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Scripta Herpetologica. Studies on Amphibians and Reptiles in honour of Benedetto Lanza: pp. 129-136, 2014
IntroductIon
Post-hatching parental cares provided by one or both parents have been doc-
umented in several species of amphibians (Wells, 2007). Anura display attend-
ance, brooding, feeding, transport and defence of egg and tadpoles and transport of
froglets (Lehtinen and Nussbaum, 2003; Wells, 2007). In Apoda, the female may
provide food to the hatchlings through modified and specialized skin tissues (Kup-
fer et al., 2006). Aquatic Urodela display egg and larvae attendance (Nussbaum,
2003; Wells, 2007), while in terrestrial species such as Plethodon cinereus (Green,
1818) and Anei des aeneus (Cope and Packard, 1881) young remain in the proxim-
ity of the mother up to four weeks after hatching (Mathis et al., 1995). Hovewer,
mother-young interactions were never described in detail to date. e first unam-
biguous evidence of post-hatching parental behaviour in terrestrial salamanders was
recently documented in the North-west Italian Cave salamander Speleomantes stri-
natii (Aellen, 1958)(Oneto et al., 2010). In that study, a cave salamander brood-
Maternal care and defence of young by the plethodontid salamander
Speleomantes strinatii (Aellen, 1951)
F O 1,2, D O 2, M V P 1,
S S 1,2*
1 Gruppo Speleologico Ligure “Arturo Issel” - Villa Comunale ex Borzino C.P. 21
16012 Busalla (GE), Italy
2 Dipartimento di Scienze della Terra dell’Ambiente e della Vita (DISTAV)
Università degli studi di Genova - Corso Europa 26, 16132 Genova, Italy
* Corresponding author: salvidio@dipteris.unige.it
129
Abstract. Egg brooding females of the North-west Italian Cave Salamander Speleomantes stri-
natii display a complex array of parental behaviours. Recently, prolonged skin contacts between
mother and young were documented by means of infra-red video recording, up to 40 days after
hatching. In this study the behaviour of two females attending their young in presence of a po-
tential predator was experimentally tested. About seven days after hatching, two adult males of S.
strinatii were introduced inside the terrarium, where two females (A and B) were both attending
eight young. In one case, female A approached female B and her young, but was repelled away.
e approaching male always elicited an aggressive behaviour of females that repelled the intruder
by head pushes and bites. is behaviour, similar to the one displayed during egg brooding, is the
first evidence of active defence of young in terrestrial salamanders.
Keywords. Speleomantes strinatii, infra-red video recording, post-hatching parental cares, young
defence.
Oneto et al.
130
ing female was recorded by infrared (IR) video technique in a terrarium kept in
complete darkness inside an underground laboratory. e two hatchlings remained
near and often climbed on the female back, resting motionless for hours without
any contact with the substrate (Oneto et al., 2010, fig. 1F). is behaviour, com-
prising repeated physical contacts between female and young, lasted for about 40
days, and during this period the female rarely abandoned the nesting site. e fe-
male’s post-hatching parental behaviour consisted in attendance at the nesting site
and in long-lasting and repeated skin contacts with her young. is was interpreted
as a true parental behaviour producing a selective advantage for the offspring, by
providing protection against fungal or bacterial infections and by increasing skin
hydration of the small-bodied young (Oneto et al., 2010). A possible protective
role of the attending female against potential predators was also suggested, but no
experimental evidence could be provided. is research, a prosecution of the previ-
ous study by Oneto et al. (2010), assessed experimentally the role of the female cave
salamander in presence of her young, by introducing a conspecific potential preda-
tor inside the terrarium.
MaterIals and Methods
Study species
e North-west Italian Cave Salamander, Speleomantes strinatii, is a complete-
ly terrestrial plethodontid endemic to SE France and NW Italy (Lanza, 2006). is
species is found from the sea level up to about 2470 m a.s.l. along streams, on hu-
mid rocky outcrops, in humid forest floors and also in subterranean natural or ar-
tificial habitats (Lanza et al., 2005; Renet et al., 2012). Sexually mature males are
recognized by the presence of a mental gland lacking in females and in immature
individuals. In the wild, nest sites and egg clutches of S. strinatii remain unknown
(Lanza, 2006), but females were observed laying 6-14 relatively large eggs in captiv-
ity (Durand, 1970; Salvidio et al., 1994; Oneto et al., 2010). During egg brooding
the female coils around the clutch, maintaining skin contacts and actively defends
it against approaching potential predators (Durand, 1970; Oneto et al., 2010).
