Is the Common Frog, Rana temporaria Linnaeus, 1758, becoming uncommon? Evidence from 23 years of monitoring brown frogs in the Pilis-Visegrád Hills, Hungary

Abstract

Regular and annual monitoring of amphibians was initiated in Hungary in 2001, including within the Pilis-Visegrád Hills, one of the driest mountain regions in northern Hungary. The area is largely covered by forest and comprises ca. 140 ponds. These ponds are relatively small, many are temporary, and water levels can decrease significantly even in those that persist throughout the year. The 23-year-old monitoring program was initiated in one pond and after some conceptual changes it is currently being undertaken in 18 ponds. The distribution of Rana temporaria in Hungary is limited to regions with a higher and cooler microclimate, and it has long been observed in the Pilis-Visegrád Hills. In the first half of the monitoring period, we observed the species in most of the sampled ponds, although we consistently detected a lower number of eggs than those of Rana dalmatina, which utilises the same ponds for breeding in the same period as R. temporaria. Rana temporaria egg clutches have experienced a significant decline from the sampled ponds, with only one pond harbouring the species in 2023. The primary cause of this range reduction is quite likely the desiccation of the Pilis-Visegrád Hills, caused by the gradual but continuous increase in average temperature and decrease and more erratic precipitation events. A second factor may be the disturbance caused by wild game in the ponds, which decrease both water quantity and quality for breeding amphibians. We also outline other potential, and unlikely, factors which have been implicated in declines elsewhere.

Full text

Introduction
Massive declines in amphibian populations were
detected at the end of the 1980s in the USA, and this
phenomenon was subsequently observed worldwide
(Blaustein and Wake, 1990). This observation caused
an alarm among ecologists, and several authors began
speculating on the factors involved in these declines,
attempting to tease out natural fluctuations and human-
induced stressors (Wake, 1991; Blaustein et al., 1994;
Pechmann and Wilbur, 1994). A number of causes were
hypothesised, including the emerging chytridiomycosis
epidemic, a potentially lethal fungal infection (Berger
et al., 1998), as well as numerous climatic factors and
anthropogenic impacts on landscapes and habitats. In the
early 2000s, the first alarming news reports, successive
speculations, and analyses about the causes gave
impetus to the retrospective processing of previously
collected population data (e.g., Alford et al., 2001). The
need for rigorous long-term local monitoring to assess
and substantiate such reported declines is now widely
recognised (Collins and Halliday, 2005; Lindenmayer
and Likens, 2010; White, 2018), before commencing
with conservation interventions.
Regular long-term amphibian monitoring was
launched in our study area, the Pilis-Visegrád Hills
of central northern Hungary, in 2001 as part of the
large-scale National Biodiversity Monitoring System
(NBmR), a broad, national multitaxon monitoring
program (MoEW, 2007; FM-TF, 2015). The NBmR
Committee originally designated six regions in Hungary
for long term amphibian monitoring but their number
increased to nine by 2020.
Frequently observed amphibian species in the study
area include Rana dalmatina (Fitzinger, 1838), R.
temporaria (Linnaeus, 1758), Bufo bufo (Linnaeus,
1758), and Lissotriton vulgaris (Linnaeus, 1758).
Occasional occurrences have also been observed for
Salamandra salamandra (Linnaeus, 1758), Bombina
bombina (Linnaeus, 1761), B. variegata (Linnaeus,
1758), Hyla arborea (Linnaeus, 1758), Pelobates fuscus
Herpetology Notes, Volume 18: 235–245 (published online on 26 March 2025)
Is the Common Frog, Rana temporaria Linnaeus, 1758, becoming
uncommon? Evidence from 23 years of monitoring brown frogs
in the Pilis-Visegrád Hills, Hungary
Brandon P. Anthony1,* and Tibor Kovács2
1 Department of Environmental Sciences and Policy, Central
European University, Quellenstrasse 51, Vienna A-1100,
Austria.
2 Hungarian Biodiversity Research Society, Hunyadvár u. 43/a,
Budapest H-1165, Hungary.
* Corresponding author. E-mail: anthonyb@ceu.edu
© 2025 by Herpetology Notes. Open Access by CC BY-NC-ND 4.0.
