http://hdl.handle.net/11606/55 Tesis Doctorales con investigaciones realizadas en ACG Tue, 09 Jun 2026 04:40:33 GMT 2026-06-09T04:40:33Z http://hdl.handle.net/11606/1581 COUNTERING INFANTICIDE: NEW PERSPECTIVES ON SEXUAL CONFLICT IN WHITE-FACED CAPUCHIN MONKEYS (Cebus imitator) Frivolity, Lauren For over 40 years, the sexual selection hypothesis of infanticide has sparked primatological interest in the evolutionary basis of this presumptively adaptive behavior. Infanticide by males has been largely accepted as a reproductive strategy in that when a new dominant sire kills unweaned infants, lactational amenorrhea ends, and females conceive more rapidly than if their infants had survived to weaning age. Thus, infanticide has been mainly investigated from the male perspective. Sexual conflict theory, which posits that males and females of the same species typically have different reproductive interests that can reduce fitness in the other sex, in general has focused on taxa with shorter life spans. A detailed study of sexual conflict in primates provides the opportunity to advance knowledge in organisms with long lifespans and complex behavior. I investigate several facets of how infanticide affects white-faced capuchins (Cebus imitator), a medium-sized platyrrhine with relatively slow life histories that experiences alpha male replacements (AMRs; change in dominant sire of group) accompanied by infanticide in the Sector Santa Rosa, Área de Conservación Guanacaste, Costa Rica. In my investigation, I found that AMR type does not predict infant survival but that infant age does, with younger infants having a greater risk of mortality. I also found that infants likely have the physiological ability to survive earlier weaning, but they do not appear to be able to wean early enough to decrease the risk of infanticide. My comparative analyses indicated that white-faced capuchins have longer lactation periods than expected based on body size. Allonursing also has the potential to function as a female counterstrategy to infanticide by enabling a faster resumption of cycling to decrease the risk of infanticide and/or decreasing the energy input that each mother makes into her young infants thereby decreasing the costs of infanticide. Finally, I found that AMRs increase reproductive synchrony and shift birth seasonality but that this shift in seasonality does not affect infant survival. Combined, my findings indicate that infanticide has a broader range of effects in white-faced capuchins than previously known and contributes to a greater understanding of sexual conflict theory. Wed, 01 Jul 2020 00:00:00 GMT http://hdl.handle.net/11606/1581 2020-07-01T00:00:00Z http://hdl.handle.net/11606/1580 THE BEHAVIOR AND ENDOCRINOLOGY OF DOMINANCE IN FEMALE WHITE-FACED CAPUCHIN MONKEYS (CEBUS CAPUCINUS IMITATOR) IN SECTOR SANTA ROSA, ÁREA DE CONSERVACIÓN GUANACASTE, COSTA RICA King-Bailey, Gillian Louisa The relationship between behavior, hormones and the environment has long been of interest to evolutionary biologists and biological anthropologists. Hormone levels vary between individuals, seasonally, and affect behavior. Research in male mammals shows dominance rank is related to androgen and cortisol levels, both of which vary with breeding season. However, even though females also produce androgens and they play a crucial role in regulating the female reproductive system, the role of androgens in the behavior of females is not well understood. White-faced capuchins (Cebus capucinus imitator) are female philopatric, medium-sized Neotropical monkeys. We characterize dominance in female white-faced capuchins, examine how rates of agonism vary with social and environmental change, and investigate the hormonal underpinnings of behavior in Sector Santa Rosa, Área de Conservación Guanacaste, Costa Rica. We find that females demonstrate only moderately linear dominance hierarchies, likely due to high kin-relatedness between females. We determined nearly the same hierarchy despite the methodology used to determine the rank order. Rates of agonism varied with dominance rank and fruit availability and we suggest that females inherit their rank from their mother, but use agonism to maintain this rank throughout their lives. Females adjust their rates of agonism such that they exhibit greater rates of agonism when ripe fruit availability is low. We propose that females need to increase agonism in order to gain access to sufficient resources to sustain themselves and their reproductive requirements. We also suggest that higher fruit availability leads to fewer bouts of agonism because there is enough fruit to occupy