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Thamnodynastes strigatus (Coastal House Snake). Reproduction.



Here, we provide information on reproductive timing, litter size, relative litter mass, and offspring morphology of T. strigatus from Brazil.
Herpetological Review 51(4), 2020
IBUKI FUKUYAMA, Graduate School of Human and Environmental
Studies, Kyoto University, Sakyo, Kyoto 606-8501, Japan (e-mail: kawashi-; RYOBU FUKUYAMA, Department of Zoology, Graduate
School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan (e-mail:
TANTILLA NIGRICEPS (Plains Black-headed Snake). PREDA-
TION. On 26 July 2015, at the intersection of FM 505 and US 90,
in Jeff Davis County, Texas, USA (30.51848°N, 104.41070°W; WGS
84) we found a Tantilla nigriceps impaled on a barbed wire fence
at a known Loggerhead Shrike (Lanius ludovicianus) larder. La-
nius ludovicianus are known to prey upon various species of rep-
tiles and amphibians (Kaufman 1996. Lives of North American
Birds. Houghton Mifflin Company, Boston, Massachusetts. 500
pp.; Clark 2011. Son. Herpetol. 24:20–22). The only previously re-
ported predators of T. nigriceps are ants (Ernst and Ernst 2003.
Snakes of the United States and Canada. Smithsonian Institution
Press, Washington D.C. 353 pp.). The T. nigriceps specimen was
collected under TPWD permit #0714-119 and accessioned in the
Sul Ross State University James F. Scudday vertebrate collections
as SRSU 6901.
HAM, Department of Biology, Geology, and Physical Sciences, Sul Ross
State University, Alpine, Texas, 79830 (e-mail:
PRODUCTION. Thamnodynastes strigatus is a medium-sized,
semiaquatic dipsadid snake (to 795 mm SVL; Bellini et al. 2014.
Herpetol. J. 24:87–96), widespread in the southern portion of
the Atlantic Forest and Pampas Grasslands of southern South
America (Nogueira et al. 2019. South Am. J. Herpetol. 14:1–274).
Reproductive data have been reported only in populations from
eastern Argentina (Bellini et al. 2014, op. cit.). Here, we provide
information on reproductive timing, litter size, relative litter
mass, and offspring morphology of T. strigatus from Brazil.
Information was obtained from one pregnant female
preserved in the Museu de História Natural Capão da Imbuia
(MHNCI 10735) and three wild-caught pregnant females that
were donated to the Instituto Butantan (São Paulo, Brazil).
Specimens were collected at various locations in the Atlantic
forest domain (southeastern and southern Brazil). The preserved
female (602 mm SVL) was collected on 27 June 2002 (early
winter), and it had 22 oviductal embryos at mid-organogenesis.
The first pregnant female (470 mm SVL) gave birth to 12
offspring on 9 October 2002. The second pregnant female (580
mm SVL) gave birth to 26 offspring on 31 October 2013. The third
pregnant female (535 mm SVL) gave birth to 13 offspring (no
date available). Timing of parturition seems to differ from other
congeners, which give birth in summer (January–March; Bellini
et al. 2014, op. cit.; Rebelato et al. 2016. An. Acad. Bras. Ciênc. 88:
1699–1709). Maternal body size and litter size seem to be higher
than observed in conspecifics from southern Brazil and eastern
Argentina (Bellini et al. 2014, op. cit.; Loebens et al. 2019. Zool.
Anz. 280:42–51), which suggests geographic variation in life-
history traits. Relative litter mass (total litter mass/body mass of
mother after oviposition; Shine 1980. Oecologia. 46:92–100) in
the first, second, and third female was 0.313, 0.609, and 0.309,
respectively. Offspring SVL and tail length were measured in two
litters. Offspring SVL averaged 151.3 ± 11.4 mm (range: 130–168
mm, N = 37), and offspring tail length averaged 42.5 ± 3.4 mm
(range: 35–49 mm, N = 37). Offspring mass and head length
were measured in one litter only and averaged 2.6 ± 0.3 g (range:
2.3–3.3, N = 26 young) and 12.8 ± 0.5 mm (range: 11.8–13.8 mm,
N = 26), respectively. Offspring sex ratio was 19M:18F (N = 2
litters). To the best of our knowledge, these are the first data on
relative litter mass and offspring morphology of the species.
SCARTOZZONI, Laboratório de Ecologia e Evolução, Instituto Butantan,
Av. Dr. Vital Brazil, 1500, CEP 05503-900, São Paulo, Brazil.
ter Snake). FORAGING COMPETITION. At 1450 h on 21 August
2018, while searching the terrestrial edge of a fen pond (49.5 m2,
< 1 m deep) in the Trinity Alps Wilderness, Trinity County, Cali-
fornia, USA (41.2383°N, 122.7362°W; WGS 84; 1984 m elev.), we
observed an adult female Rana cascadae (Cascades Frog) being
consumed simultaneously by one adult T. s. fitchi and one adult
T. a. hydrophilus. The T. s. fitchi had seized the throat and right
front limb of the R. cascadae while the T. a. hydrophilus seized
the right hind limb of the R. cascadae (Fig. 1). The R. cascadae
was alive at the beginning of our observation and attempting
to escape by lunging despite having a bleeding laceration on its
throat. The R. cascadae succumbed to its injuries at ca. 1501 h
based on a lack of limb and throat movements. Both snakes con-
tinued to struggle to gain control of the frog and each strongly
pulled on the prey in opposite directions while progressively
advancing their jaws over the frog’s head and right hind leg.
Both snakes coiled their tails around multiple sedge (Carex sp.)
and rush (Juncus sp.) stems along the pond edge to gain lever-
age while pulling on the R. cascadae (Fig. 1). During our 29-min
observation lasting until 1519 h, it appeared neither snake had
an advantage in seizing control of the prey. Regrettably, our ob-
servations ended abruptly, due to other obligations, so we were
unable to determine the outcome of this competitive foraging
Both T. a. hydrophilus and T. s. fitchi commonly forage on R.
cascadae in subalpine wetlands of northern California (Garwood
and Welsh 2005. Herpetol. Rev. 36:165; Pope et al. 2008. Biol.
Conserv. 141:1321–1331) making them functionally similar top
predators in these aquatic habitats. Although both species have
Fig. 1. Direct foraging competition by Thamnophis atratus hydrophi-
lus (seizing frog hind limb) and T. sirtalis fitchi (seizing frog throat)
on an adult female Rana cascadae, observed in the Trinity Alps Wil-
derness, Trinity County, California, USA.
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