BACKGROUND: Comparing patterns of ter- restrial and marine defaunation helps to place human impacts on marine fauna in context and to navigate toward recovery. De- faunation began in ear- nest tens of thousands of years later in the oceans than it did on land. Al- though defaunation has been less severe in the oceans than on land, our effects on marine animals are increasing in pace and impact. Humans have caused few complete extinctions in the sea, but we are responsible for many ecological, commercial, and local extinctions. Despite our late start, humans have already powerfully changed virtually all major marine ecosystems. ADVANCES: Humans have profoundly de- creased the abundance of both large (e.g., whales) and small (e.g., anchovies) marine fauna. Such declines can generate waves of ecological change that travel both up and down marine food webs and can alter ocean ecosystem functioning. Human harvesters have also been a major force of evolutionary change in the oceans and have reshaped the genetic structure of marine animal popula- tions. Climate change threatens toaccelerate marine defaunation over the next century. The high mobility of many marine animals offers some increased, though limited, ca- pacity for marine species to respond to cli- mate stress, but it also exposes many species to increased risk from other stressors. Be- cause humans are intensely reliant on ocean ecosystems for food and other ecosystem ser- vices, we are deeply affected by all of these forecasted changes. Three lessons emerge when comparing the marine and terrestrial defaunation ex-

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Marine defaunation: Animal loss in the global ocean

Turtles are a small taxon that has nevertheless attracted much attention from biologists for centuries. However, a major portion of their life cycle has received relatively little attention until recently - namely what turtles are doing, and how they are doing it, during the winter. In the northern parts of their ranges in North America, turtles may spend more than half of their lives in an overwintering state. In this review, I emphasise the ecological aspects of overwintering among turtles, and consider how overwintering stresses affect the physiology, behaviour, distributions, and life histories of various species. Sea turtles are the only group of turtles that migrate extensively, and can therefore avoid northern winters. Nevertheless, each year a number of turtles, largely juveniles, are killed when trapped by cold fronts before they move to safer waters. Evidently this risk is an acceptable trade-off for the benefits to a population of inhabiting northern developmental habitats during the summer. Terrestrial turtles pass the winter underground, either in burrows that they excavate or that are preformed. These refugia must provide protection against desiccation and lethal freezing levels. Some burrows are extensive (tortoise genus Gopherus), while others are shallow, or the turtles may simply dig into the ground to a safe depth (turtle genus Terrapene). In the latter genus, freeze tolerance may play an adaptive role. Most non-marine aquatic turtles overwinter underwater, although Clemmys (Actinemys) marmorata routinely overwinters on land when it occurs in riverine habitats, Kinosternon subrubrum often overwinters on land, and several others may overwinter terrestrially on occasion, especially in more southern climates. For northern species that overwinter underwater, there are two physiological groupings, those that are anoxia-tolerant and those that are relatively anoxia-intolerant. All species fare well physiologically in water with a high partial pressure of oxygen (PO2). A lack of anoxia tolerance limits the types of habitats that a freshwater turtle may live in, since unlike sea turtles, they cannot travel long distances to hibernate. Hatchlings of some species of turtles spend their first winter in or below the nest cavity, while hatchlings of other species in the same area, including northern areas, emerge in the autumn and presumably hibernate underwater. All hatchlings are relatively anoxia-intolerant, and there are no studies to date of where hatchling turtles that do not overwinter in or below the nest cavity spend their first winter. Equally little is known of the ontogeny of anoxia tolerance, other than that adults of all species are more anoxia-tolerant than their hatchlings, probably because of their better ossified shells, which provide adults with more buffer reserves and a larger site in which to sequester lactate. The northern limits of turtles are most likely determined by reproductive limitations (time for egg-laying, incubation, and hatching) than by the rigors of hibernation. Mortality is typically lower in turtle populations during hibernation than it is during their active periods. However, episodic mortality events do occur during hibernation, due to freezing, prolonged anoxia, or predation.

The ecology of overwintering among turtles: where turtles overwinter and its consequences

Reptile freeze tolerance: metabolism and gene expression.

Temperate species of turtles hatch from eggs in late summer. The hatchlings of some species leave their natal nest to hibernate elsewhere on land or under water, whereas others usually remain inside the nest until spring; thus, post-hatching behavior strongly influences the hibernation ecology and physiology of this age class. Little is known about the habitats of and environmental conditions affecting aquatic hibernators, although laboratory studies suggest that chronically hypoxic sites are inhospitable to hatchlings. Field biologists have long been intrigued by the environmental conditions survived by hatchlings using terrestrial hibernacula, especially nests that ultimately serve as winter refugia. Hatchlings are unable to feed, although as metabolism is greatly reduced in hibernation, they are not at risk of starvation. Dehydration and injury from cold are more formidable challenges. Differential tolerances to these stressors may explain variation in hatchling overwintering habits among turtle taxa. Much study has been devoted to the cold-hardiness adaptations exhibited by terrestrial hibernators. All tolerate a degree of chilling, but survival of frost exposure depends on either freeze avoidance through supercooling or freeze tolerance. Freeze avoidance is promoted by behavioral, anatomical, and physiological features that minimize risk of inoculation by ice and ice-nucleating agents. Freeze tolerance is promoted by a complex suite of molecular, biochemical, and physiological responses enabling certain organisms to survive the freezing and thawing of extracellular fluids. Some species apparently can switch between freeze avoidance or freeze tolerance, the mode utilized in a particular instance of chilling depending on prevailing physiological and environmental conditions.

