This collection contains the findings of scientific studies of tropical terrestrial and marine ecosystems, their components, and their conservation from Monteverde, Cuajiniquil, and other areas of Costa Rica.
This digital collection is a service of the Monteverde Institute, whose mission is to catalyze social, ecological and economic sustainability by integrating community initiatives with education, research and conservation.
Esta colección contiene los hallazgos de estudios científicos de ecosistemas tropicales terrestres y marinos, sus componentes y su conservación de Monteverde, Cuajiniquil y otras áreas de Costa Rica.
Esta colección digital es un servicio del Instituto Monteverde, cuya misión es catalizar la sostenibilidad social, ecológica y económica integrando iniciativas comunitarias con educación, investigación y conservación.
Leafcutter ants Atta cephalotes (Hymenoptera: Formicidae), common to Central and South America, have a profound caste system to ensure the cultivation of a special fungus, Leucocoprinus gongylophorus, which is their main food source. Within the caste system, the workers job is to forage and carry back pieces of leaves that are necessary for fungus farming. The minima have long been thought to be protecting the worker ants from parasitic phorid flies (Diptera: Phoridae), who have been studied to await near the entrance of the nest to land on a leaf and lay eggs on the head of the worker ant. But, there have been various studies that have suggested that hitchhikers have other functions. The other two hypotheses include cleaning the leaf and feeding from the sap. Using four methods and previous student research, I tested and analyzed the most probable function of the minima. On average, there were more hitchhikers present near the entrance of the nest than there were 6 meters away. The hitchhikers also showed to perform multiple behaviors along the trail and are most likely to react protective due to a disturbance on the leaf. Lastly, the hitchhikers ride the leaf for a long distance until the entrance of the nest, or for a short distance and get off the leaf the leaf before getting to the entrance. My study concludes that hitchhikers perform multiple functions depending on various factors, such as the time of day and the location of the trail.
Elizabeth L. McDonald
Tropical regions, especially tropical montane regions, are biodiversity hotspots for amphibians. In tropical montane forests, varying temperatures and precipitation along an elevational gradient create distinct Holdridge life-zones for the 51 species of frogs and toads in Monteverde, Costa Rica. However, changing climatic conditions, and other complex factors, have contributed to recent anuran declines in the Monteverde area and worldwide. Shifting abiotic conditions cause species to move to new areas with suitable conditions. Within this study, I establish a data set complimentary to previous baselines of anuran distributions in local areas. In doing so, current encountered distributions can be compared to expected distributions. I conducted visual and auditory surveys across 5 locations and between 4 Holdridge life-zones in the Monteverde area. In a comparison to past studies and literature, I encountered 4 species in zones that contrasted expected life-zones. However, I did not determine an upslope trend that parallels the upslope shift in abiotic conditions. Because changes are complex, it is imperative to monitor how vulnerable species react to changing environmental conditions over time.
Meghan R. Garfink
Global climate change impacts ecological relationships of all taxa and kingdoms, yet little has been documented of the impact on insects. This study documents the changing elevational range of four Azteca ant species in Cecropia trees in the Monteverde cloud forest. In Monteverde, Costa Rica, many species of Cecropia form a mutualism with Azteca in which ants receive nutrients in exchange for protection of the tree. Data was collected in May 2019 and compared to similar studies done in 1989 (Longino), 2003 (Mazzei), 2008 (Loope), and 2016 (Jensen). Since 1989, maximum elevational range of Azteca increased by 132 meters. Average elevation of all species of Azteca and Cecropia have increased significantly since 1989 as well. One species of Cecropia, C. polyphlebia, contained Azteca at 1500 m, despite historically not harboring Azteca. This data indicates that Azteca are moving upslope and inhabiting different species of Cecropia in Monteverde, potentially due to climate change.
Tropical forests, the richest ecosystems on earth, are rapidly disappearing. This is causing the loss of species at an unprecedented rate. However, there is hope to regain lost biodiversity through the process of forest regeneration. Insects, the most specious class of animals, are concentrated in the tropics. I examined the effects of reforestation on insect species composition and diversity in the canopy and understory of a premontane tropical forest in Monteverde, Costa Rica: La Calandria. I collected insects with flight interception traps and analyzed the composition and diversity of orders and hymenopteran morphospecies. I found that species composition varies with reforestation status and between the forest canopy and understory. Although the species composition is different, I found diversity between less disturbed and regenerated forest to be similar.
