Asiatic Herpetological Research

February 1992

Vol.4, pp. 123-131|

Feeding Ecology of the Caucasian Salamander {Mertensiella caucasica),with Comments on Life History
Sergius L. kuzmin

1^Institute of Evolutionary Morphology and Ecology of Animals, Russian Academy of Science, Leninsky

prospekt, 33, Moscow 117071 Russia

Abstract. -The feeding and developmental ecology of the Caucasian Salamander (Mertensiella caucasica)
were studied in western Georgia. Age changes of larval feeding rate are weak. The main food of larvae
consists of gammarids and insects. Larval prey size spectrum widens and displaces to more large objects
during ontogenesis. However age, diurnal, seasonal and habitat differences in diet are weak. The majorityof preys are consumed with negative electivity. During metamorphosis feeding does not cease. A review ofliterature on adult Caucasian Salamander feeding is presented. A comparison of larval development datawith skeletochronology suggests that metamorphosis takes place after the second wintering. Three to fiveannual rings were counted in tubular bone diaphyses of mature specimens.

Key words: Amphibia, Caudata, Salamandridae Mertensiella caucasica; Caucasus Mountains, Georgia,
feeding, larvae, electivity.

caucasica (Waga, 1876) is a stenobiont
species which lives near rocky streams inmountain forests of western Georgia andadjacent areas of Turkey (Figs. 1, 2, andPlate 1). Members of this relict genus were
widely distributed in Europe in the Pliocene(Borja and Mlynarski, 1979). Data on
Caucasian Salamander ecology are very
poor, especially on feeding ecology. The
latter are limited to food composition andfeeding behaviour in captivity (Knoblauch,
1905; Lantz, 1911; Mertens, 1942; Obst
and Rotter, 1962; Rotter, 1958;
Wolterstorff, 1942), speculations on dietbased on invertebrate fauna in theenvironment (Cyren, 1911; Hemmerlingand Obst, 1968; Lantz, 1911; Mertens,
1942), and observations and dissections of
single specimens (Basoglu and Ozeti, 1973;

1940; Knoblauch, 1905;
1913; Sikmashvili, 1970

Ekvtimishvili,

Nikolsky,

Wolterstorff etal., 1936). Quantitative dataon adult diet are presented only in papers

by Bozhansky and D.V.Semenov (1982)and Ekvtimishvili (1948).

FIG. 1. Stream habitat of Mertensiella caucasica
in Akhaldaba Region, Georgia.

Introduction

The Caucasian Salamander, Mertensiella© 1992 by Asiatic Herpetological Research

Methods
From June to August, 1985 the ecologyof the Caucasian Salamander was studied in
the Akhaldaba environs, Borzhomi (41° 51'

N 43° 23' E) region, Georgia. In the same

Asiatic Herpetological ResearchVol. 4, p. 124

February 1992

FIG. 2. Mountain forest habitat of Mertensiella caucasica in Akhaldaba Region, Georgia.

months of 1986 additional material on
newly metamorphosed salamanders wascollected. Adults were measured (snoutvent length- L., tail length- L. cd.), marked

Smirina and Sofianidu, 1985). For thesake of species' conservation I didn't makedissections of mature salamanders. I haveobtained information on their feeding fromby toe-clipping and released. Besides that,the literature cited above.

we have captured

larvaeand newly
Animals of

metamorphosed specimens.
these two age groups as wellas adult

clipped toes were fixed immediately in 5%
neutral formaldehyde solution.

Before treatment, fixed larvae were
immersed in water for several hours. I

measured them by ocular-micrometer underastereoscopic

microscopeor(larger

specimens) by vernier calliper with a
precision of 0.1 mm. Then I dried themwith filter paper and weighed them with a
To determine theprecision of 1 mg.
salamander age, numbers of annual rings infemoral (larvae) or finger (adults) bone
sections were counted (according to

To study larval and newly
metamorphosed salamander feeding, entire
Theirdigestive tracts were obtained.
contents were studied under a microscope.
The bulk of food was dried with filter paper
and weighed with a precision of 0.1 mg.
Food objects were identified and measured
under the microscope. From their linear
dimensions, reconstructed weights were
determined (for details see Kuzmin, 1984a,

1984b).

have determined percentages of eachprey category by its weight and number.
Because of incertainty of prey length andmass as measures of its size availability forI

Asiatic Herpetological Research

February 1992

Caudata, ratio dm ax /Lt. or. (see Kuzmin,1985) was used, where d max =maximum
prey diameter (width or height), Lt.
or.=width of amphibian mouth (between
hind angles of lip folds). It must be noted

Vol. 4, p. 125

1986).