Experimental setting and infrared recording
is study was conducted in the Biospeleological Station of San Bartolomeo
(390 m a.s.l.) near the village of Savignone, 25 km N of the town of Genova (Ligu-
ria, NW Italy). An experimental Plexiglass terrarium (70×50×30 cm) was kept in
semi-natural conditions, and, apart from movement restriction, all the experimen-
tal animals were exposed to the same environment as the salamander population
living in the cavity (Salvidio et al., 1994). e terrarium was located at about 20
m from the cavity entrance, where solar illumination is lacking (0.0 Lux, measured
by Deltha Ohm Luxmeter HD 8366, Padova, Italy), annual mean air temperature
is 9.7 °C (range 6.7-12.5), and relative air humidity is 95% (Salvidio et al., 1994).
Salamander behaviour was recorded by a hard-wired waterproof camera Sony Su-
Maternal care and defence in Speleomantes strinatii
131
perHADTM equipped with a Charge Coupled Device (CCD) optical sensor and
with a built-in infrared (IR) 12-led illuminator (RE-BCC6L, Digital Surveillance
Equipment, DSE Torino, Italy). e camera was suspended 1.2 m over the terrar-
ium and connected to a 10-m distant PC. During the experiments, video record-
ing was conducted in continuous with 12.5 frames per second. e video sequenc-
es were saved in the PC as 60-min packages and were visualized at normal speed
or in slow-motion by a commercial software provided by DSE (Torino, Italy). e
quality of the images was relatively low, but the moving sequences allowed to in-
terpret the behaviours unequivocally. In November 2010, two apparently gravid
females (A and B) were introduced inside the terrarium. IR recording began in Oc-
tober 2011, after the hatching of the young. All young were born by October 15
and 17 for clutch A and B, respectively. After about seven days from hatching, two
adult males (X and Y) were introduced in the terrarium for a period of three days
and their interaction with the resident females was recorded in complete darkness.
Overall, 840 hours of recording were analysed.
results
Interactions between female and young
e analysis of the IR video recordings of the two females and their young
confirmed the previous observations, conducted on one single female attending
two young (Oneto et al., 2010). Both females shared the nesting site for about 30
days with their young, that repeatedly entered in physical contact with their moth-
Figure 1. Physical contacts occurring among female A and her young immediately after hatching. In
front of the female the egg envelop is still present (photo by Fabrizio Oneto).
Oneto et al.
132
er, climbed on it’s body and rested motionless without any physical contact with
the substrate for hours. Often, this behaviour was displayed by all young simulta-
neously (Fig. 1). ese observations are a confirmation of the existence of intimate
physical contacts between mother and her young in S. strinatii (Oneto et al., 2010).
Interactions between the attending female and a possible predator
On October 17, 2011 female B left her nesting site and approached female A
and her young. e resident female touched with her head the intruding female,
probably pushing away or maybe biting. After a contact lasting about 15 sec female
B walked away and returned to her young.
Soon after being introduced in the terrarium, on October 25, both cave sal-
amander males approached the two attending females. When the intruder ap-
proached and entered inside the nesting site, the attending female became vigilant,
looking towards the intruder and walking to intercept and actively repel the male
by head contacts, pushes and in some cases bites. In only one case, the male start-
ed the contact by walking upon the motionless female that reacted biting the male
trunk and repelling the intruder (see Table 1). It was not easy to distinguish simple
physical contacts from bites, because of the perpendicular angle of the video cam-
era, but in some cases the contact between the interacting salamanders caused a ro-
tation of the male body, who was “pulled” by the female (see Fig. 2, S5), or a rapid
body twisting of the male that tried to free himself from the female’s grip. ese
Table 1. Synthesis of Speleomantes strinatii agonistic interactions between females attending their
young and intruding male. All the interactions, with the exception of (*) were started by females. Bites
were delivered only attending by females.
Female A
Female B
13
7
13
60
11
3
7
109
15
8
149
11(*)
1 bite
-
1 bite?
