Predation and Scavenging in the City: A Review of Spatio-Temporal Trends in Research
Round 1
Reviewer 1 Report
Contrary to the important meaning of the title of the reviewed manuscript: "Predation and scavenging in the city: understanding meat consumption pathways in urban ecology" authors reviewed the scientific literature on urban predation and scavenging in the line of counting the number of published papers only. Despite the urgency of the topic, the content of the reviewed manuscript only glides over the surface of the problem. Authors should describe the issue profoundly, and try to summarise and conclude results obtained in reviewed studies focused, for example, on the levels of anthropopressure, light pollution, predation risk, shelter availability, etc.
That is why I cannot recommend the manuscript for publication in its current form and strongly recommend rewriting it.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear Authors,
Thank you for doing this work. A review of studies on carnivores in cities is timely.
While I appreciate the effort to locate, review and summarize all of these studies, I have some substantive issues that I feel need to be addresses before the work is publishable.
Please find below my substantive and detailed comments. I hope you find my review useful.
Best of luck in revising your manuscript and seeing it published.
Sincerely.
Substantive and general comments:
Aims not well articulated. Importantly, the aims and objectives of this study are not well articulated in the Title, Abstract, or Introduction. I found myself well into the manuscript before a had a reasonable sense of what the authors were trying to accomplish with this work. For instance, I do not believe that this work at all improves knowledge on “meat consumption pathways in urban ecology”, despite the title. I suggest the title, abstract and Introduction be substantially revised to more specifically and overtly indicate the aim of this work.
Predictions missing. Curiously, there are no a priori predictions or hypotheses stated at the outset of this work. I would think the authors would have considered this literature review because they had some pre-concieved ideas that their were gaps or biases in the current literature that should be exposed to advance science in this field. For example, geographic or temporal biases? Focus on species with certain traits? Moreover, having a priori predictions stated in the Introduction (and backed by citations to previous work) would really help to tie the manuscript together much better, if followed through to the analyses and Discussion (see comments on Discussion below). I urge the authors to add testable predictions at the outset of their work – I believe they are already there.
AIC-based modeling strategy is not explicit. While I greatly appreciate the quantitative approach the authors took to improve our knowledge of the focus of existing literature on carnivores in cities, their modeling strategy is not well defined. Specically, I would have appreciated knowing whether they followed an “all possible models” approach with their list of covariates, or if they had a priori hypotheses that they tested (my preference)? If the latter, what was the candidate model set based upon? Clarity is required here.
Haphazard discussion. I had difficulty following the main points that the authors wished to convey in the Discussion and suggest a rewrite for clarity. As such, I do not provide many detailed edits for this section at this time. Following specific predictions that are outlined in the Introduction (as suggested above) would help to organize and tie the Discussion better to the main aims of the paper. Additionally, I feel that the Conclusions are well done. One option is to forgo the long Conclusions here and make these the Discussion (in conjunction with the first paragraph modified from the existing Discussion). The authors could expand on the main points of the Conclusions as separate paragraphs themselves. Either way, the exisiting Discussion needs a substantial refocus and revision.
Writing needs polished. There are many odd phrases and wording throughout. As well parts of the text are a bit haphazard (see Discussion above). Overall, this makes it difficult for the naïve reader to understand what the authors are trying to accomplish and convey. A careful revision aimed at improving clarity and concision is required. I have offered some editorial suggests in my detailed comments to try to help in this regard.
Detailed and editorial comments:
Line 2: The title needs some work to better reflect what this manuscript provides. The current title is not an accurate representation of the aims and objectives of the manuscript. A title that indicates that this is a review of the spatial and temporal trends in studies about urban predation and scavenging would be more appropriate. Something along the lines of “Predation and scavenging in the city: a review of spatio-temporal trends in research”
Line 13: Here and throughout the manuscript please replace the “carnivorous” with “carnivores” in most instances. The same for replacing “preys” with “prey”. These minor language errors are prevalent in the paper.