Diversity and richness of non vascular epiphytes on strangler figs: effects of elevation on emergent trees
Kimberlie M. Sullivan
The Monteverde cloud forest is characterized by its high precipitation levels, frequency of cloud immersion, and extraction of cloud water, but global climate models indicate a reduction in low level cloudiness, suggesting cloud forests may soon be replaced by forests that occur at lower altitudes. Studies found that non- vascular epiphytes are very sensitive to changes in moisture and temperature, resulting in a substantial deterioration in health, such as reduced growth rates, water holding capacity, and ability to fix nitrogen, which makes non- vascular epiphytes a compelling indicator of climate change. I conducted a survey that contrasts epiphyte diversity and species richness on emergent strangler fig trees at two elevations as well as compares diversity and species richness in the understory to the upper canopy. My survey showed lichen have the highest species richness and that there is significantly greater abundance of lichen at 1470m compared to 1200m. My study indicated that different morphospecies of lichen grow at specific elevations, with only 28% of the same morphospecies of lichen prevalent at both elevations. This study supports previous studies that found differences in epiphyte communities due to variances in microclimates along emergent trees and at different elevations.
Many frog populations are currently threatened due to a variety of reasons, but a prevalent reason is due to a fungal disease, chytridiomycosis, that attacks amphibian skin. Current studies suggest that possible resistance of chytrid fungus in certain frog populations can be attributed to the bacterial and fungal diversity found on the mucus of frog skin. In this study, I looked at whether various environmental factors can be correlated to a higher micro-biodiversity by swabbing individual frogs that were found in a variety of habitats. I swabbed 39 frog individuals in five different locations around Monteverde. I then grew fungal and bacterial colonies on agar plates to examine the biodiversity of the microbes on frog skin in respect to location, area which frog was found, and distance from water. My data shows that there was no significant difference between any of the environmental factors such as overall location of frog, the distance the frog was to the nearest source of water, and habitat that the frog was found on. The data did show significant differences in quantity of biodiversity of both bacteria and fungi in various species; and a significant increase for bacterial diversity in one species of frog that agrees with a past study. The data suggests that species may play a more prominent role in determining how much fungal and bacterial diversity is found on an individual rather than the location that the individual is in.
Animal behavior is strongly influenced by the threat of predation. This has led to the development of complex communication systems between predators and prey. In bats, many types of ultrasonic calls have been studied in depth, but low frequency distress calls have rarely been examined. In order to analyze which variables might be able to predict whether a given bat performs a distress call, I captured 36 bats and recorded their behavior and the decibel power of their calls. I found that bats of a smaller mass were more likely to engage in distress calls while bats with a greater forearm length emitted calls with greater decibel power, indicating greater energy and range. However, these findings may be biased by which species I captured. I also found that nursing bats were less likely to call than non-reproductive males and females, implying some unknown risk associated with distress calling that nursing bats needed to avoid. My findings suggest that while smaller bats may be more likely to call, the calls of larger bats are more acoustically powerful and therefore would likely be more effective at attracting bats from long distances. There is likely an unknown cost associated with distress calling in nursing bats that merits further study.
Michelle C. Temby
Corals occupy less than 1% of the surface area of world oceans but provide a home for 25% of all marine fish species. Nevertheless, corals do not get the attention they deserve in terms of their success as organisms. In my study, I analyze individual coral heads, specifically the genus Pocillopora (tentative identification: Pocillopora elegans), and their establishments in Cuajiniquil using 3 locations in Guanacaste, Costa Rica to understand why coral reefs are not establishing at some sites. These sites occur at Bajo Rojo, Bahía Thomas West, and Isla David. I recorded the size of establishing coral heads, the surrounding water temperature where each coral head occurred, the urchin cover in a 30cm radius of each coral head, the bleaching of each individual coral head, the substrate the coral was establishing on, the approximate angle of the substrate, the depth of the coral, and the surge of the water at each site. I found several potential factors responsible for the failure of Pocillopora to establish in Cuajiniquil: urchin populations that may compete with corals for substrate, strong surges that may displace larvae, and a range in coral health measured by bleaching observed at Isla David and Bajo Rojo. Pocillopora spp. are, however, establishing in larger numbers at Bahía Thomas which may be due to the weak surge, the smaller quantities of urchins, and the good health of individual establishing corals.
