Boletín de la Sociedad Zoológica del Uruguay, 2025
Vol. 34(2): e34.2.6
ISSN 2393-6940
https://journal.szu.org.uy
DOI: https://doi.org/10.26462/34.2.6
ABSTRACT
A relatively large number of defense mechanisms against
predation are known for amphibians. Herein, we report an
unsuccessful case of predation of Philodryas
patagoniensis upon Leptodactylus sp. resulted from a
species thanatosis behavior.
Key words: Defensive mechanisms, Atlantic Forest,
Snake, Anura.
RESUMEN
El gran escape: la tanatosis como una eficaz
estrategia anti-depredador en Leptodactylus sp.
contra Philodryas patagoniensis en el nordeste de
Brasil. Los anfibios presentan diferentes mecanismos de
defensa contra la depredación. Aquí reportamos un caso
de depredación no exitosa por parte de Philodryas
patagoniensis sobre Leptodactylus sp. asociado a una
defensa a través de un comportamiento de tanatosis.
Palabras clave: Mecanismos de defensa, Bosque
Atlántico, Serpiente, Anura.
Anuran amphibians exhibit a wide range of anti-
predator mechanisms, which can be categorized into
three distinct defensive phases: avoiding detection,
preventing attacks, and triggering counterattacks
(Ferreira et al., 2019). Among the vertebrates, anurans
have been pinpointed as the groups with highest
number of anti-predator behaviors (Ferreira et al.,
2019). This remarkable adaptability is a direct result of
the intense predation pressure to which they are
constantly subjected (Haddad et al., 2013).
One such defensive strategy is thanatosis, or
death-feigning, where the animal pretends to be dead
to deter predators (Toledo et al., 2010). This behavior
has been observed in a variety of taxa, including
invertebrates and vertebrates such as mammals, birds,
reptiles, fish, and amphibians (Humphreys & Ruxton,
2018; Gonzalez-Candia, 2023; Silva et al., 2024).
Thanatosis behavior has the function of protecting
the individual from predation, in interspecific or
intraspecific interactions. There are records of its
successful use by Western toad (Anaxyrus boreas)
when threatened by the Foothill yellow-legged frog
(Rana boylii) (Alvarez & Wilcox, 2022) and also by male
Nursery web spiders (Pisaura mirabilis) avoiding
predation by females during the reproductive period
(Hansen et al., 2008).
The performance of thanatosis has already been
observed in different genera of amphibians, however,
in most cases, this behavior occurs after the individual
is handled by the researcher or in controlled
Bol. Soc. Zool. Uruguay (2ª época). 2025. ISSN 2393-6940Vol. 34(2): e34.2.6
NOTA
THE GREAT ESCAPE: THANATOSIS AS AN EFFECTIVE ANTI-PREDATOR STRATEGY IN
LEPTODACTYLUS SP. AGAINST PHILODRYAS PATAGONIENSIS IN NORTHEAST BRAZIL
Vanessa do Nascimento Barbosa¹* , Élida Francisco da Silva² , Jéssica Monique da Silva Amaral² ,
4
Letícia Nunes Rezende² , Letícia Morais dos Santos³ , Frederico Gustavo Rodrigues França
¹Programa de Pós-Graduação em Ciências Biológicas, Universidade Federal da Paraíba, 58051-900, Jardim
Universitário S/N, Castelo Branco, João Pessoa, Paraíba, Brasil.
²Programa de Pós-Graduação em Ecologia e Monitoramento Ambiental, Universidade Federal da Paraíba,
58297-000, Avenida Santa Elisabete, S/N, Centro, Rio Tinto, Paraíba, Brasil.
³Licenciatura em Ciências Biológicas, Departamento de Biologia, Universidade Federal Rural de Pernambuco,
52171-900, Rua Manuel de Medeiros, S/N, Dois Irmãos, Recife, Pernambuco, Brasil.
4 Laboratório de Ecologia Animal, Departamento de Engenharia e Meio Ambiente, Centro de Ciências
Aplicadas e Educação, Universidade Federal da Paraíba, 58297-000, Avenida Santa Elisabete, S/N, Centro,
Rio Tinto, Paraíba, Brasil.
*Corresponding author: nascimentob.vn@gmail.com
Date of receipt: December 9, 2024
Date of acceptance: June 11, 2025
.
2
BARBOSA et al.
environments (Gonzalez-Candia, 2023; Santos et al.,
2024; Silva et al., 2024). In natural conditions, records
of thanatosis resulting from predation interactions are
scarce in the literature. Therefore, records of these
interactions are essential to evaluate the effectiveness
of the strategy in nature.
Leptodactylus comprises 84 species, with 61
occurring in Brazil (Segalla et al., 2021; Frost, 2024).
Many defensive behaviors are known for the genus
(e.g. Toledo et al., 2005; Sales et al., 2015; Costa &
Trevelin, 2020), including those that exhibit thanatosis,
show an adaptability that enhances their survival in
various environments by reducing predation risk
(Santiago, 2021).