most group members. Higher-ranking females exhibit higher androgen and cortisol levels. This is inconsistent with the dual-hormone hypothesis, which suggests that higher-ranking individuals have higher androgen, but lower cortisol levels. It is possible that the threat of male takeovers leads to higher stress and thus higher levels of cortisol as the threat of infanticide remains present. Androgen and cortisol levels did not vary seasonally with fruit availability. This work advances our understanding of the relationship of behavior, hormone levels and environmental changes and is especially important for a growing understanding of androgens in female primates El estudio se realizó en la subcuenca del río Tempisquito, ubicado en la parte alta de la cuenca del río Tempisque, Guanacaste, Costa Rica. La subcuenca tiene una extensión de 14,29 km2 y drena sus aguas al golfo de Nicoya. El objetivo fue analizar el comportamiento del recurso hídrico a nivel de zonas de vida de Holdridge bajo escenarios de clima actual y futuro. El modelo hidrológico SWAT, en su interface de QGIS (QSWAT), es empleado para evaluar el comportamiento de producción de agua y erosión. La calibración del modelo es realizada con el programa SWAT-CUP. Para el clima futuro se consideran dos escenarios de emisiones RCP 4.5 y RCP 8.5 al 2070 según 5 modelos de circulación general. El proceso de calibración resultó en un muy buen modelo (NSE 0,70). Los resultados indican que para el año 2070 se espera una disminución de área y desplazamiento en algunas zonas de vida actuales, mientras que en otras su área aumentará. La producción de agua futura variará entre -37,07% y 69,75% con respecto al periodo base (2008-2011). Se proyecta una variación en la erosión media al año 2070 de entre -47,20% y 228,50%. La dinámica de la redistribución de las zonas de vida vinculadas al cambio del clima afectará la producción de agua, caudales y sedimentos. http://hdl.handle.net/11606/1580 http://hdl.handle.net/11606/1579 ENVIRONMENTAL DRIVERS OF JAGUAR DISTRIBUTION, ACTIVITY, AND ABUNDANCE IN SANTA ROSA NATIONAL PARK, COSTA RICA Montalvo Guadamuz, Victor Hugo ENVIRONMENTAL DRIVERS OF JAGUAR DISTRIBUTION, ACTIVITY, AND ABUNDANCE IN SANTA ROSA NATIONAL PARK, COSTA RICA DECEMBER 2020 VICTOR HUGO MONTALVO GUADAMUZ B.S., NATIONAL UNIVERSITY OF HEREDIA COSTA RICA M.S., NATIONAL UNIVERSITY OF HEREDIA COSTA RICA Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor Todd K. Fuller Jaguars (Panthera onca) are a landscape species persisting in less than 54% of their historical distribution range; thus, the understanding of abiotic and biotic environmental factors affecting ecological interactions of this top predator in seasonal ecosystems such the dry forest is crucial for their conservation. In addition to factors affecting species ecology, some methodological constraints also could affect jaguar study outcomes leading to wrong decision-making. Data gathered from available jaguar peer- reviewed literature showed that there are large number of variables and techniques used to model jaguar distribution that did not contribute substantially to descriptions of jaguar distribution. Using the variables that do correlate with distribution (or better estimates of those variables or what they represent) such as prey abundance, protection level, distance to protected areas, landcover, road variables and vegetation, would improve estimates of jaguar distribution and abundance based on intuitive predictors. Therefore, researchers should better identify and then quantify specific casual factors affecting jaguar distribution and abundance, rather than simply describe it. Camera trap data at waterholes and pathways in Santa Rosa National Park in northwestern Costa Rica were evaluated that included two camera trap designs (50 camera traps at waterholes and on pathways during both dry/wet seasons). For 10 large mammal species (including jaguars) and four large bird species in the dry forest of northwestern Costa Rica, only capuchin monkeys (Cebus capucinus), tiger herons (Trigrisoma mexicanum), white-tailed deer (Odocoileus virginianus), and tapirs (Tapirus bairdii) showed interacting effects of location and seasonality, suggesting that these species were the most influenced by waterholes during the dry season. Data from a single female jaguar equipped with a GPS unit, and seasonal sea turtle abundance data and predation rates from track count surveys at Playa Naranjo and Playa Nancite, were analyzed to assess jaguar dependency on nesting turtles. Seasonal movements of this single female were influenced by seasonal sea turtle abundance availability, an overall