Divergent Serpentoviruses in Free-Ranging Invasive Pythons and Native Colubrids in Southern Florida, United States

Burmese python (Python bivittatus) is an invasive snake that has significantly affected ecosystems in southern Florida, United States. Aside from direct predation and competition, invasive species can also introduce nonnative pathogens that can adversely affect native species. The subfamily Serpentovirinae (order Nidovirales) is composed of positive-sense RNA viruses primarily found in reptiles. Some serpentoviruses, such as shingleback nidovirus, are associated with mortalities in wild populations, while others, including ball python nidovirus and green tree python nidovirus can be a major cause of disease and mortality in captive animals. To determine if serpentoviruses were present in invasive Burmese pythons in southern Florida, oral swabs were collected from both free-ranging and long-term captive snakes. Swabs were screened for the presence of serpentovirus by reverse transcription PCR and sequenced. A total serpentovirus prevalence of 27.8% was detected in 318 python samples. Of the initial swabs from 172 free-ranging pythons, 42 (24.4%) were positive for multiple divergent viral sequences comprising four clades across the sampling range. Both sex and snout-vent length were statistically significant factors in virus prevalence, with larger male snakes having the highest prevalence. Sampling location was statistically significant in circulating virus sequence. Mild clinical signs and lesions consistent with serpentovirus infection were observed in a subset of sampled pythons. Testing of native snakes (n = 219, 18 species) in part of the python range found no evidence of python virus spillover; however, five individual native snakes (2.3%) representing three species were PCR positive for unique, divergent serpentoviruses. Calculated pairwise uncorrected distance analysis indicated the newly discovered virus sequences likely represent three novel genera in the subfamily Serpentovirinae. This study is the first to characterize serpentovirus in wild free-ranging pythons or in any free-ranging North America reptile. Though the risk these viruses pose to the invasive and native species is unknown, the potential for spillover to native herpetofauna warrants further investigation

Burmese pythons in Florida: A synthesis of biology, impacts, and management tools

Burmese pythons (Python molurus bivittatus) are native to southeastern Asia, however, there is an established invasive population inhabiting much of southern Florida throughout the Greater Everglades Ecosystem. Pythons have severely impacted native species and ecosystems in Florida and represent one of the most intractable invasive-species management issues across the globe. The difficulty stems from a unique combination of inaccessible habitat and the cryptic and resilient nature of pythons that thrive in the subtropical environment of southern Florida, rendering them extremely challenging to detect. Here we provide a comprehensive review and synthesis of the science relevant to managing invasive Burmese pythons. We describe existing control tools and review challenges to productive research, identifying key knowledge gaps that would improve future research and decision making for python control. (119 pp

Soft-Release May Not Enhance Translocations of Wild-Caught Eastern Massasaugas (Sistrurus catenatus)

Wildlife translocation is the human-mediated movement of living organisms from one location to another for varying purposes including conservation, mitigation, and research. Hard-release translocation, or immediate release, is arguably one of the easiest, cheapest, and most well-studied translocation techniques, but it sometimes results in high mortality rates because some relocated animals make large, erratic homing movements that may put them at risk. Soft-release is a strategy that may alleviate such negative effects, as it involves containing animals in an outdoor enclosure at the release site temporarily in the hopes that they will acclimate to the new environment, thereby limiting post-release movements and increasing survival. The usefulness of soft-release translocation relative to hard-release has seen some successes, but no studies have reported on whether it would benefit translocation efforts for wild-caught snakes. Here, I conducted an experiment that tested whether soft-release might increase survival rates and limit post-translocation movements of wild-caught, adult eastern massasaugas (Sistrurus catenatus) at a large military installation in Michigan, USA. This rattlesnake species is federally listed as threatened, but individuals are often hard-release translocated at this site after they are encountered by military personnel during training activities due to the potential for snake or human injury. The outcomes of these translocations are unknown, and natural resource managers at this site and elsewhere need to be able to make informed decisions about what translocation methods best compromise both conservation and mitigation goals for these animals. To assess this, 55 soft-released (i.e. held in outdoor enclosures for approximately two weeks prior to release), hard-released (i.e. released immediately upon relocation near the enclosures), and resident control (i.e. released at capture sites) eastern massasaugas were radio-tracked at this military installation for one active and overwintering season post-release from May 2013 through November 2017. To determine if the survival of the treatments differed and to examine what variables might influence survival, snake annual survival probabilities were estimated and compared using known-fate models that included treatment, sex, body condition index, distance translocated, time, season and their interactions as variables. To determine if the movement behavior of the treatments differed, maximum dispersal distance from the release site, mean distance moved per day, activity range size, activity range length, homing, and release site fidelity were assessed. Male soft-released snakes had significantly lower survival (0.44 ± SE 0.18) than resident males (0.72 ± SE 0.21) and died from a wider variety of causes (e.g. overwintering, predation), but soft-released males did not have significantly different survival than hard-released males (0.40 ± SE 0.20) and experienced the same causes of death. Body condition index, distance translocated, time, and season did not appear to have significant effects on the survival of any treatment of male eastern massasaugas. Male movement patterns were not significantly different between any treatments. Sample sizes for translocated females and gravid females were too small to reliably analyze survival and most movement metrics, and no significant differences between treatments were found for metrics that were estimable. My findings suggest that soft-release as implemented here may not substantially enhance translocation efforts for male eastern massasaugas in that soft- and hard-release translocated snakes did not have significantly different survival and movement behaviors, so hard-release is generally recommended given that it is more efficient and cost-effective. However, given that translocated snake survival was low and that translocations have the potential to disrupt populations, I do not advise translocations for any eastern massasaugas unless immediate harm to the snakes or to humans is extremely likely. If translocations absolutely must be used but the possibility of the snakes eventually homing near their capture locations is acceptable, trends in the rattlesnake translocation literature suggest that hard-releasing individuals short distances within their original home ranges may be less detrimental to the snakes than when they are translocated long distances outside of their home ranges. If translocations must be used but the possibility of snakes homing is unacceptable, then hard-releasing male eastern massasaugas in high-quality habitats long distances from their capture sites and from anthropogenic features such as roads might prevent homing, although survival may still be low. Further experimental research is critically needed to explicitly test these ideas and other translocation variants to develop more informed management practices for imperiled herpetofauna