Results

Body Size and Skeletochronology

some later identical parameter was
successfully used in Onychodactylus

thatjaponicus feeding behaviour investigations(Kusano and Hayashi, 1985).
rate

Feedingsalamanders wasdifferent groups ofcompared by digestiveintract-fill indices:Y=-

m-1000%mm

Larger larvae (size group

had one annual ring, commonly only
vaguely expressed. On the femoral bone
sections of two newly metamorphosed
animals (captured in June and August1985) one annual ring is also recognized.
From 10 marked adults captured 13 June,
3)

Caloric content of different preys

was determined using the methods ofCummins and Wuysheck (1971). After
this, the mean caloric content of food wascounted.

Trophic niche overlap was determinedusing Morishita similarity index in the

L.
1985
mm;
(L.=66.7±1.6
cd.=171.5±4.3 mm) annual rings weresuccesfully counted in 7. Each specimen
had on the average 3.57±0.30 (3-5) rings.

form:

Diet and Feeding Baeliaviowr
2

I

Quantitylaboratoryi (HML
where pjj=percent of i-th component in thediet of j-th predator, pjk=percent if i-thcomponent in the diet of k-th predator, and0<lx<l.

To estimate feeding electivity thecontents of larval digestive tracts werecompared with the invertebrate fauna of thestream. Invertebrates were counted after
their total sampling from stream pools
where salamanders were collected.

Thefeeding electivity is estimated using Ivlev's
formula:E= r.-p.
r,+p,Where rj=percent of i-th component in thepercent in environmental
complex, and -l^E^+1. Observations on
the feeding behavior in captivity were also
pi=itsconducted

(for

—

I n
of food consumed.
Caucasianconditions
Salamanders lived some time on
endogenous yolk and transfer to active

PijPik

h=

diet,

mm

mm

(106-108 mg), 23.7-27.5(330-644(632-1400 mg).
mg) and 29.0-35.4
These three groups morphologically differ
from each other (Fig. 3). Size groups 1
and 2 contained mainly specimens that wereborn in the given year. Annual rings intheir femoral bone sections are as a ruleabsent (Fig. 4).

M-mwhere m=food mass, M=total consumer
mass.

All larvae sampled are clearly divided
by their L.: 15.4-19.5

into 3 groups

methods see Kuzmin,

feeding takes place at larval size group 1 (I.
A. Serbinova, pers. comm.). It must be
noted that all the smallest larvae found innature belong to group 1.

The latter alreadyfeed upon exogenous prey with highintensity. Yolk is not recognized in theirdigestive tracts. Furthermore, digestive
tract-fill index (J) changes slightly with
Its values are similar in differentage.
months and in different size groups (July:

40.1±5.4%;2- 34.1±4.2%; 341.5±15.2%.
group 2August:
41.8±7.2%; 3- 34.8±3.0%). Just after
metamorphosis J remains almost on thesame level (34.8±5.5%). There are little
group

1-

differences in J values between the larvae
from medium and lower stream currents
35. 4. ±7.0%
and(39.5±4.3%
respectively). Salamander larvae are more
active at night than in the daytime. The

values of J are influenced by this (L.=16-

Vol. 4, p. 126

Asiatic Herpetological Research

February 1992

groups has a weak monthly variation (1.011.24cal/mg).

Average number of preys per digestive
increases with larval size fromtract

3.00±0.43 (group1) to

4.88+1.43 (group3).

Food spectrum of larvae widens

inontogenesis. Along with widening, there isa marked displacement of prey size

spectrum to larger and larger objects (Tabled
1, A, B). Maximum values of max/Lt.or.
reached 62.6%.

The main food of salamander larvae are
gammarids and larval insects (Table 2).
The smallest invertebrates, Ostracoda andHydracarina, occur in the diet of smallest
salamanders. Generally, age changes ofFooddiet are weak (see Table 2).

by prey numbers are: for2and0.82; 20.73; 1 and 3

similarity (h')

groups 1
and 3-0.61. For weight proportions they
are 0.80, 0.73,

and 0.52, respectively.

Likewise in summer (group 2 - June andAugust: Ix' =0.97 by prey number and0.50 by weight) and day (group 1: 12-13h
and 01 h: K'=0.82 and 0.75) larval diets
Larval foodchanged very slowly.
differences are slightly more appearent inmedium and lower stream

currents(1^=0.59 and 0.42).

