Žiga FIŠER et al: The utility of non-genetic data collected during genetic monitoring... / »SOS Proteus« – FIELD NOTE 
Biotehniška fakulteta Univerze v Ljubljani in Nacionalni inštitut za biologijo, Ljubljana, 2017 
35 
The utility of non-genetic 
data collected during genetic 
monitoring of proteus 
populations 
 
Uporabnost ne-genetskih podatkov, 
pridobljenih med genetskim 
monitoringom močerila 
 
Žiga FIŠER1, Valerija ZAKŠEK1, Magdalena 
NĂPĂRUȘ-ALJANČIČ2, Gregor ALJANČIČ2,  
Teo DELIĆ1, Peter TRONTELJ1  
1Department of Biology, Biotechnical Faculty, 
University of Ljubljana, Jamnikarjeva 101,  
SI-1000 Ljubljana, Slovenia; E-mails: 
ziga.fiser@bf.uni-lj.si, valerija.zaksek@bf.uni-lj.si, 
teo.delic@bf.uni-lj.si, peter.trontelj@bf.uni-lj.si 
2Tular Cave Laboratory, Society for Cave Biology, 
Oldhamska cesta 8a, SI-4000 Kranj, Slovenia;  
E-mails: magda.aljancic@gmail.com, 
gregor.aljancic@guest.arnes.si 
 
Proteus anguinus is the only obligate cave 
vertebrate of the European continent (Aljančič et 
al. 1993, Parzefall et al. 1999) and a Dinaric Karst 
endemic (Sket 1997). In the past decades, 
population declines of this charismatic species 
have been reported from a number of localities 
(Sket 1997, Hudoklin 2011). However, only 
recently initiatives have been undertaken to 
develop and establish schemes for monitoring 
population numbers and distribution. As a part of 
these initiatives, various new methodological 
approaches have been tested: a) in situ 
underwater animal tagging (Balázs et al. 2015),  
b) detection via environmental DNA (Aljančič et al. 
2014, Gorički et al. 2017, Vörös et al. 2017), and 
c) genetic monitoring (Trontelj & Zakšek 2016). 
 
Genetic monitoring as described in Trontelj & 
Zakšek (2016) requires catching substantial 
numbers of live proteus. In order to maximize the 
amount of scientific information obtained once an 
individual is caught, besides DNA, a number of 
other biological data are collected. These include 
body length and mass as well as observations on 
anomalies such as injuries, pigmentation, gravidity, 
parasites, etc. Body size can be used to assess 
population demography and, conjointly with data 
on injuries and parasites, even health of 
populations. Taking into account possible fixed 
differences in body size between proteus phyletic 
lineages, ecological conditions of cave systems can 
be inferred. Long term monitoring of animals’ body 
size reveals life-history traits, which have been so 
far investigated mostly in captive individuals bred 
in cave laboratories (e.g. Briegleb 1962,  
Durand & Delay 1981, Juberthie et al. 1996, 
Aljančič & Aljančič 1998). In this contribution, we 
present first results based on non-genetic data 
obtained during the fieldwork for the genetic 
monitoring of proteus. 
 
In 2015 and 2016, we extensively sampled proteus 
in several Slovenian caves. These were selected to 
represent populations from all major mitochondrial 
DNA lineages of proteus (Trontelj et al. 2009). 
Each year, we caught about 900 individuals, most 
of them in the Postojna-Planina Cave System. This 
is probably the largest dataset ever assembled for 
natural populations of proteus. Animals were 
caught using diving equipment and hand nets. 
First, a DNA sample was non-invasively taken from 
each individual using a skin swab. Then, body 
length and mass were measured, the animal was 
thoroughly examined for anomalies, photographed, 
and released back to the cave river.  
 
The demographic structure of populations was 
tentatively assessed by estimating the proportion 
of reproductively capable individuals in a 
population. Relying on data from proteus bred in 
captivity (Durand & Delay 1981, Juberthie et al. 
1996, Voituron et al. 2011), we assumed that  
20 cm long animals are at least 18 years old and 
almost certainly already sexually mature. 
According to preliminary results, the proportion of 
reproductively capable individuals differed between 
our samples from different proteus populations. 
For example, in the Črna jama population we 
caught almost exclusively sexually mature animals, 
while in the cave Vetrovna jama pri Laški kukavi 
these represented only about one quarter of all 
individuals found. 
 