Abstract. Regular and annual monitoring of amphibians was initiated in Hungary in 2001, including within the Pilis-Visegrád
Hills, one of the driest mountain regions in northern Hungary. The area is largely covered by forest and comprises ca. 140
ponds. These ponds are relatively small, many are temporary, and water levels can decrease significantly even in those that
persist throughout the year. The 23-year-old monitoring program was initiated in one pond and after some conceptual changes
it is currently being undertaken in 18 ponds. The distribution of Rana temporaria in Hungary is limited to regions with a higher
and cooler microclimate, and it has long been observed in the Pilis-Visegrád Hills. In the first half of the monitoring period,
we observed the species in most of the sampled ponds, although we consistently detected a lower number of eggs than those
of Rana dalmatina, which utilises the same ponds for breeding in the same period as R. temporaria. Rana temporaria egg
clutches have experienced a significant decline from the sampled ponds, with only one pond harbouring the species in 2023.
The primary cause of this range reduction is quite likely the desiccation of the Pilis-Visegrád Hills, caused by the gradual but
continuous increase in average temperature and decrease and more erratic precipitation events. A second factor may be the
disturbance caused by wild game in the ponds, which decrease both water quantity and quality for breeding amphibians. We
also outline other potential, and unlikely, factors which have been implicated in declines elsewhere.
Keywords. amphibian decline, climate change, European agile frog, Common frog, Rana dalmatina

Brandon P. Anthony & Tibor Kovács
236
(Laurenti, 1768), and Pelophylax esculentus complex
(Linnaeus, 1758) (Vági et al., 2013). The current
focus of data collection is on two syntopic species, the
Common Frog, R. temporaria, and the European Agile
Frog, R. dalmatina.
The Common Frog is a relatively robust member
of the Family Ranidae and the largest of the so called
‘brown frog’ group. Although it has a wide range across
Europe (IUCN SSC Amphibian Specialist Group,
2022), it occurs with a rather mosaic pattern in Hungary,
primarily in the northern and western hilly ranges
(Vörös et al., 2014). Due to its restricted thermal needs
the species lives at higher elevations or some lower
areas of the Pilis-Visegrád Hills where the local climate
is cooler and more humid than in the drier lowlands
(Vági et al., 2013). The Common Frog primarily prefers
forested habitat types and mostly breeds in small and,
in many cases, seasonal ponds in Hungary (Hettyey et
al., 2003).
Multi-year studies from Sweden (Loman and
Andersson, 2007), Italy (Tiberti, 2015), Scotland
(Paterson, 2017), Bavaria (Malkmus and Weddeling,
2017), and Denmark (Fog, 2024) have shown stable
or increasing Common Frog populations. However,
localised declines have been noted in Switzerland
(Gerlach and Bally, 1992; Meyer et al., 1998), Britain
(Cunningham et al., 1996), Italy (Tiberti, 2011;
Chiacchio et al., 2022), Poland (Pabijan et al., 2023),
and Austria (Kyek et al., 2017).
Due to its restricted distribution in Hungary, variable
population trends elsewhere in Europe, coupled with
its interspecific competition with the Agile Frog in the
study area (Hettyey et al., 2014) and Batrachochytrium
dendrobatidis being first observed in the Common Frog
in the study area as early as 2004 (Baláž et al., 2014),
this species’ population trend is the focus of this paper.
Materials and Methods
Study area. The Pilis-Visegrád Hills are located approx.
30 km north of Budapest (Fig. 1A). The area covers
approximately 387 km2 and its highest elevation reaches
756 m (UNESCO-MAB, 2017). Annual precipitation is
approx. 650–700 mm depending on the elevation and
the exposure, and annual mean temperature between
1991 and 2020 varied between 8.5–9.5°C (OMSZ
n.d.). The study area has minimal agricultural influence
and the major forest types are oak (Quercus cerris/Q.
petraea), oak-hornbeam (Q. cerris/Carpinus betulus),
and beech (Fagus sylvatica). The region is moderately
dry, and there are only seven permanent streams. Due to
the relatively low precipitation, the number of natural
pools and ponds is low, and most are artificial watering
or wallowing places created for wild game.
Breeding habits. Most of the forest ponds in Pilis-
Visegrád Hills are shallow, of anthropogenic origin, and
their primary function is to provide water for wild game.
