Using movement to inform conservation corridor design for Mojave desert tortoise

Hromada, Steven J.; Esque, Todd C.; Vandergast, Amy G.; Dutcher, Kirsten E.; Mitchell, Corey I.; Gray, Miranda E.; Chang, Tony; Dickson, Brett G.; Nussear, Kenneth E.

doi:10.1186/s40462-020-00224-8

Cited by 17 publications

(21 citation statements)

References 90 publications

(138 reference statements)

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“…The fact that these amphisbaenians move so little suggests that they have a limited mobility and dispersal capacity in comparison with other reptiles. Thus, damaging natural areas where these amphisbaenians live could directly endanger a population, because individuals could not be able to move and naturally recolonize undamaged or restored nearby areas [ 76 ]. Moreover, if there was a low dispersal ability it may result in low genetic diversity and high levels of inbreeding, which can in turn increase the risk of extinction of isolated populations [ 77 , 78 ].…”

Section: Discussionmentioning

confidence: 99%

Going underground: short- and long-term movements may reveal the fossorial spatial ecology of an amphisbaenian

et al. 2021

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Background The movement and spatial ecology of an animal depends on its morphological and functional adaptations to its environment. In fossorial animals, adaptations to the underground life help to face peculiar ecological challenges, very different from those of epigeal species, but may constrain their movement ability. Methods We made a long-term capture-recapture study of the strictly fossorial amphisbaenian reptile Trogonophis wiegmanni to analyze its long-term movement patterns. We also used passive integrated transponder (PIT) telemetry to detect and follow undisturbed individuals underground, obtaining data of their short-term movement patterns. Results Amphisbaenians showed a high site fidelity, moving short distances and over small areas, and spending some days without any noticeable movement, even under favorable conditions. We also found differences in movements between sexes and age classes. Conclusions This movement and spatial strategy can be related to the energetic constrains of underground burrowing, or to the low metabolic requirements of fossorial reptiles, as distances and areas covered were much smaller than for epigeal reptiles of similar size. Individual differences probably reflect differential reproductive and social requirements of males and females, and that younger individuals might show more floating behavior until they can settle in a territory. This study is a rare example describing the movement ecology of a fossorial species and may contribute to the general understanding of the factors that affect space use and movement decisions in animals.

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Section: Discussionmentioning

confidence: 99%

Going underground: short- and long-term movements may reveal the fossorial spatial ecology of an amphisbaenian

et al. 2021

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“…There is a growing body of work demonstrating the versatility of newer analytical methods (Noonan et al, 2018), and how they can be applied to the coarser and zero-inflated radio-telemetry data (Averill-Murray, Fleming, & Riedle, 2020; Hromada et al 2020; Silva et al 2020). Reptile spatial ecology so far has largely failed to capitalise on the wealth of analytical options available, namely integrating movement information explicitly into estimations of space-use.…”

Section: Discussionmentioning

confidence: 99%

Lots of movement, little progress: A review of reptile home range literature

Crane

Silva

Marshall

et al. 2020

Preprint

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Reptiles are the most species-rich vertebrate group with a broad diversity of life history traits. Biotelemetry is an essential methodology for reptiles as it compensates for several limitations when studying their natural history. We evaluated trends in reptile spatial ecology studies focusing upon quantifying home ranges for the past twenty years. We assessed 290 English-language reptile home range studies published from 2000-2019 via a structured literature review investigating publications’ study location, taxonomic group, methodology, reporting, and analytical techniques. Substantial biases remain in both location and taxonomic groups in the literature, with nearly half of all studies (45%) originating from the USA. Snakes were most often studied, and crocodiles were least often studied, while testudines tended to have the greatest within study sample sizes. More than half of all studies lacked critical methodological details, limiting the number of studies for inclusion in future meta-analyses (55% of studies lacked information on individual tracking durations, and 51% lacked sufficient information on the number of times researchers recorded positions). Studies continue to rely on outdated methods to quantify space-use (including Minimum Convex Polygons and Kernel Density Estimators), often failing to report subtleties on decisions that have substantial impact on home range area estimates. Moving forward researchers can select a suite of appropriate analytical techniques tailored to their research question (dynamic Brownian Bridge Movement Models for within sample interpolation, and autocorrelated Kernel Density Estimators for beyond sample extrapolation). Only 1.4% of all evaluated studies linked to available and usable telemetry data, further hindering scientific consensus. We ultimately implore herpetologists to adopt transparent reporting practices and make liberal use of open data platforms to maximize progress in the field of reptile spatial ecology.

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“…In addition to being an impermeable barrier, there is conflicting evidence on how roads indirectly affect movement of Mojave desert tortoises. In some cases, tortoises have longer steplengths when near low-traffic roads and shorter steps near highways 32 , 34 , but sometimes tortoises avoid roads altogether 35 . These long-term indirect impacts of exclusionary fencing on near-highway tortoise movement behaviors are not yet well-understood.…”

Section: Introductionmentioning

confidence: 99%

Indirect impacts of a highway on movement behavioral states of a threatened tortoise and implications for landscape connectivity

Harju,

Cambrin,

Berg

2024

Sci Rep

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Roads have often been identified as barriers to the movement of free-ranging animals. However, whether restoration of landscape connectivity across roadways can mitigate barriers to movement is insufficiently understood in light of indirect effects of roads on wildlife movement. We GPS-tagged free-ranging Mojave desert tortoises (Gopherus agassizii) to quantify movement behavioral states using hidden Markov models in relation to a major highway and to document use of existing, permeable culverts. We then used the observed movement behaviors to parameterize simulations of tortoise movement to evaluate alternative culvert designs and placements for enhancing connectivity across the roadway. Tortoises were most active during mid-day, in warm temperatures, and when close to the highway. The highway affected transition probabilities between movement states, as females were more likely than males to switch to an energy-demanding traveling movement state, remain in that state, and move farther than usual within that state. In contrast, males were more likely than females to continue in the low-energy resting state when close to the highway, but if traveling, to travel farther than usual. We observed two highway crossings by a tagged tortoise, which was a higher rate of crossing than in simulated tortoises. Simulated crossing rates increased with culvert size and culvert density, and size and density appeared more important for crossing than if culverts were placed singly or in pairs. Existing culvert densities across the region appeared potentially sufficient for long-term genetic connectivity, but only if retrofitted to allow for tortoise access and passing. We concluded that existing highway traffic may indirectly depress tortoise populations adjacent to the highway, particularly via negative impacts to female movements, and that existing culverts in washes should be retrofitted to allow for periodic tortoise crossings to improve structural connectivity for occasional passage.

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Using movement to inform conservation corridor design for Mojave desert tortoise

Cited by 17 publications

References 90 publications

Going underground: short- and long-term movements may reveal the fossorial spatial ecology of an amphisbaenian

Going underground: short- and long-term movements may reveal the fossorial spatial ecology of an amphisbaenian

Lots of movement, little progress: A review of reptile home range literature

Indirect impacts of a highway on movement behavioral states of a threatened tortoise and implications for landscape connectivity

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