Monteverde Institute: Tropical Ecology and Conservation

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  Effects of lek location and female presence on dancing behavior in long-tailed manakins (Chiroxiphia linearis), June 2018

  Dennis Finger

  Sexual selection, the process by which individuals of one biological sex select mates of the other sex, often leads to the formation of displays, ornaments, and weapons to improve mating success. Long-tailed manakins (Chiroxiphia linearis) exhibit a unique example of sexual selection in their bright plumage, long tails, and coordinated lekking dances. I investigated sexual selection by analyzing dancing behavior of long-tailed manakins in Monteverde, Costa Rica. I filmed leks to measure the effects of dance variant (Cartwheel or Up-Down), lek location, and female presence on variation in dance features. Cartwheel bouts of dancing occurred only when the female was found on the dancing branch, while Up-Down bouts occurred only when the female was on a nearby branch or not present at all. I found that dance features did not vary with lek location, but Up-Down male coordination did vary by lek. In addition, Up-Down bouts varied with female presence, as males jumped faster when females were nearby. Female sexual selection was a strong determinant of dance features, leading to bouts that resembled each other and showed limited variation. Bouts did vary, however, in coordination and jump rate, showing that lek location and female presence can affect manakin dancing behavior.

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  Euglossine bee composition along an altitudinal gradient on the Caribbean and Pacific Slopes of the Tilarán Mountains, Costa Rica, June 2018

  Sakoya Hart

  Bees not only contribute significantly to ecosystem biodiversity, but as pollinators they are responsible for facilitating the reproductive processes of many tropical forest plants. As tropical forests are fragmented and destroyed, euglossine bees are under increasing threat of habitat loss and population declines. Understanding their altitudinal and geographical distributions is a critical aspect needed for future conservation efforts. I sampled at four different altitudes along the Pacific slope and three different altitudes along the Caribbean slope. I used three different chemical scents: Methyl Salicylate, Eugenol, and Cineole, as baits to attract male Euglossine bees to sample their populations. The chemical Methyl Salicylate had the highest visitation rate by the highest number of species. Bee visitation was higher on warm, clear days, early in the morning. I captured and identified 128 Euglossine bees representing 11 species at various sampling sites across the Tilarán Mountains of Costa Rica. On both the Pacific and Caribbean slopes, I found a negative correlation between species richness and abundance as altitude increased. The Caribbean slope showed higher abundance and diversity in euglossine bees.

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  Food finding using olfaction by scorpion mud turtles (Kinosternon scorpioides), June 2018

  Megan M. Graham

  The mechanism used to locate food varies between animals, whether it be by olfaction, vision, hearing, touch, taste, or some combination of these. Many turtle species rely on vision and olfaction to find prey. I designed an experiment to test if scorpion mud turtles (Kinosternon scorpioides) can find food using olfaction by placing the turtles in Rio Cuajiniquil with three nondescript capsules containing sardine chunks and three empty, control capsules. Observations of six turtles’ interactions with the capsules suggested that they can locate food through olfaction; however, only one statistical analysis was significant which was that the turtles were more likely to bite full capsules than empty capsules.

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  Foraging and feeding guild characteristics in relation to fishes chased from Microspathodon dorsalis nesting territories, June 2018

  Jenna Sparks

  Recognizing nest predators is an important adaptation for successful reproduction. Nest guarding ability is likely, in part, a sexually selected trait. Male giant damselfish (Microspathodon dorsalis) defend by chasing and biting at fishes that encroach upon their nests. In my study, I observed the relationship between intruder fish phenotype and behavior and response of 16 guarding males. In a series of 10-minute observation periods, I determined that Acapulco damselfish (Stegastes acapulcoensis) were chased away the most times. To account for variability of fish presence, I additionally noted the number of chases by resident M. dorsalis, standardized for the number of appearances of other species. The most frequently chased species was panamic sergent majors (Abudefduf troschelli). Based on these results, I considered the common foraging and feeding guild characteristics in S. acapulcoensis, A. troschelli and other species I observed. S. acapulcoensis and A. troschelli, known grazers of the Pomacentridae family, prefer the algae M. dorsalis cultivates in its garden. However, I also observed S. acapulcoensis and other M. dorsalis feeding on the eggs of a M. dorsalis nest.