John Wade Carson
La Calandria Forest is a coffee plantation-turned-reforestation project located in Los Llanos, Monteverde, Costa Rica. One of the species that seems to be successful in this forest is Atta cephalotes leaf cutter ants (Hymenoptera: Formicidae). I studied A. cephalotes foraging and nesting behavior to better understand their ecological relationships within a tropical forest ecosystem. I recorded the location of A. cephalotes nests and foraging sites with a GPS, and then identified plant species that these leaf cutter ants foraged from. After collecting data for two weeks: I created a map of A. cephalotes nests and their corresponding foraging sites, calculated foraging distances for each nest, calculated the nest density of an 11-hectacre segment of La Calandria, and analyzed the foraged plant species composition. I concluded that: 1) Most A. cephalotes nests resided either in clearings or along the forest edge. 2) Different ant colonies never crossed paths, and avoided foraging in each other’s territory. 3) La Calandria had an A. cephalotes nest density of 1.55 nests/ha. This is higher than values commonly found for tropical primary forest, but lower than the nest densities of forests adjacent to agriculture. 4) A. cephalotes foraged from a variety of plant species, but Inga punctata comprised 26.4% of the targeted forage sites. 5) On average, larger nests (33m) traveled farther than smaller nests (18m) to forage from plants.
Samantha V. Abarca and Camille A. Ornburn
Species of the family Pomacentridae, including damselfishes, provide parental care and show territorial behavior. Microspathodon dorsalis, Giant damselfishes, are known to be especially territorial within their nesting sites and will attack other species that go within a few meters of their nests. Another species known as Stegastes acapulcoensis, Acapulco damselfish, are often seen to inhabit near the Giant damselfish nests. From 11 May 2019 to 18 May 2019, we studied the aggressive behavior of Giant damselfish and Acapulco damselfish at multiple sites on the coast of Cuajiniquil, including Bajo Rojo, Bahía Thomas, and Jack’s Point. We observed how often Giant damselfish and Acapulco damselfish would attack each other and individuals within their own species. We also observed other factors that can influence aggressiveness such as location of nests, algae presence, the face color of Acapulco damselfish, and the number of damselfishes around each nesting site. Our results indicate that when near their nests, Giant damselfish are more aggressive than Acapulco damselfish. Furthermore, Giant damselfish chase away Acapulco damselfish more often than conspecifics. Also, Giant damselfish are more aggressive towards Acapulco damselfish with brown faces compared to Acapulco damselfish cream faces. This study gives insight to the aggressive behavior of two species of damselfish near Giant damselfish nests.
Excess livestock waste can pollute water sources. Limited access to clean energy leads to burning of fossil fuels such as propane. Biodigesters treat animal manure, converting it into a nutrient-rich fertilizer and methane gas for fuel. I tested different substrate mixtures (including pig manure co-digested with goat manure, chicken manure, and whey) in a lab setting, measuring methanogenic potential of each treatment in order to test one in the biodigester. I also tested the effect of water-towaste ratio on gas production. Treatments containing pig manure, either alone or codigested with other manure types, produced the most gas. Mixtures containing whey produced the least gas. In the field, I tested a mixture of pig and goat manure against the control conditions of 6:1 water-to-pig manure ratio. The experimental treatment significantly increased flame height but did not significantly increase the total burn time.
