Dr Mike Plummer E: [email protected] T: +1 501 281 5286 W: https://www.researchgate.net/profile/Michael_Plummer2 Naturally awesome/Shutterstock.com Naturally Exploring the Hibernating Behaviour of Smooth Softshell Turtles References Research Objectives • Plummer, M. and O’Neal, C. (2019). Aerobic Prof Plummer studies various aspects of the ecology of Pushups: Cutaneous Ventilation in Overwintering softshell turtles, both in the field and in the laboratory. Smooth Softshell Turtles, Apalone mutica. Journal of His research typically involves undergraduate students. Herpetology, 53(1), 27–31. • Plummer, M. and Pappas, M. (2010). Le Trionyx mutique. Chéloniens, 18, 8–15. Personal Response • Plummer, M. and Burnley, C. (1997). Behavior, Hibernacula, and Thermal Relations of Softshell Turtles What fascinates you most about Smooth Softshell (Trionyx spiniferus) Overwintering in a Small Stream. Turtles and what are the main characteristics that Chelonian Conservation and Biology, 2(4), 489–493. set them apart from other aquatic turtles? As a result of their lack of a hard shell and their Detail thin vascular skin, the physiology of softshell turtles is unlike that of most turtle species, which have hard bony Department of Biology shells and thick skin that limit water and gas exchange Box 12251 with their environment. In this respect, the physiology Harding University of softshell turtles is more like that of amphibians, Searcy, Arkansas 72143 rather than most other reptiles, which makes for some USA interesting research on their sometimes unreptilian-like biology. In the final analysis, however, I got hooked on softshells when I was just a kid because they are really Bio Mike Plummer is Professor Emeritus in the Department cool and charismatic animals! of Biology at Harding University where he taught biostatistics and vertebrate biology for 44 years. He holds What are you planning to study next? a PhD from the University of Kansas and a MS from Utah I am currently collaborating with Dr Sean Doody of State University. Prof Plummer’s research focuses on the the University of South Florida in a study of latitudinal ecology of snakes and turtles. variation in nesting in A. mutica and other turtle species. Like much of my research, this study will involve Collaborators undergraduate students at Harding University. Caleb O’Neal, Undergraduate Student, Harding University, currently a graduate student at Missouri State University. Biology︱Mike Plummer In contrast to other turtle species, Apalone mutica raise and lower the posterior portion of their body periodically and intermittently, performing a Exploring the ‘push-up’-like movement. Hibernating Behaviour of Smooth Softshell Turtles In contrast with other species any types of aquatic turtles of softshell turtles for many years, with of aquatic turtles, softshell hibernate underwater, surfacing the hope of better understanding the turtles cannot survive long Monly at the end of the winter. unique mechanisms that promote their without oxygen and this affects During this hibernation period, some survival during winter. how they hibernate in the species bury themselves under the winter. Instead of fully burying sediment at the bottom of the body APALONE MUTICA: AN AQUATIC themselves into the substrate of water they inhabit, which typically TURTLE THAT CAN BREATHE at the bottom of a body of contains very little or no oxygen. To THROUGH ITS SKIN water and staying there, they survive for prolonged periods of time The Smooth Softshell Turtle (Apalone must periodically raise parts of under the sediment, however, turtles mutica) is a small primarily carnivorous their body above the sediment need to be able to effectively utilise turtle with an elongated head and a to breathe in oxygen that is metabolic pathways that produce lactic soft, leather-like shell, which belongs dissolved in the water. Mike acid. This process closely resembles the to the Trionychidae family. So far, Plummer, Professor Emeritus at ways in which human athletes recover researchers have identified two different Harding University, has carried when they run out of oxygen after subspecies of Apalone mutica with out a study investigating the intense physical activity. different head and eye configurations, extinct due to damage to their hibernating behaviour of dubbed A. m. mutica and A. m. calvata. environment, those softshells living softshell turtles and how they Smooth Softshell Turtles (Apalone in rivers, such as Apalone mutica, sustain aerobic respiration mutica) cannot tolerate a buildup In their youth, the top portion of these appear to be particularly vulnerable. throughout the winter. of lactic acid, thus they need to softshell turtles is typically light-brown, In fact, these turtles have very specific continuously obtain the oxygen brown or greenish-brown, presenting ecological needs that make them dissolved in water via their thin vascular small dark spots and bacilliform particularly susceptible to the pollution skin. As a result, when they hibernate rods arranged in a specific pattern. caused by human activities. they are unable