Depauperate Small Mammal Assemblage in Wolin National Park (Poland): Effects of Insular Isolation, Topography, and Vegetation

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Review of “Depauperate Small Mammal Assemblages in the National Park Protecting Land-Bridge Island Habitats Are Shaped More by Topography Than by Plant Communities”

 

This manuscript presents an interesting study on small terrestrial mammal trapping in Wolin National Park (Poland), along with comparisons and interpretations of the recorded assemblage. The study is valuable, but the English is somewhat convoluted, affecting readability and comprehension. I strongly recommend that the authors revise the manuscript for grammatical accuracy, either with the assistance of a fluent English speaker or through AI-based language tools.

 

The title, while mostly clear, could be refined for better readability and precision. A slight grammatical revision would be:

"Depauperate Small Mammal Assemblages in a National Park Protecting Land-Bridge Island Habitats Are Shaped More by Topography Than by Plant Communities."

 

However, beyond grammatical adjustments, the title does not fully reflect the content of the manuscript. The study is based on a single national park, a relatively short trapping effort, and a discussion of topography versus vegetation that constitutes only a minor section (Section 4.5, less than one page out of 23). To better align with the manuscript’s focus, I suggest a more accurate title, such as:

"Depauperate Small Mammal Assemblage in Wolin National Park (Poland): Ecological Remarks."

 

The abstract also contains several minor grammatical issues. Below is a revised version for improved clarity and conciseness:

 

Terrestrial small mammal species typically assemble according to plant communities, but their assemblage structure is influenced by multiple factors, including large-scale geographic patterns. Despite their ecological significance, small mammals are often underrepresented in biodiversity assessments, and many Polish national parks have lacked comprehensive surveys. This is also the case for Wolin National Park (WNP), Poland’s only national park located on a coastal marine island, previously noted for its unique bat fauna. Here, we surveyed small mammals in WNP using live and pitfall trapping, identifying only nine species—the lowest richness among the five regional national parks (which host 11–13 species based on trapping data alone). Rarefaction analysis indicated a very low probability of detecting additional species with further sampling. This unexpectedly low richness is likely linked to insular isolation and the park’s location at the edge of the regional distributions of three species. Cluster analysis revealed a key pattern in WNP’s small mammal assemblages: a division between two distinct landscape units—moraine hills and the alluvial delta—where Apodemus flavicollis and Apodemus agrarius, respectively, were the predominant species. This division had a greater influence on assemblage clustering than the local vegetation.

 

These grammatical refinements further underscore the need for a comprehensive linguistic revision of the manuscript.

 

Main Concerns

My primary concerns relate to methodological aspects:

 

Trapping Effort: The duration of trapping was very limited—only two days per site, repeated in two consecutive months within a single season. This brief effort may not fully capture the diversity and structure of the assemblage.

Lack of Marking for Recaptures: The absence of individual marking prevents distinguishing new captures from recaptures, which could lead to an overestimation of dominant species and underrepresentation of rarer species.

Both factors raise concerns regarding the interpretation of species richness and assemblage composition. The frequent emphasis on the "astonishing" poverty of the recorded assemblage throughout the manuscript may, at least partially, result from methodological limitations rather than ecological factors alone. I strongly encourage the authors to discuss these methodological constraints and their potential effects on the reported findings.

 

Additionally, the comparison of trapping data with owl pellet-derived assemblages introduces another unavoidable bias. The differences between these two sampling methods are well-documented (see, for example, Formoso et al. 2016. Unraveling the patterns of small mammal species richness in the southernmost aridlands of South America. Journal of Arid Environments 134(Part B):136-144, and references therein). A discussion of these methodological disparities would strengthen the manuscript.

 

Additional Comments

Moderate to minor concerns and further suggestions have been included as comments in the annotated PDF.

 

Overall, this study provides a valuable contribution based on an interesting field effort. The data are analyzed in multiple ways and well integrated into the regional context. However, some of the methodological choices made during fieldwork likely impact the results and should be addressed in a more in-depth discussion.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Poor English, revision much needed

Author Response

This manuscript presents an interesting study on small terrestrial mammal trapping in Wolin National Park (Poland), along with comparisons and interpretations of the recorded assemblage. The study is valuable, but the English is somewhat convoluted, affecting readability and comprehension. I strongly recommend that the authors revise the manuscript for grammatical accuracy, either with the assistance of a fluent English speaker or through AI-based language tools.

Done

The title, while mostly clear, could be refined for better readability and precision. A slight grammatical revision would be:

"Depauperate Small Mammal Assemblages in a National Park Protecting Land-Bridge Island Habitats Are Shaped More by Topography Than by Plant Communities."

However, beyond grammatical adjustments, the title does not fully reflect the content of the manuscript. The study is based on a single national park, a relatively short trapping effort, and a discussion of topography versus vegetation that constitutes only a minor section (Section 4.5, less than one page out of 23). To better align with the manuscript’s focus, I suggest a more accurate title, such as:

"Depauperate Small Mammal Assemblage in Wolin National Park (Poland): Ecological Remarks."