The Patagonian green racer Philodryas
patagoniensis (Girard, 1858) has a generalist diet that
includes arachnids, small mammals, birds, fishes,
reptiles, and amphibians (Hartmann & Marques, 2005;
Quintela & Loebmann, 2019; Chuliver & Scanferla,
2024). Among amphibians, the family Leptodactylidae
constitutes a significant portion of their diet,
representing 13% of the total documented prey items
(Machado-Filho, 2015).
On February 13, 2020, an adult P. patagoniensis
(~1 m total length) was observed attempting to prey on
an individual of the Leptodactylus aff vastus in a
restinga environment within the Barra do Rio
Mamanguape Environmental Protection Area, Rio
Tinto, north coast of Paraíba, northeast Brazil (6° 46'
42.32" S, 34° 55' 20.35" W; WGS 84; altitude 7 m). At
7:18 am, the snake started the predation attempt by
biting the amphibian abdomen, which emitted an
agonistic vocalization. After approximately 10 seconds,
the amphibian ceased vocalizing and displayed
thanatosis, at this point, we start recording, the snake
continues biting the amphibian's head for another 14
seconds.
While the amphibian remained in thanatosis, P.
patagoniensis bits the head region (Fig. 1A),
immobilizing it for approximately 15 seconds. The
snake then bitten to the left forelimb (Fig. 1B) for four
seconds, followed by an attempt to ingest the
amphibian from the lower limbs (two seconds), another
an attempt to ingest the amphibian head-first for three
seconds and a brief bite to the left forelimb (<one
second) And the frog did not stop the thanatosis
behavior. The snake then repositioned frog belly on the
back of the frog for nine seconds. Shortly thereafter, the
snake returned, biting the amphibian head region for 14
seconds, dragging its body for less than 1 meter, and
ultimately retreating in the opposite direction.
Despite its behavior of death-feigning, the frog, at
all times, presents movements in its vocal sac,
indicating continuous breathing and makes a discreet
movement of its legs when the snake passes over it
(Fig. 1C; see 1:01 min of the video), indicating that it
was alive throughout the entire process of attempted
predation. In the present study, the frog showed a slight
movement when the snake passed over it, shrinking its
legs and tilting its head slightly, adopting a potential
escape behavior (Ferreira et al., 2019), however, after
the movement, the amphibian returned to the
thanatosis posture. Apparently, breathing is not
impaired in the behavior of playing dead, given that the
amphibian remained breathing throughout the
predation attempt, which was also reported for
Pristimantes ramagii (unpublished data) and
Silverstoneia flotator (Klank et al., 2023).
The thanatosis behavior lasted one minute and 30
seconds (video: https://youtu.be/r-r1dqFwu6Q). After
the snake left, the recording was stopped, and
approximately 10 seconds later, the amphibian
resumed its normal posture and jumped toward the
sandbank.
Although snakes have been documented preying
on dead animals (Barbosa et al., 2022), active prey is
generally more susceptible to predation than inactive
prey (Macdonald, 1973). Anuran amphibians can
sustain thanatosis for up to five minutes, during which
they may camouflage with their surroundings or
release odorous secretions to enhance the illusion of
being dead (Toledo et al., 2011; Lourenço-de-Moraes
et al., 2016). However, this Leptodactylus remained
still, with only movements of the vocal sac, until the
snake moved away completely, resuming the jumping
position and leaving the site of the attempted predation.
We believe that the “cameraman” had no influence
on the snake's decision to leave, as he remained still,
away from the snake, following the process, only
zooming the camera in and out, where the snake
releases the frog and moves away calmly, not showing
signs of running away.
Our observation highlights the effectiveness of
thanatosis as an anti-predator strategy in
Leptodactylus under natural conditions. The event
underscores the significance of this behavior on the
individual's survival, contributing to the growing body of
knowledge on the death-feigning in anurans. Future
studies and the record of field observations like that,
could help to understand the prevalence and adaptive
advantages of thanatosis across different populations
and environmental contexts, further elucidating its role
in predator-prey dynamics and its connection with
amphibian respiration, whether the immobility of the
limbs would be more important than the total reduction
of respiration.
We thank Rafael de Brito Costa for the imagens and
video recordings and the Instituto Chico Mendes de
Conservação da Biodiversidade (ICMBIO) for the
collection permit (SISBIO nº 74327-1). VNB, EFS and
LNR thank the National Council for Scientific and
Technological Development (CAPES) for PhD
scholarship and master's scholarship (grant numbers
88887.713778/2022-00, 88887.935257/2024-00 and
88887.956872/2024-00).
Bol. Soc. Zool. Uruguay (2ª época). 2025. ISSN 2393-6940Vol. 34(2): e34.2.6
3Thanatosis as an Effective Anti-Predator Strategy
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Fig. 1. Philodryas patagoniensis attempting to prey on a Leptodactylus sp. exhibiting thanatosis behavior in a restinga environment
of northeast Brazil. A- Snake's attempt to ingest the head of the Leptodactylus; B- Snake's attempt to ingest the amphibian through
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Section Editor: Raúl Maneyro
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