Dairy cows were domesticated about 10,500 years ago and have been used for milk production ever since. In Costa Rica, they usually live in herds in pastures, therefore they spend most of their time near each other. Research shows they have hierarchies which can be influenced by size, age, and lactation cycle. In this study, I set out to find the social hierarchy in a herd of heifers who are of similar age and size, and do not have a lactation cycle. I traveled to La Finca Paraíso to observe heifers for a total of 12 hours, and recorded every time a heifer gave or received an aggressive or affectionate act. I recorded the order the heifers traveled from one pasture to a new pasture, and twice a day, I recorded the spacing of each heifer in relation to the other individual heifers. The data did not support a strong social hierarchy in the herd. There are many factors that could have influenced the lack of social hierarchy in the herd: change in heifer composition of the herd, time of observation, or time heifers spent laying/resting.
Brianna R. Kennedy
Bats are commonly affected by parasites known as bat flies in the families Nycteribiidae and Streblidae. It is important to understand bat flies and their effects on bat populations due to their ubiquity. Differences in roosting behaviors, led me to believe that female bats would carry more bat flies than males. I investigated the difference in bat fly abundance between the sexes in a variety of species in Monteverde included in the genera Carollia (n = 9), Sturnira (n = 5), Lonchorhina (n = 1), Micronycteris (n = 1), Artibeus (n = 6), Glossophaga (n = 1), Desmodus (n = 1), Platyrrhinus (n = 1), and Myotis (n = 19) for a total of 44 bats. In order to investigate the effect of the presence of bat flies on overall health, I chose to focus on two indicators of health. This included different body temperatures collected from the underarm, belly, membrane, and forearm along with the effect on the presence of holes and scars in the wing membrane as this is where the bat flies are commonly found. No significant difference in the average abundances of bat flies between sexes was found (males = 0.70 ± 1.06, females = 0.86 ± 1.49). My findings do not support the idea that females carry more bat flies compared to males. No significant correlation was found between having bat flies and holes or scars; as well as between the abundance of bat flies and body temperatures. I did not find evidence that the presence of bat flies has an effect on these health parameters.
Richard R. Urbina
Mangroves are known to be a nursery to fishes and other animals, but they have not been as studied as other ecosystems in the world. This study is about learning the difference in the number of fish species of the mangroves compared to the bays. I went out at night with a boat and a plankton net to tow in the mangroves and the bays near Cuajiniquil, Costa Rica. Afterwards I compared the number of morpho-species of the mangroves and the bays. There was a difference in the number of morpho-species with the mangrove having 12, the bay having 3 and 3 being found in both areas. My study shows that there are more morpho-species in the mangroves compared to the bays.
Sabertooth blennies (Plagiotremus azaleus) benefit from aggressive mimicry and schooling with conspecifics
Olivia A. Weaver
Mimicry serves as a marker of a longstanding and evolutionary complex relationship, though studies on mimicry are notoriously difficult to execute, as there are many factors to consider. In interspecific relationships that are reported to exhibit both frequency dependent and frequency independent mimicries, evaluating the benefits of association are especially complex. The relationship between the Sabertooth Blenny Plagiotremus azaleus and the Cortez Rainbow Wrasse Thalassoma lucasanum is proposed to be one of both aggressive and social mimicry, with the former species acting as the mimic and the latter as the model. However, previous observations as well as my own have observed large conspecific schools of P. azaleus, a phenomenon that ignores the traditional assumptions of frequency dependent mimetic relationships. In this study, I sought to review the benefits that P. azaleus incur from their likeness and association with T. lucasanum, and to investigate what benefits P. azaleus might derive from associating with themselves. The results of this study support the established claims that P. azaleus enjoy increased predation success when associating with their model, which in turn supports the presumed aggressive mimicry between the blenny and T. lucasanum. Although sample sizes were too small to determine significant benefits they might derive from associating with each other, low P-Values hint at hypotheses that conspecific schools of P. azaleus are chased by fish less often than when they are either solitary or associating with their models. I propose that the complexities in P. azaleus behavior may be the result of the interaction between aggressive and social mimicry it is reported to exhibit, or that, like P. rhinorhynchos, P. azaleus could possess facultative mimicry and so choose when to perform mimicry.