We propose the following title, but we are open to accept Your proposal as well, leaving it to the Editor’s decision:

Depauperate Small Mammal Assemblage in Wolin National Park (Poland): effects of insular isolation, topography and vegetation

The abstract also contains several minor grammatical issues. Below is a revised version for improved clarity and conciseness:

“Terrestrial small mammal species typically assemble according to plant communities, but their assemblage structure is influenced by multiple factors, including large-scale geographic patterns. Despite their ecological significance, small mammals are often underrepresented in biodiversity assessments, and many Polish national parks have lacked comprehensive surveys. This is also the case for Wolin National Park (WNP), Poland’s only national park located on a coastal marine island, previously noted for its unique bat fauna. Here, we surveyed small mammals in WNP using live and pitfall trapping, identifying only nine species—the lowest richness among the five regional national parks (which host 11–13 species based on trapping data alone). Rarefaction analysis indicated a very low probability of detecting additional species with further sampling. This unexpectedly low richness is likely linked to insular isolation and the park’s location at the edge of the regional distributions of three species. Cluster analysis revealed a key pattern in WNP’s small mammal assemblages: a division between two distinct landscape units—moraine hills and the alluvial delta—where Apodemus flavicollis and Apodemus agrarius, respectively, were the predominant species. This division had a greater influence on assemblage clustering than the local vegetation.”

Done, accepted, thank You.

These grammatical refinements further underscore the need for a comprehensive linguistic revision of the manuscript.

Done

Main Concerns

My primary concerns relate to methodological aspects:

Trapping Effort: The duration of trapping was very limited—only two days per site, repeated in two consecutive months within a single season. This brief effort may not fully capture the diversity and structure of the assemblage.

The trapping effort (14 sites, 1098 trap-nights) is, indeed, limited and the results may not fully reflect the diversity of small mammals of the Park. However, the same applies to the four other remaining national parks, which we compared to WPN. The authors provide the following trapping efforts for the remaining parks (number of sites/number of trap-nights): 21/3150, 18/540, 8/1440, 37/1637. We believe all those samples are comparable and if the number of trap-nights in the particular national park is 49% of that in the WPN, yet the species richness in the first park is still 44% higher, it is hardly a low sampling effort in the WPN to be blamed, especially when the more selective trap types were used in the remaining four parks (¾ parks with only live traps and one with limited application of pitfalls). What we believe is crucial for the determination of the actual species richness in the particular area is not the trapping effort but the sample size, i.e. the number of captures/captured individuals, which is a much better parameter to standardize samples among sites/regions/habitats differing in sampling intensity (Willot 2001). The latter in WPN is the second highest among the compared national parks. Notably, the highest species richness was obtained in the park with the lowest number of captured individuals, clearly undersampled, if the species accumulation curves are taken into account.

To make it clear, we provided the information about 1) the total number of trap-nights in WPN (line 154 and Table S2), 2) ranges of the total numbers of trap-nights and sites in the compared parks in the text (line 175-176) but also raw data (numbers for each park) in the Supplementary Materials (Table S2).

Lack of Marking for Recaptures: The absence of individual marking prevents distinguishing new captures from recaptures, which could lead to an overestimation of dominant species and underrepresentation of rarer species.

We referred to that concern in lines 436-431. It remains uncertain, however, if that problem is universal. In one of the national parks we compared our results to (Słowiński National Park, SNP), animals were marked and both numbers, individuals and captures, were provided in the publication (Tab. 1 in Rychlik et al. 2020). Yet, both datasets provided almost identical structure of dominance in small mammal assemblage, with no statistically significant difference (χ²=10.29, df=9, p=0.3) and slightly higher dominance of the most numerous species (A. flavicollis, 20% vs. 29%) as the only notable difference.

Both factors raise concerns regarding the interpretation of species richness and assemblage composition. The frequent emphasis on the "astonishing" poverty of the recorded assemblage throughout the manuscript may, at least partially, result from methodological limitations rather than ecological factors alone. I strongly encourage the authors to discuss these methodological constraints and their potential effects on the reported findings.

As we explained above, all that methodological concerns apply also to the other locations we compared. They were usually sampled during 1-2 seasons, usually with comparable and sometimes with much lower trapping effort, mostly (¾) with a lower number of captures/individuals, often with much more selective traps used than in our study, yet they revealed notably higher species diversity if the species accumulation curves are taken into account. The number of individuals captured in WPN - a much better measure of sampling effort than the number of nights (Willot 2001) - was the second highest among the compared parks (SNP - 410, WNP - 397, DNP - 323, LOVNP - 292, WMNP - 80). So not only our study was based on limited trapping effort but also all the other surveys we compared our study to - if so, then our conclusion about unexpectedly low species richness seems to be valid, especially when no new species were added to the list since the 7th site (out of 14) and since the 188th capture/individual (out of 397). However, we included all those concerns in the discussion (lines 409-429) and conclusions (lines 738-742).