Line 13: Delete “can”
Line 14: Replace “conservationist” with “conservation”. Same for at Line 306.
Line 16: I don’t think it is fair to say that this topic “remains apparently overlooked”. There are a number of papers on the topic, as your review demonstrates. I suggest replacing the above term with “lacks syntheses”, or similar.
Line 16: Delete “In the present study,”. Unneccessary.
Line 18: Replace “as a research topic” with “in research”. This is more in line with what you did, in my view.
Line 19: Replace “revised” with “reviewed”
Line 21: It is unclear what is meant by “less studied and not necessarily been in the core of cites”. Please reword and clarify.
Line 26: Replace “attending to” with “given”
Line 33: Delete “even”
Line 34: Delete “successfully”. They either thrive or don’t thrive...
Line 34: Delete “have great environmental tolerance and behavioral flexibility”
Line 34: Perhaps include the following paper (and others) in relation to threatened species in greater abundance in urban areas – Thomas and Jung. 2019. Life in a northern town: rural villages in the boreal forest are islands of habitat for an endangered bat. Ecosphere 10(1):e02563. 10.1002/ecs2.2563
Line 38: Here and throughout the text replace “refuses” with either “refuse” or “garbage”.
Line 40: Replace “carnivorous species” with “carnivores”
Line 40: Delete “in the last decades” and replace “approach” with “appreciation” and replace “preponderence” with “prevelance”
Line 44: Delete “even”
Line 45: Replace “strictly carnivorous” with either “hypercarnivore” or “obligate carnivores”
Line 46: Please be specific that you mean red fox here and provide the scientific name.
Line 46: Delete “different”
Line 51: Delete “diverse”
Line 64: Delete “mere”
Lines 70-72: This sentence is good and useful, but it appears to be in the wrong place in the Introduction. I suggest moving it earlier in the Introduction, perhaps at the very beginning (i.e., before Line 30).
Line 73: Replace “analyze” with “review” and “in” with “on”
Line 83: Delete “international”
Line 84: Replace “select” with “selecting”
Line 84: Delete the last part of this sentence, starting with “, to ensure that we have....”
Line 94: How were these papers “pre-selected”
Line 95: Replace “predation/scavenging” with “predation or scavenging” and replace “and / or” with “or”
Line 96: What is “anthropic” mean? Please find a better word that is more clear here.
Line 98: What is meant by “human scavenge”? Please clarify.
Line 100-103: I am having trouble following this sentence. I don’t know what the authors are trying to convey here. Please reprhase for clarity.
Line 101: How did you define a “scavenger species”, given that many carnivores scavenge at times. Please define and provide an example species or two.
Line 107: Replace “moment” with “year”
Line: 109: But, I thought studies that took place in nature reserves were excluded – see Line 97.
Line 112: It is important to specify how “carnivore level” was defined and used here; rather, than simply cite Wilman et al. This is particularly important because it comes out as a key covariate in your GLM models in Table 1 (although weakly).
Lines 113-114: a couple of missing or extra spaces between words.
Line 115-116: I think I know what the authors mean here, but it is confusing as written. Please rephrase for clarity.
Line 130: “Taxonomic” should not be capitalized in this sentence.
Line 142: Delete “ – “
Line 151: Replace “in” with “by”
Line 152: “Tropical” should not be capitalized here. Same for “Deserts” and “Taiga” in the next line.
Line 154: Replace “less than 1%” with “<1%”
Line 154: Replace “Regard” with “Regarding”. Same for Line 186.
Line 155: Replace “articles” with “studies”
Line 162: These test statistics should be in parentheses – for example, “(t = ...., df = ..., P = ...)”
Line 166: Delete “in the graph.”
Line 178: This is not clear. How do two studies not contain information on at least one species? Please reword for clarity.
Line 206: Remove italics at the end of the figure caption, and spelling error of “represented”
Line 211: Delete the part of the sentence in parentheses “(only 5 in the ....)”. Irrelevant.