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  Foraging behavior and substrate preference of the mangrove warbler (Setophaga petechial bryanti) in North-Western Pacific Mangroves of Costa Rica, June 2018

  Michael K. Spaeth

  Mangrove Warblers (Setophaga petechia bryanti) reside in mangrove habitats that are at continuous risk of human alteration and destruction. The purpose of this study was to investigate the foraging behavior of Mangrove Warblers and whether they prefer a specific species of mangrove for foraging in the North-Western Pacific Mangroves of Costa Rica. I investigated this by observing Mangrove Warblers forage at different mangrove tree species throughout a mangrove habitat along Rio Cuajiniquil in Cuajiniquil, Costa Rica. My primary finding was that Mangrove Warblers occur more frequently in Red Mangroves (Rhizophora mangle) and Black Mangroves (Avicennia germinans) while foraging. Furthermore, Mangrove Warblers tended to forage for a longer duration of time in White Mangroves (Laguncularia racemosa) before leaving the substrate. Understanding Mangrove Warblers’ foraging preference in mangrove ecosystems helps convey how they will respond to a continuously decreasing habitat type.

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  Growth variation of lettuce (Lactuca sativa) and cilantro (Coriandrum sativum) seedlings with different types of compost, June 2018

  Ashley Anderson

  Compost is decomposed organic material from households, farms, and restaurants. Compost is used in organic agriculture to replenish the soil with nutrients such as carbon, nitrogen, phosphorus, and potassium. There are different methods of composting, such as bokashi fermentation, aerobic decomposition, and vermicomposting. Each method of composting as well as the composition of compost provides plants with a different proportion of nutrients. The purpose of this study was to compare the growth of cilantro and lettuce seedlings in five types of compost, manure compost, coffee vermicompost, food waste vermicompost, food waste compost, fish feces, and a control of just soil. I grew 66 cilantro and 66 lettuce seedlings in small plastic bags with each of the compost treatments at a farm in San Luis, Costa Rica. I measured the number of leaves on each seedling and the height of each seedling before and after treatment. The seedlings grown in food waste vermicompost had the greatest height growth, 6.4 + 1.4 cm for lettuce and 3.4 + 0.54 cm for cilantro. Food waste compost also had high plant growth, 5.6 + 1.04 cm for lettuce and 2.5 + 0.69 cm for cilantro. The seedlings grown in coffee vermicompost, fish feces, and the control had the lowest growth. The manure compost yielded greater growth than the fish feces and soil control, but still had less growth than the food waste compost and food waste vermicompost. These results suggest that using compost for gardening yields greater growth than not using any compost. This study concludes that vermicompost from food waste provides the best nutritional requirements for seedlings.

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  Life history of Charoxus rove beetle (Coleoptera: Staphylinidae) in Ficus pertusa (Moraceae), June 2018

  Sydney Schalk

  Rove beetles of the genus Charoxus are a group that takes advantage of the obligate mutualistic relationship between fig trees (Ficus sp.) and their pollinating Agaonidae wasps. I examined 101 fig syconia from the species Ficus pertusa and recorded the number of living fig wasps, the stage of development of the fig, the numbers and morphs of beetles found, and the presence of a hole in the fig. I found a relationship between the stage of fig development and how common fig wasps and rove beetles were. I also found a relationship between the number of fig wasps in a fig syconium and which morph of beetle I found. I ran an experiment to determine what their food source is inside of the fig as well. The rove beetles eat the fig wasps but I did not find a statistically significant preference for either pollinating or parasitic fig wasps. I analyzed where they pupated and which larvae developed into which adult morphospecies. Few of the larvae survived and developed into adults, but the larvae beetle morphs that developed into adults confirmed that the larvae and adults were the same species. I found that both larvae and adult beetles were common in the syconia and both the adults and larvae occurred in three different morphs. Their abundance suggests that they affect the close fig tree-fig wasp symbiosis.

