GPS Technology for Semi-Aquatic Turtle Research

Global positioning system (GPS) telemetry units are now small enough to be deployed on terrestrial and semi-aquatic turtles. Many of these GPS units use snapshot technology which collects raw satellite and timestamp data during brief periods of data recording to minimize size. We evaluated locations from snapshot GPS units in stationary tests and on wood turtles (Glyptemys insculpta) in northeastern Minnesota. Stationary GPS units were placed in wood turtle habitat to evaluate location accuracy, fix success rate, and directional bias. The GPS fix success rate and accuracy were reduced in closed canopy conditions and when the stationary GPS unit was placed under a log to simulate wood turtle hiding behavior. We removed GPS location outliers and used a moving average calculation to reduce mean location error in stationary tests from 27 m (SD = 38) to 10 m (SD = 8). We then deployed GPS units and temperature loggers on wood turtles and collected 122,657 GPS locations and 242,781 temperature readings from 26 turtles from May to September 2015 and 2016. Location outliers accounted for 12% of locations when the GPS receiver was on a turtle. We classified each wood turtle location based on the GPS location and by comparing temperature profiles from river, sun, and shaded locations to the temperature logger on the turtle. We estimated that wood turtles were on land 68% (SD = 12) of the time from May to September. The fix success rate for land locations was 38% (SD = 9), indicating that wood turtles often use habitats with obstructed views of the sky. Mean net daily movement was 55 m (SD = 192). Our results demonstrate that snapshot GPS units and temperature loggers provide fine-scale GPS data useful in describing spatial ecology and habitat use of semi-aquatic turtles

Temperature-dependent sex determination in the viviparous lizard Eulamprus tympanum