Metamorphosed

salamander

foodcomposition changes sharply due to habitatchange (see Table 2). Terrestrial insects
become dominant. Food becomes more
and more diverse with age. Crustaceans,arachnids and insects are the main adultsalamander's prey (see Table 2). At thesame time interpopulational differences infortheir feeding are insufficient:Akhaldaba (Bozhansky and Semenov,1982) and Baniskhevi (Ekvtimishvili,
FIG. 3. Caucasiaan Salamanders of different ages.
A- larvae of three size groups (1-3); B- newly
metamorphosed specimen; C- adult specimen.

17 mm: 01 h - 53%; 12-13 h - 40%).

Mean caloric content of food of different

1948)

samples

percents.

h.'=0.87

bynumeric

Sexual differences in diets areabsent (Bozhansky and Semenov, 1982).

Apart from food items, plant remains,nematods(innewlyparasitic
sand
soil
and
salamanders)metamorphosed
were found in the digestive tracts ofAsiatic Herpetological Research

February 1992

different stages.

Feeding

electivity.

— This has beenstudied in June larvae. Limoniidae arepositively elected by the larvae of group 3(E=+0.52), whereas in the diet of younger
ones, these insects are not found.

L.

35x

Electivity to a close family, Chironomidae,

decreases during ontogenesis (group 1:
E=-0.13; 2: -0.42; 3: -1). The larvae ofgroup 3 ignored the smallest object Ostracoda (E=-l). This prey is consumed
almost unselectively by smaller larvae(groupE=+0.03;1:

Gammaridae
electivity (1:

are

2:

utilized+0.06; 2:Vol. 4, p. 12730--0.05).

with-0.32; 3:

weak+0.23).

Salamanders of all three groups negatively

25-

selected Trichoptera (1: -0.73; 2: -0.42; 3:-0.43).

Feeding behaviour. In captivity, larvae(L.=30-35 mm) noticed the large prey(Gammaridae 3-10
long, Planaria
about 10 mm) from distances of 10-16 mm,
approached up to 2-3 mm and attacked.
Planaria orientation in the mouth takes 1020 seconds; larger gammarids, about 40
seconds. In natural conditions salamander

20-

mm

15-

T

larvaeexhibit diurnal foraging more
frequently than adults. Among the latter
this is observed mainly in wet and darkplaces.
During the winter salamanderfeeding ceases. In the summer they forage
in shallow water more frequently than inearly spring and autumn (Ekvtimishvili,1948). Under the water adults waited formoving invertebrates (Knoblauch, 1905).

nFIG. 4.

The number of annual rings (n) in thesections of femoral bone diaphyses of young
Caucasian Salamanders of different body oength(L.).

A- larvae, June; B- Larvae, Augues; C- newly

metamorphosed specimens.

This may be an adaptation to foraging in aenvironment.
According to
Knoblauch (1905), salamander feeding
requirements do not decrease even at 9°C.
lotic

My observations reveal the upper thermal
limit of adult foraging activity as 23-25°C

range.

At these temperatures animals

respond to

approaching invertebrates, but

don't make attempts to catch them.

group 1 consists of recently hatched larvaethat have began their active feeding. Group
3 is metamorphic. Their share in larval
samples markedly decreased to August due
to entering land by metamorphs. Thus, thelack of annual rings in the bones of most ofthe

specimens from groups

1

and 2

indicates their birth was mainly in the given

1968;

Animals larger than 27 mm andnewly metamorphosed specimens had one
annual ring, so they had survived one
The largest specimens of a
wintering.
birth
given
year only slightly differ fromthe smallest that had wintered. This could

Hemmerling and Obst, 1968; Koroljov,

be explained by a prolonged salamander

1986; Mertens, 1942; my data).

breeding period.

year.

Discussion

Fromspringtoautumn larvae ofdifferent size groups are found in streams(Berg,

1910;

Cyren,

1911;

Evidently

Asiatic Herpetological ResearchVol. 4, p. 128

TABLE 1.

Prey size composition of Caucasian Salamander larvae (June, 1985).

