Male and Female Bats Have Similar Numbers of Bat Flies Kennedy 1 Male and f emale b ats h ave s imilar n umber of b at f lies Brianna R. Kennedy Department of Ecology, Evolution, and Marine Biology University of California, Santa Barbara EAP Tropical Biology and Conservation Program, Spring 2019 7 June 2019 ABSTRACT 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 . D ifferences 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. I n order to investigate the effect of the presence of bat flies on overall health, I chose to focus on tw o 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 Â± 1.06, females = 0.86 Â± 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. M urciÃ©lagos ma chos y hembras tienen un nÃºmero similar de moscas RESUMEN a estas moscas y sus efectos en las poblaciones de murciÃ©lagos debido a su ub icuidad. Las diferencias de comportamiento de los murciÃ©lagos en cuanto a los sitios donde se resguardan, me hicieron pensar que murciÃ©lagos hembras podrÃan llevar mÃ¡s cantidad de moscas que los murciÃ©lagos machos. Yo investiguÃ© la diferencia en abundancia de las moscas de murciÃ©lagos entre ambos sexos en una variedad de especies que capturÃ© en Monteverde, incluidos los gÃ©neros Carollia (n=9), Sturnira (n=5), Lonchorhina (n=1), Micronycteris (n=1), Artibeus (n=6), Glossophaga (n=1), Desmodus (n=1), Platyrrh inus (n=1), and Myotis (n=19) para un total de 44 individuos. Para investigar los efectos de la ocurrencia de las moscas en la salud general de los murciÃ©lagos, considerÃ© dos indicadores de su salud. Incluyendo las temperaturas debajo de un brazo, de el ab domen, de la membrana del ala y del antebrazo, asÃ como tambiÃ©n la cantidad de huecos y de cicatrices en las alas, que es donde comÃºnmente se encuentran las moscas. No encontrÃ© diferencia significativa en la abundancia media de las moscas entre ambos sexos
Male and Female Bats Have Similar Numbers of Bat Flies Kennedy 2 (machos x = 0.70 Â± 1.06, hembras x = 0.86 Â± 1.49). Mis hallazgos no apoyan la idea de que las hembras lleven mÃ¡s moscas en comparaciÃ³n con los machos. No hubo correlaciÃ³n entre la cantidad de moscas y la cantidad de huecos, tampoco con la cantidad de cica trices, ni entre la abundancia de moscas y las temperaturas registradas. No encontrÃ© evidencia de que la presencia de las moscas en los murciÃ©lagos tuviera efecto en estos parÃ¡metros de salud. Bats are the second most abundant order of mammals in the world , making up more than half of the amount of species of mammals found in Costa Rica. They stand out among other orders of mammals due to the high proportion of species that are social and exhibit very complex and variab le social behaviors -including their diet, their roosting behaviors and their occupancy of different niches (Kerth 2008). Bats serve as important hosts for many ectoparasites including several groups of flies, mites and ticks. (Wenzel et al. 1966) . The mo st common ectoparasite in bats are the bat flies , which are blood sucking pupiparous flies that are obligate parasites of bats. Bat flies are part of the order Diptera and the family Nycteribiidae ; or the close relative family Streblidae ; meaning that all bat flies cannot be categorized into one family (Wenzel et al. 1966) . Patterson et al. (1998) reported that 153 species of Strebilidae are found in the Western . Hemisphere on different species of bats; whereas only 37 species o f Nycteribiidae are found. The very common social behaviors of bats provide a n easy mechanism for bat flies to spread within a colony. In most species, females form so called maternity colonies to rear their young communally, whereas males are solitary, form groups of their own, or join female groups (Kerth 2008) . Female colonies have been studied with great detail. However, the formatio ns of male colonies ha ve not been studied very much possibly due to the lesser frequency of them ; or the lack of knowledge as to why males would form colonie s . It has been hypothesize d that the formation of male colonies relates to information transfer, which would not require as much time in physical contact with each other compared to the behaviors of female colonies (Levin et al. 2013). This difference between general lifestyles of male and female bats could potentially lead to a difference in abundance of bat flies between sexes. B at flies feed on blood and live at the expense of the host, meaning that health may be at risk. Parasites can many times transmit infections and diseases which can indirectly affect a number of host functions due to trade offs in the allocation of resources. This can often be seen by changes in immune r esponses such as increased antibody production and fevers (Devevey et al. 2008). This concept has not been deeply studied in bat s so it would be interesting to see how these aspects of bat ecology connect . In this study, I addressed the question: Is the abundance of bat flies on bats correlated with the sex and overall health of the bat?
