Atascadero, CA, United States
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Daren Riedle J.,12 SE 25th Avenue | Kuhns E.H.,North Carolina State University | Munscher E.C.,SWCA Environmental Consultants | Munscher E.C.,The North Alliance | And 5 more authors.
Herpetological Conservation and Biology | Year: 2016

Since 2007 the Turtle Survival Alliance - North American Freshwater Turtle Research Group (NAFTRG) has surveyed aquatic turtles in Volusia Blue Spring State Park, Orange City, Florida, USA. Here, we provide population parameters for the three most common freshwater turtle species, the Peninsula Cooter (Pseudemys peninsularis), Florida Red-bellied Cooter (Pseudemys nelsoni), and the Loggerhead Musk Turtle (Sternotherus minor minor), estimated from six years of mark and recapture data at Blue Spring State Park. The population estimates for the 1.9 ha study area were P. nelsoni 62 ± 2, P. peninsularis, 240 ± 6, and S. m. minor, 252 ± 7. Although, the turtle population densities at Volusia Blue Spring appear robust for the habitat size, use of reverse-time capture-recapture models suggest that recruitment is minimal and recapture rates declined between sampling periods. Specific stressors that may be influencing population growth rates include bank erosion and lack, or loss, of nesting habitat, increasing winter use by West Indian Manatees (Trichechus manatus) and subsequent loss of aquatic vegetation, and additional competition with invasive fish and turtle species. © 2016. J. Daren Riedle. All Rights Reserved.


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.


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.


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.


Hinderle D.,San Diego State University | Lewison R.L.,San Diego State University | Walde A.D.,Walde Research and Environmental Consulting | Deutschman D.,San Diego State University | And 2 more authors.
Journal of Wildlife Management | Year: 2015

Translocation of threatened or vulnerable species is a tool increasingly used for conservation and management. However, in some species, homing and movement behaviors may undermine the success of translocation efforts. For the federally protected Agassiz's desert tortoise (Gopherus agassizii), translocation is a strategy used to manage declining populations, yet homing behavior in this species is poorly understood. To explore homing behavior and movement patterns after translocation, we radio tracked 80 tortoises during a 2-phase experimental translocation. Phase 1 included 40 tortoises that were translocated, then monitored for a period of 37 days (21 Sep-28 Oct 2009), and phase 2 included a different group of 40 tortoises that were translocated and then monitored for 186 days (13 Apr-20 Oct 2010). In both phases, we assigned tortoises randomly to 1 of 3 treatment groups: translocated (displaced 2, 5, or 8 km from their source location), handling control, or control. After translocation, 20% of the translocated tortoises were able to navigate to their source location, and translocation distance had an effect on their ability to navigate home. We found 44% of tortoises in the 2-km translocated group returned home; 1 tortoise in the 5-km group, and no tortoises in the 8-km translocated group returned. The time required to reach home ranged from 5 to 37 days for the 2-km group, and 34 days for the 5-km group. We deemed tortoises to have homed successfully if they returned to their source location within 37 days of translocation as this reflected the duration of phase 1 and allowed for a balanced comparison between the 2 phases. We found that translocated tortoises moved at least 1.5 times more overall than the control groups, with some individuals moving >10 km from the translocation site. These patterns persisted even after accounting for seasonal and sex differences in distance traveled. By identifying homing behaviors and quantifying post-translocation movement patterns, this experiment addressed a key data gap in tortoise behavior that may limit the efficacy of tortoise translocation efforts. Our results point to the need to account for behavioral responses of tortoises to minimize risk to translocated individuals and maximize the success of translocation projects. © 2014 The Wildlife Society.


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.


