Exotic Prey Facilitate Coexistence between Pumas and Culpeo Foxes in the Andes of Central Chile

Round 1

Reviewer 1 Report

Exotic Prey Drive Coexistence Between Pumas and Culpeo Foxes in the Andes of Central Chile

The paper compares the three-dimensional ecological niche of two predator species in order to highlight the mechanism of species coexistence in the predator-prey community. It is an interesting and complex study, and the ms is in general clear, well written and accompanied by nice and informative figures. The discussion is well organised and supported by data, even though a broader discussion of the role of fruits in the diet of Culpeo foxes and in the mechanism of trophic segregation between the two predators will improve the paper (see my comments to L797-798).

Here I list further minor suggestions:

L 389-390. Please check the reference (65) as it seems unrelated to the description of the diet indexes.

L 396. It is not clear to me how can you say that for fox RPO does not significantly differ from Biomass, if RBM has not been calculated.

L 427 and following and fig. 3. In Fig 3 I see a high degree of overlap of the error bars (except those of foxes), and I believe that finding actual differences among the capture rates, except for foxes, could be highly speculative. For example, it seems that a “higher capture rate in fall-winter than in spring-summer” can be observed only for rabbits and small mammals in RNCR. Again, capture rates of hare, rabbit and small mammals are almost the same, and it seems difficult to highlight solid differences. Probably the standard error is not the best way to compare capture rates, maybe you can try to run a multivariate comparison, but without this further statistical analysis, I think that the paragraph should be revised with more caution.

L 576: You write that “Guanacos exhibited more nocturnal activity in the fall-winter” but it seems to me that guanaco activity is well distributed along the 24 ours with a slight peak in the morning

L 590-591: consider English revision

L620: the total number of scats is 158+48, isn’t it?

L635: is a so small difference in B index (0.07 vs 0.06) indicative of an actual difference in trophic niche breadth?

Figure 8: Please, check the numbers reported in the figure, for example RPO of hare are 29% for pumas and 2% for foxes, but in lines 631-632 RPOs are 20.5% and 4% respectively.

L757: You write that “Pumas had low temporal overlap with small mammals, especially in winter” but in Fig 6 the lower overlap occurs in spring-summer

L758-763. Probably the lack of association between puma and guanaco activity time is simply due to the fact that guanaco does not seem consumed by pumas in your study area, probably due to guanaco low density, as you write in L780. Probably this par. could be revised for more clarity.

L797-798: In my opinion, the high consumption of fruits by Culpeo foxes is the more relevant element of trophic segregation with pumas, and the paper will greatly benefit by a broader discussion of this point. Predators can exhibit different feeding strategies. Some species are obligate carnivores that consume almost exclusively animal prey (e.g. the wolf: Bosch et al 2014 Br. J. Nutr. 21: 1-15), others are opportunistic predators that can seasonally consume high quantities of fruits and that are more carbohydrate tolerant, e.g. the pine marten (Remonti et al 2016 Oikos 125: 1233-1240) or the red fox (e.g. Lanszki, J. et al. 2007. Wildl. Biol. 13: 258–271). The feeding strategies of puma and foxes seem to follow this pattern, with the medium-sized predator that shows an opportunistic behaviour that allows to exploit temporary, highly profitable resources such as fruits, and the grater predator that seems strictly carnivore. The trophic flexibility of Culpeo foxes could be a further important ecological factor that allows species coexistence.

 

Author Response

Dear reviewer: Thank you very much for your review and feedback. We have taken care carefully of every single comment, and we feel that the manuscript has imrpoved significantly. Please see the attached file with specific notes and actions taken in response to your comments. Thank you very much!

Author Response File: Author Response.docx

Reviewer 2 Report

 

REVIEW OF DIVERSITY-888585

 

Dear Authors,

 

I enjoyed reading about your work on niche overlap between two carnivores in Chile. Clearly, a lot of work went into collecting and analyzing these data. This is a thorough study which looks at niche overlap by examining several niche axes simultaneously, which is rare in the literature. Well done. Moreover, the results have important implications for conservation at the local site and, perhaps, more broadly where carnivores prey on exotic prey. Thank you for doing this work.