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  Microbial diversity found on Anura in the Monteverde area, June 2018

  Lilly Helmuth-Malone

  The microscopic world of fungi and bacteria have a significant effect on the organisms they grow on and can have either a beneficial or detrimental effect on said organism. Frogs are especially vulnerable to microbes due to their permeable skin, which leaves them susceptible to such pathogens as chytrid fungus. This project aims to discover the different types of fungal and bacterial morphologies found growing on frogs. In order to learn more about these microbes, I swabbed 34 frogs from nine species found at four different locations in the Monteverde area and cultured the swabs on two different types of agar: potato dextrose agar and tryptone soy agar. I found 84 different fungal morphologies and 61 different bacterial morphologies after 48 hours of incubation at 30°C. After analyzing the data, I suggest that there is no clear correlation between morphologies growing on a frog’s skin and the specific species of frog; additionally, there is great variation amongst the microbes growing on different species of frogs, and even amongst individuals of the same species of frogs.

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  Microfiber density in relation to elevation and pollution source in two freshwater streams in Monteverde, Costa Rica, June 2018

  Madison Juul

  Freshwater streams and rivers are known pathways of microplastics, and account for between 1.14 and 2.4 million tons of plastics that end up in oceans. Among these microplastics are synthetic microfibers, which can shed directly from clothing or break off from larger pieces of plastic. Microfiber durability and small size makes particles difficult to remove and increases the likelihood of harming aquatic organisms. Despite their prevalence in waterways, few studies have been conducted regarding the impact of microplastic materials on freshwater ecosystems. The aim of this study was to determine the presence and pervasiveness of microfiber particles in Quebrada Cuecha and Quebrada Máquina in Monteverde. In Quebrada Cuecha, I tested microfiber density in relation to a potential source of pollution. In Quebrada Máquina I tested microfiber density in relation to elevation. Surface samples and net samples of microplastics were collected using a 10 mL vial and a 500 µm mesh net. Microplastics, all of which were microfibers, were observed in 66 out of 70 samples. The Monteverde Cheese Factory might have a significant impact on the concentration of microfibers in Quebrada Cuecha, and microfiber concentration in relation to elevation is not significant in Quebrada Máquina.

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  Mosquito (Diptera: Culicidae) distribution in Cuajiniquil, Guanacaste, Costa Rica, June 2018

  Ah’Shirae Arana

  Understanding mosquito distribution can lower the risk of people affected by mosquito borne illnesses. This two-part study aims to present the distribution of potential disease-carrying mosquitoes located in Cuajiniquil, Guanacaste, Costa Rica. In the first part of the study, I analyzed mosquito oviposition preference by placing receptacles filled with river water in homes and mangroves for nine days. I found no larvae in these experimentally placed containers. In the second part of my study, 137 mosquitoes were captured and identified to species from four different locations of the area. Four genera were identified with Aedes as the most abundant genus. At least eight species were identified including Anopheles punctipennis, a species capable of transmitting malaria.

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  Presence and diversity of mammals across microhábitats in San Luis, Monteverde, Costa Rica, June 2018

  Liesel Davis

  The transformation from natural to human-dominated landscapes is occurring rapidly throughout much of the world. In San Luis, Costa Rica, undisturbed forest land has been converted into farmland, introducing crops for agriculture and free-ranging domestic animals. The aim of this study was to observe how relative local mammal abundance has been impacted by these anthropological factors. I sampled three locations in San Luis: a coffee plantation (Café Bella Tica), a farm containing domestic animals (Marco Marín’s farm), and a forest microhabitat. To collect data, I used trail transects, miscellaneous observations, Sherman rodent traps, and camera traps over the course of 14 days. I found a total of seven wild mammal species and 42 wild mammal sightings across the three microhabitats. Four mammal species were found among the coffee plantation (variegated squirrel Sciurus variegatoides, olingo Bassaricyon gabbii, spiny pocket mouse Heteromys desmarestianus, deer mouse Peromyscus mexicanus), three were on the farm with domestic mammals (variegated squirrel, agouti Dasyprocta punctata, hispid cotton rat Sigmodon hispidus), and three were in the forest (white-faced capuchin Cebus imitator, agouti, deer mouse). The farm with domestic dogs and cats contained more arboreal wild mammals than terrestrial, which may suggest substantial predatory behavior from the domestic pets. With no significant species richness difference across microhabitats, these results indicate that either human presence is not negatively impacting mammal diversity in San Luis, or that the effect from nearby plantations actually diminished diversity in the studied forest habitat.