Additionally, the comparison of trapping data with owl pellet-derived assemblages introduces another unavoidable bias. The differences between these two sampling methods are well-documented (see, for example, Formoso et al. 2016. Unraveling the patterns of small mammal species richness in the southernmost aridlands of South America. Journal of Arid Environments 134(Part B):136-144, and references therein). A discussion of these methodological disparities would strengthen the manuscript.

We add a comment on that in lines 609-614. We are fully aware that owl pellet analysis is a great tool for small mammal surveys, it should be noted however that it produces spatially robust data that are very useful when revealing large-scale distribution patterns (e.g. within the whole country or biogeographical region, like Patagonia) but it becomes much less useful when we aim at collecting data about detailed distribution of small mammals within Central European national park or their selection towards particular habitats/plant communities in a patchy, anthropogenically altered landscape. In the case of comparing pellet and trapping data - yes, it has been documented that pellets are less selective and detect significantly more species (Heisler et al. 2016) but the sample in that metaanalysis is strongly biased towards ‘cage-type’ live traps (Sherman, Tomahawk, Longworth, wooden ones) while includes only one study based solely on pitfalls, similar to that used in our survey. As it is already known that live traps and snap traps are generally selective against shrews (we discuss it in chapter 4.2), it should be no surprise that these particular animals (along with arvicoline voles) were usually those species found in pellets but not trapped. That only study based solely on pitfalls provided one of the lowest number of species undetected in traps but found in pellets (2) (Heisler et al. 2016). Of course, the meta-analysis was done with available studies but it weakens the general conclusion that trapping always detects fewer species.

Additional Comments

Moderate to minor concerns and further suggestions have been included as comments in the annotated PDF.

1. Why most of the trapping localities were located on the borders and almost nothing was sampled to the interior of the park? Please explain

We aimed at a good representation of plant communities contributing to the diversity of the park vegetation. Paradoxically, most of the interior is occupied by only a few, exclusively forest communities, usually not even the best preserved or undisturbed. Even the most typical habitat of the Park, fertile beech forest, has the ‘best’ patches near the coast, close to the upper cliff edge. All the wetland and non-forest habitats are near the borders, e.g. ‘upland wetland forests’ exclusively around those inland lakes, the only inhabited forester’s lodge with a garden and well-developed oak-hornbeam forest were also there. Similarly, active cliffs, treeless dunes, and pine forest on dunes were located along the sea coast and nowhere else.

2. [Traps were set in lines] Why? Please explain the rationale behind the trapping design.

It is very prosaic, mostly associated with logistics. We wanted to apply the same distribution of traps within the site for ALL sites. Some of those habitats were very hard to walk through, especially these wetland forests (I, IV), with abundant hollows filled with quite deep water, overlapping with equally abundant coarse woody debris and high herbaceous layer, being an obstacle to view, therefore forming a trap line was the best solution, allowing detection of each trap relatively fast, without unnecessary prolongation of each control (thus maximizing safety of the trapped animals) and reducing damage to the vegetation. It was simply the easiest way to navigate from one trap to another. For some sites, it was the only way to arrange the traps, as the habitat patches were of a rather linear nature (cliff, dunes) or the only access to the patch was along some sort of linear structure (a dike between two canals in VII). There were, indeed, habitats, where the traps could be easily arranged in a grid (saltmarsh, dry meadow, beech forests), however, as we did not test for differences in population densities (like in the CMR method), we did not need that, so to obtain relatively uniform trapping design, we decided to use trap-line. We are not convinced if we need to explain the whole ‘decision tree’ in the manuscript - for the species composition and diversity both trapping designs (lines and grids) are equally good.

3. [Rattus norvegicus and Mus musculus] since they are invasive and synanthropic species, please exclude them in the discussion.

Kindly disagree. Despite various classifications as such, both these murids are hardly invasive in the specific Central European context. The brown is, indeed, alien but rather post-invasive in 21. century (while the original 16th-century invasion was restricted to settlements) but even now, after 400 years, its impact on natural ecosystems is minimal. It is a species of economic not conservation concern. House mouse appeared in Europe around 1000 BC, with the spread of prehistoric agriculture, hard to say if it should be considered an alien - was it accidentally introduced by humans or it spread naturally to anthropogenic habitats, either buildings or arable land, like swifts and skylarks? And it does not, certainly, fulfill the definition of ‘invasive’ in Central Europe, despite being an obvious invasive in many other parts of the world. If the landscape of the WNP (and the other NP used for comparison)  consists also of synanthropic habitats, therefore synanthropic species have to be included in the analysis and, at least minimally, discussed.

We followed the remaining advice and comments left in the text, changing the manuscript accordingly.

Comments on the Quality of English Language

Poor English, revision much needed

Done

References

Heisler, L.M.; Somers, C.M.; Poulin, R.G. Owl pellets: a more effective alternative to conventional trapping for broad-scale studies of small mammal communities. Methods Ecol Evol 2016, 7, 96-103. DOI: https://doi.org/10.1111/2041-210X.12454

Rychlik, L. S.; Eichert U. M.; Kowalski, K. 2020. Diversity of small mammal assemblages in natural forests and other habitats of the Słowiński National Park, northern Poland - preliminary results. In A. Vössing (Ed.), Nationalpark-Jahrbuch Unteres Odertal, III, 66–71.

