We have developed a project using Thermochron iButtons (miniature temperature dataloggers) to study desert box turtle thermal ecology. By attaching the iButtons to the carapaces of the animals, and pre-programming them to record at 15 minute intervals, we can easily see when the animals are emerging from their burrows, how long they are active, and when they re-enter shelter. Compared with iButtons at stratified heights in the environment, one can actually come up with a fairly solid time budget for these animals. In addition, we have a small strip of keratin from many of the captured turtles. This strip holds a sequence of every growth ring an animal has produced over its life, similar to a tree ring chronology. Together with blood plasma and red blood cell samples, we can model the nutritional ecology of these turtles, via stable isotope analyses, over the course of their lives. We will combine available climate data with growth ring measurements and iButton temperature profiles, to paint a robust and revealing picture of the ecology of an otherwise obscure inhabitant of the Sevilleta, the desert box turtle.
Animals are opportunistically located via road and pedestrian surveys, as well as via radio telemetry.We will characterize the thermal ecology and time budgets (i.e. amount of time spent basking, foraging, quiescent) of desert box turtles Thermochron ibuttons are small, 3g, programmable temperature collection devices. These ibuttons will have one end of a snap glued to the surface, which will be snapped into the other end of a snap which is epoxied to one of the costal scutes of the turtle. This attachment will not interfere with turtle activities, such as breeding. The ibuttons will be programmed to record temperatures at set intervals, and opportunistically collected and downloaded onto a computer (1 to 4 times a summer). The snap allows the ibutton to be snapped on and off the turtles shell with ease. The snap, ibutton, and epoxy will total 6 or 7 grams, well within established weight guidelines. We will also put ibuttons into turtle-relevant locations within the environment in order to be able to put the turtle temperature chronologies into an environmental context. This procedure will allow us to examine the time budgets of the animals, i.e. time of burrow emergence, amount of time spent basking and foraging, and how weather influences these variables. This ties very well into our investigation into the nutritional ecology of these animals.To characterize the diet of an individual over its life, we will use a model saw to cut a 10-15mm wide strip of scute keratin from the second costal scute, bisecting all of the growth rings. These growth rings are then separated in the laboratory under a scope with a razor, and run for stable isotopes of carbon and nitrogen. In addition, blood samples are taken (dorsal venous sinus), and centrifuged to plasma and red blood cell components. These two components have disparate generation times, such that the isotope signal is integrated over shorter (plasma) or longer (RBC) periods of time. Casts (via dental alginate) and photographs are taken of the second costal scute, which allows us to measure the individual widths of growth rings. In this manner we can characterize how good or bad a given year was for a turtle via how much, or how little it grew in a season. Animals are injected with .1ml of doubly labeled water (3:1, 18O:D---98% 18O and 99.8% D). After overnight equilibration, a blood sample is taken. The animals are released, and the washout rates of the labeled isotopes are captured via another blood sample ~ 2 weeks later. This allows us to measure field metabolic rate.
Growth rings are separated in the lab via a razor blade and a dissecting scope. Scute keratin samples from individual rings are then packaged in tin capsules to be run for carbon and nitrogen stable isotopes in a mass spectrometer. Blood is centrifuged to separate plasma and red blood cell components, which are then also packaged in tin capsules and run for carbon and nitrogen isotopes. Blood taken for field metabolic rates is distilled (for water) in a vacuum line, and then run for D and 18O.
Animals are searched for via pedestrian and road surveys during times when they are most active, i.e., mornings, evenings, and after rainfall. In addition, a subset of animals are outfitted with epoxied, 7-9g transmitters and relocated every 2 weeks to study field metabolic rates.
This study has several components:iButtons are used to study activity and model time budgets. Here we seek to have at least 4 weeks of temperature readings for a minimum of 10 animals. Strips of scute keratin are collected, encompassing all of the growth rings on a given scute. Here we seek to have at least 25 animals analyzed. Growth ring width series are taken from second costal scute casts taken in the field. We seek to have at least 25 animals measured. Doubly labeled water is used to characterize field metabolic rates on the Sevilleta. (We will compare these data with those of animals just north of the Sevilleta, in a grazed environment.) Here we seek to have data on at least 3 males and 3 females.
Other field crew member: Hilary Lease
Additional Study Area Information
Study Area Name: McKenzie Flats
Study Area Location: The northeast section of the Sevilleta, stretching from Black Butte south to the canyon and east to the Los Pinos. McKenzie Flats, between black Butte, 5 Points, Palo Duro Canyon, and the old McKenzie headquarters ranch building site.Elevation: 1615 m
Vegetation: The terrain was generally mixed-species desert grassland, dominated by black grama (Bouteloua eriopoda), blue grama grass (B. gracilis), sand muhly (Muhlenbergia arenicola), various drop seeds and sacatons (Sporobolus spp.), purple three-awn (Aristida purpurea), and burrow grass (Scleropogon brevifolia). Shrubs were common in Five Points area; these were creosote bush (Larrea tridentata) and snakeweed (Gutierrezia sarothrae).
Soils: Turney Series: fine-loamy, mixed, thermic Typic Calciorthids. Berino Series: fine-loamy, mixed, thermic Typic Haplargids.
Hydrology: Surface water only during rain events, no arroyos. Run on plain for Los Pinos Mountains.
Landform: McKenzie Flats is a broad, nearly flat grassland plain between the Los Pinos Mountains and the breaks on the east side of the Rio Grande.
Geology: Deep (20,000 ft) alluvial and eolian deposits.
Climate: Long-term mean annual precipitation is 243 mm, about 60% of which occurs during the summer. Long-term mean monthly temperatures for January and July are 1.5°C and 25.1°C, respectively.
Site history: McKenzie Flats encompasses an area of approximately 50 square miles. McKenzie Flats was one of the primary livestock grazing areas of the Sevilleta NWR. The ranch headquarters buildings and corrals were located at the junction of Legs C and D of this coyote survey. Cattle have been excluded from the site since 1974-76.North Coordinate:34.3592South Coordinate:34.3592East Coordinate:106.691West Coordinate:106.691
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