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Gretchen Erika Anderson

Publications and source records attributed to Gretchen Erika Anderson.

12 recordsLinked to original sources
USGS2025

Wild Burmese python nest site selection, thermogenesis, and brooding behaviors in the Greater Everglades Ecosystem

Invasive Burmese pythons ( Python bivittatus ) are extremely cryptic animals. Although their conservation status in their native range is Vulnerable, in the Greater Everglades Ecosystem (Florida, USA) they have become a dominant destructive force and usually are immediately removed whenever found. This poses a paradox where removals are occurring, yet the study and understanding of python ecology is needed to inform removal methods. An important component of life history includes the nesting season, but little is known about python nest site selection, nest brooding, thermogenesis, or hatching success in the wild. Here, we present the first complete and most detailed report of oviposition and brooding for this biologically significant time period of a female Burmese python. We describe anthropogenic nest site selection, document the extent of shivering thermogenesis, describe brooding behaviors, and provide photo-documentation of complete hatching of the largest python clutch on record.

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USGS2024

Flooding-induced failure of an invasive Burmese Python nest in southern Florida

It is important to understand the factors affecting the reproductive success of an invasive species to estimate population size and develop management plans. There remains much we do not understand about the reproductive biology of invasive Burmese Pythons in both their native and invasive range. Oviposition site selection is an important factor in determining reproductive success as nesting is a vulnerable period in the life of reptiles. Flooding can be particularly influential for nesting outcomes and success of developing embryos in habitats that experience periods of heavy rainfall or seasonal flooding. It is not clear how seasonal flooding may impact oviposition site selection by females or hatchling survival of Burmese Pythons in Florida. On 10 May 2023, a radio-transmitted female python oviposited in a hollow log and during incubation all eggs were completely submerged for variable amounts of time. All eggs were collected (n = 78) and dissected to confirm fertilization and assess the stage of embryo development. Two eggs were found to be infertile, while the remaining fertile eggs contained embryos that died at various stages of development. The observed failure of this python nest was a direct result of oviposition site selection by the female. The frequency at which females lay eggs in suboptimal locations in southern Florida is currently unknown. This maladaptive behavior would suggest Burmese Pythons have fitness levels below theoretical optima.

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USGS2023

Florida Kingsnake (Lampropeltis floridana) consumes a juvenile Burmese Python (Python molurus bivitattus) in southern Florida

The Burmese python (Python molurus bivittatus) is an invasive constrictor established across southern Florida. These snakes are dietary generalists with large home ranges and broad habitat requirements and their introduction has had severe impacts on native species and ecosystems in the region. We describe the first observation of a Florida kingsnake (Lampropeltis floridana) that consumed a hatchling Burmese python.

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USGS2023

Maximum clutch size of an invasive Burmese Python (Python bivittatus) in Florida, USA

Native to southeastern Asia, the Burmese Python (Python bivittatus Kuhl 1820) is an invasive species established in southern Florida (Snow et al. 2007; Krysko et al. 2016; Krysko et al. 2019). Pythons are documented as having negative effects on the Greater Everglades Ecosystem and they have proven to be a complex problem for managers trying to control populations (Guzy et al. 2023). This species can move long distances (Pittman et al. 2014; Hart et al. 2015), use diverse habitats (Hart et al. 2015; Walters et al. 2016; Bartoszek et al. 2021a), consume a wide range of vertebrate prey items (Romagosa et al. 2022; Guzy et al. 2023 and citations therein), and has few documented predators (Bartoszek et al. 2021b; Mccollister et al. 2021; Currylow et al. 2023). Another factor that likely has contributed to the success of Burmese Pythons as an invasive species is their reproductive output (Reed et al. 2012). Though data are limited, clutch sizes of pythons in Florida range from 22–84 (mean = 49; see Currylow et al. 2022a and citations therein). Herein we report, to the best of our knowledge, the largest number of eggs in a single wild python nest recorded to date in Florida.

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USGS2023

Natives bite back: Depredation and mortality of invasive juvenile Burmese pythons (Python bivittatus) in the Greater Everglades Ecosystem

