Several species of amphibians are known to inhabit
subterranean habitats. While some species are obligatory
cave-dwelling (e.g., Proteus anguinus Laurenti, 1768),
others tend to use caves only for limited periods of their
lives (Peck, 1974; Romero, 2009). At least 17 species of
amphibians that belong to the Italian herpetofauna have
on occasion been found in caves or other underground
spaces and several of them occasionally breed in
subterranean sites. Here we provide the first evidence
of a population of yellow-bellied toads (Bombina
variegata) exploiting a subterranean habitat (Fig. 1).
The range of Bombina variegata (Linnaeus, 1758)
includes most of eastern, central, and southern Europe.
It extends from the Carpathian Mountains in the east
to France in the west and southern Italy in the south
(Gollmann et al., 1997). The species inhabits different
kinds of freshwater environments, including ephemeral
ponds, slow-moving streams, artificial basins and
troughs, and it is usually considered a heliophile species
(Bauer, 1987; Guarino et al., 1996). It is found from
sea level up to elevation 2200 m (Petrov, 2007), and
it is generally active from April–October (Bressi and
During a study between April and November 2017
we monitored a population of B. variegata pachypus3
(Bonaparte, 1838), the Apennine yellow-bellied toad,
and discovered that it was exploiting subterranean
spaces in addition to its usual habitat. The study site
(Fig. 2) is located in the southern Apennine Mountains,
about 20 km NW of Salerno, at an elevation of 600
m, in an area characterized by vegetation primarily
composed of maqui and several species of oaks (e.g.,
Quercus cerris, Q. ilex). The study site is located inside
the “Lauro Mountains” Site of Community Importance.
In the monitored area there are (i) three concrete-made
artificial basins used as troughs, (ii) a large cave, and (iii)
a system of smaller caves. The largest cave measures
about 15 m at its longest point, 7 m at its widest, with
maximum ceiling height of 5 m. The cave’s floor is to
90% of its surface covered in water throughout the year.
The maximum water depth is ca. 30 cm. The cave is of
natural origin but was artificially modified in the past
for use as a water reservoir.
During our surveys, we ascertained the presence of
several specimens of B. v. pachypus inside the main
cave. We monitored the site for a total of seven times
(always during the daytime) and located individuals
of B. v. pachypus in the main cave during each visit.
Individuals observed in the smaller caves were always
impossible to be captured due to the difficulties of the
terrain. We also recorded the presence and reproductive
activity of Bufo bufo (Linnaeus, 1758) and Salamandra
salamandra (Linnaeus, 1758). Whereas there have been
reports for the presence and reproduction in hypogeous
habitat (Bonini et al., 1999; Manenti et al., 2011), this
is the first time that B. v. pachypus is reported for such
We used a mark & recapture method in order to
understand whether individuals occurring in the main
cave were always the same individuals. Given that the
genus Bombina is characterized by an individualised
belly pattern (Delarze et al., 2000), photographing the
Herpetology Notes, volume 11: 967-969 (2018) (published online on 19 November 2018)
First record of Bombina variegata (Linnaeus, 1758)
in a cave environment
Valerio Giovanni Russo1,*, Luca Francesco Russo1, Luca Coppari2, and Tommaso Notomista1
1 Associazione Ardea, via Ventilabro 6, 80126 Naples, Italy.
2 Amphibian Evolution Lab, Vrije Universiteit Brussel, Plainlaan
2, 1050 Brussels, Belgium.
* Corresponding author. E-mail: valerio.giovanni.russo@gmail.
3 7he taxonomic position of B. v. pachypus is still subject to some
debate, with some authors considering it a full species (e.g.,
Nascetti et al., 1982; Lanza and Corti, 1993; Szymura and
Gollmann, 1996) and with others just recognising its validity
as a subspecies (Speybroeck et al., 2010).
Valerio Giovanni Russo et al.
ventral side of animals found inside and outside the
cavern allowed us to reliably identify every individual.
Individual pattern recognition is known as the least
invasive method for marking amphibians (Loafman,
1991). For photo identification we used the I3S Pattern
software (Van Tienhoven et al., 2007).
Results demonstrated that individuals found inside
the cave would subsequently be found outside and
vice versa, confirming that the cave was not working
as a trap and that specimens were able to freely move
in and out. Moreover, individual recognition allowed
us to recognize how healthy animals were. Specimens
always found in the cave showed, at least at a first sight,
good health conditions, suggesting that during their
stay in the hypogeous habitat toads are not suffering
of starvation or other issue related to the conditions
of a cave environment. We found between four and
nine specimens in the main cave. Of the 44 specimens
marked in the entire area, 17 were found at least once in
the main cave.
We do not know why this population uses the
subterranean habitat. It has been shown in other species
(e.g., Prather and Briggler, 2001) that the use of cave
spaces could be due to a need for lower temperatures and
higher levels of humidity, but it would be speculative to
Figure 1. An individual of Bombina variegata pachypus found inside one of the caves of the study site.
Figure 2. Map of Italy (A) and specific location of the Site of
Community Importance “Lauro Mountains” (dark grey area
in B). (C) The exterior of the study site where some of the
smaller caves and one of the artificial troughs are visible.
assert this here. Studies to analyse how this population
copes with the hypogeous habitat, if feeding occurs
in the cave and what prey items may be consumed, at
which stage of their life these frogs begin to use the cave
environment, if they reproduce inside it, or whether the
cave is mainly used as a refuge during colder periods,
are currently ongoing.
Our findings refute any evidence that B. v. pachypus
could be a strictly heliophilic species. Furthermore,
it is becoming clear that even for well-studied taxa,
there is still work to be done in order to more fully
understand their biology and ecology. Considering that
this subspecies may be suffering a population decline
throughout its range and is protected by national and
international legislation, improving the knowledge about
its ecology is critical for building better conservation
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First record of Bombina variegata in a cave environment 969
Accepted by Hinrich Kaiser