Willott, S.J. (2001), Species accumulation curves and the measure of sampling effort. Journal of Applied Ecology, 38: 484-486. https://doi.org/10.1046/j.1365-2664.2001.00589.x

Reviewer 2 Report

Comments and Suggestions for Authors

Manuscript details:
Manuscript ID: diversity-3494059
Title: Depauperate small mammal assemblages in the national park protecting land-bridge island habitats are shaped more by topography than plant communities 

 

Review

This paper investigates the structure of small mammal assemblages in a Central European national park, revealing an unexpectedly depauperate species composition compared to the regional fauna and local land cover variability. In addition, the study examines whether the similarity of small terrestrial mammal assemblages is primarily influenced by plant communities or robust topography within the unique coastal landscapes of the southern Baltic Sea region.

The manuscript presents the field survey of small mammals, determining species composition and richness, and relating the results to habitat composition and topography. The study fills a gap in knowledge of small mammal biodiversity in Polish national parks and provides insights into how insular isolation and topographic variation affect small mammal populations. The authors used both live and pitfall traps in different habitat types. Statistical analyses, including species accumulation curves and cluster analysis, are used. The manuscript is well organized, with a logical flow from introduction to discussion and a clear connection between research objectives and results.

However, it has critical points to be addressed, as there are several weak points in this study:

1. Small sample size and short investigation time;
2. Unclear trapping effort
3. Conclusions too broad and not supported by scarce results.

For the first comment, the authors should at least show how many years of surveys in other national parks they compare were done (from the rarefaction curves, all were undersampled). Since the authors cite papers from Lithuania, I can recommend another one with evaluation of trapping effort to use in the discussion:

BALČIAUSKAS, L., & JUŠKAITIS, R. (1997). DIVERSITY OF SMALL MAMMAL COMMUNITIES IN LITHUANIA (1. A REVIEW). Acta Zoologica Lituanica, 7(1), 29–45. doi:10.1080/13921657.1997.10541423 

Second comment: A table of trapping effort by sampled site or habitat would help, but would not solve the problem of under-sampling. This should at least be addressed in the discussion. However, I suggest adding a small chapter on limitations of the study.

As for the third critical comment, the authors try to be big, like "Central European National Park", "depauperation", etc.. I do not think it is possible to draw very general conclusions from a one-year study. Trapping and owl pellet data from 1962 and 1966 from Wolin Island are NOT directly comparable, as they include owl pellet data (please check, there are good publications with comparison of trapping and prey).

I also suggest to think about the term "depauperation". Authors have no evidence that species composition is reduced. They might have three more species next year. Maybe live trapping is not as good method as snap trapping used in Pucek's time? To continue the comparison with Lithuania, there are 2 more papers:

Juškaitis, R., & Ulevičius, A. (2002). Kuršių Nerijos nacionalinio parko smulkieji žinduoliai. Theriologia Lituanica, 2, 34-46. Authors got 8 species of small mammals in 39 localities of the Curonian Spit, with trapping effort 1875 trap days. Paper is in Lithuanian, so might not be available to the authors.

Balčiauskas, L., Skipitytė, R., Balčiauskienė, L., & Jasiulionis, M. (2019). Resource partitioning confirmed by isotopic signatures allows small mammals to share seasonally flooded meadows. Ecology and Evolution, 9(9), 5479-5489. https://doi.org/10.1111/1749-4877.12571  Here the authors show how long-term trapping results on the island of Rusnė, also a coastal area, vary from year to year.

This is not a request to cite recommended papers, just to show how to improve the statements used in the reviewed manuscript.

 

• Other comments
• Title: obviously too long, pretending to be a short summary. When shortening, please also consider keywords.
• Abstract
• Focus on key findings, not details and methodology.
• Introduction
• Lines 39 and 40 - two references have not been numbered, they are also missing in the references.
• Materials and Methods
• There are differences in trapping methods and length in different sites. Please summarize trapping effort, and later analyze species composition according to trapping effort
• Please explain in methods, how you are able to identify Microtus voles. Pucek’s work is in Polish, but as far as I know it, he presented teeth of all species as a key.
• Describe used program as required by MDPI.

Results

Line 185 – wrong species name

Figure 2: the same color scheme was used for three different things. It is misleading at first glance. Can this be changed?

Discussion

Line 285: I strongly disagree… my experience is over 30 years of trapping, and there are three issues in sampling: sampling effort, duration in years, and habitat selection. All three are important. Rethink what you wrote. Rarefaction curve is not absolute… one owl might change it in a month.

Forester's lodge - is it permanently occupied? If not, why expect a house mouse or rat?

Apodemus sylvaticus: were you really able to distinguish this species in live traps?