home range size of 89 km2 did not differ statistically across turtle and non-turtle seasons, and during turtle seasons this collared female tended to stay mostly near the coastline. With regard to camera placement and seasonality on photo rates of jaguars and nontarget species, from June 2016 to June 2017 I deployed 58 camera traps at trail and off-trail locations in a grid array. I recorded 64 species of amphibians, reptiles, birds and mammals for which I calculated and compared relative abundance indexes (RAI: no. of independent photos/100 trap nights). For jaguars, I identified a high RAI of males at trail locations and high rates of female jaguars at off trail locations. Analysis of predator and prey interactions indicated temporal avoidance at trail locations. Density estimation using spatial capture-recapture models registered 19 jaguar individuals (11 males; 8 females), and a population density of 2.6/100 km2 (95% [CI] 1.7-4.0) jaguar females and 5.0/100 km2 jaguar males (95% [CI])3.4-7.4). Camera location placement might bias sex individual detections and subsequent estimates based on telemetry and camera trap data. Long-term studies of jaguar populations might give more realistic and useful insights to conservation if researchers paid more attention to species’ behavior and interactions that could be biasing results. Thus, it is important to continuously rethink the “what?” and “how?” of the things we are doing in conservation science to effectively understand ecological processes. Additional observations from this study suggest some large herbivores are more sensitive to changes of climate than other species; therefore, jaguar studies should continue to tackle the effects of climate variability on prey species and their relationships with large predators in a unique ecosystem such the tropical dry forest. Tue, 01 Dec 2020 00:00:00 GMT http://hdl.handle.net/11606/1579 2020-12-01T00:00:00Z http://hdl.handle.net/11606/1578 CORRIDOR USE, HABITAT SELECTION, AND ROUTE CHOICE BY FOREST BIRDS IN THE FRAGMENTED TROPICAL DRY FORESTS OF COSTA RICA Gillies, Cameron Scott Tropical forests hold the majority of the world’s biodiversity, but face tremendous threats from agricultural expansion. Among these forests, dry forests have already undergone extensive clearing and only 2% of the original tropical dry forest remains in Mesoamerica. In such fragmented landscapes, the movement of individuals among subpopulations is fundamental to long term population persistence. Despite the importance of movement, little is known about how forest-dependent birds move through fragmented areas and use connecting habitat elements, like corridors. To address this deficiency, I translocated individuals of two species of forest birds with differing forest dependence in three treatments in the fragmented tropical dry forests of northwestern Costa Rica: along a riparian corridor, along a fencerow, or across pasture. I then followed their return trajectories with unprecedented resolution, recording positions approximately every 15 min for up to four days. Detailed route information yielded four main conclusions. First, riparian corridors facilitated the movement of the forest specialist barred antshrike (Thamnophilus doliatus). In riparian corridor treatments, returns to their original territories were faster and more likely, they selected forest habitat more strongly, and they traveled further from the forest edge. Second, fencerows were not sufficient corridors for the specialist, which generally chose longer routes in forest rather than more direct routes via fencerows. Third, individuals adjusted their behaviours based on habitat context. In addition to changes by the specialist in riparian corridor treatments (above), the generalist rufous-naped wren (Campylorhynchus rufinucha) selected forest more strongly in riparian corridor treatments and selected edge habitat more strongly with decreases in forest cover. Finally, the specialist chose more forested steps when they were far from their territories and when in forest habitat. They preferred steps ending in stepping stones (isolated trees) when available routes had low forest cover, but avoided them when forest cover was higher. I conclude that forested habitat and corridors benefit the movement of forest specialist birds and the conservation of these habitats will be important in this landscape and likely others. Furthermore, stepping stones may be an important element for the movement of birds through the most inhospitable matrix where forested alternatives do not exist. Tue, 01 Jan 2008 00:00:00 GMT http://hdl.handle.net/11606/1578 2008-01-01T00:00:00Z