Browsing by Autor "A. J. Noss"

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Chelonoidis carbonaria (Testudines: Testudinidae) Activity Patterns and Burrow use in the Bolivian Chaco
(2013) A. J. Noss; Rossy R. Montaño F.; Fernando Soria; Sharon L. Deem; Christine V. Fiorello; Lee A. Fitzgerald
In the Bolivian Chaco, the tortoise Chelonoidis carbonaria is an important reptile for indigenous people for subsistence purposes and in traditional medicine. This article describes research on seasonal activity, daily activity, and burrow use for the species at two long-term research camps in the Kaa-Iya del Gran Chaco National Park. The principal research method is the use of internal and external temperature dataloggers in 15 individuals over a two-year period. Tortoises reduce their activity in the dry season, and are not active when air temperatures are below 20°C or above 37°C, though they can be active outside burrows at any time of year. Body temperature varies from 4°C in winter (monthly average of minimum daily temperatures) to 38°C in summer (monthly average of maximum daily temperatures). The instantaneous difference between body and environmental temperature could be as great as -23°C or 12°C, but the monthly average was between -2°C and 4°C. Tortoises rely principally on shelters including fallen trees, dense bromeliad ground cover, and leaf mulch; but also use armadillo burrows and rock crevices. They use multiple shelters / burrows over time, occasionally sharing shelters with other individuals. Burrow use is important both in cold periods as well as in hot and dry periods. The dataloggers provided extremely detailed data on body and environmental temperature, but the implantation caused problems in several individuals and the procedure may need modifications.
Comparison of density estimation methods for mammal populations with camera traps in the <scp>K</scp>aa‐<scp>I</scp>ya del <scp>G</scp>ran <scp>C</scp>haco landscape
(Wiley, 2012) A. J. Noss; B. Gardner; Leonardo Maffei; Erika Cuéllar; R. Montaño; Alfredo Romero‐Muñoz; R. Sollman; Allan F. O’Connell
Abstract Sampling animal populations with camera traps has become increasingly popular over the past two decades, particularly for species that are cryptic, elusive, exist at low densities or range over large areas. The results have been widely used to estimate population size and density. We analyzed data from 13 camera trap surveys conducted at five sites across the K aa‐ I ya landscape, B olivian C haco, for jaguar, puma, ocelot and lowland tapir. We compared two spatially explicit capture–recapture ( SCR ) software packages: secr , a likelihood‐based approach, and SPACECAP , a B ayesian approach, both of which are implemented within the R environment and can be used to estimate animal density from photographic records of individual animals that simultaneously employ spatial information about the capture location relative to the sample location. As a non‐spatial analysis, we used the program CAPTURE 2 to estimate abundance from the capture–recapture records of individuals identified through camera trap photos combined with an ad hoc estimation of the effective survey area to estimate density. SCR methods estimated jaguar population densities from 0.31 to 1.82 individuals per 100 km 2 across the K aa‐ I ya sites; puma from 0.36 to 7.99; ocelot from 1.67 to 51.7; and tapir from 7.38 to 42.9. Density estimates using either secr or SPACECAP were generally lower than the estimates generated using the non‐spatial method for all surveys and species; and density estimates using SPACECAP were generally lower than that using secr . We recommend using either secr or SPACECAP because the spatially explicit methods are not biased by an informal estimation of an effective survey area. Although SPACECAP and secr are less sensitive than non‐spatial methods to the size of the grid used for sampling, we recommend grid sizes several times larger than the average home range (known or estimated) of the target species.