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Natural History Note: Agkistrodon conanti (Florida Cottonmouth) and Python bivittatus (Burmese Python). Diet and Predation.

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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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Herpetological Review 52(4), 2021
860 NATURAL HISTORY NOTES
SQUAMATA SNAKES
AGKISTRODON CONANTI (Florida Cottonmouth) and PY-
THON BIVITTATUS (Burmese Python). DIET and PREDATION.
Python bivittatus is established in the Greater Everglades Eco-
system in southern Florida, USA. Documented predators on
pythons in Florida include Alligator mississippiensis (American
Alligator; Snow et al. 2006. Herpetol. Rev. 37:81), Drymarchon
couperi (Gulf Coast Indigo Snake; Andreadis et al. 2018. Herpe-
tol. Rev. 49:341–342), Crocodylus acutus (American Crocodile;
Godfrey et al. 2021. Herpetol. Rev. 52:641–642), Lynx rufus (Bob-
cat; McCollister et al. 2021. Southeast. Nat. 20:N55–N59), and
possibly Ursus americanus floridanus (Florida Black Bear; Mc-
Collister et al. 2021, op. cit.).
We documented mortality events of hatchling and juvenile
P. bivittatus while conducting radiotelemetry studies in the
Greater Everglades Ecosystem. Hatchling P. bivittatus were
captured from the wild and implanted with 6.2-g or 9.0-g radio
transmitters (models RI-2CM or SI-2, Holohil Systems, Ltd.,
Ontario, Canada) following the surgical methodology of Reinert
and Cundall (1982. Copeia 1982:702–705) or modified from
Amlaner and Withgott (1995. In Cristalli et al. [eds.], Proceedings
of the 13th International Symposium on Biotelmetry, pp. 251–
256) and the anesthesia and analgesia protocol of Bryant et
al. (2010. Aust. Vet. J. 88:443–448). Neonates were released ca.
24 h after surgery between July and September 2020 at their
point of capture. The habitat at these locations comprised low-
elevation swamp dominated by cypress (Taxodium spp.) domes,
pinelands (Pinus spp.), and mixed prairie/marsh forested
habitat within either Picayune Strand State Forest (Picayune
SSF) in Collier County, or Big Cypress National Preserve (BICY)
in Collier, Miami-Dade, and Monroe counties, Florida, USA. We
subsequently radiotracked study animals 1–2 times per week.
At 1036 h on 3 August 2020, a neonate P. bivittatus (female;
age ca. 1 mo, 57 cm SVL, 66 cm total length, 108 g; measured
4 July 2020) was radio-tracked to a mixed woodland location
in Picayune SSF. The hatchling was not visible at the point
of the strongest radio transmitter signal but we observed an
adult Agkistrodon conanti basking under mixed grasses and
ferns at the site. Once disturbed, the A. conanti retreated
and the signal weakened. We removed the antenna from the
receiver and confirmed that the peak signal emanated from
cottonmouth location, after which we left it without further
disturbance. Subsequently, at 0948 h on 6 August 2020, we
radio-tracked the same transmitter frequency to a location 0.6
km from the previous location and again determined the signal
to be emanating from an A. conanti. We then safely captured
and transported the animal for a radiograph (Fig. 1, top). We
sedated, measured (63 cm SVL, 74 cm total length, 317 g), and
determined the animal to be female by probing. We safely
contained the animal until the transmitter was expelled on 10
August 2020 and then released the animal at its capture location
at 0900 h on 11 August 2020.
Our second observation began at 1105 h on 31 May 2021
in BICY. We tracked the juvenile P. bivittatus (female; age ca.
10 mo, 88 cm SVL, 98 cm total length, 396 g; measured 26
May 2021) to the base of a cypress tree but could not attain a
visual observation. We searched at the location of strongest
signal in a pile of fallen tree limbs and discovered an A. conanti
with an obvious food bolus. At 1206 h we again tracked the
signal to the A. conanti, which had moved ca. 10 m from the
original location. We confirmed the predation event on 4
June 2021 via radiography (Fig. 1, bottom) and released the
A. conanti at its original capture location the same day. Using
the radiographs scalebar and ImageJ software (Schneider et
al. 2012. Nat. Methods 9:671–675), we measured the A. conanti
to be 87 cm SVL and 108 cm total length. No further attempts
to attain physical information on the animal were made to
Herpetological Review 52(4), 2021
NATURAL HISTORY NOTES 861
ensure minimal handling stress and low overall disturbance.
We continued to regularly track the snake until it expelled the
transmitter ca. 25 d later.
Agkistrodon conanti are generalist predators and have
been recorded consuming 27 snake species, as well as carrion
(Ernst and Ernst 2011. Venomous Reptiles of the United States,
Canada, and Northern Mexico: Volume 1. Johns Hopkins
University Press, Baltimore, Maryland. 193 pp.; Grajal-Puche
et al. 2016. Herpetol. Rev. 47:307). Our observations add P.
bivittatus to this list. Though the image from Picayune SSF (Fig.
1, top) is indistinct between the predator and prey excepting
the study animal’s transmitter, the image from BICY (Fig. 1,
bottom) displays the skull and vertebral column of the juvenile
study animal, showing that it was consumed tail-first.