Male and Female Bats Have Similar Numbers of Bat Flies Kennedy 3 MATERIALS AND METHODS To begin the study and capture bats we set mist nets during the period of May 7 th to May 29 th . These mist nets were first set in a location near the San Gerardo Field Station in the The mist nets w ere opened at night following sunset . While the mist nets were opened, I move d away from the nets, coming back to check for bats in intervals of 1 5 minutes. I f a bat was present, I remove d the bat from the net with the help of Federico and place d it in a cloth bag. After removal of all of the bats from the net from that time interval, I measure d the mass of each bag with the bat inside. Then, working with one b at at a time, I identif ied the sex of the bat and determine d if there are any scars or holes in the membrane of the wing . I then inspect ed the bat s fur and wings looking for bat flies. I remove d all of the bat flies that I f ound on each bat and store d the m in small labeled vials for later i dentification . After the bat fly removal, I measure d the forearm of the bat, as this is an important characteristic that is indicative of species. I then determine d the species of the bat. Next, I measured the temperatur e of the bat using an EXTECH Instruments IR T hermometer and the underarm temperature using a Microlife MT 19E1 D igital Flexible Tip T hermometer. I of a previous capture . This process was repeated in two more locations near the Monteverde Institute in the Crandell Memorial Reserve and in Bajo del T igre . The bat w as then released, and the mass of the empty bag w as recorded to determine the mass of the bat. This process w as done for each bat captured during the 1 5 minute interval s . Following the collection of data, analysis was conducted to determine the significance of trends and differences in my findings. T test s w ere conducted to determine the significance of the difference in the average number of bat flies between male and female bats for all species and for Myotis pilosatibi ali s. In addition to this, chi squared tests were used to determine the association between having bat flies and having holes and scars. RESULTS In this study, we captured 44 bat s ; including 21 females and 23 males. All of the captured bats were of 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 ) . Bat fly abundance was recorded for each of these 44 individuals. Bat flies were found on 1 7 individuals (9 males and 8 females) in the Carollia , Sturnira , Artibeus , Glossophaga , Desmodus , and Myotis genera.
Male and Female Bats Have Similar Numbers of Bat Flies Kennedy 4 Figure 1. Belly temperatures for all bat captures with varying number of bat flies. These values were collected using a laser thermometer to find the surface temperature of the ventral side of the bat . There is not a significant correlation between the number of bat flies and belly temperatures (R 2 = 0.0229). Figure 2. Wing membrane temperatures for all bat captures with varying number of bat flies. These values were collected using a laser thermometer to find the surface temperature of the wing membrane of the bats . There is not a significant correlation between the number of bat flies and wing membrane temperatures (R 2 = 0.0006). 0 5 10 15 20 25 30 35 0 2 4 6 8 Belly Temperature (degrees celsius) Number of Batflies 0 5 10 15 20 25 30 0 2 4 6 8 Membrane Temperature (degrees celsius) Number of Batflies
Male and Female Bats Have Similar Numbers of Bat Flies Kennedy 5 Figure 3. Forearm temperatures for all bat captures with varying number of bat flies. These values were collected using a laser therm ometer to find the surface temperature of the forearm of the bats . There is not a significant correlation between the number of bat flies and forearm temperatures (R 2 = 0.001). Figure 4. Underarm temperatures for all bat capture with varying number of bat flies. These values were collected using a digital thermometer to find the temperature of the underarm of the bats. There is not a significant correlation between the number of bat flies and underarm temperature s (R 2 = 0.0646) . For all of the types of temperatures taken of each of the bats including belly, membrane, forearm, and underarm, there is no correlation between the number of bat flies and temperature as seen by the R 2 values of each of the previous graphs. 0 5 10 15 20 25 30 0 2 4 6 8 Forearm Temperature (degrees celsius) Number of Batflies 0 5 10 15 20 25 30 35 40 45 0 0,5 1 1,5 2 2,5 3 3,5 Underarm Temperature (degrees celsius) Number of Batflies