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  Prevalence, effect, and cause of apical meristem termination in the endemic Ocotea monteverdensis (Lauraceae) in Monteverde, June 2018

  Noah Bennett

  Ocotea monteverdensis is an endangered tree in the Lauraceae family endemic to the Monteverde, Costa Rica region. It consistently displays evidence of terminated apical meristems (TAMs). I explored the prevalence, effect and cause of TAMs in young O. monteverdensis trees. I measured height, DBH and herbivory as indicators of fitness and compared these factors between trees with TAMs and those without. After analyzing data from 220 trees across four different test sites, I found that TAMs were present at every test site across a wide range of heights. Between trees with TAMs and those without TAMs, I found that there was no statistical difference in DBH and in one case there was no statistical difference in height. One test site showed that trees with TAMs were significantly shorter than trees without TAMs. Thus, TAMs can have a negative effect on tree fitness. The reason for why only one site experienced a negative effect from TAMs is unknown. Possible theories include the variation in environmental factors and land-use history between the two sites. Regarding the cause of the TAMs, I did not find a definitive answer, though I did manage to largely rule out the hypotheses that vertebrates eat the apical meristem or that galls cause TAMs. In conclusion, I recommend that TAMs should continue to be studied by O. monteverdensis conservationists because they can negatively affect tree fitness.

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  Priorities of Octopus vulgaris: feeding or den enhancement?, June 2018

  Calla Lloyd-Lim

  Animals must choose between avoiding possible death or increasing energy input by feeding. Octopuses, in particular, have evolved various strategies to avoid predation and thereby cope with increased physical vulnerability. As soft-bodied creatures, they lack the hard shell that defines the typical molluscan body plan. To protect themselves, they seek shelter in dens, which is where they spend most of their daytime hours. Although foraging during the day is limited, they leave their protective structures to hunt when necessary. In this study, I evaluated the priorities of 10 wild octopuses, specifically Octopus vulgaris, by exploring the choices they made between protection and food acquisition. I presented individual octopuses with clams, rocks, and shells in two separate, filmed tests to determine (1) if in an exposed den, octopuses prefer food or protection, and (2) if they prefer specific materials for den enhancement. Octopuses did not display a preference in choices of rocks versus clams or rocks versus shells. Additionally, individual octopuses who demonstrated a particular anti-predator behavior were more likely to demonstrate other anti-predator behaviors. I serendipitously discovered that these octopuses display consistent behavioral plasticity. This change in behavior as a result of stimuli exposure could account for their lack of material preference. Octopuses regularly responded to items around their dens, but individuals varied among all trials. All octopuses showed diverse levels of activity and interactions with surrounding objects.

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  Reasons for movement in hermit crabs, Coenobita compressus, June 2018

  Alexandra K. Lee

  Coenobita compressus, more commonly known as the Ecuadorian hermit crab, can be found across the pacific coast of Costa Rica. If you go to a beach along this coast, you often see these crabs walking around in all directions without clear aim. In my study, I examined the reasons for these crabs’ movement, and hypothesized that they were motivated by food, water, shells, and sun avoidance. I offered crabs shells and food and monitored their behavior before and after. If the hermit crabs’ movement was motivated after I provided them with said food or shells, and their movement should slow or stop. I indeed found that this was the case, and that crabs were motivated to move by the desire for shells and food. I also noted the crabs’ sun avoidance behaviors during this time. I then put crabs in water and recorded the time it took for them to leave it. I found that crabs hid from the sun by resting under rocks, and that they consistently tried to quickly escape the water. Therefore hermit crabs are also motivated to move by the desire to avoid water and the sun. Tests involving multiple food items revealed that some crabs switch between foods while others stay at one food, and that crabs have food preferences. Different foraging strategies and food preferences may also influence how a crab moves in regards to finding food.