Burmese pythons use a wide variety of Florida habitats
and are considered semi-aquatic in that they are associated
with freshwater wetland habitats in their native and invasive
ranges (Bartoszek et al. 2021. Ecosphere 12:e03564; Smith
et al. 2021. Sci. Rep. 11:7014). During the summer months,
hatchling pythons disperse from their natal sites, often using
waterways and wetlands to travel (Pittman et al., pers. comm.).
Hydrologically dynamic wetlands serve as foraging grounds
for juvenile and adult A. conanti as well (Eskew et al. 2009. J.
Zool. 277:179–186). Despite the relatively large size of a neonate
python, our findings indicate they are vulnerable to predation
by A. conanti. Native species’ dietary expansion to include
invasive pythons could have some minor ecological impact on
either species (e.g., habitat selection, population dynamics,
disease spread, dispersal, etc.) and could be areas of further
research.
We thank S. Bredin, J. Draxler, M. Goetz, and L. McBride
for assistance in the field; J. Noble and A. Sigward for primary
help with the radiography and anesthesia; J. Conlin, P. Cryan,
C. Deskins, S. Hanser, M. Kirkland, M. McCollister, T. Pernas,
L. Rodgers, Rookery Bay National Estuarine Research Reserve,
and A. Sizemore for project support and help in facilitating
the animal care and use authorizations; and S. Goetz, E.
Metzger, and R. N. Reed for helpful assistance with earlier
versions of this note. These activities were authorized under
the U.S. Geological Survey Fort Collins Science Center IACUC
2021-07_Emergency_Authorization, Florida Fish and Wildlife
Conservation Commission Special Purposes Permit SP-21-
0008, and EXOT-20-72. Funding and in-kind support were
provided by the South Florida Water Management District,
National Park Service, U.S. Geological Survey (USGS) Greater
Everglades Priority Ecosystems Program, USGS Biological
Threats Program, USGS Fort Collins Science Center, University
of Florida, Florida Fish and Wildlife Conservation Commission,
Zoo Miami, Naples Zoo Conservation Fund and private
philanthropy to the Conservancy of Southwest Florida. Any
use of trade, firm, or product names is for descriptive purposes
only and does not imply endorsement by the U.S. Government.
IAN BARTOSZEK, Conservancy of Southwest Florida, 1495 Smith
Preserve Way, Naples, Florida, USA (e-mail: ianb@conservancy.org);
GRETCHEN E. ANDERSON, U.S. Geological Survey, Fort Collins Science
Center, South Florida Field Station in Everglades National Park, 40001
SR 9336, Homestead, Florida, USA; IAN EASTERLING, Conservancy of
Southwest Florida, 1495 Smith Preserve Way, Naples, Florida, USA; JIL-
LIAN M. JOSIMOVICH, U.S. Geological Survey, Fort Collins Science
Center, South Florida Field Station in Everglades National Park, 40001
SR 9336, Homestead, Florida, USA; ALEX FURST, Conservancy of South-
west Florida, 1495 Smith Preserve Way, Naples, Florida, USA; FRANK N.
Fig. 1. Radiograph verification of the predation events on young,
radiotelemetered Python bivittatus by adult Agkistrodon conanti
from two locations in the Greater Everglades Ecosystem. The 2020
observation (top) was in Picayune Strand State Forest, Florida, USA,
and the 2021 observation (bottom) was in Big Cypress National Pre-
serve, Florida, USA. Radiographic vouchers were deposited with the
Florida Museum of Natural History, University of Florida (UF 192270,
192271).
Herpetological Review 52(4), 2021
862 NATURAL HISTORY NOTES
RIDGLEY, Conservation and Research Department, Zoo Miami, 12400
SW 152nd Street, Miami, Florida, USA; AUSTIN L. FITZGERALD, AMY A.
YACKEL ADAMS, and ANDREA F. CURRYLOW, U.S. Geological Survey,
Fort Collins Science Center, South Florida Field Station in Everglades Na-
tional Park, 40001 SR 9336, Homestead, Florida, USA (e-mail: acurrylow@
usgs.gov).
... Although it has been presumed that other native ophiophagous predators consume juvenile Burmese pythons, sparse records of depredation events have been made. These include one instance of depredation by an eastern indigo snake (Drymarchon couperi Holbrook, 1842; Andreadis et al. 2018), two instances by Florida cottonmouths (Agkistrodon conanti Gloyd, 1969;Bartoszek et al. 2021), and mention of three American alligators (Pittman and . The prevalence with which native predators consistently recognize and incorporate invasive pythons into their diet is unknown. ...
... We documented three Florida cottonmouth depredations on juvenile pythons, the first of which was discovered 31 May 2021 and confirmed by radiography ( Figure 2; further described in Bartoszek et al. 2021). The two subsequent instances occurred on 01 and 08 October 2021. ...
... Florida cottonmouth (Agkistrodon conantiGloyd, 1969) in-situ (left) that consumed a telemetered juvenile Burmese python (Python bivittatus Kuhl, 1820) and confirmed by radiography (right; used with editorial permission and further described inBartoszek et al. 2021). Subject was discovered in the field on 31 May 2021 in Big Cypress National Preserve, Florida, USA. ...
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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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