Line 320: this seems to be an under sampling.

Finally, comparisons with the other land bridge islands would be helpful.

Conclusions

Similar to the extension of the discussion, they are too generalized for the limited material (especially only one season).

Background

Did funders have a role in ... (see template for clarity).

References

Check against template for correct format. There are minor typos/mistakes in formatting.

 

In general, the paper could be accepted after a major revision. I would also suggest using less categorical expressions and generalizations, given the limited amount of material,

Author Response

This paper investigates the structure of small mammal assemblages in a Central European national park, revealing an unexpectedly depauperate species composition compared to the regional fauna and local land cover variability. In addition, the study examines whether the similarity of small terrestrial mammal assemblages is primarily influenced by plant communities or robust topography within the unique coastal landscapes of the southern Baltic Sea region.

The manuscript presents the field survey of small mammals, determining species composition and richness, and relating the results to habitat composition and topography. The study fills a gap in knowledge of small mammal biodiversity in Polish national parks and provides insights into how insular isolation and topographic variation affect small mammal populations. The authors used both live and pitfall traps in different habitat types. Statistical analyses, including species accumulation curves and cluster analysis, are used. The manuscript is well organized, with a logical flow from introduction to discussion and a clear connection between research objectives and results.

However, it has critical points to be addressed, as there are several weak points in this study:

1. Small sample size and short investigation time;
2. Unclear trapping effort
3. Conclusions too broad and not supported by scarce results.

For the first comment, the authors should at least show how many years of surveys in other national parks they compare were done (from the rarefaction curves, all were undersampled). Since the authors cite papers from Lithuania, I can recommend another one with evaluation of trapping effort to use in the discussion:

BALČIAUSKAS, L., & JUŠKAITIS, R. (1997). DIVERSITY OF SMALL MAMMAL COMMUNITIES IN LITHUANIA (1. A REVIEW). Acta Zoologica Lituanica, 7(1), 29–45. doi:10.1080/13921657.1997.10541423 

Thank You for that reference, I missed it somehow. I noted however that despite notably lower trapping effort than in Lithuanian national parks (or the other, equally large, protected area), our sample size, i.e. the number of individuals captured is quite similar to Lithuanian samples. Which I repeated a few times in responses to both reviewers, it is the number of individuals that matters when assessing if estimations of diversity with rarefaction curves are based on sufficient material.

Second comment: A table of trapping effort by sampled site or habitat would help, but would not solve the problem of under-sampling. This should at least be addressed in the discussion. However, I suggest adding a small chapter on limitations of the study.

There WAS a chapter (4.2) about limitations of the study already, focused, however, almost exclusively, on the type of traps. We added an additional paragraph about limited sampling effort and lack of individual marking, which might lead to underestimation of diversity (due to overrepresentation of the most common species). See lines 409-441. Matters of density fluctuations - and, consequently, methodological limitations, as they might strongly affect species composition, depending on the year the study was conducted, were already discussed in chapter 4.3 (lines 514-562), while the problem of using trapping instead of owl pellet analysis in lines 609-614.

As for the third critical comment, the authors try to be big, like "Central European National Park", "depauperation", etc.. I do not think it is possible to draw very general conclusions from a one-year study.

We try to be big not because of choice but because we try to publish the results of the regional faunistic survey in an international journal. At least the first author feels strong nostalgia for the old, good times, when a similar paper could be titled ‘A contribution to the small mammal fauna of the Wolin National Park’, lacked any serious statistical analysis or general, ecological conclusions (and was written in Polish or Lithuanian) but those times are, maybe unfortunately, gone. We believe it is still a valuable approach when local case studies are put into a broader framework or we do seek a more general importance in those studies.

We hope we make it clear that we provide several, not always mutually exclusive, alternative explanations for our results. However, even if the total time of trapping may not seem very impressive, compared to the other regions, especially those in Lithuania, our sample was saturated. No new species were added to the list since the 7th site (out of 14) and since the 188th capture/individual (out of 397). But we do mention the possibility that some species were in an extreme low-density phase of population cycle/fluctuation. It seems, however, quite unlikely, as those ‘lacking’ species are either non-cyclic or do not express such strong fluctuations as dominant forest rodents, profiting from mast years. I doubt adding next season or two would make a difference. The same happened with bats in WPN, which we sampled, indeed, two seasons, obtaining an insane sample size, yet no additional species was neither captured nor detected in the second year (Ciechanowski et al. 2023).

“Central European National Park” was put there not to be big but to show that we write about a case study, exemplifying something of broader interest.

Finally, we decided to reduce the weight of some statements in the Conclusions that, indeed, may one perceive as ‘too strong’ compared to the evidence behind them (line 710-742).

Trapping and owl pellet data from 1962 and 1966 from Wolin Island are NOT directly comparable, as they include owl pellet data (please check, there are good publications with comparison of trapping and prey).