-
1 bite
1 bite
-
-
-
-
1 bite
1 bite
1
2
3
4
5
6
1
2
3
4
5
6
Contact (N) Duration time (sec) Notes
(*) The duration time starts when the female bites the male
Maternal care and defence in Speleomantes strinatii
133
Figure 2. Stills (S1-S8) from infrared video footage recorded on October 25, 2011, showing the in-
teractions between female A and intruding male Y. In still (S1) the following letters indicate: A and
B the attending females; (a1) and (b1) their young; X and Y the males. is sequence is described in
detail in the text.
Oneto et al.
134
agonistic behaviours were observed 6 times in both females, for a total of 107 and
299 sec respectively (Table 1). In all cases, the female forced the intruder to exit
from the nesting site. An example of these interactions is given in Fig. 2, that was
composed by eight video stills (S1-S8) taken from the full video footage. is se-
quence refers to the encounter occurred on October 25, 2011, between the two sal-
amanders A (female) and Y (male). e complete action lasted about 3 min and is
here described in detail:
S1) at 16h 24m 57s: female A walks from the young (a1) on a strait line towards
the intruder Y;
S2) at 16h 25m 04s: female’s head “touches” the intruder’s neck, the physical con-
tact was maintained for about 12 sec; at time 16 25 15 the two individuals de-
tached;
S3) at 16h 25m 26s: the female engages again in a physical contact that lasted 58
sec;
S4) at 16h 26m 29s: the female bites the intruder’s right hind-leg, pulling it with
energy;
S5) at 16h 26m 36s: the male is half turned on his right side by the pulling female;
S6) at 16h 26m 46s: the male free himself and moves away from the female;
S7) at 16h 27m 11s: the female “touches” (probably bites) the posterior part of the
male’s trunk;
S8) at 16h 27m 17s: the male walks outside the nesting site, and the female-male
interaction ends.
dIscussIon
is study, as the one by Oneto et al. (2010), proves the importance of record-
ing the social behaviour of Speleomantes salamanders in semi-natural settings and
not in completely artificial laboratory conditions. In this study, IR video recording
were obtained in total darkness, without disturbing the focal individuals, unless by
restraining their movements inside the terrarium. Indeed, some of the previous de-
scribed parental behaviour of S. strinatii were obtained in completely artificial set-
tings and therefore were only partially described (Durand, 1967, 1970). e post-
hatching parental behaviour recorded during this study (e.g. complete skin contacts
of young that actively climbed on the mother), confirms the observations reported
by Oneto et al. (2010) on a single female attending two young. Moreover, the fe-
male interactions occurring several days after hatching with a potential predator
(i.e. an adult male introduced in the terrarium) gave new insights in the parental
behaviour of the species. Both experimental females repeatedly displayed an aggres-
sive behaviour towards the male intruder that was intercepted, pushed, sometimes
bitten and always repelled away from the young. It is interesting to note, however,
that in all cases the attending female was aggressive towards the intruder individu-
al (male or female) but not vice versa. ese results are of interest because territo-
rial agonistic behaviour has never being demonstrated in Speleomantes (Zanetti and
Maternal care and defence in Speleomantes strinatii
135
Salvidio 2004; Sguanci et al., 2010) and therefore aggressive behaviour seems to be
limited only to the defence of the egg clutch (Durand, 1970; Oneto et al., 2010)
and young (this study). e presence of eggs and/ or young seems to give to the fe-
male a social status that is perceived as dominant by other approaching individuals
of the species.
In any case, the agonistic behaviour recorded in this study clearly exposed the
female to the possible risk of being bitten, wounded and possibly impaired by the
approaching predator, that was an adult salamander of similar size. Costly behav-
iours, in terms of energy investment and of risk-taking, fulfil Trivers’s (1970) defi-
nition of parental care, demonstrating that the attending S. strinatii female actively
defended its young, up to about 10 days after hatching. ese results provided the
first evidence of “young defence” in Urodela (Jaeger and Forester, 1993; Duellman
and Trueb, 1994; Nussbaum, 2003) and enlarge our knowledge on salamander pa-
rental behaviour that appear much more complex than previously assumed (Mathis
et al., 1995).
Acknowledgments. Temporary capture permits were obtained from the Italian Ministry of En-
vironment (DPN-2010-0010807).
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