Short and long distance translocations: Movement and survival in eastern box turtles (_Terrapene carolina carolina_)

*Background/Question/Methods*

Human development represents a serious threat to wildlife populations through continued habitat loss and incidental mortality from construction activities. Resource managers responsible for protecting species with legal status or high public profile are faced with difficult decisions on how to best manage populations located in construction zones. One approach to mitigate mortalities is to relocate individuals. The effectiveness of translocation for reptiles and amphibians has been questioned, with studies often reporting higher mortality and increased movements of translocated individuals. Translocations of reptiles and amphibians have primarily involved moving animals long distances, well beyond an individual’s home range. For reptiles this means finding new nesting, foraging, and overwintering sites, which may be problematic. Moving individuals only short distances, within their home range, may reduce those problems. As part of the mitigation plan for a highway construction project in central Maryland, groups of eastern box turtles (Terrapene carolina carolina) were translocated both short distances (<0.5km), and long distances (~5km). To investigate differences in survival and movement patterns among long distance translocation, short distance translocation, and non-translocation groups, I tracked 94 turtles (31 long distance translocation, 29 short distance translocation, and 34 non-translocation) using radio telemetry. 

*Results/Conclusions*

Eleven animals died during the first activity season after translocation (April through November 2008). The mortalities included two long distance translocation, six short distance translocation, and three non-translocation animals. The causes of mortality included road kill, construction activity, and unknown (1, 4, and 6 mortalities respectively). All construction related mortalities were a result inadequate exclusion fencing to keep turtles from trespassing back onto the construction site. All mortalities due to construction were either non-translocation or short distance translocation animals. Eleven other individuals were located at least once within the construction zone, suggesting that without our intervention mortality rates would have been much higher. Preliminary results for movement show that turtles in the non-translocation group had the lowest average movements while long distance translocation animals had the greatest average movements. Long distance translocation turtles also chose overwintering sites farther away from their initial overwintering sites than either short distance translocation or non-translocation turtles (average distance from original site of 261.8m, 155.6m, and 124.3m respectively). This suggests that movement patterns of short distance translocation turtles are more like native turtles.
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Driven polymer translocation through nanopores: slow versus fast dynamics

We investigate the dynamics of polymer translocation through nanopores under external driving by 3D Langevin Dynamics simulations, focusing on the scaling of the average translocation time $\tau$ versus the length of the polymer, $\tau\sim N^{\alpha}$. For slow translocation, i.e., under low driving force and/or high friction, we find $\alpha \approx 1+\nu \approx 1.588$ where $\nu$ denotes the Flory exponent. In contrast, $\alpha\approx 1.37$ is observed for fast translocation due to the highly deformed chain conformation on the trans side, reflecting a pronounced non-equilibrium situation. The dependence of the translocation time on the driving force is given by $\tau \sim F^{-1}$ and $\tau \sim F^{-0.80}$ for slow and fast translocation, respectively. These results clarify the controversy on the magnitude of the scaling exponent $\alpha$ for driven translocation.Comment: 6 pages, 7 figures, to appear in EPL (Europhysics Letters

Evaluation of Potential Translocation Sites for an Imperiled Cyprinid, the Hornyhead Chub

Translocation of isolated species into suitable habitats may help to secure vulnerable, geographically limited species. Due to the decline of Wyoming Hornyhead Chub Nocomis biguttatus, conservation actions, such as the translocation of populations within the plausible historical range, are being considered to improve population redundancy and resiliency to disturbance events. Translocation of Wyoming Hornyhead Chub must be rigorously evaluated because a hatchery stock does not exist, so all fish used in translocations will come from the wild population. We present an approach to identify the best available translocation sites prior to translocation efforts taking place. We evaluated fish community composition and habitat conditions at 54 potential translocation sites for Hornyhead Chub within 12 streams of the North Platte River basin of Wyoming. We used two analyses to identify translocation sites that were most similar to currently occupied Hornyhead Chub sites on the Laramie River: hurdle models to predict hypothetical abundance of Hornyhead Chub at translocation sites and nonmetric multidimensional scaling with fish community and habitat conditions. Presence and abundance of Hornyhead Chub were positively related to a lack of nonnative predators and to habitat features characteristic of backwater and velocity refuge habitats (e.g., minimum water velocity and width-to-depth ratio). We used a rank scoring system to weight the outcomes of each analysis, and the highest-ranking translocation sites occurred at a historically occupied locality, the Sweetwater River. Our approach may be appropriate for other at-risk species with isolated distributions and little historical data

Probability distributions for polymer translocation

We study the passage (translocation) of a self-avoiding polymer through a membrane pore in two dimensions. In particular, we numerically measure the probability distribution Q(T) of the translocation time T, and the distribution P(s,t) of the translocation coordinate s at various times t. When scaled with the mean translocation time , Q(T) becomes independent of polymer length, and decays exponentially for large T. The probability P(s,t) is well described by a Gaussian at short times, with a variance that grows sub-diffusively as t^{\alpha} with \alpha~0.8. For times exceeding , P(s,t) of the polymers that have not yet finished their translocation has a non-trivial stable shape.Comment: 5 pages, 4 figure

Polymer Translocation in Crowded Environments

We study the effect of the crowded nature of the cellular cytoplasm on the translocation of a polymer through a pore in a membrane. By systematically treating the entropic penalty due to crowding, we show that the translocation dynamics are significantly altered, leading to novel scaling behaviors of the translocation time in terms of chain length. We also observe new and qualitatively different translocation regimes depending upon the extent of crowding, transmembrane chemical potential asymmetry, and polymer length.Comment: 4 figure

Influence of polymer-pore interactions on translocation

We investigate the influence of polymer-pore interactions on the translocation dynamics using Langevin dynamics simulations. An attractive interaction can greatly improve translocation probability. At the same time, it also increases translocation time slowly for weak attraction while exponential dependence is observed for strong attraction. For fixed driving force and chain length the histogram of translocation time has a transition from Gaussian distribution to long-tailed distribution with increasing attraction. Under a weak driving force and a strong attractive force, both the translocation time and the residence time in the pore show a non-monotonic behavior as a function of the chain length. Our simulations results are in good agreement with recent experimental data.Comment: 4 pages, 5 figures, Submitted to Phys. Rev. Let