We are aware of that and do not claim that they are perfectly comparable, it is only a hypothesis, an additional hint that the species in question were present on the island. They should be present in the Park as well, so the lack of them in our sample is suspicious. We were really astonished that in such habitats not a single Micromys minutus was captured, at least if You use pitfalls. But we do provide alternative explanations, like long-term fluctuations in population densities. We add a short discussion about the comparability of trapping and pellets (lines 609-614).

I also suggest thinking about the term "depauperation". Authors have no evidence that species composition is reduced. They might have three more species next year.

Might be, indeed, and long-term data from the island of Rusnė confirm such a possibility (thank You for that citation, by the way!). However, if You have four other national parks in the same broad geographic region, some of them much more undersampled than ours’ in terms of trapping effort and most of them with much lower number of captured individuals but in all of these parks more species were captured, genuine difference in species richness and diversity is a more plausible explanation than population density falling so low that the species remains undetected only in one of that parks? So I think the term ‘depauperate’ (compared to mainland parks) or (if You prefer something that links the whole thing rather to state than process) ‘species-poor’ quite probably reflect the small mammal assemblages of the WPN, compared to the other NP in the region. We should mention that we include ALL the national parks in the Polish Baltic Sea Coast and Lower Oder Catchment, for which the data about small mammals were available, so there was no cherry-picking!

Of course, trapping in any area lasting 10 or 15 years may reveal more species than during 1-2 years but the final result is probably a cumulative number of species which does not have to mean that such a number of species does coexist in one place at any time. It reflects rather genuine changes in species presence - animals do migrate, even small ones (otherwise, what Neomys fodiens would do in the dry pine or pine-oak stands in Białowieża Primeval Forest? - see Aulak 1970), while local populations can really go extinct all the time (or emigrate!), the sites are repopulated again etc.. It is at least equally probable that all M. minutus died out or emigrated completely from that constantly flooded meadow on Rusnė, at least to the nearest dikes, as that they became so rare that they became completely undetectable. I am not even sure if application of environmental DNA would solve such dilemmas as eDNA could persist quite long in the soil.

Maybe live trapping is not as good method as snap trapping used in Pucek's time?

While it is possible (we do not know if there is enough data to test that hypothesis), however it is not a problem here, as along live traps (if You mean Sherman) we used pitfall traps. And the latter are well proven to be much better than BOTH live- and snap traps, being much less selective, thus providing much more balanced picture of small mammal assemblages, even if their application is not possible on every site (e.g. those of hard, rocky surfaces are excluded from pitfall trapping). See our discussion in chapter 4.2, lines 354-395.

To continue the comparison with Lithuania, there are 2 more papers:

Juškaitis, R., & Ulevičius, A. (2002). Kuršių Nerijos nacionalinio parko smulkieji žinduoliai. Theriologia Lituanica, 2, 34-46. Authors got 8 species of small mammals in 39 localities of the Curonian Spit, with trapping effort 1875 trap days. Paper is in Lithuanian, so might not be available to the authors.

Thank You, Lithuanian text is not a problem, as the paper contains tables with captions in English, as well as an English summary. Although 39 sites (instead of 14 in our case) may, indeed be an example of undersampling in our study, as they provided much higher habitat variability (even if undetectable in such broad habitat groupings), yet 1875 trap days changed really nothing, if the authors captured only 300 individuals, a sample comparable to ours. Curiously, the study cited above, revealed a marginally lower species richness than ours. Sadly it did not cover the whole variability of habitats within the Curonian Spit National Parks, e.g. no trapping was conducted on treeless dunes, which are a prominent element of that park’s landscape.

Balčiauskas, L., Skipitytė, R., Balčiauskienė, L., & Jasiulionis, M. (2019). Resource partitioning confirmed by isotopic signatures allows small mammals to share seasonally flooded meadows. Ecology and Evolution, 9(9), 5479-5489. https://doi.org/10.1111/1749-4877.12571  Here the authors show how long-term trapping results on the island of Rusnė, also a coastal area, vary from year to year.

Thanks again, we included it in our discussion, it changes perspective a bit.

This is not a request to cite recommended papers, just to show how to improve the statements used in the reviewed manuscript.

We understand, yet we used them, interesting papers, indeed.

• Other comments
• Title: obviously too long, pretending to be a short summary. When shortening, please also consider keywords.

Rewritten to “Depauperate Small Mammal Assemblage in Wolin National Park (Poland): effects of insular isolation, topography and vegetation”, I hope it is shortened enough. I was taught since my MSc studies, that keywords SHOULD NOT be included in the title, as the content of title is searched by internet browsers and indexed by bibliometric databases separately, so keywords are meant to expand the chance of an article to be found.

• Abstract
• Focus on key findings, not details and methodology.
• Introduction
• Lines 39 and 40 - two references have not been numbered, they are also missing in the references.

Done

• Materials and Methods
• There are differences in trapping methods and length in different sites. Please summarize trapping effort, and later analyze species composition according to trapping effort

Thank You for that advice, we summarized that now in the Materials and Methods, Results (fig. 3-4) and Table S2, however, the trapping effort is not a reliable index of sample size, the number of individuals/capture is (Willot 2001).