to lay still under While adult males retain this pattern, sediment for long periods of time and in females this pattern is gradually A characteristic that distinguishes occasionally must reach the water replaced by an irregular and marble- softshell turtles from some other column to breathe. Biologists have been like pattern. aquatic turtles is that they require studying the skin breathing mechanisms significant amounts of oxygen to The researchers monitored the Smooth softshell turtles are native to survive while under water and their behaviour of 25 Apalone mutica North America, where they have been metabolism can only be sustained specimens in an outdoor pond. observed in 23 U.S. states, ranging by extracting this oxygen from the from Pennsylvania to New Mexico and water. While other turtles may also the Florida panhandle region. Apalone have this ability, in Apalone mutica, mutica are generally found in medium it is particularly advanced, as they Apalone mutica are able to take in and and large unpolluted rivers with strong are able to take in and release gases release gases via their thin and highly currents and clean sand banks. Their via the thin and highly vascularised period of activity generally goes from skin of their mouth, throat, anus and vascularised skin of their mouth, throat, the end of March/beginning of April body surface. When the oxygen in the to the middle of October, but they can water surrounding them is depleted, anus and ventral body surface. sometimes go into hibernation earlier therefore, the turtles must move or come out sooner, depending on the around in their environment, or move as it prevents them from laying still or THE HIBERNATION BEHAVIOURS climate in the regions they inhabit. specific body parts, to actively seek burrowing deep for prolonged periods OF SOFTSHELL TURTLES out ‘new’ water that contains more of time under the sediment at the Although many past studies have tried While many turtle populations oxygen. This characteristic unavoidably bottom of rivers or ponds, like some to gain a better understanding of turtle Psychotic Nature/Shutterstock.com Psychotic worldwide are at risk of becoming affects their hibernation strategies, species of turtles do. hibernation strategies, the specific researchoutreach.org researchoutreach.org free-ranging Spiny Softshell Turtles the turtles. Essentially, the colder (Apalone spinifera), a close relative of the water around them was, the less Apalone mutica, hibernate by burying frequently they pushed their body up themselves in sediments at the bottom to breathe. This is not surprising, as of the streams they inhabit, which cold water can hold greater quantities contain varying mixtures of mud, sand of oxygen than warm water, thus it may and gravel. The sites where these fulfil their needs for a longer period turtles retire for the winter are not of time. usually situated in the deepest part of a stream or river and are typically less To study the push-up behaviour they than a meter under the level of the observed more closely, Prof Plummer water, which is enough to prevent them and O’Neal also simulated the from reaching the water surface and conditions of winter in the aquaria they breathe in air, as they do during their set up inside their laboratory where period of activity. they could measure the actual oxygen content of the water. Their experiments Moreover, Prof Plummer and Burnley confirmed that Smooth Softshell observed that Spiny Softshells bury Turtles hibernating in water with high This image, taken through nine inches of cloudy water in the outdoor pond, shows the ‘up’ themselves under a few centimetres oxygen content execute ‘push-ups’ less movement of the push-up, the frequency of which was correlated with water temperature. In cold water, the turtles perfomed ‘push-ups’ less frequently. of sediment, as this allows the turtles frequently than those placed in water to reach up when necessary to obtain containing less oxygen. oxygen from the water taken into their mouth and throat. They also found that Overall, the observations gathered by Apalone mutica repeatedly perform the body temperatures of this softshell the two researchers show that Smooth species as it is hibernating ranged Softshell Turtles intermittently ‘push-up’ an aerobic ‘push-up’ movement, which between 1.5 and 16.2 °C and closely above the sediment they are buried in allows their skin to absorb oxygen in the resembled the temperature of its while hibernating in order to breathe surrounding environment. and survive throughout the winter. surrounding water. This ‘aerobic’ respiration mechanism While this is an interesting example creates currents that allow the turtles mechanisms and behaviours that gathered valuable observations using of a turtle hibernation strategy, to replenish the layer between their facilitate the survival of Apalone mutica radiotelemetry techniques, which can different softshell species have vascularised skin and oxygenated water during the colder months remained infer the movements/behaviours of unique characteristics that affect how in their surroundings.