Line 217: Replace “revised has in scavenging” with “reviewed have scavenging in”
Line 225: Insert “a” before “possible”
Line 255: I appreciate the authors pointing to this being a “first approximation”. Just a comment.
Line 291: Replace “interacting with” with “in”
Line 292: Replace “constant” with “consistent” or “predictable”
Line 293: Replace “lesser possibilities of a correct waste management” with “poor waste management practices”.
Line 294: Delete “,”
Line 295: Replace “a great meat incorporation in their diet” with “a predominately meat-based diet”
Line 298: Please include the scientific names for all species at first use.
Line 299: Replace “analyzed” with “reviewed”
Line 301: Replace “call” with “urge”
Line 303: Delete “properly”
Line 307: Delete “occassional or constant”
Line 326: The references listed are largely well formatted, but there are several errors that need corrected. Please pay attention to the font of journal titles and make sure all scientific names are italicized throughout, for instance.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
The authors have selected an interesting topic, predation and scavenging in urban dominate landscapes, key in a new and increasing research discipline, urban ecology and conservation. In my opinion, it is a novel review work that contributes with a great deal of information to a subject little studied to date, ordering and characterizing current knowledge as well as identifying gaps of knowledge, useful to focus future research efforts. At this stage, I think that some point of the manuscript need to be checked. The use of the terms carnivore and/or carnivorous sometimes are confusing. In addition I find the statistical analysis section a bit confusing and I think that some clarifications are needed. Below, you will find specific comments and suggestions which I consider useful to improve the manuscript.The authors have selected an interesting topic, predation and scavenging in urban dominate landscapes, key in a new and increasing research discipline, urban ecology and conservation. In my opinion, it is a novel review work that contributes with a great deal of information to a subject little studied to date, ordering and characterizing current knowledge as well as identifying gaps of knowledge, useful to focus future research efforts. At this stage, I think that some point of the manuscript need to be checked. The use of the terms carnivore and/or carnivorous sometimes are confusing. In addition I find the statistical analysis section a bit confusing and I think that some clarifications are needed. Below, you will find specific comments and suggestions which I consider useful to improve the manuscript.
Specific comments
L13. Add species after carnivorous.
L46. The red fox instead the fox, because you use a specific reference for this species. Furthermore, you should use the scientific names for species once they are cited at the first time, e.g. the red fox, barn owls, coyote, raccoon, etc.
L45. Add species after carnivorous.
L64. Do you refer on general way to “carnivorous species” instead carnivores? Carnivore/s is commonly used to refer to mammalian carnivorous species in scientific literature (order Carnivora). The same for the line 68, and others cases throughout the manuscript. Please, clarify this because sometimes the reading is a little confusing.
L74. …an integrative…
L77. …focused on…
L84. “databases” instead “data”.
L86. Point after “cities”. I found several other punctuations and similar mistakes, e.g. L75; L242; L254; L256. Check it.
L81-103. Systematic literature review
Commonly, systematics reviews also includes grey literature (scientific reports, PhD and Master thesis, scientific papers not included without JCR impact, etc). Grey literature, or evidence not published in commercial publications, can make important contributions to a systematic review. This scientific literature may be found by google scholar but also by a “snowball” method. Please clarify if you only use scientific papers and why to ensure that the review methods used are repeatable. See:
Haddaway & Bayliss 2015. Shades of grey: Two forms of grey literature important for reviews in conservation.
Paez 2017; Gray literature: An important resource in systematic reviews.
L.112. I think that Wilman et al. 2014 also includes a “scavenging level”. Wouldn't it be more appropriate to include it in scavenging models rather than carnivory level?
L114. “Circadian rhythm” or “daily activity” better than daily rhythm. I have checked that you use the second one in Table 2.
L123-136. Statistical analyses
-In Poisson GLMs, log link function is usually used and recommended to avoid negative fitted values. Why do you use identity as link function?