 

Overall, my comments are minor. While I could quibble on issues such as the selection of various similarity or overlap indices (e.g., Gladfelter-Johnson’s versus Levin’s, and so forth), that would just be quibbling. The analyses are well done and my substantive issue (below) are really focused on the presentation of the manuscript, which I believe needs a fair bit of work to make your research more readable. Below I provide substantive and detailed comments aimed at providing greater focus and concision to the manuscript.

 

Again, this is a nice study that I enjoyed learning about. Best of luck in revising your work. I hope to see it soon published.

 

SUBSTANTIVE COMMENTS:

 

1. Predictive framework needs to be more explicit. Throughout the manuscript it is apparent that the authors had some a priori “expectations” about what they would find. This is great; however, it is scattered throughout the manuscript, often first appearing in the Methods or Results, inappropriately (e.g., Lines 292 and 361). The writing would be much stronger if the Introduction was focused on providing a priori predictions (hypotheses), based on niche theory and the biology of the studied species. These predictions would then be followed throughout the text in each section, helping to tie everything together more clearly for the reader. Again, I believe much of this is already in the manuscript, but a bit haphazardly.

 

2. Small sample sizes should be addressed. The study design for the camera aspect of this work is reasonable, but not optimal. Few sites were sampled with cameras (especially for VV&LC) and for short, and different, time periods. This limited inferences in the protected area especially, and comparison of the spatial overlap across the whole study area. Yet, the authors do not provide a rationale for their sampling strategy in the Methods or, more importantly, discuss much on how their design may have limited spatial inferences in the Discussion. I would prefer to see the authors address the limitations of their sampling design.

 

3. Methods need clarification. Related to the above, in some instances choices made for sampling or analyses require further clarification. I have provided some exampes below in the detailed comments (e.g., Line 197, 220, 373, and others).

 

4. Text needs polished. This and comment 1 above are my main issues with the current work. While I applaud the authors for examining spatial, temporal, and diet overlap at the same time, the result is a long manuscript. To make this “work”, the authors need to be really focused in what they present in the manuscript (see comment 1 above). Unfortunately, the text is quite long, not logically arranged at times (text in wrong sections or not well ordered), and there is much extranous information that is not critical to the central aims of the study. This is distracting from the main aim of the study. As such, the text could be significantly polished to provide focus and concision. In the detailed comments below I provide a number of suggestions that may be help in that regard.

 

DETAILED COMMENTS:

 

Line 2: Perhaps replace “drive” with “facilitates” in the title. I do not think that drives is the correct term here.

 

Lines 6-11: the affliations/contact information is inconsistent among institutions/authors. Please make all of them similar in detail.

 

Line 14: Throughout the Abstract, please add scientific names for all species at first mention (unless this is not the format for Diversity, of course).

 

Line 29: The concluding sentence may be overstated. Do we really know that guanacos would be necessary (nice for sure, but perhaps not necessary). Would they not likely segregate along a different axis? Importantly, for competition to occur the resource needs to be limiting. Is prey limiting for these predators. I suggest rethinking the concluding sentence and framing it around these thoughts rather than without hare or guanaco both predators can persist – which I am skeptical of without stronger evidence.

 

Line 36: Perhaps replace “has been broadly addressed by many researchers” with “is of broad interest to ecologists”, or something similar.

 

Line 40. Notwithstanding the excellent citation #5 used here, the term “limiting similarity theory” is not widely used nowadays (I could be wrong here). The term I have heard much more frequently for this concept is “the competitive exclusion principle”. You may wish to use it instead.

 

Lines 45-48: An obvious formatting error seperating a paragraph.

 

Lines 56-58: Replace “predator species” with “carnivores” and delete “carnivore” later in the sentence. More importantly, I suggest you consistently use “carnivore(s)” throughout and avoid or limit the use of “predator(s)”.

 

Line 59: Replace “within its temporal niche dimension” with “temporally”

 

Line 61: Reword “temporal activity pattern segregation”. Awkward.

 

Lines 61-65: Summarize. The details are not necessary. But keep all the citations.

 

Line 66: Delete this sentence. Irrelevant.