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  Sea urchins reduce fish grazing on algae, June 2018

  Alice Beittel

  Overfishing of reef ecosystems poses a threat to key trophic interactions that regulate the food competition between fish and the sea urchin, Diadema mexicanum. An important ecosystem engineer, D. mexicanum can help control for positive coral growth at intermediate levels but at high levels can erode coral reefs and at low levels results in algae dominated reefs. Due to the overfishing of echinoderm-predators in Bahía de Cuajiniquil, Costa Rica. D. mexicanum populations are less regulated and have the potential to outcompete other herbivorous fish. My overarching question is how does Diadema mexicanum grazing impact fish feeding intensity? To answer this question, I first examined if fish are grazing on different slopes to understand overlaps between fish and urchin feeding locations. I observed 45 rock patches of three rock slope categories (horizontal, sloped, and vertical) for the number of urchins present, fish visitations, and fish grazing events. There are significantly more fish visitations to rock of slopes 0-30 degrees but there is not a significant difference of number of grazing events between rocks with 0-30 degree, 30-60 degree, and 0-90 degree slopes. A second way to understand competition dynamics between species is to use exclude one competitor from a food source and measure the response of the other competitor. I installed ten exclosures on flat rock substrates to prevent herbivory by sea urchins and fish for a period of 5 continuous days. After I removed my exclosures, I observed more fish grazing events and higher species diversity. Both herbivorous and carnivorous fish fed from the post-exclosures plots. Sea urchins are indirectly competing with herbivorous and carnivorous fish for rock-substrate food resources. Conservation of Diadema mexicanum predators will be key to helping restore coral reef systems and rebalance trophic interactions.

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  The effects of forest fragmentation on avian nest predation in the Monteverde region, June 2018

  Sara Gibbons

  Habitat fragmentation is the division and reduction of a large, continuous area of habitat into smaller pieces. In nearly all cases tropical rain forest fragmentation has led to a loss of local species due to an increase in predators, a shift in microclimate, and a decrease in habitat area. Forested avian species are especially affected, showing a significant decrease in abundance and nest success in forest fragments. I investigated the predation rates on thrush nests in two fragmented sites. The first site was La Calandria, which is an isolated forest patch. The second site was Bajo Del Tigre which is a larger, more connected forest fragment. I placed 15 artificial nests along three transects in each site for a week to observe predation. I found a higher predation rate in the smaller, more isolated forest fragment. The type of predation varied between the fragments, suggesting different predator composition between isolated fragments and continuous forest. Also, there was no relationship between the distance from the edge and the predation rate; however, this may be due to the limited distance studied. There was a direct decrease in predation as the density of plant coverage around the nests increased. No relationship was found between the density of plant coverage and distance from the edge. These findings have important implications for conservation efforts, and suggest that fragmentation can be a threat to bird egg survival.

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  The flowering biology and pollination ecology of Burmeistera parviflora (Campanulaceae: Lobelioideae), June 2018

  Alexandra Howell

  Understanding a taxon’s pollination biology and floral characteristics can help shed light on that group’s evolution. The genus Burmeistera (Campanulaceae: Lobelioideae) is a young but diverse genus that is almost exclusively bat-pollinated. This group’s radiation has likely been caused, in part, by changes to floral characteristics that have evolved to reduce competition for successful pollinators. In this study I examined the pollination biology of B. parviflora in the cloud forests of Monteverde, Costa Rica because this species is an apparent exception to this genus’ bat-pollinated trend. I addressed who pollinates B. parviflora by monitoring the flowers for floral visitors, determining peak hours of nectar production, and assessing how the species’ morphology aligns with bat, hummingbird, or insect pollination syndromes. Hummingbirds appear to be the primary pollinator of B. parviflora. This led to the examination of whether sharing a pollinator group with bat and hummingbird-pollinated B. tenuiflora has resulted in interspecific pollen transfer by addressing the rate at which interspecific and conspecific pollen transfer occurred for both species. Interspecific pollen transfer appears to occur, though it is even more rare than conspecific pollen deposition. Because of this potential for interspecific pollen transfer, I examined what morphological differences occur to reduce competition caused by interspecific pollen transfer between B. parviflora, B. tenuiflora, and a third, exclusively bat-pollinated species, B. cyclostigmata. All three species had very different sets of floral traits, with traits that determine pollen or stigma placement on the pollinator differing the most between them. By illuminating B. parviflora as another exception to Burmeistera’s bat-pollinated trend, this study aims to improve the baseline understanding of pollination syndromes and the role they play in plant evolution, in order to better predict and understand how high-elevation inhabitants, such as members of Burmeistera, may be affected in the face of changing climate patterns.