Abstract There are a remarkable variety of sex determination systems among different animal taxa. In most animals, sex is determined chromosomally. Although in an increasing number of animals sex determination has been found to be influenced primarily by the environment. Species with genotypic sex determination (GSD) have their sex determined at the time of fertilization, by genetic factors alone and those with environmental sex determination (ESD) have their sex determined by environmental factors that act after fertilization. Temperature-dependent Sex Determination (TSD), whereby the sex of the developing embryos depends on the temperature at which they develop is widespread in oviparous reptiles and occurs in all crocodilians, marine turtles and tuatara examined to date and is common in many freshwater turtles and lizards. SECTION ONE Temperature-dependent sex determination (TSD) was never expected to occur in viviparous reptiles, as thermoregulation by pregnant females would result in relatively stable gestation temperatures. Temperature-dependent sex determination and viviparity goes against all the basic assumptions that TSD occurs in oviparous reptiles where temperatures within a nest vary widely. However, skewed sex ratios as a result of incubation temperature indicated the possibility of TSD in the viviparous lizard Eulamprus tympanum. In my first experiments I show the first recorded case of a viviparous reptile with TSD. The developing embryos of the viviparous skink E. tympanum are subject to TSD, with gestation temperature having a highly significant effect on sex and warmer temperatures giving rise to male offspring (Chapter 1). Sex is fully determined at the time of birth and can be differentiated histologically into testes or ovaries (Chapter 2). The morphology and histological characteristics of the gonads of neonatal E. tympanum resulting from the treatment temperatures described in chapter 1 illustrate that sex in E. tympanum is easily distinguished at the time of birth and corresponds with the presence or absence of hemipenes. Males are histologically characterised by an elongated gonad consisting of seminiferous tubules with either no cortical epithelium or, if present at all, in a very thin band. If they are present, Mϋllerian ducts, showing signs of degeneration, are attached to the kidney by a shortened mesosalpinx. Females are histologically characterised by an irregularly shaped gonad consisting of a thick cortical epithelium that occasionally contains oocytes. The Mϋllerian ducts are obvious structures attached to the kidney by a fibrous mesosalpinx. The presence or absence of hemipenes is a reliable technique for determining sex in newborn E. tympanum. Sex determination is easiest to perform on neonates within the first few days of birth as hemipenes become increasingly difficult to evert as neonates age, however, with practice they are easily identified without full eversion. SECTION TWO The thermal biology of E. tympanum in the field is restricted by both the thermal properties of their habitat (Chapter 3) and behavioural modifications when faced with a predation threat (Chapter 4). The available temperatures in the field suggest that TSD is biologically relevant in the species and not just a laboratory artefact; E. tympanum can attain mean selected temperatures achieved in the laboratory but the proportion of time at the temperature is restricted. Females actively thermoregulate in the field, although they are restricted in their efficiency of thermoregulation by environmental constraints, for example, microhabitat structure, weather conditions, predator avoidance and social ranking. The highly territorial nature and high densities of E. tympanum present in Kanangra Boyd National Park potentially force less dominant individuals into less favourable habitats that are significantly cooler. An important point is that gravid females in more favourable habitats in the period encompassing the middle third of development (the assumed sex determining period) are selecting higher temperatures, with lower variance and have greater thermoregulatory efficiency than during the rest of pregnancy, therefore, thermoregulating more precisely during this thermosensitive period (Chapter 3). Chemosensory cues provide important information on the risk of predation. Hence, chemoreception is a common mechanism used by many species to detect the presence of, and subsequently respond to, a potential predator. The perceived risk of predation may force retreat to sub-optimal conditions, forcing a trade-off between the risk of predation and the ability to acquire resources. The basking regime maintained by gravid female E. tympanum, can directly alter sex ratios of offspring produced through temperature-dependent sex determination (Chapter 1). The avoidance of predator scents may restrict basking ability and in turn alter the sex of offspring produced. I measured responsiveness to chemical cues using tongue flicks as an indicator of chemical discrimination in females of different reproductive condition. I then measured activity and basking behaviour of gravid and non-gravid females in experimental enclosures in the presence of various chemical stimuli to determine if basking opportunity is compromised by the presence of a predator scent. Females respond differently depending upon reproductive condition, with gravid females responding most significantly to a predator scent. Activity, basking frequency, and time spent in the open (basking duration) are significantly reduced in gravid females in the presence of a predator stimulus. Under laboratory conditions, gravid females modify their behaviour and forego the opportunity to bask when there is a perceived predation risk (Chapter 4). SECTION THREE As female viviparous reptiles can regulate the temperature of the embryo by maternal temperature selection (Chapter 1), the occurrence of TSD in E. tympanum opens the possibility for females to select the sex of offspring. Reproducing females may benefit by facultatively adjusting their investment into sons over daughters or vice versa, in response to population wide shifts in adult sex ratios. Female E. tympanum, can manipulate the sex of their offspring in response to sex imbalances in the population using temperature-dependent sex determination (Chapter 5). When adult males are scarce, females produce male-biased litters and when adult males are common, females produce female-biased litters. The cues used by a female to assess the adult population are not known, but presumably depends upon the female's experience throughout the breeding season and is the subject of further investigation (Chapter 6). The maternal manipulation of offspring sex ratio in E. tympanum suggests a selective advantage of temperature-dependent sex determination. Any facultative sex ratio response needs to recognise the scarcity of one sex in order to overproduce that sex in the next generation; offspring sex ratio will vary inversely with adult sex ratio. Maternal sex allocation in E. tympanum is linked with population (or adult) sex ratio (Chapter 5), and one of the mechanisms by which females recognise an imbalance may be linked to visual recognition of males (Chapter 6). Females maintained throughout pregnancy without any male stimulus produce entirely male offspring (Chapter 5). In contrast females exposed to male stimulus produce both sexes (Chapter 5). Females respond differently to varying degrees of male stimulus and visual recognition of males in a population may be more important than chemoreception. In the absence of visual cues, females produce more male offspring, even when chemosensory cues are present (Chapter 6). The study system presented here offers many advantages over oviparous species with TSD, due to E. tympanum being relatively short lived and fast maturing. Thus, the fitness consequences over multiple generations as a result of gestation can be investigated. Viviparity allows maternal control of embryonic temperature during gestation and a means of maternal sex allocation. Until now the maternal side of TSD and sex allocation has been where the mother deposits her eggs and the allocation of sex steroid hormones at oviposition, both of which have been difficult to study. The work presented and the study system itself should inspire great interest in TSD and viviparous reptiles

Temperature-dependent sex determination in the viviparous lizard Eulamprus tympanum