Of ca. 140 ponds identified in the Pilis-Visegrád Hills,
approximately 50–60 are used for reproduction by both
R. dalmatina and R. temporaria with strong temporal
overlap. Common Frog breeding lasts only a few days,
and the offspring leave the water in July.
Consistent with Fog’s (2024) observation in Denmark,
the two species lay their eggs in discrete fashion in the
Pilis-Visegrád Hills: R. temporaria oviposits at pond
edges in agglomerations, while R. dalmatina in isolated
Figure 1. (A) Location of the Pilis-Visegrád Hills region in Hungary, (B) Location of 18 amphibian forest pond sampling sites in
Pilis-Visegrád Hills (Map data from OpenStreetMap®).

clutches anywhere in the pond where suitable substrate
is available, in at least 5–10 cm of water depth, muddy
or rocky bottoms, and preferably with wooden branches
or emergent vegetation to which egg clutches can be
affixed (Fig. 2).
Monitoring protocol. In the first year of monitoring,
we surveyed the entire amphibian community in only
one forest pond (A1; see monitored pond location
codes in Table 1 and Fig. 1B), but as the concept and
application of monitoring changed, we increased the
number of ponds to five by 2002 (B), eight by 2003
(C), 15 by 2014 (D), 16 by 2015 (E), and 18 by 2021
(F). Criteria for pond selection included (i) physical
permanence (e.g. wheel tracks and cavities created by
upturned trees were excluded), (ii) ease of access, (iii)
surface area > 10 m2, and (iv) minimal or no water flow
(e.g. creeks with small dams were excluded).
The elevation of the ponds ranged from 260–615 m,
the surface area from 28–6182 m2, the maximum water
depth from 10–150 cm, and the sediment depth from
0–40 cm (Table 1). No monitoring took place in 2011
due to government budget constraints.
The timeframe of the monitoring period covered the
annual breeding season of the two species between
mid-March and mid-April. The NBmR monitoring
protocol consists of five visits to each pond. The first
visit occurred usually in the first week of February
when the general conditions of the ponds are checked
(presence of water, evidence of large-scale proximate
habitat alterations due to clear-cutting, etc.). The second
visit was usually conducted in mid-March when we
calculated, by the current weather conditions, that the
first clutches should have been laid. Then, in intervals of
4–5 days, we visited two more times until we observed
that the number of clutches did not increase. One final
visit was made after the breeding season when the water
level and the success of the tadpole development was
checked.
The actual objects of the surveys are the egg clutches
since their observation and identification is much
more reliable than that of adult animals (Loman and
Andersson, 2007; Tiberti, 2015). Egg clutches were
identified to species following Hettyey et al. (2014)
using four parameters: clutch size, shape, position,
and egg jelly translucency. Each pond was surveyed
for egg clutches by walking slowly around the pond
perimeter and, if needed, by wading through the pond
along parallel transects of 2–3 m width. This enabled
the visual observation of the entire pond. Each of the
visits involving egg clutch observations lasted between
10 and 70 min.
Driven by our monitoring data, we hypothesised that
there would be no significant change in egg clutches of
either R. dalmatina or R. temporaria across our sampled
ponds in the 23-year period of our monitoring, nor in
the various adjustments of our pooled ponds (5 ponds,
8 ponds, 15 ponds, 16 ponds, 18 ponds). To test our
hypotheses, we first calculated the population trend
for both species at each of the 18 ponds using the non-
parametric Mann-Kendall Test to determine whether
a time series has a monotonic upward or downward
population trend, and then used the same test across our
pooled ponds. The Mann-Kendall Test does not require
that the data be normally distributed or linear. Alpha
level was set at 0.05, continuity correction was applied,
and confidence interval (Sen’s Slope) was set at 95%.
We used Kendall’s tau-b (τb) values as a measure of
the strength and direction of the trend in our reporting
(Daniel, 1990). In addition, simple linear regression
was used to test if pond parameters (elevation, surface
area, water depth, and sediment depth) significantly
predicted peak (maximum) egg clutch values across all
our ponds.
Is the Common Frog becoming uncommon? Evidence from 23 years of monitoring 237
Figure 2. Commonly seen position of Rana dalmatina and R.
temporaria clutches in small bodies of water, here in Újhálási
Dagonya Pond, Hungary. Photo by Tibor Kovács.