 

Line 67: Move this sentence to the end of the next paragraph, where it fits and flows better.

 

Lines 80-109: These two paragraphs are awkward and a bit out of place. I suggest moving some of the details into the Study Site subsection, and the more pertinent pieces into the last paragraph.

 

Lines 113-118: I do not believe it is necessary to state how you did the work in this sentence. This too belongs in the Methods. Rather, it would be important to include predictions here instead. What did you expect to find for spatial overlap, for instance, and why? The why should bring in both general ecological theory as per the opening paragraphs of the Introduction, as well as the specific biology of the species involved as per lines 80-109. Do the same for temporal overlap and dietary overlap.

 

Line 127: “Camera” should be in all lower case letters.

 

Line 129: Delete “years”

 

Line 131: “The” should be in all lower case letters.

 

Line 173: Delete “year” and “years”

 

Lines 174-176: Move this sentence to the bottom of the paragraph. Discuss the sampling (study) design first.

 

Line 192: Please provide the mean and standard deviation here.

 

Line 192: How periodically? Please provide a mean, SD, and range here.

 

Line 197: Please provide some description of how species were “clearly different individuals”

 

Line 200: The symbol used for 30 minutes is incorrect (for geographic coordinates). Please replace “CR30’” with “CR30min”

 

Lines 198-208: Other than capture rates, what is this information giving us in relation to the three main objectives of the study. Please provide the reason for collecting/presenting these metrics. It is unclear.

 

Line 201: Please start this paragraph briefly with WHY you did this analysis, not WHAT analysis you did. This will help the work flow much better from the Introduction onward and be more clear to the reader.

 

Lines 212-215: Occupancy modeling is well known to most researchers. Please delete this sentence.

 

Line 220: What is the rationale for using 3-day sampling periods? Can you provide references from other studies using similarly short sampling sessions for occupancy modeling? This seems odd to me. Why would you not use month, for instance, and have 4 sampling sessions?

 

Line 223: Delete this sentence.

 

Lines 230-231: Great. Using a small number of a priori predictor variables is preferable to a larger suite without a lot of biological basis. However, you should first tell us why these variables are likely influential first, then where you got the data. I suggest flipping this paragraph and the next in order and tweaking the text so they flow together a bit better. Alternatively, you may wish to consider turning the text in lines 238-258 into a new table to increase its readability. There are lots of examples in other papers of this (e.g., Thomas et al. Global Ecology and Conservation 17:e00562) – just a suggestion.

 

Line 313: This sentence is not necessary and could be deleted.

 

Line 361: This long sentence is an excellent example of what would be better in the Introduction as a prediction that is being tested. Please move to the Introduction. There are similar sentences, or part thereof, in the Methods that are predictions that would be better suited to the Introduction (e.g., Lines 292-295). Good stuff; wrong place.

 

Line 367: It is remarkable to me that you found so many scats with this method. Just a comment.

 

Line 373: What was an “old or degraded scat”? Note that some dried-out looking scats in arid habitats can be quite fresh, and vice-versa (e.g., see: Jung and Kukka 2016. Wildlife Biology 22:160-166).

 

Line 389: Here and elsewhere, please edit for concision. For instance, replace “For pumas, given they consume large prey” with “Given pumas consume large prey”.

 

Line 505: Another example of awkward phrasing: “Fox site use probability”. Please look for others throughout and write more clearly.

 

Line 510: Replace “expectation” with “our prediction”

 

Line 531: Delete “and” before “Chile”

 

Line 540: Delete “According to the 2-way circular ANOVA, ”

 

Line 630: Typo. Correct “bt”.

 

Line 634: Is there a typo here? These niche breadth values look almost the same, which is not what the text says. Please clarify.

 

Line 637: What do you base an overlap of 30% as extremely low? Can you provide citations? In a similar study of dietary overlap, I would have considered 0.30 as low-moderate overlap (e.g., Jung et al. 2015. Journal of Wildife Management 79:1277-1285). The point, however, is that I don’t think that 0.30 is extremely low; rather it is low-moderate in my view, so you will need to defend this a bit or modify your views somewhat.

 

Line 643: This sentence would be more appropriate in the Discussion.