Abstract There are a remarkable variety of sex determination systems among different animal taxa. In most animals, sex is determined chromosomally. Although in an increasing number of animals sex determination has been found to be influenced primarily by the environment. Species with genotypic sex determination (GSD) have their sex determined at the time of fertilization, by genetic factors alone and those with environmental sex determination (ESD) have their sex determined by environmental factors that act after fertilization. Temperature-dependent Sex Determination (TSD), whereby the sex of the developing embryos depends on the temperature at which they develop is widespread in oviparous reptiles and occurs in all crocodilians, marine turtles and tuatara examined to date and is common in many freshwater turtles and lizards. SECTION ONE Temperature-dependent sex determination (TSD) was never expected to occur in viviparous reptiles, as thermoregulation by pregnant females would result in relatively stable gestation temperatures. Temperature-dependent sex determination and viviparity goes against all the basic assumptions that TSD occurs in oviparous reptiles where temperatures within a nest vary widely. However, skewed sex ratios as a result of incubation temperature indicated the possibility of TSD in the viviparous lizard Eulamprus tympanum. In my first experiments I show the first recorded case of a viviparous reptile with TSD. The developing embryos of the viviparous skink E. tympanum are subject to TSD, with gestation temperature having a highly significant effect on sex and warmer temperatures giving rise to male offspring (Chapter 1). Sex is fully determined at the time of birth and can be differentiated histologically into testes or ovaries (Chapter 2). The morphology and histological characteristics of the gonads of neonatal E. tympanum resulting from the treatment temperatures described in chapter 1 illustrate that sex in E. tympanum is easily distinguished at the time of birth and corresponds with the presence or absence of hemipenes. Males are histologically characterised by an elongated gonad consisting of seminiferous tubules with either no cortical epithelium or, if present at all, in a very thin band. If they are present, Mϋllerian ducts, showing signs of degeneration, are attached to the kidney by a shortened mesosalpinx. Females are histologically characterised by an irregularly shaped gonad consisting of a thick cortical epithelium that occasionally contains oocytes. The Mϋllerian ducts are obvious structures attached to the kidney by a fibrous mesosalpinx. The presence or absence of hemipenes is a reliable technique for determining sex in newborn E. tympanum. Sex determination is easiest to perform on neonates within the first few days of birth as hemipenes become increasingly difficult to evert as neonates age, however, with practice they are easily identified without full eversion. SECTION TWO The thermal biology of E. tympanum in the field is restricted by both the thermal properties of their habitat (Chapter 3) and behavioural modifications when faced with a predation threat (Chapter 4). The available temperatures in the field suggest that TSD is biologically relevant in the species and not just a laboratory artefact; E. tympanum can attain mean selected temperatures achieved in the laboratory but the proportion of time at the temperature is restricted. Females actively thermoregulate in the field, although they are restricted in their efficiency of thermoregulation by environmental constraints, for example, microhabitat structure, weather conditions, predator avoidance and social ranking. The highly territorial nature and high densities of E. tympanum present in Kanangra Boyd National Park potentially force less dominant individuals into less favourable habitats that are significantly cooler. An important point is that gravid females in more favourable habitats in the period encompassing the middle third of development (the assumed sex determining period) are selecting higher temperatures, with lower variance and have greater thermoregulatory efficiency than during the rest of pregnancy, therefore, thermoregulating more precisely during this thermosensitive period (Chapter 3). Chemosensory cues provide important information on the risk of predation. Hence, chemoreception is a common mechanism used by many species to detect the presence of, and subsequently respond to, a potential predator. The perceived risk of predation may force retreat to sub-optimal conditions, forcing a trade-off between the risk of predation and the ability to acquire resources. The basking regime maintained by gravid female E. tympanum, can directly alter sex ratios of offspring produced through temperature-dependent sex determination (Chapter 1). The avoidance of predator scents may restrict basking ability and in turn alter the sex of offspring produced. I measured responsiveness to chemical cues using tongue flicks as an indicator of chemical discrimination in females of different reproductive condition. I then measured activity and basking behaviour of gravid and non-gravid females in experimental enclosures in the presence of various chemical stimuli to determine if basking opportunity is compromised by the presence of a predator scent. Females respond differently depending upon reproductive condition, with gravid females responding most significantly to a predator scent. Activity, basking frequency, and time spent in the open (basking duration) are significantly reduced in gravid females in the presence of a predator stimulus. Under laboratory conditions, gravid females modify their behaviour and forego the opportunity to bask when there is a perceived predation risk (Chapter 4). SECTION THREE As female viviparous reptiles can regulate the temperature of the embryo by maternal temperature selection (Chapter 1), the occurrence of TSD in E. tympanum opens the possibility for females to select the sex of offspring. Reproducing females may benefit by facultatively adjusting their investment into sons over daughters or vice versa, in response to population wide shifts in adult sex ratios. Female E. tympanum, can manipulate the sex of their offspring in response to sex imbalances in the population using temperature-dependent sex determination (Chapter 5). When adult males are scarce, females produce male-biased litters and when adult males are common, females produce female-biased litters. The cues used by a female to assess the adult population are not known, but presumably depends upon the female's experience throughout the breeding season and is the subject of further investigation (Chapter 6). The maternal manipulation of offspring sex ratio in E. tympanum suggests a selective advantage of temperature-dependent sex determination. Any facultative sex ratio response needs to recognise the scarcity of one sex in order to overproduce that sex in the next generation; offspring sex ratio will vary inversely with adult sex ratio. Maternal sex allocation in E. tympanum is linked with population (or adult) sex ratio (Chapter 5), and one of the mechanisms by which females recognise an imbalance may be linked to visual recognition of males (Chapter 6). Females maintained throughout pregnancy without any male stimulus produce entirely male offspring (Chapter 5). In contrast females exposed to male stimulus produce both sexes (Chapter 5). Females respond differently to varying degrees of male stimulus and visual recognition of males in a population may be more important than chemoreception. In the absence of visual cues, females produce more male offspring, even when chemosensory cues are present (Chapter 6). The study system presented here offers many advantages over oviparous species with TSD, due to E. tympanum being relatively short lived and fast maturing. Thus, the fitness consequences over multiple generations as a result of gestation can be investigated. Viviparity allows maternal control of embryonic temperature during gestation and a means of maternal sex allocation. Until now the maternal side of TSD and sex allocation has been where the mother deposits her eggs and the allocation of sex steroid hormones at oviposition, both of which have been difficult to study. The work presented and the study system itself should inspire great interest in TSD and viviparous reptiles