Brandon P. Anthony & Tibor Kovács
238
Name Site Code WGS4 N WGS4 E elevation
(m)
area
(m
2
)
max depth
(cm)
sediment
(cm)
monitoring
period
R. temporaria R. dalmatina
max mean τ
b
max mean τ
b
János-tó A1 47.71427 19.01975 410 6182 150 10 2001-2023 55 11.1 -0.555*** 711 418.3 0.065
Alsó-hosszúrét B2 47.71551 19.02274 380 196 110 5
2002-2023
0 0.0 --- 106 51.4 -0.301*
Paprét felső B3 47.73925 19.01167 484 306 50 40 15 1.6 -0.373* 162 71.6 0.394**
Paprét középső B4 47.73888 19.01189 484 294 110 40 19 4.7 -0.591*** 142 82.8 -0.381**
Paprét alsó B5 47.73795 19.01352 480 194 30 30 72 12.0 -0.690*** 101 44.4 -0.373**
Jeges 1 C6 47.72664 19.01583 545 226 30 20
2003-2023
9 1.0 -0.451** 121 35.4 -0.349**
Jeges 2 C7 47.72715 19.01643 545 397 80 15 20 3.6 -0.379* 225 95.9 -0.228
Jeges 3 C8 47.72684 19.01679 545 181 30 0 25 4.9 -0.592*** 105 25.6 -0.288*
Szarvasszérű alsó D9 47.72941 19.00691 530 289 50 5
2014-2023
11 1.9 -0.426 73 25.6 -0.135
Szarvasszérű felső D10 47.72998 19.00862 540 207 30 10 3 0.3 -0.348 33 9.6 -0.163
Erdészház-kicsi D11 47.73827 19.01210 470 31 40 5 0 0.0 --- 8 4.2 -0.398
Erdészház-nagy D12 47.73828 19.01211 470 59 60 5 18 3.3 -0.544* 21 10.4 -0.405
Paprét-dagonya D13 47.73666 19.01410 475 28 30 30 2 0.2 -0.348 29 11.6 -0.405
Újhálási dagonya D14 47.74319 19.00252 440 141 60 20 68 31.0 -0.200 160 44.8 0.289
Újhálási tó D15 47.74292 19.00382 440 157 30 20 25 6.1 -0.680** 92 46.5 0.467*
Süldős E16 47.73464 19.01908 462 110 10 20 2015-2023 26 2.9 -0.471 114 62.3 -0.111
Mélymocsár F17 47.70762 19.04016 260 1331 60 10 2021-2023 0 0.0 --- 219 126.7 -0.333
Hubertus F18 47.73488 18.92402 615 275 60 20 13 11 -0.816 52 45.0 0.333
Note: * p < 0.05, ** p < 0.01, *** p < 0.001
Table 1. Pond parameters (coordinates, elevation, surface area, maximum water depth, maximum sediment depth), monitoring period, maximum egg clutch number, mean egg clutch number per
year, and Kendall Tau-b coefficient for both species. Tau-b values in bold are significant.

Results
We conducted a total of 1255 visits to the 18 ponds
sampled over the 23-year monitoring period, resulting
in 251 recorded egg clutch observations (Appendix 1).
Rana dalmatina appears unambiguously first to the
breeding ponds, and the entire breeding season of R.
temporaria is embedded within that of R. dalmatina,
with 100% temporal overlap (personal observation).
Currently, at the beginning of the breeding season
(second half of March), R. dalmatina arrive first, and
egg-laying can take up to 2–3 weeks. In contrast, R.
temporaria usually appear a week later and mating is
limited to 5–6 days (personal observation).
A total of 64,805 egg clutches were recorded, of
which 96.2% were R. dalmatina and only 3.8% were
R. temporaria. The proportion of R. temporaria to R.
dalmatina egg clutches ranged between only 0.6%
(2023) to 16.8% (2015), with a mean of 7.0% ± 0.049
across all years. Rana temporaria showed population
declines in all 15 ponds where it had been present, with
significant declines occurring in nine ponds (Table 1).
Rana dalmatina was present in all ponds and in much
greater numbers than R. temporaria (where that species
occurred), and the former showed significant declines
in five of the 18 ponds with significant increases in two
ponds.