• Please explain in methods, how you are able to identify Microtus voles. Pucek’s work is in Polish, but as far as I know it, he presented teeth of all species as a key.

Pucek’s book contains two parallel keys - one for external ID features and one for skulls. Teeth are described in the key for skull identification. Pucek (or rather Ruprecht, who wrote the chapter about Arvicollidae, as they were distinguished as a separate family in the 80.) DOES PROVIDE external features for the Microtus species (or, better, Microtini tribe now). Leaving aside M. subterraneus (which was Pitymys then and has five plantar pads, instead of regular six), all the three lowland Polish Microtus spp. can be, according to that key, identified by the combination of tail and hindfoot length and coloration of the fur. It goes as follow:

1. Fur on the back fawn/buff, hindfoot usually <17 mm - Microtus arvalis

1* Fur on the back reddish, hindfoot usually >17 mm - 2

2 Tail usually <40 mm - Microtus agrestis

2* Tail usually >40 mm - Microtus (recently Alexandromys) oeconomus

The most often expressed objection to that key is the expression ‘usually’, Ruprecht himself wrote that juvenile individuals can be hard (if possible) to identify based on that features, so teeth (possible to be examined post mortem only) is probably the best ID feature, especially between M. agrestis and M. (A.) oeconomus. The same problem with ‘usually’ applies, however, to cranial and dental features, so it should not be treated as a 100% solution as well. The very same book writes about populations of M. agrestis which inheritably lose the 5th triangle on M² and populations of M. arvalis that inheritably add the 5th triangle on the same tooth. Making it worse, according to Ruprecht, a small minority of individuals in both species, have foramen mandibulare in the ‘wrong’ place (i.e. not in the place typical for their respective species). Strikingly, in case of skull and teeth, Ruprecht did not insert the word ‘usually’ before every feature provided. The problem can be only partially solved by subtle differences in fur coloration but we extended the possibility of correct identification by using coloration of tail (bicolored, with white ventral side, in case of M. agrestis and M. (A.) oeconomus, uniformly coloured, dark, in case of M. arvalis - Aulagnier et al. 2009). In case of M. agrestis and M. oeconomus, the species pair hardest to identify and with the strongest habitat niche overlap (both occur predominantly in humid habitats), gladly no individuals with tail length between 40 and 50 mm were captures, so we got either those huge voles with equally huge tails (50-60 mm) that could be securely classified as M. oeconomus and those small ones (with tails <40 mm), with much smaller bodies as well, which we classified as M. agrestis. Could we guarantee You that no individual was misidentified? Of course not, but this is the bane of work with morphologically similar taxa, while even such prosaic scientific activity as species identification is not about certainty, only about probability. Yes, individuals with external features for M. agrestis or M. arvalis, yet appearing to be, judging from their teeth, just juvenile M. oeconomus, do happen and we have met them in our own career. We can only be glad that we do not have M. levis (rossiaemeridionalis), as e.g. in Lithuania.

All these features are available in the cited literature, Pucek’s key has an earlier English version, available to non-Polish readers (which we cited), so we are not sure if we should enlarge the already gargantuan text to describe in detail some of the features that everyone can read about. These features were not invented or proposed by us, so usual practice is rather to provide the source of an ID key, instead of copying its content to the next work. We add, however, a second source for the species’ identification, that of Aulagnier et al. and referred to the potential bias in dataset, associated with relying solely on external but not dental features in the Discussion (lines 441-444)

• Describe used program as required by MDPI.

The Instructions to Authors state only: “New methods and protocols should be described in detail while well-established methods can be briefly described and appropriately cited. Give the name and version of any software used and make clear whether computer code used is available.” We have described ClustVis, even if it is an open-access online application; the source of that program was also cited [35, 36]. PAST is a widely available and broadly used freeware, a popular alternative to commercial statistical packages, we named it, including the used version (5.1) and pointed to particular statistical procedures, when that program was used (adding citation of the program’s manual - [29]). We believe there is no need to further describe it.

Results

Line 185 – wrong species name

The names in the original line 185 were (and are): Eurasian pygmy shrew Sorex minutus Linnaeus, 1766 and Eurasian water shrew Neomys fodiens (Pennant, 1771). Which of them are wrong? They are in accordance with Wilson and Reeder’s “Mammal Species of the World” (2005) and the respective volume of “Handbook of the Mammals of the World” (Lynx).

Figure 2: the same color scheme was used for three different things. It is misleading at first glance. Can this be changed?

Unfortunately, color scheme in ClustVis is fixed.

Discussion

Line 285: I strongly disagree… my experience is over 30 years of trapping, and there are three issues in sampling: sampling effort, duration in years, and habitat selection. All three are important. Rethink what you wrote. Rarefaction curve is not absolute… one owl might change it in a month.