A. Proportions d m ax/Lt. or.,dmax.mm0.1-0.51%(n=13)

February 1992

Vol. 4, p. 129

Asiatic Herpetological Research

TABLE 2. Prey taxonomic spectrum of Mertensiella caucasica in ontogenesis. 1-3

February 1992-

larval size groups;

1-% by prey number; 2-% by prey weight. For
juv.
adults from Baniskhevi (n=67) data of Ekvumlshvili (1948); from Akhaldaba (n=21) data of Bozhansky and-newly metamorphosed specimens; by horizontal:

Semenov(1982).

Asiatic

Vol. 4, p. 130

Herpe to logical Research

Salamander larvae feed on, as comparedwith larvae of limnophilous tailed
Narrow
amphibians (Cyren, 1911).
ofrelatively
consisting
trophic spectrum
large invertebrates as far as low occurenceof small forms in stream samples served asMuseumAcademy mission toEzhegodnik
Museya Imperatorskoi

of Imperial

Caucasusin1909].

Zoologicheskgo.
Academii Nauk 15:153-170.

percentage of larval Trichoptera insalamander diets may be connected with
their low electivity. Probably the latter isdue to the difficulty of swallowing thisenergetically improfitable prey (sand casemass could be of 5-6 times heavier than thefood object).

1973.

Tiirkiye

Ege Universitesi matbaasi,

Bomova-Izmir. 155pp.

Positive electivity in larval feeding is
weakly expressed. Evidently, their dietreflects mainly the available invertebrate
composition in the environment. A low(in Russian).

BASOGLU, M. AND N. OZETI.
amphibileri.

its indirect confirmation.

February 1992

(in Turkish).

BORJA, SANCHIZ, F. DE, AND M. MLYNARSKI.
1979.
Pliocene salamandrids (Amphibia
Acta zoologica cracov

Caudata) from Poland.
24(4):175-188.,

BOZHANSKY, A. T. AND D. V. SEMENOV.

1982.

[Materials on biology of Mertensiella caucasica(Amphibia, Urodela)]. Zoologichesky Zhurnal.
61(8): 1188-1192. (In Russian).

CUMMINS, K. W. AND J. C. WUYSHECK.

1971.

Caloric

The environmental conditions of the
Caucasian Salamander are very uniform
and almost unchanged since Pleistocene
Indirect(Wolterstorff et al., 1936).
confirmation of an endemic ecologicalequivalents for investigations inInternazionale
ecological energetics.
Vereinigung fur theoretische und angewandte
Limnologie, Mitteilung N 18. Stuttgart. 162
pp.

CYREN, 0.

the parasitological data. The
Caucasian Salamander is the host of four

1911. Beitrage zur Kenntnis deskaukasischen Feuersalamanders, Salamandra
caucasica (Waga), seiner Lebensweise undparasitic nematod species. Three of them
are specific for this amphibian (Lomakin,

Fortpflanzung. Berichte der Senckenbergischen
naturforschenden Gesellschaft in Frankfurt am

1982; Sharpilo, 1976, 1978; Timofeeva
and Sharpilo, 1979).
Thus, the highCaucasian Salamander trophic niche

Main 42:175-189.

patternisstability at each step of its life history
reflects the stenobiont state of this species

in

the

western Transcaucasianrelictecosystems.

N.

1940.

[Amphibians of

district].

Trudy

biologischeskiikh stanzij Narkomprosa GSSR,
Tbilisi 1940(1):1 10-121. (in Russian).

1948.
[Feeding of
Caucasian Salamander (Mertensiella caucasica

EKVTIMISHVILI, Z. S.

AcknowledgmentsD.

EKVTIMISHVILI, Z. S.
Borzhom-Bakuriani

Tarkhnishvili

has

Trudy Zoologicheskogo Instituta
Waga)].
Academii Nauk Georgian SSR 1948(8):239-

carefully

245. (in Georgian).

provided for me the translation of papers in

Georgian and I. A. Serbinova with theinformation on the start of larval feeding in
the laboratory. They jointly with R. V.
Tartarashvili gave me important assistancein the field.

E. M. Smirina has seen bone

sections and proposed valuable remarks.
L. N. Kuzmin gave important help insalamander photography.

For all these

HEMMERLING, J., AND F. J. OBST.

1968.

Zur

Normalentwicklung von Mertensiella caucasia
Salamandra(Amphibia, Salamandridae).
1968(4):4-9.

KNOBLAUCH, A.

1905.

Der kaukasische

Feuersalamander, Salamandra caucasia (Waga).
Berichte der Senckenbergischen naturforschenden

Gesellschaft in Frankfurt am Main 36:89-1 10.

persons I express my sincere gratitude.

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