Examination of pooled pond data shows that even
though fluctuations occurred, R. dalmatina remained
stable and showed no significant population trends over
the various time periods (Table 2; Fig. 3). In contrast, R.
temporaria populations showed a significant decrease
at the sites where longer monitoring had been conducted
(5 and 8 ponds), and continue to show declines (although
not significant) at the shorter period monitoring sites
(15, 16, and 18 ponds). In fact, the species disappeared
entirely from 14 of 15 ponds where its presence was
detected at the beginning of the surveys, with only
seven egg clutches being observed in one of our 18
ponds sampled in 2023.
We found that the peak count for species egg clutches
was only significantly positively correlated with R.
dalmatina and pond surface area (R2 = 0.90, F(1,16) =
144.49, p < 0.001). Other tested pond parameters were
found to be non-significant in our sampled ponds.
Is the Common Frog becoming uncommon? Evidence from 23 years of monitoring 239
Figure 3. Total number of Rana temporaria (Rtemp; blue) and R. dalmatina (Rdal; orange) egg clutches observed at the eight
ponds sampled from 2003–2023.

Discussion
Our long-term monitoring of brown frog egg clutches
constitutes the first reported significant population
decline of R. temporaria in Hungary and, to our
knowledge, in Eastern Europe. The factors influencing
the observed decline are not yet known, but here we
offer some informed insights and hypotheses to be
further tested, discussed in order of factor likelihood.
Probable factors. Climate change has been
demonstrated to have both direct and indirect effects
on amphibian populations generally, due in part to
their highly permeable and sensitive skin, unshelled
and desiccation-prone eggs, limited dispersal ability,
and high site fidelity (Blaustein et al., 2010; Li et al.,
2013; Steigerwald, 2021). Climatic change has also
been indirectly implicated in R. temporaria declines
specifically (Neveua, 2009; Pastorino et al., 2023)
and has been posited (although not tested) in reported
declines of R. temporaria in alpine landscapes in Austria
(Kyek et al., 2017) and Italy (Chiacchio et al., 2022).
We surmise this factor is also largely responsible for our
observed decline. Application of climatic models show
a shift in the climate throughout Hungary, including
an increase of mean annual temperature of approx.
1.7°C within the Pilis-Visegrád Hills between 1981 and
2020 (OMSZ, n.d.). However, it is not clear how this
shift towards a warmer climate is affecting amphibian
populations in our study region and requires further
investigation. On a continental scale, Araújo et al.
(2006) modelled the forecasted gains and losses of both
amphibians and reptiles across Europe due to climate
change and have shown that amphibians with limited
dispersal ability are likely to experience substantial
losses in the higher elevations in Eastern Europe.
Our observation is that after the 2012 drought, the
complete desiccation of some temporal breeding ponds in
spring became a more frequent phenomenon (Appendix
1) and after this period many of the ponds previously
used for breeding by R. temporaria yielded no further
egg clutches of this species. Since R. temporaria lays
its eggs at the shallower edges of breeding ponds, they
are at a much greater risk of desiccation than the eggs
of R. dalmatina when water levels decrease. It was a
frequent observation during our 23 years of monitoring
that when all R. temporaria eggs were dry, a significant
number of R. dalmatina eggs survived in the central,
deeper parts of the pond.
Secondly, we hypothesise that the observed decline
may also be due to pond disturbance by wild game. In
the past decade, the wild game stocks of Pilis-Visegrád
Hills have increased, particularly of wild boar, Sus
scrofa (OVA, 2018). After 2015, a series of mild winters
occurred, contributing to the overwintering survival
of wild game. The wallows of wild boar, roe deer
(Capreolus capreolus), and red deer (Cervus elaphus)
have caused significant damage to some pond edge
ecosystems (Fig. 4), and it appears that in some cases
R. temporaria are unable to tolerate the combination
of reduced water level and habitat destruction. For
Brandon P. Anthony & Tibor Kovács
240
Table 2. Population trends across pooled sampled sites from 2002–2023. Tau-b values in bold are significant.
Number of ponds 5 8 15 16 18
Observation period 2002-2023 2003-2023 2014-2023 2015-2023 2021-2023
R. dalmatina
τ
b
0.010 -0.011 -0.067 -0.278 1.000
n 21 20 10 9 3
R. temporaria
τ
b
-0.726**** -0.739**** -0.315 -0.423 -0.333
n 21 20 10 9 3
**** p < 0.0001
Figure 4. Wild game damage to Újhálási Dagonya Pond,
Hungary. Photo by Tibor Kovács.