-I fail to understand which the sampling unit in the analyses is. Is it the study? If it is,
- I did not find any evaluation about models fit, and how models were affected or not by overdispersion. In Poisson GLMs this last is especially important since parameter SE estimates may be biased.
-In ecology research the most commonly used CI is 95%. Is not incorrect the use of 85% CI, but I find reasonable to explain the reasons why you select this confidence level in your research to identify informative parameters.
L159. The United Kingdom instead United Kingdom.
L162. At 95% or 85% significance level? In any case, perhaps this result or analysis is not necessary since its effect on studies number or in species features are not analysed and discussed.
L180-188. Sometimes you use “n” and other times “N” for the sample size. Use the correct according to the journal format.
L194. Carnivorous species level or Carnivory level? I think that the second one.
L210-215. In general, most of scavenging studies have been conducted in cities from developed countries. In this cities it would be expected a low availability of carcases/carrion because the existing of deficient cleaning services in the most developed countries. Have you tested/evaluated how scavenging studies in urban areas and periurban area have been performed in developed or undeveloped countries? On this sense, is it possible that scavengers and the ecosystem services that they provide will be more important in undeveloped countries than in developed?
L.272-273. More than striking, is disturbing. Both domestic predators are worldwide considered as a serious threat for biodiversity conservation. Can we assume the same for urban ecosystems, or on the contrary cats and dogs play a key function as predators/scavengers in urban ecosystems (sometimes the only mammalian predators)? I think that this is a key result in your review, and you have a good opportunity to discuss this in a short paragraph.
L291. Do you refer to carnivorous species, both predators and scavengers?
L293-296. According to your best models, Order and Class are excluded to explain the features of both predators and scavengers, so why medium size mammals?
Tables
-Wouldn't it be more appropriate if Table 2 appears first with the ranking of models, and then table 1, where the coefficients of the best models are shown?
-Table 1 y 2: In the main text of your manuscript, you describe Carnivory level as explanatory variable. However in these tables you use Carnivore level. Use the correct form, in my opinion Carnivory level.
Table 2: L206. Change to D2, as is shown in the table´s head.
Suplementary Material
-In SP1 and SP2, you use Figure 1 and Figure 2 respectively, but actually you are showing tables. I understand that this is a mistake, and there are not Figures in the supplementary material section, at least I didn´t find them.
-Please, include a reference list with the full bibliographic references for each used study. Only a little number is included in the references list in the manuscript. I consider this useful to have a quickly identification in order to consult any paper which might be particularly interesting to potential readers.
Author Response
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Author Response File: Author Response.docx
Reviewer 4 Report
This paper is an interesting review on predation and scavenging in urban area, a topic which is deserving a growing interest as authors show in results. The manuscript is well written except some typos (for example two full stops line 256). However I suggest a major revision for three main reasons: 1- some results should be more detailed, 2- the discussion should be thoroughly revised. Moreover there is a need to define both the terms predation and scavenging, which are surprisingly absent in the introduction. This is important to restrict the field of the review to some orders of animals (as the list of species is only given as supplementary material), for example no bat species preying on insects is considered.
Results start with the number of papers used for this review and their temporal distribution. A comparison with the distribution of scientific papers on the same topic in natural habitats would have been interesting. The distribution per biome follows (please consider one decimal for all percentages), and I don’t understand why authors insist on two biomes where cities are scarce. Again there is no comparative element, but we shall wait the discussion. Figure 3 is useless as it shows only six numbers that could easily be given in the text. On the contrary the list of species, one of the most interesting result, is relegated to supplementary material contrary to poorly informative models which should be supplementary material.
Parts of the discussion include new results (for example lines 239-252) and don’t try to explain them. The discussion begins with the major interest of predation over scavenging in the studies. First, aren’t there more predators than scavengers among animals, particularly among vertebrates? This is another lack of comparative data already suggested above. Second, the main discussion on this topic starts line 254 with the feeding ecology of species. Why does the discussion on the geographic distribution of studies lie between these two parts? I think that the discussion should better start by the paragraph on the increasing interest for urban ecology before focusing on the predation / scavenging studies.