No statistical method is ‘absolute’, i.e. it only estimates the probability of difference between samples or relationship between variables, not the iron-clade truth. However, if the rarefaction curve approaches the asymptote (‘becomes flat’), while the confidence intervals do not overlap between WPN on one side and DNP-LOVNP-SNP on the other side, probability of changing the differences in species richness falls to very low. Yes, we are aware about those problems (limited sampling effort, only one year of trapping and habitat selection) and do discuss them accordingly. Habitats were diverse enough to cover those selected by all the species expected to occur in the region, even if the synanthropic one (a garden around a forester’s lodge) was sampled not enough. It is, on the other hand, my [Mateusz Ciechanowski] experience (24 years of small mammal trapping, even if the majority of my publications focuses on bats) led me to serious amazement that well developed, partially flooded, alder forests, few meters from lake shores and stream banks provided almost no water shrews, while lush reed beds and sedge communities - not a single harvest mouse, despite captured dozens of individuals from the other species.

Forester's lodge - is it permanently occupied? If not, why expect a house mouse or rat?

Yes, it is permanently occupied, one of the Park’s foresters not only lives but also works there. We add that information in Table 1.

Apodemus sylvaticus: were you really able to distinguish this species in live traps?

We use a two-step approach. First we check the neck collar/patch. If it is a yellow collar or a round, large patch of the same colour on the neck/breast, we assume it is A. flavicollis. If there is either a narrow, yellow stripe in the same place or there is no yellow patch/spot at the ventral side of the animal at all, we make a digital photo of the tail to count epidermal rings on a computer (by making dots in Paint or similar graphic program). Combination of both features (only narrow yellow stripe or lack of any yellow patch and the number of rings on the tail <170) is treated as pointing to A. sylvaticus. These features are not our invention, they are written in Pucek’s key and Aulagnier’s atlas. We may securely assume that no A. uralensis occurs in northwestern Poland, making it a much easier job than in Lithuania or southern Poland.

Line 320: this seems to be an under sampling.

If You refer to dormice in that comment, it is more likely that they are absent from the WPN now. The manuscript is a part of broader mammalian diversity assessment in the WPN, when we looked for glirids also applying the other methods, more feasible for that group (night acoustic surveys for G. glis, search for feeding signs of both G. glis and M. avellanarius; no bird boxes are present in the WPN stands, unfortunately). This is, however, of minor concern, as dormice are not typical epigeic species, even if they are sometimes captured in ground-level traps. We mentioned them in the Discussion only because they are, technically, small mammals. They were not captured in any of the compared national parks either.

Finally, comparisons with the other land bridge islands would be helpful.

As we wrote in chapter 4.3 (lines 588-597), such data from the Baltic Sea basin, or central and northern Europe, are extremely scarce, the most valuable is that Danish MSc thesis, we do cite it, even if it is unpublished (but available on the institute’s website). It remains in stark contrast with bat fauna, which were analysed in detail for Swedish islands, including species-area and species-isolation relationships (Ahlén 1983). Species’ lists for the other coastal or land-bridge islands in northern Europe do exist, we added citations for Waddenzee (Frisian) islands of Germany and the Netherlands but they are results of long-term accumulation of data from trapping and owl pellets, not dedicated trapping surveys that could assure us if all that species occurred in the same time. We compare it to the results from coastal, estuarine, hydroelectric reservoirs and lakes from the Nearctic and (in one case) Eastern Palearctic, from where several nice studies, testing for both species-area and species-isolation relationships, are available (lines 577-587).

Conclusions

Similar to the extension of the discussion, they are too generalized for the limited material (especially only one season).

This is why we added the alternative explanations in the conclusion (lines 738-742). However, neither the difference among the compared parks nor the spatial segregation of species between the two parts of the WPN (‘landscape units’) could not form by chance only, due to undersampling. The phenomenon may not be permanent but seem to be real, leaving aside the probable explanation.

References

Check against template for correct format. There are minor typos/mistakes in formatting.

Done

In general, the paper could be accepted after a major revision. I would also suggest using less categorical expressions and generalizations, given the limited amount of material,

OK, we try our best in reducing those categorical expressions but some level of generalization is required if the paper has to be something more than just a local faunistic survey. And if the sample size is sufficient (based on species accumulation curves, it is quite probable, even if far from certainty), we can use it for a case study of importance exceeding the local faunistics, with more general implications for small mammal ecology.

References

Ahlén, I. (1983). The Bat Fauna of Some Isolated Islands in Scandinavia. Oikos, 41(3), 352–358. https://doi.org/10.2307/3544093

Aulagnier S. et al. 2009. Mammals of Europe, North America and the Middle East. A&C Black, London.

Aulak, W. Small mammal communities of the Białowieża National Park. Acta Theriol. 1970, 15, 465–515.

Ciechanowski, M.; Wikar, Z.; Borzym, K.; Janikowska, E.; Brachman, J.; Jankowska-Jarek, M.; Bidziński, K. Exceptionally Uniform Bat Assemblages across Different Forest Habitats Are Dominated by Single Hyperabundant Generalist Species. Forests 2024, 15(2), 337. https://doi.org/10.3390/f15020337

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Thank you for revision, I have no further comments.