example, when in 2017 the number of R. temporaria
eggs dropped to zero in one of our sampled ponds that
had been exposed to heavy wild game activity (Újhálás
tó), the number of eggs in a nearby (< 100 m) pond
(Újhálás dagonya) suddenly increased (see Appendix 1
(A)), suggesting a migration by frogs seeking a more
suitable oviposition site nearby. However, as dispersal
distances are greatly limited for anurans (Cayuela et al.,
2020), more isolated ponds harbouring amphibians will
be more vulnerable to such disturbance effects.
Potential factors. A third factor that may (at least
in part) be responsible for the decline is the emerging
chytridiomycosis disease caused by the fungal pathogen
Batrachochytrium dendrobatidis (hereafter Bd;
Longcore et al., 1999). Although there was evidence of
some infected R. temporaria individuals in the northern
area of our study area in 2004 (Baláž et al., 2014),
the most recent investigation between 2009 and 2015
on the presence of Bd across nine regions in Hungary
found zero positive of 78 samples from nine amphibian
species (including R. temporaria) in the Pilis-Visegrád
Hills (Vörös et al., 2018). In fact, none of the 150 brown
frogs sampled for that nation-wide study were found
to be Bd positive. However, we acknowledge that this
zoonoses is dynamic, and its prevalence and potential
impact should be part of systematic surveillance
programs (Canessa et al., 2014).
Last, interspecific competition has previously been
reported between R. dalmatina and R. temporaria in
breeding ponds in the Pilis-Visegrád Hills (Hettyey et
al., 2014), in which heterospecific amplexus resulted
in a decrease of the average fertility success of R.
dalmatina, although interspecific competition during
the larval stage was not tested and may be worthy
of targeted investigation. In contrast, however, we
observed a long-term decline only in R. temporaria and
we assume that this aspect of interspecific competition
is not a contributing factor in our case.
Unlikely factors. Previous attempts to disentangle the
determinant factors of amphibian population declines
have also included the persistence of woody debris in
Poland (Pabijan et al., 2023). They demonstrated that
amphibian abundance, biomass, and body condition
were higher in old growth versus managed forest
stands. However, as forestry practices have not changed
dramatically and only R. temporaria has declined
from our study area, we do not believe that this is a
determinant factor in our case. A second factor that is
unlikely to be present is dietary competition between
the two species, which was shown to be non-significant
in Romania (Hodisan et al., 2010). Third, since we did
not observe any carcasses of either juveniles or adults at
our sites, it is unlikely that periodic mass die-offs have
occurred because of ‘red-leg disease’, which has been
implicated in mass mortalities in Britain (Cunningham
et al., 1996) and in mountain ponds in Italy (Tiberti,
2011). Finally, Meyer et al. (1998) postulated that the
decline of R. temporaria at one of their three studied
sites in Switzerland was due to the introduction of
predatory fish, which we can safely rule out in our study
since fish are absent in all the sampled ponds.
In conclusion, with the increasing amount of
interdisciplinary and multifactorial effort being applied
to discern the decline of amphibian populations (Hof et
al., 2011; Falaschi et al., 2019), it is clear that determinant
factors often work in additive or cumulative fashion.
What is equally clear is that a more detailed hypothesis-
driven investigation and monitoring program beyond the
requirements of the NBmR is needed to explicate these
possible factors (and others) on the fate of amphibian
populations in the Pilis-Visegrád Hills. To this end,
in addition to expanding the number of our sampling
ponds to 40–50, we are now collaborating with relevant
stakeholders to design and implement such a program
that involves a microclimate monitoring network,
wild game exclusion test sites, and further exploring
interspecific relationships between the focal species.
Acknowledgments. We thank Pilis Parkerdő Zrt and Duna-Ipoly
National Park Directorate for support, and Paul Ashley, CEU
Masters students and MBKT members for data collection. We
also thank Anastasia Kvasha for the production of Fig. 1. Last, we
thank the Editor-in-Chief, the Associate Editor, Balázs Vági, and
one anonymous reviewer for constructive comments on earlier
versions of this article.