Burmese pythons (Python bivittatus Kuhl, 1820) are one of the world’s largest snake species, making them a highly successful and biologically damaging invasive predator in the Greater Everglades Ecosystem, Florida, USA. Though we have knowledge of python diet within this system, we understand very little of other interactions with native species. Effects native species have on invasive pythons, especially in the juvenile size class, are of particular interest as the prevalence of mortalities would inform potential population growth and trophic dynamics with native prey species. Native ophiophagous predators in Florida feed on smaller native snake species and it is unknown if they consistently recognize similarly sized juvenile invasive pythons as prey items. Using radiotelemetry, we found at least four native species within Big Cypress National Preserve that were implicated in juvenile python deaths, including three Florida cottonmouths (Agkistrodon conanti Gloyd, 1969), five American alligators (Alligator mississippiensis Daudin, 1802), one hispid cotton rat (Sigmodon hispidus Say and Ord, 1825), and three mesomammals. One mortality was the result of an attempt to subdue a prey item 106% the size of the python, constituting the largest predator:prey size ratio ever reported in this size class. This finding may indicate that phenotypic variation in individual juvenile pythons includes behavior that could be maladaptive within the novel Florida environment. Here we describe some of the first confirmed cases of non-anthropogenic mortality in juvenile Burmese pythons in Florida and present evidence that invasive pythons in this size class are now being incorporated into the diets of native species in its invasive range Burmese pythons (Python bivittatus Kuhl, 1820) are one of the world’s largest snake species, making them a highly successful and biologically damaging invasive predator in the Greater Everglades Ecosystem, Florida, USA. Though we have knowledge of python diet within this system, we understand very little of other interactions with native species. Effects native species have on invasive pythons, especially in the juvenile size class, are of particular interest as the prevalence of mortalities would inform potential population growth and trophic dynamics with native prey species. Native ophiophagous predators in Florida feed on smaller native snake species and it is unknown if they consistently recognize similarly sized juvenile invasive pythons as prey items. Using radiotelemetry, we found at least four native species within Big Cypress National Preserve that were implicated in juvenile python deaths, including three Florida cottonmouths (Agkistrodon conanti Gloyd, 1969), five American alligators (Alligator mississippiensis Daudin, 1802), one hispid cotton rat (Sigmodon hispidus Say and Ord, 1825), and three mesomammals. One mortality was the result of an attempt to subdue a prey item 106% the size of the python, constituting the largest predator:prey size ratio ever reported in this size class. This finding may indicate that phenotypic variation in individual juvenile pythons includes behavior that could be maladaptive within the novel Florida environment. Here we describe some of the first confirmed cases of non-anthropogenic mortality in juvenile Burmese pythons in Florida and present evidence that invasive pythons in this size class are now being incorporated into the diets of native species in its invasive range.

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USGS2022

Egg retention in wild-caught Python bivittatus in the Greater Everglades Ecosystem, Florida, USA

Retention of eggs in oviducts beyond the normal oviposition period is a common problem for captive reptiles, but the occurrence of egg retention in wild populations is largely unknown. The Burmese python ( Python [molurus] bivittatus ; Kühl 1820) is an oviparous snake native to south-eastern Asia that is now established in southern Florida. From 2011–2019, invasive Burmese pythons were opportunistically removed from Everglades National Park and Big Cypress National Preserve, humanely euthanised, and necropsied to determine reproductive condition. A total of 258 females of reproductive size were found to exhibit various stages of oviposition which generally aligned with purported annual reproductive timing. However, we encountered five pythons during the post-ovulatory period (Aug–Feb) showing signs of recent oviposition with retained eggs. Most of these cases comprised a small number of retained eggs, likely representing some portion of the total clutch. Because this condition is nearly absent in wild animal literature, our observations suggest retained eggs in wild snakes may be more common than previously assumed, possibly slowing or otherwise impacting population growth. However, we recognise that for an invasive species like the Burmese python in Florida, the egg retention rate may be higher in the non-native range compared to the native range due to maladaptation to novel habitats or environmental conditions. Additional research is needed to determine the exact causes of egg retention and investigate the implications for population dynamics on this and other snake species.

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USGS2022

Face-off: Novel depredation and nest defense behaviors between an invasive and a native predator in the Greater Everglades Ecosystem, Florida, USA

We describe several photo-documented novel interactions between intraguild predators in southern Florida—the native bobcat ( Lynx rufus ) and the invasive Burmese python ( Python bivittatus ). Over several days we documented a bobcat's depredation of an unguarded python nest and subsequent python nest defense behavior following the return of both animals to the nest. This is the first documentation of any animal in Florida preying on python eggs, and the first evidence or description of such antagonistic interactions at a python nest.

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USGS2022

Increasing the efficiency and power of camera traps for EDRR & ecological monitoring

Invasive species are an ever-growing concern for Florida, especially in important environments like the Greater Everglades Ecosystem. One of the best ways to fight back against invasives is the use of the “Early Detection, Rapid Response” (EDRR) system. The earlier we can detect the presence of a nonnative species, and the faster we respond, the better our chance of stopping its spread. For years, USGS Fort Collins Science Center has been working closely with the National Park Service to use trail cameras to observe the presence of any nonnative species and to monitor research assets in remote locations. Currently, we are working in Everglades National Park to detect invading Black and White Tegu lizards as well as in Big Cypress National Preserve researching the invasive Burmese python and monitoring their nest sites (did you know bobcats eat python eggs!?).

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USGS2021

Agkistrodon conanti (Florida Cottonmouth) and Python bivittatus (Burmese Python). Diet and Predation

Python bivittatus is established in the Greater Everglades Ecosystem in southern Florida, USA. Documented predators on pythons in Florida include Alligator mississippiensis (American Alligator; Snow et al. 2006. Herpetol. Rev. 37:81–81), Drymarchon couperi (Gulf Coast Indigo Snake; Andreadis et al. 2018. Herpetol. Rev. 49:341–342), Lynx rufus (Bobcat; McCollister et al. 2021. Southeast. Nat. 20:N55–N59), and possibly Ursus americanus floridanus (Florida Black Bear; McCollister et al. 2021. op cit.). We documented mortality events of hatchling and juvenile P. bivittatus while conducting radiotelemetry studies in the Greater Everglades Ecosystem.

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