Male and Female Bats Have Similar Numbers of Bat Flies Kennedy 6 Figure 5. The average nu mber of bat flies in the different sexes for all of the bat species collected . There is not a significant difference between the average number of bat flies in male and female bats of all collected species. Overall, females were found to carry a greater number of bat flies compared to males ( female = 0.857, male = 0.696). There is no significant difference in the average abundance of bat flies between the sexes (t = 0. 41 , df = 36, P = 0.68 ). The error bars in Fig. 5 overlap greatly indicating the wide range of numbers of bat flies for both male and female bats. Fig ure 6. The average number of bat flies in the different sexes for the Myotis pilosatibi ali s species. There is not a significant difference between the average number of bat flies in male and female bats of this species. A similar result came from the analysis of the difference in the average number of bat flies between males and females of the Myotis pilosatibialis species . I decided to analyze this relationship in a specific species to keep more variables constant to better isolate the relationship between the sex of the bat and the number of bat flies. There is no significant difference in the number of bat flies between s exes (t = 0. 54 , df = 36, P = 0.60 ). Again, the error bars in Fig. 6 overlap greatly indicating the wide range of numbers of bat flies for both male and female bats of this species. 0 0,5 1 1,5 2 2,5 Female Male Average Number of Batflies 0 0,5 1 1,5 2 2,5 3 3,5 4 Female Male Average Number of Batflies
Male and Female Bats Have Similar Numbers of Bat Flies Kennedy 7 Figure 7. The frequency of holes in the wing membrane of bats in the presence of bat flies versus the absence of bat flies. There is no significant difference in the frequency of holes in the wings under these different conditions. Generally, there were more bats w ithout holes in the wing membrane (n = 34) than ones with holes (n = 10). Although bats with bat flies had a higher frequency of having holes than the ones without bat flies , I found that there is no t a significant association between having bat flies and holes ( 2 = 0.50, df = 1, P = 0.48). Figure 8. The frequency of scars in the wing membrane of bats in the presence of bat flies versus the absence of bat flies. There is no significant difference in the frequency of scars in the wings under these diffe rent conditions. Contrary to the presence of holes in the wings, there were more bats with scars on their wings (n = 30) compared to ones without scars (n = 14). Again, although bats with bat flies had a higher frequency of having scars than the ones with out bat flies, through a chi squared test, I found that there is not a significant association between having bat flies and scars ( 2 = 0.164, df = 1, P = 0.28). 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 Batflies No batflies Frequency Holes No Holes 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 Baflies No Batflies Frequency Scars No scars
Male and Female Bats Have Similar Numbers of Bat Flies Kennedy 8 DISCUSSION Ultimately, the average number of bat flies are not significantly different between male and female bats and there are no significant correlations between different temperatures of the bat and number of bat flies. In addition to this , there was no signific ant association between the presence of bat flies and holes or scars in the wing membrane. Based on knowledge about the difference s in roosting and general social behaviors of male and female bats, one could predict that females would have more bat flies than males. Generally, females are more commonly found in colonies whereas males are much more solitary and less social (Carter et al. 2015). Although this generalization about differences in behavior les which are difficult to study in the field , leading bats to be very underrepresented as compared to other social mammals in the field of behavioral ecology (Kerth 2008). Although there are no significant differences between the number of bat flies found on male and female bats across all species in this study and the specific species of Myotis pilosatibialis , there may be other factors of bat behavior that are understudied that lead to this unexpected similarity . Sex and age are factors that are thought to play a role in selecting habitat due to differences in physiological or behavioral imperatives which leads to the complexity of group compositions (Angell et al. 2013). The complexities of roosting behaviors may serve as an explanation for the similar a bundances of bat flies in both male s and females. Although females appear to normally exclude males from their nursery colonies, for some species in changing habitats , males are present in these colonies. The presence of males in these colonies provides th ermoregulatory benefits which can outweigh the cons of having males in the colony . This mixed composition also allows opportunities for increased breeding success (Angell et al . 