E. O. Hanabusa
Cane toad tadpoles (Rhinella marina) form aggregations in shallow water while feeding. To investigate their social feeding preferences, this study sampled tadpoles from a human-made pond on the property of Estación Biológica Monteverde. These tadpoles were given choices of feeding alone or in a group, and feeding with different group sizes. Individual tadpoles were placed in an aquarium with a built-in choice chamber, with a starting chamber that had two pathways that lead to the two different options. Overall, the tadpoles spent a greater amount of time remaining in the start of the aquarium than by the given options. These preferences of the tadpoles suggest that they prioritize their own safety over the option of exploration of a new situation.
Stenomicra are a genus of small, often yellowish flies of the family Periscelididae (Diptera). The Stenomicra I studied live in leaves of Heliconia sp. and Calathea sp. in Monteverde, Costa Rica. While not much is known about their biology, I suspected that some factors may influence whether or not they will be found on a particular leaf. I proposed that the amount of matter found within the rolled leaves, other arthropods within the leaves, and the stage of the rolled leaf affect whether or not the Stenomicra flies inhabit them. I found that none of the above factors contribute to whether or not you will find them on a rolled leaf; as long as it is even a little rolled, it is likely that they will be there, and they do not require a certain amount of matter in order to inhabit a leaf. I found that number of arthropods in a leaf does not affect the amount of matter in a leaf as well. I also suspected that the ephemeral phytotelmata of these rolled leaves may serve as the larval home of Stenomicra, so I clipped off the bases of the leaves so that I could search for larvae under a microscope. I found two fly larvae in the matter inside the rolled leaves, one of which is Stenomicra. Because of this, it may be possible that the Stenomicra that inhabit these rolled leaves complete their entire life cycle within them.
Alexandra D. Reep
Hemileia vastatrix, or Coffee Rust, is a fungal parasite on coffee tree leaves that has devastated coffee crops across South and Central America. While a variety of synthetic fungicides and fertilizers are currently used to combat the pathogen, there is a dearth of information available to farmers for more sustainable alternatives. This experiment assessed the effectiveness of six treatments: three forms of compost tea (CT), a Mountain Microorganism (MMO) solution, a Mokave inorganic compound fertilizer, and a Control group in combating Coffee Rust infections. I measured the changes in mean fungal lesion size before and after treatment on 270 leaves over a six-day period. I found the greatest increase in mean lesion size in the untreated Control leaves, followed by Mokave-treated leaves. I found the greatest decrease in mean lesion size in Vermicompost CT, followed by Bokashi CT, Kitchen Waste CT, and Mountain Microorganism solution, respectively. Further, I assessed the microbial richness of the four organic treatments using unique morphospecies and found that mean lesion size was most effectively reduced by treatments with a higher richness of microbial morphospecies.
This study attempts to describe communication and behavior among Crocodylus acutus hatchlings. By understanding when and why vocalizations occur, new insight can be found regarding extant ancestors of crocodilians including dinosaurs. In Cuajiniquil, Costa Rica, I observed two Crocodylus acutus nests and captured five crocodile hatchlings. I observed the captured hatchling and its siblings recording vocalizations and movement patterns. After catching a random hatchling, it vocalized distress calls, and in response, the siblings would vocalize and approach the captive. These results support the hypothesis that a distress call of a hatchling seeks help from sibling crocodiles. An acoustical analysis displayed a similar spectrogram for the distress call of the captive and the response of sibling hatchlings. This echoing of the captive’s distress call could possibly alert or call for the mother crocodile.
Bivalve water filtration provides important ecosystem services that can help to offset anthropogenic pollution and other human induced ecosystem imbalances. Pinctada mazatlanica, Pteria sterna, and Modiolus capax are bivalves that grow on fish mariculture nets filtering fish feces from the water. Bivalves can help make fish mariculture a more sustainable alternative to overfishing. However, freshwater from extreme storms threaten these species. Tropical Storm Nate caused salinity changes in marine ecosystems resulting in widespread destruction. Little was known about how Tropical Storm Nate affected bivalves. In my study, I addressed the question: How are survivorship and filtration rates of Pinctada mazatlanica, Pteria sterna, and Modiolus capax affected by salinity changes? I exposed nine replicates of Pinctada mazatlanica, Pteria sterna, and Modiolus capax to fresh, brackish, and saltwater, then tested for wáter filtration ability, and survivorship. Fresh and brackish water reduced survivorship after 24 hours for Pteria sterna, and after 48 hours for Pinctada mazatlanica and Modiolus capax. In addition, Pteria sterna survived for less time across all treatments. Modiolus capax had the highest survivorship in freshwater after 48 hours. These species can filter silt from saltwater, but not fresh or brackish water. Depending on the duration and severity of the tropical storm, most of my study species are likely to die from the freshwater. If they survive however, they can help the ecosystem recover after a storm by filtering excess silt out of saltwater.