Walde A.D.,The North Alliance | Walde A.D.,Walde Research and Environmental Consulting | Munscher E.C.,The North Alliance | Walde A.M.,Walde Research and Environmental Consulting
Southeastern Naturalist | Year: 2016

We present data on large Chelydra serpentina (Snapping Turtle) from 4 freshwater springs in Florida located in Wekiwa Springs, Volusia Blue Spring, Peacock Springs, and Manatee Springs state parks. Several of the turtles captured at Wekiwa Springs and Volusia Blue Springs are larger than the previous Florida record for this species. In the past, Snapping Turtles in Florida have been considered a distinct species or a clearly defined subspecies, however, recent genetic techniques have shown that they are not well-differentiated evolutionary lineages, and therefore Snapping Turtles in Florida are not unique from those in the rest of the range. These large southern individuals do not follow the expected trend of decreasing size with decreasing latitude. The nature of spring environments, particularly the warm, constant temperatures which facilitate year-round growth appears to be producing record-sized Snapping Turtles in Florida when compared to other Florida localities. Additional studies should investigate the chelonian communities in Florida's spring habitats to determine if these special environments are producing unique populations.


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).


Latch E.K.,University of Wisconsin - Milwaukee | Latch E.K.,Center for Conservation and Evolutionary Genetics | Boarman W.I.,Conservation Science Research and Consulting | Walde A.,Walde Research and Environmental Consulting | Fleischer R.C.,Center for Conservation and Evolutionary Genetics
PLoS ONE | Year: 2011

Characterizing the effects of landscape features on genetic variation is essential for understanding how landscapes shape patterns of gene flow and spatial genetic structure of populations. Most landscape genetics studies have focused on patterns of gene flow at a regional scale. However, the genetic structure of populations at a local scale may be influenced by a unique suite of landscape variables that have little bearing on connectivity patterns observed at broader spatial scales. We investigated fine-scale spatial patterns of genetic variation and gene flow in relation to features of the landscape in desert tortoise (Gopherus agassizii), using 859 tortoises genotyped at 16 microsatellite loci with associated data on geographic location, sex, elevation, slope, and soil type, and spatial relationship to putative barriers (power lines, roads). We used spatially explicit and non-explicit Bayesian clustering algorithms to partition the sample into discrete clusters, and characterize the relationships between genetic distance and ecological variables to identify factors with the greatest influence on gene flow at a local scale. Desert tortoises exhibit weak genetic structure at a local scale, and we identified two subpopulations across the study area. Although genetic differentiation between the subpopulations was low, our landscape genetic analysis identified both natural (slope) and anthropogenic (roads) landscape variables that have significantly influenced gene flow within this local population. We show that desert tortoise movements at a local scale are influenced by features of the landscape, and that these features are different than those that influence gene flow at larger scales. Our findings are important for desert tortoise conservation and management, particularly in light of recent translocation efforts in the region. More generally, our results indicate that recent landscape changes can affect gene flow at a local scale and that their effects can be detected almost immediately.


Emblidge P.G.,Pennsylvania State University | Emblidge P.G.,U.S. Geological Survey | Nussear K.E.,University of Nevada, Reno | Esque T.C.,U.S. Geological Survey | And 3 more authors.
Endangered Species Research | Year: 2015

In the Mojave Desert of the southwestern United States, adult Agassiz's desert tortoises Gopherus agassizii typically experience high survival, but population declines associated with anthropogenic impacts led to their listing as a threatened Species under the US Endangered Species Act in 1990. Predation of adult tortoises is not often considered a significant threat as they are adapted to deter most predation attempts. Despite these adaptations, some populations have experienced elevated mortality attributed to predators, suggesting that predation pressure may occasionally increase. During the tortoise activity seasons of 2012 and 2013, we observed unsustainably high mortality in 1 of 4 populations of adult desert tortoises (22 and 84%, respectively) in the western Mojave Desert in the vicinity of Barstow, CA. Photographic evidence from trail cameras and examination of carcass condition suggest that American badgers Taxidea taxus-a sometimes cited but unconfirmed predator of adult tortoises-may have been responsible for some of the mortality observed. We discuss the American badger as a plausible predator of a local tortoise population, but recommend further investigation into these events and the impacts such mortality can have on tortoise persistence. © The authors 2015.

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