The relationship between body length and mass 
was statistically modelled using a power function 
(see legend to Fig. 1 for more details). Preliminary 
results on the length-to-mass relationship in four 
proteus populations for which we had roughly 
similar sample sizes are shown in Fig. 1. 
Substantial differences were found between some 
of these populations. The populations from the 
subterranean Pivka and Reka Rivers differed most. 
At the maximal length of about 30 cm, animals 
Žiga FIŠER et al: The utility of non-genetic data collected during genetic monitoring... / »SOS Proteus« – FIELD NOTE 
NATURA SLOVENIAE 19(1): 35-37 
36 
from the subterranean Reka River were almost 
twice as heavy as animals from the subterranean 
Pivka River. Whether this difference is genetically 
determined or the consequence of differences in 
food abundance and quality between cave 
systems, remains to be investigated. 
 
Some individuals, whose mass was much lower 
than expected for animals of their length, were 
found to be infested with parasites. If a connection 
between infestation and low body mass is 
confirmed by additional cases, such outliers could 
be used to estimate population health. In Planina 
Cave, about 6% of individuals had some minor 
body injuries, mostly cuts in the tail fin and 
missing toes. This percentage was similar in both 
years of sampling, as was the percentage of 
individuals with at least some darkly pigmented 
patches of skin (about 7%). 
 
Genetic identification of captured individuals 
provides an opportunity to assess changes in body 
size. Within a year, none of the 73 so far identified 
recaptured individuals from Planina Cave has 
grown more than one centimeter in length. Their 
change in mass was much more variable, showing 
increase and decrease of up to 8 g. As body mass 
can markedly change already after feeding or 
defecation, this variability needs to be taken into 
account before making conclusions about changes 
in body mass. 
 
Taken together, the fieldwork undertaken in our 
genetic monitoring scheme produces, as a side 
product, a number of additional data that are 
relevant for the biology and conservation of this 
unique and enigmatic amphibian. 
 
Acknowledgements 
We are grateful to Aja Zamolo, Ana Miglioranca, 
Andrej Hudoklin, Anja Kos, Borut Lozej, Ciril Mlinar 
Cic, Claudio Bratoš, Daniela Eilers, Dare Hribar, 
Darja Kolar, Edvard Gregorčič, Ester Premate, 
Franc Kljun, Frank Körner, Gabriela Enache, Gregor 
Bračko, Jan Gojznikar, Jerneja Rovtar, Kaja 
Vukotić, Katarina Novak, Katarina Tušar, Katja 
Leban, Lilijana Bizjak Mali, Lisa Fisler, Ljerka Lah, 
Lucija Slemenšek, Luka Mrzelj, Maja Jelenčič, Maja 
Sever, Manca Velkavrh, Marjeta Konec, Matej 
Simčič, Mike Patton, Mitja Prelovšek, Nataša Sivec, 
Nika Šumer, Primož Gnezda, Rok Kostanjšek, Rožle 
Kaučič, Ryan Riegg, Sandi Vidrih, Sašo Weldt, 
Sebastjan Kovač, Selena Trontelj, Špela Borko, 
Špela Gorički, Tadeja Balanč, Tajda Gredar, 
Tatjana Kordiš, Tobias Trontelj, Urška Ratajc, 
Vinko Kukman, Žan Kuralt, and Živa Hanc for their 
help with the fieldwork. This study was funded by 
the Slovenian Research Agency (Project number 
L1-6731), and co-funded by the Slovenian Ministry 
of the Environment and Spatial Planning and the 
Centre for Cartography of Fauna and Flora (CKFF). 
The research was performed in accordance with 
permits No. 35601-132/2014-4 and No. 35601-
26/2016-4 issued by the Slovenian Environment 
Agency. 
 
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Figure 1. Relationship between body length and mass in four populations of Proteus anguinus. The power function  
M = a Lb (M – mass, L – length, a – intercept, b – slope) was linearized and fitted to the log-transformed data. When 
length increases by 1%, mass increases by b%. 
Slika 1. Odnos med telesno dolžino in maso pri štirih populacijah močerila (Proteus anguinus). Odnos opisuje potenčna 
funkcija M = a Lb (M – masa, L – dolžina, a – presečišče, b – naklon), ki smo jo najprej linearizirali, nato pa ocenili 
vrednosti parametrov a in b za logaritemsko transformirane podatke. Pri povečanju telesne dolžine za 1 % se masa 
poveča za b %.