2013). During this investigation, the temperature in Monteverde was starting to decrease and precipitation increased entering the rainy season . These climatic factors may have caused this type of change in roosting behaviors for the bats in this study leading to a greater probability of spreading bat flies between male and female bats since bat fly pupae develop on the walls of the roosts before colonizing the host (Dick et al. 2007). Social behaviors of bats are very species specific and are difficult to generali ze into one description. Due to this it is difficult to pin point mechanisms of bat fly transfer among individuals across all species. Reproduction is an important factor to consider when assessing the interaction between male and female bats. Despite this , species of bats in Costa Rica tend to reproduce during the spring months ( Tschapka 2005) . This study included 8 pregnant females and 7 females that were nursing. The fact that this data was collected during a time in which male s and females were in more contact with one another for the purposes of reproduction could serve as an explanation for the lack of difference in bat fly abundances as mating is a probable mechanism for the transfer of bat flies between individuals. Some males, however, roost with g roups of females in harems year round and may therefore experience the same parasite dynamics as females ( Frank et al. 2016 ) . Bat flies lay eggs that develop on the walls of roosts, providing an easy mechanism for finding hosts. Therefore , bats that use roosts and employ more protected roosting behaviors have more parasites (Dick et al. 2007). Seasonal roosting behavior or specie s specific roosting behavior could potentially serve as explanations for my result s .
Male and Female Bats Have Similar Numbers of Bat Flies Kennedy 9 Environmental factors may have affected the temperatures measured from the bat. Upon removal of the bats from the mist nets, the bats were kept in cloth bags until they we re ready to be processed. The differing time in which each bat was in the bag with reduced physical activity could have led to variable decreases in their body temperatures leading to the wide range of body temperatures collected. B at flies are obligate parasites living at the expense of their host, the bat ; because of this I predict ed that with an increasing number of bat flies, the overall health of the bat w ould decrease exhibiting an increase in temperature , and an increase in holes and scars in the w ing membranes. The indicators of health used in this investigation did not show any significant correlation with the number of bat flies found on the bats. Of course, overall health has many factors and cannot be determined with just two types of observati ons. Although bat flies exhibit a variety of morphological adaptations, which suits them for the two physical substrates offered to them by their bat hosts, the fur and the flight membranes , they do not seem to have a direct physical effect on these parts based on observations (Dick et al. 2006). Although an increased abundance of bat flies did not have a negative effect on different body temperatures and the presence of holes and scars in the wing membranes of bats, this does not mean they are not being affected by them at all. The possibilities of future investigations of such affects are endless despite the convoluted behaviors o f bats. ACKNOWLEDGEMENTS I would like to thank Federico Chinchilla who took on the role as my primary advisor. Without him I would not have been able to do this project and learn how to properly handle bats. I would also like to thank Ana Moreland who was my fieldwork partner, and although we had different projects, we worked together to process the bats in a timel y fashion. Additionally, I would like to thank Frank Joyce , the Monteverde Institute , and the San Gerardo field station in for providing me with a space to set mist nets. Lastly , I would like to thank Richard LaVal for his time in discussing my project and his expertise in the study of bats. LITERATURE CITED Angell, R . L . Sexual segregation and flexible mating patterns in temperate bats. Plo s one 8,1: e54194. Carter, G . , and L . Leffer. Social Grooming in Bats: Are Vampire Bats Exceptional? PloS One, Public Library of Science, 7 Oct. 2015, www.ncbi.nlm.nih.gov/pmc/articles/PMC4596566/ . Devevey, G . 2008. Developmental, Metabolic and Immunological Costs of Flea Infestation in the Common Vole. Functional Ecology 22 ( 6 ) 1091 1098. Dick, C . W, and B . D. Patterson. 2007. Against All Odds: Explaining High Host Specificity in Dispersal Prone Parasites. Internatio nal Journal for Parasitology 37 ( 8 9 ): 871 876 . Dick, C . W. and B . D. Patterson. 2006. Bat f lies: o bligate e ctoparasites of b ats. Micromammals and Macroparasites, pp. 179 194 .