 

Line 660: In general, the Discussion would flow better if it were linked to predictions/hypotheses made at the outset in the Introduction.

 

Line 704: Replace here and throughout “expectation” with “our prediction”

 

Line 707: Extra space typo.

 

Line 721: Yes, I agree with this recommendation. But, is it possible that there is a much simpler explanation: that is, both carnivores were queing into habitats used by lagomorphs and small mammals as prey? Its not the habitat per se that or other subtle factors. We came to that as a simple conclusion in Thomas et al. 2019 (cited above). But we measured habitat use by the prey species, which was not done here.

 

Line 730: Suggest deleting this sentence. I don’t think that statements of primacy for a geographic location are of interest in international journals (perhaps regional journals, though).

 

Lines 746-768: These three paragraphs mostly reiterate the results. Delete much of this and instead focus on interpretation of the results instead.

 

Line 789: Alternatively, vischacha are not well captured by the cameras in your study design (e.g., something about their behaviour, or wrong habitat types sampled).

 

Line 805-807: Another example of where the text can be edited for concision.

 

Line 808-812: Is this paragraph necessary? I would suggest that this is an example of extranous information that is captured elsewhere in the text, but distracts somewhat from the overall aims of the study. Keep in mind, this is not an diet or ecology study per se, rather it is a comparison of niche overlap between two carnivores so keep the text focused on that.

 

Line 822: Typo: “Givem”

 

Line 826: I think the Conclusion are really well done. Good job.

 

Line 846: With guanaco present already in the study area, albeit in apparently low numbers, I would replace “reintroduction or re-establishment program” with “population augmentation”. Alternatively, and a better approach in my view, it would apparently be important to identify and remove threats to them so numbers can naturally rebound, particularly in VV&LC and other adjacent areas.

 

Figure 2: Perhaps interesting, but not at all germane to the central aims of the study. I suggest either deleting this figure or moving it to supplemental information to reduce the overall length of the manuscript?

 

Figure 3: Useful, but not particularly germane to the central aims of the study. Can this be moved to supplemental information to reduce the overall length of the manuscript?

 

Figure 6: Nice figure. Can it be made bigger (e.g., landscape)?

 

Figure 8: This is a super figure. Well done.

Author Response

Dear reviewr: Thank you very much for the detailed review!

We carefully took cre of your comments and we feel that the manuscript has improved a lot.

Please see the attached documents for details on the specific action taken in response to your comments.

Author Response File: Author Response.docx

Reviewer 3 Report

This is a very interesting manuscript in a well-crafted study. There is a lack of temporal replication at sites with effectively only one year’s data collected. This limits the generality of the results but given the relatively simple features of the study site and the interaction between the predators and introduced prey species, the results are worthy of publication. The authors have undertaken a comprehensive analysis of data that have been carefully vetted for statistical independence. The presentation of the results is excellent with the inclusion of graphics that aid immediate interpretation of the species/cohort represented. However, the reference to multiple figures and/or tables (line 453, 457) was somewhat disorderly. One would expect each table/figure to be examined in an orderly process and the inclusion of multiple tables/figures might indicate unnecessary duplication. This was not the case but the authors should revise according to convention.

The manuscript is well-written but there are a few minor errors as detailed in the following:

Line 26, 704. Indict is a legal term about charging a person for a crime. I assume the authors meant indicating not indicting.

Line 243: water in areas

Line 324: types of resources

Line 361-2: to those of their

Line 456: effect supported and strong – missing verb?

Line 573: just past midnight

Line 590: with both hares and

Line 611: ,but no seeds

Line 617: ,but no reptiles

Line 822: Given we

 

Author Response

Dear reviewer:

Thank you for your review! We limited citing multiple tables and figures to improve clarity.

Please see the attached word document for details on the specific actions taken in response to your comments.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I am satisfied with the answers to my comments and I recommend to accept the paper for publication

Author Response

Dear reviewer:

thank you very much, again, for your valuable feedback, comments and suggestions to the first version of the manuscript. We really appreciate it, and we all feel the manuscript improved a lot after taking care of your comments.

Best regards,

Christian Osorio.