Quantifying Thermal‐Imager Effectiveness for Detecting Bird Nests on Farms

We conducted a designed experiment to test whether having a thermal‐imaging camera available affected researchers’ nest detection rates when searching for bird nests in cropland and grassland habitat in an agricultural landscape of Iowa, USA, in 2016. With known active nests present, naïve observers searched for nests with and without a thermal imager available. We did not find a difference in detection probabilities, although only a large difference would have been detectable with our sample size. Extraneous heat signatures from reflected solar radiation and dense vegetation were key factors limiting the usefulness of thermal imagers for locating nests

Monitoring food quality using sensor technology from harvest to home

A food quality sensor is a device that responds to some property associated with food quality and transforms the response into a signal (1). This signal may provide direct information about the quality factor to be measured or may have a known relationship to the quality factor. On-line food quality sensors operate directly in the process stream, giving a real-time signal that relates to the quality factor in question. Therefore, an online sensor has the advantage of giving an immediate measurement allowing processes to be adjusted if necessary (1). This thesis is based on 3 projects describing the design and development of on-line food quality sensor systems for specific food applications as`outlined below: Project 1: Development of an autonomous, wireless pH and temperature sensing system for monitoring pig meat quality. Project 2: Development of a web-based wireless temperature sensing system for the fishing industry. Project 3: Development of on-package sensors to detect shellfish. Projects 1 & 2 describe pH and temperature sensors which are coupled with wireless communications to create autonomous, wireless sensing devices capable of delivering data in real-time to a remote PC where the data can be analysed or automatically uploaded onto the internet via specifically designed web-enabled software. Project 3 focuses on the development of pH sensitive polymer membranes that change colour in response to spoilage volatiles released by shellfish packed in sealed containers. Field trials performed with the aid of Irish food industries and collaborating Irish research institutes played a major role in obtaining the results for each of the mentioned projects. These include the Department of Food and Nutritional Sciences, University College Cork; Galtee Meats, Mitchelstown, Co. Cork; Bord Iascaigh Mhara (BIM) coastal staff and Errigal Iasc, Carrick, Co. Donegal. The following thesis gives a detailed account of the recent challenges faced by the Irish food sector including the detection of poor quality pig meat, traceability and temperature control within the fishing industry and methods to evaluate seafood spoilage. The research activities carried out to overcome such challenges are discussed including the potential impact on the Irish food industry

Wood Turtles (Glyptemys insculpta) in Northeastern Minnesota: An Analysis of GPS Telemetry and a Population Assessment

University of Minnesota M.S. thesis.August 2017. Major: Integrated Biosciences. Advisor: Ron Moen. 1 computer file (PDF); vii, 63 pages.Wood Turtle (Glyptemys insculpta) populations have experienced declines across their North American extent of occurrence and are listed as a state threatened species in Minnesota. To improve our understanding of the current conservation status of the species in northeastern Minnesota, we performed a snapshot comparison study using data from population surveys in 1990 and 2015. Our snapshot comparison indicated relative abundance, adult sex ratio, and juvenile-adult ratio did not differ between years. Thus, we found no evidence of Wood Turtle population change in a 40 km river system in northeastern Minnesota over the last 25 years. We also evaluated the positional data quality of snapshot GPS devices at a study area, for use in freshwater turtle research. GPS stationary tests in four different cover types were used to evaluate location accuracy, fix success rate, and directional bias of GPS devices in Wood Turtle habitat. These tests demonstrated that positional data quality is reduced in closed canopy conditions. Utilizing the results for these tests, we developed a GPS screening procedure for turtle locations. We collected 122,657 locations and 399,606 temperatures readings from the carapace of 26 Wood Turtles from May to September 2015 and 2016. We removed locations with high horizontal dilution of precision values, locations farther from surrounding points than a predefined distance, biologically impossible movements, and then used moving averages to estimate turtle locations. The screening procedure removed 10% of GPS locations, and reduced mean location error from 26 m (SD = 33) to 11 m (SD = 12). We also developed a methodology to compare ambient temperature profiles from water, sunny, and shaded locations to the temperature of a turtle’s carapace, to define a turtle’s location as land or water. Our results suggest that snapshot GPS technology and temperature loggers provide temporally unbiased and abundant GPS data useful in describing spatial ecology and habitat use of semi-aquatic turtles