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  The importance of mammal diversity in seed dispersal: distance and seed diversity, June 2018

  Griffin Nicholson

  Plants rely on seed dispersal in order for seeds to escape the vicinity of the parent plant, reach an uncompetitive habitat, or be transported to a suitable site for establishment. Zoochory by mammals is an important aspect of seed dispersal with abundance of mammals known to increase the amount of seed dispersal. However, mammal diversity is also important as different mammals disperse different number of seed species as well as different seed species entirely. Different mammals can also disperse seeds different distances. This study looked at the diversity of seeds dispersed by different mammal species in the Monteverde area, the level of overlap in seeds dispersed amongst the mammal species, and if plants are highly specific in their dispersal by mammals or more general. In addition, this study compared the distance coatis and agoutis dispersed seeds. I found that the mammal species surveyed dispersed a high diversity of seeds, with coatis dispersing the most diverse species of seeds. There was little overlap between different mammal species in what they were dispersing. Mammals, as highlighted by the diversity of seeds each species dispersed, tended to be generalist dispersers; however, plant seeds were only dispersed by one species of mammal. For distance comparison, I found that coatis dispersed seeds significantly greater distances than agoutis. Overall, my results showed that mammal diversity is important for seed dispersal as different mammal species disperse seeds different distances and different plants need different mammals for successful dispersal.

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  Thermoregulatory behavior of Sceloporus malachiticus, June 2018

  Sofia Vámos

  Most species of lizards control their thermoregulation through certain behaviors. This can include basking under the sun and moving into shade, changing body position in relation to the sun and moving to shaded regions. In this project I observed two different Sceloporus malachiticus lizard groups to evaluate their thermoregulatory behaviors. I evaluated the aspects of body, substrate and air temperatures, behavior and flight distances for both groups. My results showed that while air and substrate temperatures were significant factors in the lizard’s thermoregulation, substrate temperatures played a stronger role. Furthermore, lizards showed increased activity earlier in the mornings and exhibited resting behaviors through most of the days. There was no significant correlation found between flight distance and body temperature.

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  Water quality of Quebrada Cuecha: effects of the effluent from the Monteverde cheese factory, June 2018

  Heather Lindsay and Megna Patel

  We sampled 13 sites in close proximity to the Monteverde cheese factory along Quebrada Cuecha in Monteverde, Costa Rica. To assess water quality, we tested multiple parameters including conductivity, water temperature, total dissolved solids, pH, dissolved oxygen, nitrates, phosphates, turbidity, and salinity. We also looked for the presence of fecal coliform bacteria, collected samples of benthic macroinvertebrates, calculated the percent shade cover, and analyzed the soil composition at each site. A single water quality index (WQI) was generated from selected parameters to comprehensively compare overall water quality at each site to determine whether it decreases after the aggregation of pipes from the Cheese Factory. We found that at each site the WQI values indicated “good” water quality. Affirming this, Corydalidae and Ephemeroptera, two families of benthic macroinvertebrates that indicate “good” water quality, were found both upstream and downstream from the Cheese Factory. Our data showed that water quality fluctuates moving from upstream to downstream, and there was no distinct decrease in water quality along Quebrada Cuecha. Keeping this in mind, the decrease in dissolved oxygen, sudden increase in turbidity, and presence of fecal coliform bacteria along the stream indicate that there may be potential sources of pollution entering the system from the Cheese Factory and higher upstream.