Tevin Brown, Grant Larson, and Sofia Calvo
Research question: Does the new forest provide the same services and functions as the secondary forest?
Assessment of greywater parameters throughout treatment sites at the Monteverde Institute and Los Pinos Hotel
Alexandra Arriaga Covarrubias
Water is crucial in all aspects of life; therefore, the way in which we treat water directly impacts our future. Greywater results from humans’ interaction with water in their everyday life, but what we do with the greywater can have various effects on the environment and us. This study tests the effectiveness of two primary grey water treatment systems at Los Pinos Hotel and the Monteverde Institute in Monteverde, Costa Rica. Six sections of each system were tested for a variety of parameters: temperature, dissolved oxygen, salinity, conductivity, total dissolved solids, and pH. Although both locations use preliminary and primary treatment systems for their greywater, the end values of the six parameters varied per site. Los Pinos Hotel had a significant increase in salinity, conductivity, and total dissolved solids and a significant decrease in dissolved oxygen. While, the Monteverde Institute had a significant increase in temperature and a significant decrease in dissolved oxygen and PH. The differences in the results could be due to the differences in grey water quantity and quality that flow throughout the systems. Los Pinos Hotel system only treats laundry water; whereas, the Monteverde Institute treats grey water from their kitchen, bathroom sinks, and showers. The changes in the greywaters from start to end indicate the effects that Los Pinos and the Monteverde Institute have on their environment.
Avian frugivory and displays of aggression on güitite (Acnistus arborescens) in Monteverde, Costa Rica
Competition for food is evident in many living beings and essential for the continuous survival of a species. Some animals will show dominance or aggression by scaring other animals away that are at or near their food source. I observed trees of the species Acnistus arborescens (Güitite), from the Solanaceae family, for two weeks in order to learn more about what species of birds feed on its orange fruits, where on the tree they feed, and if they show aggression by flying onto the tree towards other birds, defined as the other birds flying away subsequently. I conducted my observational study in the Monteverde, Cerro Plano, and Santa Elena area in Costa Rica during the month of May 2018. I sat about ten meters away from the tree and conducted a continuous observation every five minutes. Every five minutes, if there were birds, I would note the number, species, if they were eating, where on the tree they were eating (horizontally and vertically), and if they showed signs of aggression. There were twelve different species that foraged on the Güitite tree. I found that the Great-tailed Grackle (Quiscalus mexicanus) visited the tree to forage on its fruits the most. The Great-tailed Grackle was also the most aggressive, showing six instances of aggression towards birds of both the same and different species. I conducted a chi squared test and found that the Grackle significantly preferred foraging on the bottom outer portion of the tree.
Wing shape and size determines the manner of flight in all organisms with wings, and this is especially true for butterflies and moths. Flight is energetically costly, so selection may have acted on these organisms to create the most optimal wing shape for the activities in which different species engage. In this study, I recorded ten measurements of length, width, and area for each specimen in order to determine if different species of butterflies converged on a particular shape of wing based on their habitat. I also considered the similarities of their wing shape based on their phylogenetic relatedness. The results show that individuals share similar wing shapes with other members within their subfamily as long as they live in similar habitats. This result shows that there is a level of phylogenetic inertia, or similarity due to sharing a common ancestor, that determines the wing shape of butterflies, however, that is not the only explanation. Butterflies vary in wing shape for a variety of reasons, such as camouflage or flight pattern, but habitat is also one of the determinants of shape.