Male and Female Bats Have Similar Numbers of Bat Flies Kennedy 10 Frank, H . K 2016. Anthropogenic impacts on Costa Rican bat parasitism are sex specific. Ecology and E volution 6 ( 14 ): 4898 909 . Kerth, G. 2008. Causes and Consequences of Sociality in Bats. OUP Academic, Oxfor d U niversity Press , academic.oup.com/bioscience/article/58/8/737/381072. Levin, E . Bats of a Gender Flock Together: Sexual Segregation in a Subtropical Bat. PloS One, Public Library of Science, www.ncbi.nlm.nih.gov/pmc/articles/PMC3575394/#pone.0054987 Safi3 . Patterson, B . 1998 . Distributional Evidence f or Cospeciation b etween Neotropical Bats and t heir Bat Fly Ectoparasites. www.researchgate.net www.researchgate.net/publicat ion/235970472_Distributional_Evidence_for_Cospeciatio n_between_Neotropical_Bats_and_their_Bat_Fly_Ectoparasites . Tschapka, M. 2005. Reproduction of the Bat Glossophaga c ommissarisi (Phyllostomidae: Glossophaginae) in the Costa Rican r ain f orest d uring f rug ivorous and n ectarivorous p eriods . Biotropica 37 ( 3 ): 409 415. Wenzel, R . L. 1966 . The Streblid Batflies of Panama (Diptera Calypterae: Streblidae). Field Museum of Natural History .
Male and Female Bats Have Similar Numbers of Bat Flies Kennedy 11 Appendix A Figure 9. Average number of bat flies in each of the genera of the bats that were captured. Appendix B Males Females Myotis Carollia Artibeus Sturnira Glossophaga Lonchorhina Micronycteris Desmodus Platyrrhinus Figure 10. Proportions of individuals with bat flies by genus. Grey boxes indicate individuals with bat flies and 0 0,5 1 1,5 2 2,5 3 Avergae Number of Bat Flies Genus
Male and Female Bats Have Similar Numbers of Bat Flies Kennedy 12 Appendix C Table 1. Species of bat flies found on each bat. Bat # Species of bat Sex Number of Bat flies Species of bat fl y 1 Hairy Tibia Myotis Female 7 Mastoptera minuta 3 Hairy Tibia Myotis Male 2 Mastoptera minuta 6 Sturnira mordax Female 2 Strebla Weidemann 9 Hairy Tibia Myotis Male 4 Mastoptera minuta 11 Sturnira Male 1 Trichobioides perspicillatus 12 Sturnira Female 1 Megistopoda Maccquart 13 Carollia sowelli Female 1 Synthesiostrebla Townsend 19 Sturnira hondurensis Female 2 Megistopoda Maccquart 20 Hairy Tibia Myotis Male 1 Mastoptera minuta 27 Hairy Tibia Myotis Male 1 Mastoptera minuta 29 Hairy Tibia Myotis Fema l e 2 Mastoptera minuta 32 Carollia Male 2 Synthesiostrebla Townsend 34 Hairy Tibia Myotis Male 3 Mastoptera minuta 38 Hairy Tibia Myotis Female 1 Mastoptera minuta 40 Hairy Tibia Myotis Male 2 Mastoptera minuta
Male and Female Bats Have Similar Numbers of Bat Flies Kennedy 13 Appendix D Table 2 . Raw Data : Observations from each bat caught.