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  Species specificity between ectoparasites and rats in Monteverde, Costa Rica, December 15, 2017

  Kathy Dao

  To determine if there is species specificity between ectoparasites and their host rats, I set up Sherman traps in various locations in Monteverde to capture rats. Once I obtained the rats I removed any ectoparasites present and observed them under a dissecting microscope for morphological characteristics. Species specificity is defined for this study as the prevalence of a certain type of ectoparasite to a specific species of rat. From my results, I determined that there is species specificity between ectoparasites and their host rats. Lice were species specific to the Cloud-dwelling Spiny Pocket Mouse, fleas to the Mexican Deer Mouse, ticks to the Fulvous Pygmy Rice Rats and Mexican Deer Mouse. Yellow mites were species specific to the Mexican Deer Mouse, Watson’s Climbing Rat, and Cloud-dwelling Spiny Pocket Mouse. Red mites were specific to the Fulvous Pygmy Rice Rat. Brown mites and octopus mites were specific to the Alston’s Singing Rat. The Hispid Cotton Rat that was caught contained no ectoparasites. The presence of pseudoscorpions in the Spiny Pocket Mouse further introduced a new variable that can potentially explain this species specificity, at least partially, for its predation on some ectoparasites. Hair morphologies of the rats were further examined in an attempt to explain the mechanism behind the species specificity.

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  Activity patterns of Costa Rican bat species, December 2017

  Nicole Orsi

  In Costa Rica, bats are important nocturnal pollinators and seed dispersers. In this study, I investigated how diet type, species, levels of moonlight and moon phases, and nightly weather influenced the activity of bats. To do this, I used mist nets and an ultrasound detector for 11 nights to capture bats and record their species, sex, diet, and forearm length. Each night two to four mist nets were open from 17:30 to 20:00 and checked at 20 minute intervals. Nets were placed in Bajo del Tigre, the Monteverde Institute, San Luis, the Crandell Memorial Reserve, and La Estación Biológica Monteverde. I compared the time of each bat captured in terms of species and diet, and the number of individual bats captured per night to the corresponding moon phase, moon altitude, and weather. Of 23 total bats caught, 9 were different species. I found no clear species-specific activity patterns. When comparing data across different diet types (insecti-vore, frugivore, nectarivore), there was a clear pattern of insectivore activity peaking around 18:00, nectarivore activity around 19:00, and frugivore activity occurring throughout the mist netting period. This finding is corroborated by the fact that peak insect activity occurs immediately after sunset and is therefore the optimal feeding time for insectivores. The activity of nectar bats could be correlated with what time the desired flower opens. As for frugivorous bat, fruits are a widely available and stable food source which could explain their generalized activity. With regard to moonlight, more bats were captured during periods with less moonlight. This finding is described by “lunar phobia” which is exhibited in some animals due to decreased prey availability and higher susceptibility to predation. Finally, there was some indication that the pre-vious night’s weather had an effect on bat activity the following night.

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  Adaptive significance and abundance of bioluminescent dinoflagellates in the Cuajiniquil Bay, December 2017

  Zac Durall

  Bioluminescence in nature is a phenomenon that is found in many different organisms, including fungi, fish and bacteria. Of bioluminescent organisms, dinoflagellates are some of the most common. Despite their abundance, the ecological function of the bioluminescence in dinoflagellates is not fully understood. In my study I attempted to explain the ecological function of this bioluminescence by observing dinoflagellate abundances at different times of day. I collected water samples in the Cuajiniquil Bay in Costa Rica, over the course of seven days, and counted the total number of organisms that I found. This was done to try to find a relationship between time of day and abundance of dinoflagellates. In my study I found that dinoflagellate abundance is generally higher at night than during the day. This finding supports my hypothesis that bioluminescence is a predator defense. Their bioluminescence may be more effective when it’s dark, making them less susceptible to predators.

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  An analysis of temporal and frequency niches during the dawn chorus of birds in Monteverde, Costa Rica, December 2017

  Brianne Nguyen

  Many animals communicate using acoustic signals, making frequency bands a limited resource. To deal with this, animals can partition themselves into acoustic frequency niches. Species of insects, anurans, and birds have been observed to call at discrete frequencies when sharing space with each other. In this study, I recorded and analyzed the temporal and frequency overlap in bird calls around dawn in Monteverde, Costa Rica over the course of ten days. I found very little temporal overlap in the sample I recorded. The calls that did overlap often also overlapped in frequency. My results suggest that frequency niches are not a major method used to improve communication among the birds in Monteverde, at dawn, in late November. This data outlines the use of frequency bands by birds in Monteverde and is the first step in understanding the bioacousitic ecology of the area.