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CALIFORNIA STATE UNIVERSITY, NORTHRIDGE Niche Segregation Between two Armadillos in the Southern Pantanal, Brazil A thesis submitted in partial fulfillment of the requirements For the degree of Master of Science in Biology, By Jeffrey Mark Esparza May 2021 The thesis of Jeffrey Mark Esparza is approved: _________________________________________ ____________ Dr. Tim Karels Date _________________________________________ ____________ Dr. Casey terHorst Date _________________________________________ ____________ Dr. Fritz Hertel, Chair Date California State University, Northridge ii Acknowledgements This thesis would not have been possible without the extended help from so many different sources. First and foremost, I’d like to thank my thesis advisor and mentor, Dr. Fritz Hertel. Dr. Fritz Hertel always respected me as scientist and challenged me to think things through on my own. His respect and encouragement in the lab and in the field helped mold my thesis and I would not have been a successful candidate without his expertise. Thank you to my committee members Dr. Tim Karels and Dr. Casey terHorst for the extended mentorship. Dr. Tim Karels was a wealth of knowledge in ecology and always challenged me to think about this project from an ecological perspective. Dr. Casey terHorst not only listened to my endless questions on my project, but provided key insight on how to navigate academia as an early career ecologist. Thank you to CSUN Graduate Studies Thesis / Dissertation Support Program and to the MARC/RISE Program (Grant # GM063787) for funding my thesis project and graduate program. I’d also like to thank Dr. MariaElena Zavala for sponsoring my RISE position for the first two years of the graduate program. I made countless connections and friends through RISE and I am forever grateful for the opportunity to be part of scientific collective dedicated to increasing diversity and inclusivity in STEM. Thank you to all the friends I made here in this graduate program. It was a pleasure to wander the halls of the third floor and chat with everyone about our passion for scientific discovery. I’d specifically like to thank my lab mates, Jake Holmes, Elliott Bloom, and Rennie McIntosh, for the extended feedback on my thesis proposal and defense. Furthermore, I’d like to iii thank all the faculty and staff in the Department of Biology for their never-ending wisdom and expertise in all areas of biology. Thank you to Dr. Anthony Giordano for the mentorship with this project and beyond. Special thanks to Gabby Palomo for the help in organizing my camera-trap data with her expert knowledge with R. Thank you to Henrique Villa Boas Concone for his dedicated help with my thesis proposal, field support, data analysis, final manuscript, and friendship. Henrique’s expert knowledge of the Pantanal was inspiring and his passion for conservation fueled mine. This project would not have been possible without his help and I am forever appreciative for the opportunity he provided me. Finally, thank you my family for nurturing and encouraging my passion for nature from such an early age. And special thanks to Melissa, Robert, and Daisy, for the never-ending love, support, and patience during this graduate program. This master’s degree was not a single accomplishment, but a shared one within our little family. iv Table of Contents Signature Page……………………………………………………………... ii Acknowledgments…………………………………………………………. iii Abstract……………………………………………………………………. vi Introduction………………………………………………………………... 1 Materials and Methods…………………………………………………….. 4 Results ……………………………………………………………………... 7 Discussion…………………………………………………………………. 9 Literature Cited……………………………………………………………. 15 v Abstract Niche Segregation Between two Armadillos in the Southern Pantanal, Brazil By Jeffrey Mark Esparza Master of Science in Biology The Pantanal of Brazil is the largest tropical wetland in the world and home to one of the highest diversities of armadillos with up to five extant sympatric species. Among these species are the similarly sized nine-banded armadillo (Dasypus novemcinctus) and six-banded armadillo (Euphractus sexcinctus), both highly specialized diggers with varying diets. I investigated how these two armadillos partitioned their resources and facilitated coexistence by exploring multiple aspects of their ecology including space use and activity time through camera trapping, and substrate and habitat preference in forest and open habitats. I found no significant difference between burrows in both locations (forest and grassland). There was a significant difference in activity between both species with the nine-banded armadillo exhibiting more nocturnal activity and the six-banded armadillo exhibiting more diurnal activity. Both species