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Is the Common Frog becoming uncommon? Evidence from 23 years of monitoring 243

Appendix 1
(A) Rana temporaria egg clutches (Note: Yellow highlighted cells represent years when pond was completely dry at start of breeding season)
Year János-
tó
Alsó
Hosszúrét
Paprét
alsó
Paprét
középső
Paprét
felső
Jeges
1
Jeges
2
Jeges
3
Szarvasszérű
alsó
Szarvasszérű
felső
Újhálás
dagonya
Újhálás
tó
Paprét
dagonya
Erdészház
kicsi
Erdészház
nagy Süldős Mélymocsár Hubertus
2001 44
2002 55 0 11 14 15
2003 15 0 72 19 0 6 3 17
2004 31 0 60 19 0 0 0 8
2005 0 0 22 0 0 0 0 5
2006 30 0 6 4 1 1 15 8
2007 24 0 40 8 6 9 11 7
2008 0 0 12 0 5 4 0 12
2009 30 0 23 17 0 0 20 25
2010 0 0 5 4 0 0 0 10
2011 no monitoring conducted
2012 0 0 0 3 0 0 12 0
2013 9 0 0 10 6 0 8 0
2014 0 0 0 0 0 0 0 0 0 0 23 21 0 0 0
2015 6 0 0 0 0 0 3 3 6 3 38 25 2 0 18 26
2016 0 0 0 0 0 0 0 0 2 0 22 4 0 0 9 0
2017 0 0 0 0 0 0 0 2 11 0 29 10 0 0 5 0
2018 0 0 0 0 0 0 0 0 0 0 63 0 0 0 0 0
2019 0 0 0 0 0 0 0 0 0 0 62 0 0 0 1 0
2020 1 0 0 0 0 0 0 0 0 0 68 1 0 0 0 0
2021 0 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 13
2022 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 13
2023 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 7
Appendix 1.
(A) Rana temporaria egg clutches (Note: Yellow highlighted cells represent years when pond was completely dry at start of breeding season)
Brandon P. Anthony & Tibor Kovács
244

Appendix 1. Continued.
(B) Rana dalmatina egg clutches (Note: Yellow highlighted cells represent years when pond was completely dry at start of breeding season)
(B) Rana dalmatina egg clutches (Note: Yellow highlighted cells represent years when pond was completely dry at start of breeding season)
Year János-
tó
Alsó
Hosszúrét
Paprét
alsó
Paprét
középső
Paprét
felső
Jeges
1
Jeges
2
Jeges
3
Szarvasszérű
alsó
Szarvasszérű
felső
Újhálás
dagonya
Újhálás
tó
Paprét
dagonya
Erdészház
kicsi
Erdészház
nagy Süldős Mélymocsár Hubertus
2001 452
2002 524 78 72 112 74
2003 671 68 65 107 42 121 72 105
2004 680 90 61 138 52 51 225 41
2005 305 29 42 88 25 18 141 11
2006 611 51 81 98 46 32 69 15
2007 102 70 40 111 31 56 54 16
2008 65 82 94 129 96 71 101 44
2009 651 67 52 61 34 81 124 70
2010 255 100 11 82 42 31 85 28
2011 no monitoring conducted
2012 0 0 0 142 114 0 98 0
2013 141 0 0 121 74 0 194 0
2014 245 21 101 57 93 22 64 0 5 0 5 21 16 6 10
2015 269 106 65 33 63 25 86 30 30 21 26 23 29 7 19 25
2016 581 84 45 43 78 38 77 59 39 33 13 31 16 7 15 70
2017 447 55 44 66 67 47 90 15 41 14 160 45 14 8 21 89
2018 466 73 35 39 42 39 98 40 73 3 56 85 6 6 9 69
2019 585 26 29 52 92 17 75 0 0 0 27 92 1 0 4 114
2020 711 37 39 25 72 33 78 22 34 7 12 25 4 8 14 86
2021 306 19 5 69 94 12 30 0 12 4 19 39 9 0 0 21 219 37
2022 573 16 10 96 162 1 98 0 0 0 72 41 0 0 0 35 76 52
2023 562 8 41 70 111 12 58 15 22 14 58 63 21 0 12 52 85 46
Accepted by Frederic Griesbaum
Is the Common Frog becoming uncommon? Evidence from 23 years of monitoring 245