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Atascadero, CA, United States

Harless M.L.,ITS Corporation | Harless M.L.,Loma Linda University | Walde A.D.,ITS Corporation | Walde A.D.,Walde Research and Environmental Consulting | And 3 more authors.
Herpetological Conservation and Biology | Year: 2010

Home range estimation as a measure of spatial utilization is an important tool in the management of wildlife. Operational methods of defining the spatial requirements of an animal differ in sampling regime and interpretation. The two most commonly used estimators, the minimum convex polygon (MCP) and the fixed kernel (FK), each provide a different measure of land use, yet, together allow for a better understanding of the spatial needs of a particular animal. Sampling frequency, the number of individuals, and other user-defined inputs differentially affect home range estimates using these two procedures. For the comparison of either MCP or FK estimates to be reliable, these variables need to be as similar as possible across studies. We conducted an intensive radio-telemetry study on a large number of Desert Tortoises (Gopherus agassizii) to determine an optimal sampling effort for home range estimation using both the MCP and FK estimates, and to identify factors important to space use by this species. Data were parsed into sampling regimes representative of previous home range studies in an effort to compare estimates across studies. Home range estimates using the MCP were over two times larger in this study when compared to previous studies on the Desert Tortoise in the Mojave Desert. Results indicated that an increased sampling frequency inflates MCP estimates, while providing more use-specific detail and decreasing area for FK estimates. Analyses demonstrated home range area to be greatly affected by choice of estimator (MCP or FK), sampling regime, and sex. We recommend an intensive and systematic sampling effort to better define home range estimates; as well as, to provide comparable data across studies for this and other species of herpetofauna. Both home range estimators provide valuable information on the biological needs of the Desert Tortoise and should be identified as a priority in land use investigations and conservation decisions for this species. Source


Munscher E.C.,SWCA Environmental Consultants | Walde A.D.,Walde Research and Environmental Consulting | Stratmann T.,Clemson University | Butterfield B.P.,Freed-Hardeman University
Herpetology Notes | Year: 2015

The genus Pseudemys represents some of the largest emydid turtles in North America. Surprisingly, many in this genus are poorly studied and despite their large size little is known about their growth. Using mark-recapture data we examined extreme growth in two Pseudemys species, Pseudemys peninsularis and P. nelsoni in a protected spring system in central Florida. Ten immature individuals were captured, marked, and recaptured with inter-capture time intervals between 364-1682 days that allowed us to calculate growth rates and determine gender. The P. peninsularis individuals showed growth rates that ranged from 30.38 to 74.29 mm/year, representing annual increases in size of 23–104.6%. The P. nelsoni individuals grew slower with growth rates that ranged from 19.96 to 42.15 mm/year, representing annual size increases of 14.6–42.2%. Growth within a species was not significantly different between males and females; however, between species the slightly smaller P. nelsoni females grew at a slower rate than P. peninsularis females. We believe that this extreme growth can be attributed to a combination of several different factors including adaptation to predation, living in a habitat that offers year-round growth conditions, and/or the result of the introduction of an energy rich, non-native food source. © 2015, Societas Europaea Herpetologica. All rights reserved. Source


Aiello C.M.,U.S. Geological Survey | Aiello C.M.,Pennsylvania State University | Nussear K.E.,U.S. Geological Survey | Walde A.D.,Walde Research and Environmental Consulting | And 6 more authors.
Animal Conservation | Year: 2014

Wildlife managers consider animal translocation a means of increasing the viability of a local population. However, augmentation may disrupt existing resident disease dynamics and initiate an outbreak that would effectively offset any advantages the translocation may have achieved. This paper examines fundamental concepts of disease ecology and identifies the conditions that will increase the likelihood of a disease outbreak following translocation. We highlight the importance of susceptibility to infection, population size and population connectivity - a characteristic likely affected by translocation but not often considered in risk assessments - in estimating outbreak risk due to translocation. We then explore these features in a species of conservation concern often translocated in the presence of infectious disease, the Mojave Desert tortoise, and use data from experimental tortoise translocations to detect changes in population connectivity that may influence pathogen transmission. Preliminary analyses comparing contact networks inferred from spatial data at control and translocation plots and infection simulation results through these networks suggest increased outbreak risk following translocation due to dispersal-driven changes in contact frequency and network structure. We outline future research goals to test these concepts and aid managers in designing effective risk assessment and intervention strategies that will improve translocation success. © 2014 The Zoological Society of London. Source


Jackson F.D.,Montana State University | Varricchio D.J.,Montana State University | Jackson R.A.,Montana State University | Walde A.D.,Walde Research and Environmental Consulting | Bishop G.A.,St. Catherines Island Sea Turtle Program
Palaios | Year: 2015

Dinosaur reproductive biology is often inferred from the biology of extant taxa; however, taphonomic studies of modern nest sites have focused exclusively on avian, rather than reptilian species. We documented eight Agassiz's desert tortoise (Gopherus agassizii) nests and ten loggerhead sea turtle (Caretta caretta) nests. Gopherus agassizii excavated burrows up to 70 cm long and laid rigid-shelled eggs 10-12 cm below the burrow floor. The 19 cm × 12 cm depressions consisted of hard consolidated sand surrounded by a 3-4-cm-high rim and contained 2-5 hatched eggs in a single layer. These hatched egg bottoms represent ∼ 25% of the original egg, and five of 27 contained fully developed dead neonates. Desiccated membrane separated from the egg interior forming pockets that filled with eggshell and sand. Of 106 and 79 eggshell fragments in the hatched egg and surrounding sand, 48% and 23% occurred concave up, respectively. However, the combined numbers of eggshell fragments inside the eggs and in the immediately surrounding sand approximates the 60:40 ratios at in situ avian nests. Therefore, this ratio may provide reliable evidence for hatching sites regardless of the incubation strategy employed by the adult. Caretta caretta nests differed from those of tortoises in their greater depth (∼ 50 cm) and occurrence in moist, cohesive sand. Clutches contained over 100 pliable-shelled eggs that tore and collapsed upon hatching, without brittle fracture. Failed eggs in two clutches showed five development stages, indicating that the deaths occurred over an extended time period. With the exception of predation, the G. agassizii and C. caretta nests showed no significant eggshell or hatched eggs above the egg chamber. Copyright © 2015, SEPM (Society for Sedimentary Geology). Source


Munscher E.C.,SWCA Environmental Consultants | Walde A.D.,Walde Research and Environmental Consulting | Riedle J.D.,Environmental Planning Group | Kuhns E.H.,University of Florida | And 2 more authors.
Chelonian Conservation and Biology | Year: 2015

The Florida softshell turtle, Apalone ferox (Schneider 1783) is considered common and easily visible in many freshwater habitats throughout its range. However, very little population research has been completed on the species due to difficulties associated with capture and long-term marking. We have conducted a mark-recapture study of this species since 2007 as part of a long-term freshwater turtle population monitoring program at Wekiwa Springs State Park, Apopka, Florida. From 2007 to 2012 we captured 56 individual Florida softshell turtles with 101 total captures. The malefemale ratio was 12.6 and females were larger than males. Population estimates were 92 adults and 49 juveniles with a total estimate of 141 Florida softshell turtles in the 2.67-ha study site. Our data from a protected population centrally located within the species range provide a baseline for comparison to other populations. © 2015 Chelonian Research Foundation. Source

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