Abstract

The alligator snapping turtle (Macrochelys temminckii), the largest freshwater turtle in North America, faces numerous threats, with population declines and range contractions suspected to have occurred across its historic range. Previous research studying movement patterns and microhabitat use of M. temminckii has mostly been conducted in large, open, lentic environments and few studies have been conducted in small, lotic habitats. We investigated the movement and microhabitat use of adult female and juvenile M. temminckii within Bonaldo Creek, a small tributary of the Angelina River in eastern Texas. Six M. temminckii were monitored (two or three relocations per week) via radiotelemetry from July 2008 to September 2009. We found that the linear home range for adult females (405.1–1395.5 m) was longer than that of the unsexed juveniles (439.7–996.9 m), although movement frequency was similar between groups. Juveniles utilized a smaller subset of microhabitats compared to adult females. Adult females utilized microhabitats with abundant submerged structure, while overhanging vegetation was an important microhabitat feature for juveniles. The broader microhabitat use we observed in adult females may have been influenced by seasonal factors, highlighting the need for more long-term, seasonal assessments of M. temminckii movement and microhabitat. Such investigations will bolster our understanding of the spatial and temporal factors that influence M. temminckii populations in different systems.

Abstract

This study examined the invertebrate fauna from three deep wells located at the Uvalde National Fish Hatchery in south-central Texas. These wells provide a water source from geological strata of the southern boundary of the Edwards Aquifer ranging in age from Lower Cretaceous to Recent. Forty-seven collections, sampled on a continuous basis from November 2020 to January 2022, produced a total of 738 specimens comprising 15 different species. These collections reveal a diverse crustacean assemblage along with dominant numbers of the stygobiotic snail Balconorbis uvaldensis. This study provides a preliminary survey for future investigations of unidentified crustacean species as well as revealing seasonal variations in the reproductive life cycle of Balconorbis uvaldensis.

Robert F. McMahon is a Professor Emeritus in the Department of Biology at the University of Texas at Arlington where he also served as Associate Dean of Science and Dean of the Honors College. Since joining the Department in 1972, Dr. McMahon has studied the population dynamics and physiological ecology of invasive marine and freshwater molluscs, including the freshwater golden clam, Corbicula fluminea, the zebra mussel, Dreissena polymorpha, the giant apple snail Pomacea maculata and the marine brown mussel, Perna perna. His studies of these invasive species included their growth rates, physiological adaptations, environmental limits, and methods for control. He has served as a member of national and regional invasive species panels including the National Invasive Species Advisory Committee, the Western Regional Panel on Aquatic Invasive Species and presently serves on the Gulf and South Atlantic Regional Panel on Aquatic Invasive Species. For his research contributions to the biology and control of invasive species, he received the National Invasive Species Council's Invasive Species Lifetime Achievement Award in 2015.

Dr. McMahon has a worldwide reputation for his research on the biology and control of invasive molluscs. He has published over 100 articles, technical reports and book chapters on aquatic invasive molluscs and continues to conduct research with colleagues on the biology and control of invasive zebra mussels in Texas. He was awarded a Fulbright Research Fellowship to Trinity College, Dublin Ireland in 1979-80, a Certificate of Achievement by The Western Regional Panel on Aquatic Invasive Species in 2016, the Award for Distinguished Record of Research from the University of Texas at Arlington in 1990, and was named the Texas Academy of Science Texas Distinguished Scientist in 2023.