RuthvenVervet monkey (Chlorocebus pygerythrus) vocalizations have been the subject of considerable research, most notably for their putative language-like qualities. While this focus has inspired a productive research effort investigating vocal communication in non-human primates, it has diverted attention away from other, non-linguistically inspired mechanisms by which vocal signals exert their effects on receivers. My research focuses on two vocal classes, grunts and alarm calls, and how their acoustic structures vary according to sender-specific attributes, including age, sex, body size, and identity - all of which have the potential to influence receiver response. I recorded calls from three wild groups of vervet monkeys over a 7-month period on the Samara Game Reserve, South Africa. I used random forest models to determine whether grunts varied in structure in relation to caller age, sex, identity and context, and whether alarms varied with sex and caller identity. I performed a cluster analysis to determine whether alarms segregated into different call types based on variation in acoustic structure. Finally, I used a series of mixed effects models to determine whether call structure in males and females correlated with overall body size (using body weight as a proxy). I found grunts varied in structure with age and sex, but not among individuals or contexts. Alarm calls varied with both sex and identity. My cluster analysis identified two qualitatively distinct alarm call types corresponding to the calls of males and females respectively. My analysis demonstrated that the relationship between body weight and the distribution of acoustic energy throughout alarm calls differed between the sexes. Relative to females, acoustic energy in the calls of males was concentrated at disproportionately lower frequencies. These results suggest that alarm calls may be under selection to exaggerate caller body size and/or extend the effective range of these signals in males. My results highlight that vocalizations can vary in structure along a number of dimensions simultaneously. While it is possible that in some instances, vocalizations convey specific information surrounding their context of production, it is likely that the mechanisms by which vocal signals exert their effects on receivers are more numerous and diverse.
- ItemOpen AccessFigs Are More Than Fallback Foods: The Relationship between Ficus and Cebus in a Tropical Dry Forest(2011-10-03) Parr, Nigel A.; Melin, Amanda D.; Fedigan, Linda MarieIn many studies on primate feeding ecology, figs (Ficus spp.) are characterized as fallback foods, utilized only when preferred sources of food are unavailable. However, for white-faced capuchin monkeys (Cebus capucinus) living in northwestern Costa Rica, figs are a consistently important resource and may increase groupwide energy intake. We investigated whether visits to figs affect ranging and behavioural patterns of capuchins. Although daily range length and average travel speed do not differ on days when fig trees are visited, capuchins spend more time in directed travel and more time stationary on “fig days”. Capuchins also increase time spent foraging for fruit and decrease time spent foraging for invertebrates on days when figs trees are visited. Capuchins experience higher energy intake and lower energy output on “fig” days. Thus, the patterns of foraging for figs support an energy-maximization strategy and constitute an important nutritional resource for capuchins.
- ItemOpen AccessIntraspecific niche divergence in foraging and habitat use in wild Costa Rican capuchin monkeys(2019-09-20) Williamson, Rachel Elaine; Melin, Amanda D.; Fedigan, Linda Marie; Pavelka, Mary McDonald; Neuhaus, PeterPermanent social grouping, while rare among mammals, is routine in primates. Group-living increases intraspecific foraging competition, but niche divergence, i.e. differences in food selection and microhabitat use, may help mitigate competition. I investigated whether niche divergence occurs in wild white-faced capuchins (Cebus capucinus imitator) based on their age and/or sex classes and found that: 1) immature monkeys spent more foraging time on fruits and embedded invertebrates than adults. Females spent more time on fruits than males, but males foraged more on embedded invertebrates and difficult-to-process fruits; 2) immatures and males foraged more in the lower canopy; 3) adults and males foraged more on the forest floor; 4) immatures and females foraged more on small branches; and 5) immatures foraged more on angled branches. These results indicate that age- and sex-specific patterns are present. This likely reduces the experience of intraspecific foraging competition and may help facilitate group-living.