exhibited minimal overlap in their activity, with the highest amount occurring during the onset of the evening. This study suggests temporal segregation as a sufficient ecological strategy to reduce competitive interactions between these two armadillos. Future studies would benefit from assessing alternative niche axes between species in other ecoregions. vi Introduction Niche partitioning and other methods of coexistence such as competition can be found across the globe in a variety of taxa and systems. Often times, species partition resources as a method of reducing competition and thus promote coexistence (Rosenzweig and Sterner 1970, Schoener 1974, Wilson and Yoshimura 1994, Gravel et al. 2011). In fact, species that often have high overlap in certain niche dimensions may not be able to coexist (Hutchinson 1957). If overlap among species begins to occur in an area, it may be in the best interest of individuals to expend energy traveling to less populated areas rather than compete for resources (Schoener 1974). Thus, space and habitat would be considered an important niche axis (Schoener 1974, Rosenzweig 1981). For example, in Mexico, three species of tree-climbing nuthatches partition their habitat and space use by foraging on different areas of a tree (thin branches, thick branches, trunk) (Lara et al. 2015). In Haiti, 7 species of Anolis lizards occupy different perch and habitat types depending on their movement type and body and limb proportions (Moermond 1979). A second important niche axis is food type (Schoener 1974). Resource partitioning to reduce dietary overlap is a common strategy seen in a variety of species. In New World monkeys, the diversity of coexisting primates is a great example of dietary shifts. Rosenberger (1992) showed that the high diversity of New World primates likely occurs through extensive dietary zones with species consuming different sources of food including exudate (tree sap), insects, nuts, fruits, and leaves depending on body size. Finally, time is another niche axis that can often be partitioned to avoid competition (Schoener 1974, Wilson and Yoshimura 1994). Temporal segregation is a common behavioral mechanism that can be used to reduce competition if there is already overlap in diet and space (Schoener 1974, Di Bitetti et al. 2010). Camera trapping is a useful method to measure activity patterns among species and has revealed extensive evidence to support temporal segregation. Among carnivores, temporal segregation has been documented in tropical forests (Di Bitetti et al. 2010), high elevation deserts (Lucherini et al. 2009), and tropical wetlands (Bianchi et al. 2016). In order to maintain coexistence, high overlap on any niche axis is usually accompanied by avoidance on another axis (Stewart et al. 2003). In North America, Mule deer (Odocoileus hemionus), North American elk (Cervus elaphus), and introduced cattle (Bos taurus) all exhibit low overlap in their diet during the summer season despite significant overlap in habitat use 1 (Stewart et al. 2002, Stewart et al. 2003). In South America, two species of brocket deer in the Atlantic rainforest overlap in space but exhibit temporal segregation (Ferreguetti et al. 2015). Finally, it is possible for there to be minimal overlap in multiple niche dimensions, as seen among the maned wolf (Chrysocyon brachyurus), crab-eating fox (Cerdocyon thous), and hoary fox (Lycalopex vetulus) with varied differences in diet, habitat, and activity patterns in the Brazilian Cerrado (Jacomo et al. 2004). Thus, it is essential to understand multiple niche axes to appropriately consider methods of resource partitioning. The Pantanal is the largest tropical wetland in the world (Alho 1988) and is located predominantly in the Brazilian state of Mato Grosso do Sul. With more than 150 species of mammals, the region is one of South America’s biodiversity hotspots (Tomas et al. 2010) The tropical wetlands of southern Brazil are home to a high diversity of armadillos, with up to five extant sympatric species (Tomas et al. 2010). Armadillos are New World mammals that comprise 21 species (Wetzel 1985, Vizcaíno and Milne 2002) between the families Dasypodidae and Chlamyphoridae of the order Cingulata (Wilson and Mittermeier 2018). They exhibit unique adaptations for different degrees of fossoriality (digging lifestyle) (Vizcaino et al. 1999, Vizcaino and Milne 2002), a diet that consists of varying proportions of insects, fruits, animal prey, and plant material (Redford 1985), a protective bony armor comprised of dermal ossicles (Vizcaíno and Milne 2002), and range in sizes from the 13 cm 120 g pink fairy armadillo (Chlamyphorus truncatus) (Merritt Jr. 1985, Superina 2011) to the 30 kg giant armadillo (Priodontes maximus) (Carter et al. 2016). With over 20 extant species,