http://www.units.miamioh.edu/cryolab/publications/documents/Costanzoetal2008.pdf

Physiological ecology of overwintering in hatchling turtles

Understanding the space use patterns of a population may provide crucial information regarding land management decisions, such as delineation of protected areas. Herein we provide a comprehensive analysis of factors affecting the space use of Desert Tortoises in the west Mojave Desert, including physical, social, and environmental variables. Our objectives were to determine how spatial overlap, as well as multiple parameters of burrow use, influence home range size of this species. Male tortoises were significantly larger than females and exhibited very different patterns of space and burrow use; however, body size did not affect these variables. Male home range (100% MCP) and core area (50% MCP) size averaged 65% and 73% larger than those of females. Burrow use by males and females affected core area size, but not home range area. Females exhibited a strong male bias in overlap of both estimates of space use and burrow sharing, while using a significantly lower number of burrows per year. However, males overlapped and shared burrows with a similar number of tortoises of either sex. In addition, a high degree of home range overlap between individuals suggests a lack of territoriality in this population, although this warrants further analysis. These results suggest that social factors may not be the primary determinants of space use in this Desert Tortoise population.

Home Range, Spatial Overlap, and Burrow Use of the Desert Tortoise in the

We quantified home range size and philopatry in ornate box turtles, Terrapene ornata ornata, with minimum convex polygons (MCP) and 95% Kernel areas (K) calculated from radio telemetry data in Iowa during 1999–2001. We also analyzed philopatry by mark-recapture data during 1994–2000. Ten adult turtles were followed every other day from May to Sep. 2000 and seven of the turtles were followed in 2001. Mean monthly MCP and K home ranges of males and females did not significantly differ. Mean annual MCP and K home ranges for males were significantly larger than those of females. For an individual, monthly MCP home ranges overlapped on average 19.3% between years and K home ranges overlapped an average of 6.0%. There were no significant differences in annual or monthly home range overlap between sexes for K home ranges, but MCP monthly home range overlap was significantly larger for males. Annual MCP home ranges overlapped on average 40.9% between years and K annual home range overlap averaged 6.8%. S...

Home Range and Philopatry in the Ornate Box Turtle, Terrapene ornata ornata, in Iowa

The carapace temperatures of ornate box turtles (Terrapene ornata ornata) were monitored by affixing temperature dataloggers during two winters, 2001–2002 and 2003–2004. The dataloggers recorded temperature every 3 h to the nearest 0.5 C. Date of burrowing in the fall, emergence time in the spring and temperatures 48 h prior to emergence were analyzed along with the entire temperature profile of the turtles during the winter. In 2003–2004 soil temperatures from the surface to 0.75 m depth were also monitored. Most turtles did not experience freezing temperatures during either winter, but two turtles were below freezing for up to 54 consecutive days during winter 2001–2002. During 2001–2002, eight of nine turtles began burrowing within 7 d of each other in the fall, and all nine emerged within 7 d of each other in the spring. During 2003–2004, fall burrowing for 16 turtles occurred within 14–21 d, and emergence happened within 15 d. Overwintering periods varied between 172–201 d, which was interme...

https://bioone.org/journals/The-American-Midland-Naturalist/volume-153/issue-2/0003-0031(2005)153[0370:TEOOOB]2.0.CO;2/Thermal-Environment-of-Overwintering-Ornate-Box-Turtles-Terrapene-ornata-ornata/10.1674/0003-0031(2005)153[0370:TEOOOB]2.0.CO;2.pdf

Thermal Environment of Overwintering Ornate Box Turtles, Terrapene ornata ornata, in Iowa

Like many fragmented reptile populations, the ornate box turtle (Terrapene ornata ornata) is located in isolated, often small, populations in eastern Iowa. If populations are to remain viable, genetic diversity within these populations must be maintained, which is done most efficiently by migration among populations. Population viability was accessed using 3 microsatellite loci to determine population genetic structure in 2 locally dispersed subpopulations of ornate box turtles. Although these subpopulations were determined to be 1 large population with the normal range of heterozygosity, further examination revealed evidence of genetic divergence from a once larger population that is now geographically separated into fragments. We concluded that the central population studied was genetically healthy, and with proper management that continues to promote gene flow, the population should remain viable in the near future.

https://bioone.org/journals/Chelonian-Conservation-and-Biology/volume-7/issue-1/CCB-0653.1/Migration-Gene-Flow-and-Genetic-Diversity-Within-and-Among-Iowa/10.2744/CCB-0653.1.pdf

Robert W. Black

Papers

Home Range and Philopatry in the Ornate Box Turtle, Terrapene ornata ornata, in Iowa

Thermal Environment of Overwintering Ornate Box Turtles, Terrapene ornata ornata, in Iowa

Migration, Gene Flow, and Genetic Diversity Within and Among Iowa Populations of Ornate Box Turtles (Terrapene ornata ornata)