- ItemOpen AccessLandscapes of change: the ecology of white-faced capuchins over space and time(2014-07-18) Campos, Fernando Alonso; Fedigan, Linda MarieAs global change accelerates, there is a growing imperative to understand how wild animals respond to changing environments. I investigated how environmental variability, both in the short term (seasonality and habitat differences) and the long term (changing climate and habitats), shapes the behavioral ecology of white-faced capuchins (Cebus capucinus) in a highly seasonal dry forest mosaic in Costa Rica. I used a multi-scale approach with the ultimate goal of gaining a more complete understanding of how individual-level selective pressures scale up over space and time to affect group and population dynamics. Perceived predation risk, based on alarm-call responses to distinct predator classes, varied among habitat types and was greatest in mature forest. The capuchins adjusted their anti-predator vigilance behavior to changing levels of perceived risk. Feeding efficiency varied over both space and time and was greatest during the wet season and in mature forest habitats, which were both associated with higher energy intake rates and lower energy expenditure rates. The hot dry season also favored smaller home ranges, with high-use zones concentrated around patches of mature evergreen forest. These findings demonstrate that environmental variability plays a key role in driving the spatial ecology of capuchin individuals and groups. Because the dry season is associated with greater energetic deficits, the capuchins' increased preference for mature forest and more compact use of space during the dry season may be a behavioral adjustment aimed at maximizing use of the most productive foraging areas and reducing travel, perhaps at the expense of safety. Finally, I examined spatial and demographic patterns in the growing capuchin population over multiple decades in relation to quantitative information on how the environment changed over the same period. The availability of evergreen habitats varied with the strength of the previous wet season, which in turn was strongly coupled with global climatic and oceanic cycles. Following extreme drought periods, population growth slowed, mean group size decreased, and reproductive rate declined. Future work will aim to develop a deeper understanding of how climate change will affect primate populations and to expand the scope and generality of this research to a global scale.
- ItemOpen AccessMaternal and Nonmaternal Infant Handling in Colobus vellerosus(2018-05-09) Gibson, Allyson; Sicotte, Pascale; Notman, Hugh; Fedigan, Linda MarieThis project investigated whether variation existed in durations of maternal and nonmaternal received by infants (when controlling for infant age) in wild Colobus vellerosus monkeys. I examined whether variation in handling durations was associated with infanticide risk using behavioral data collected from 16 infants ranging in age from newborn to 78 weeks. Maternal handling constituted the bulk of ‘total’ handling received by infants. Individuals varied in the duration of handling they received. Less maternal handling occurred in unstable groups, and male infants receiving more handling. Neither maternal nor nonmaternal handling responded to all infanticide risk factors. These results suggest that handling is a flexible behavior, but it is not yet entirely clear what factors handlers respond to, and why. One potential explanation is that, when infanticide poses a higher threat, mothers decrease infant-contact time to facilitate faster infant development while nonmothers increase handling as a form of protection.
- ItemOpen AccessTrichromatic perception of flower colour improves resource detection among New World monkeys(Nature Scientific Reports, 2018-07-18) Hogan, Jeremy D.; Fedigan, Linda Marie; Hiramatsu, Chihiro; Kawamura, S.; Melin, Amanda D.Many plants use colour to attract pollinators, which often possess colour vision systems well-suited for detecting flowers. Yet, to isolate the role of colour is difficult, as flowers also produce other cues. The study of florivory by Neotropical primates possessing polymorphic colour vision provides an opportunity to investigate the importance of colour directly. Here we determine whether differences in colour vision within a mixed population of wild dichromatic and trichromatic white-faced capuchins (Cebus capucinus imitator) affect flower foraging behaviours. We collected reflectance data for flower foods and modelled their chromatic properties to capuchin colour vision phenotypes. We collected behavioural data over 22 months spanning four years, determined the colour vision phenotype of each monkey based on amino acid variation of the L/M opsin gene from fecal DNA, and compared foraging behaviours of dichromats and trichromats. Most flowers were more conspicuous to trichromats, and trichromats foraged in small flower patches significantly more often. These data demonstrate a difference in wild primate foraging patterns based on colour vision differences, supporting the hypothesis that trichromacy enhances detection of small, ephemeral resources. This advantage, which may also extend to other foods, likely contributes to the maintenance of colour vision polymorphism in Neotropical monkeys.
- ItemOpen AccessVariation in the Timing of Nutritional Weaned Age in Colobus vellerosus(2018-09-04) Rissling, Tianna C.; Sicotte, Pascale; Katzenberg, Mary Anne; Fedigan, Linda MarieThe transition between infancy and juvenility occurs once nutritional independence is achieved. Weaning, weaned age, and weaned event are all landmarks during this transition but are ill defined. In this thesis, I reviewed the literature on the transition from infancy to juvenility. I then examined the factors that influenced this transition from nutritional dependence to independence, and survivorship in a wild, folivorous primate. I compiled behavioural records from 83 infants from a population of Colobus vellerosus. Infants were weaned earlier when they lived in a good quality home range. Most weaned events occurred during or prior to peaks in easy to process foods. New juveniles were also more likely to survive when their weaned event coincided with high food availability. These findings suggest that food availability is the most influential factor determining when during the year, and at what age, infants transition to juveniles.