Concerning the low number of studies on scavenging in Europe, there is no explanation or at least an hypothesis. The reader must wait line 247 to suppose that the management of waste is different than in some other continents. The explanation is more explicit in the conclusion line 293: “in countries and cities with lesser possibilities of a correct waste management”. Isn’t it a bit late?
Concerning the ignorance of this topic in “many countries in Africa, and most of Asia and Latin America”, don’t you think that the answer is given lines 251-253? Obviously these regions offer a large quantity of waste to scavengers but why do you write “may also” when for sure the scientific studies are scarce in those countries. Here again a comparison of the scientific production on the same topics in natural habitats would have been relevant. Moreover, in those countries where the main concern is the conservation of endangered species and the number of scientists is low, don’t you think that urban ecology is a poorly relevant topic. This should be discussed.
At last, the last lines of the discussion from line 276 could be easily deleted.
Minor comments
Lines 13, 15 and 45: for my dictionary “carnivorous” is an adjective.
Line 46: should read “red fox”
Line 49: what about hyenas?
Line 56: delete “it”.
Line 180: Passeriformes (as you wrote Accipitriformes).
Line 184: “most” instead of “more”?
Line 186: contained information on one or more species. Urban scavengers, appearing in five or more different articles, were Vulpes…”.
Line 206: is the end of the line correct?
Line 255: “needed” instead of “need”.
In references scientific names are not italicized.
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
In my opinion, the authors revised the previous version of the manuscript in a proper way, and they responded for all my earlier comments. That is why I see that the manuscript in the current version is suitable for acceptation with only minor comments (listed below).
In my opinion, the authors revised the previous version of the manuscript appropriately, and they responded to all my earlier comments. That is why I see that the current version of the manuscript is suitable for acceptation with only minor comments (listed below).
In the Introduction part of the ms in the sentence describing different sources of food in cities (L. 87 - 89) on the first place should be located human food (garbage) which change not only predators' foraging behaviour but also other aspects of their ecology (space use, activity pattern, intra and interspecific interactions).
I also suggest that in Conclusion, authors will write that future studies on predators in cities should focus not only on the type of food or one particular predator species but mainly on how the location of food resources, their availability and predictability influence on the ecology of predators.
Author Response
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Author Response File: Author Response.docx
Reviewer 2 Report
Thank you for addressing my comments about your manuscript. I feel that this is a much improved manuscript that is an important contribution to our knowledge about carnivores in urban environments.
Having said that, there are many instances were the text can use some light polishing to correct minor grammatical issues. I advise a thorough proof read by more than one author before publication.
Thank you for doing this work. I look forward to seeing it published.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
The authors have made a great effort to improve the manuscript. I have been able to verify how they have responded to all the comments and have made the proposed changes, including new statistical analysis. Overall I think the manuscript has been improved. I only have some minor comments (see below).
-I think that my comment about the use of “carnivore/s” or carnivorous species (Coment 5 in the author’s response letter) has not been interpreted correctly, perhaps because I did not explain it well at all. I mean that the use of “carnivores” is more appropriate for mammalian species belonging to order Carnivora (e.g. canids, felids, mustelids, etc), i.e. when you are referring specifically to this group of species. The use of “carnivorous species” is not incorrect when you refer to all species that feed on meat which includes carnivores and other species “meat-dependent” such raptors or some reptiles (carnivorous species but not carnivores).
For instance, in L74 (diversity-991933-peer-review-v2) you replaced “carnivorous species” by “carnivores”. In my opinion you are referring not only to carnivore species, i.e. mammalian species from order Carnivora, just the contrary you are referring to a broad group of species that feed on meat. Another example in L80. Here “carnivorous species” I think is the correct term, because include raptors and other “carnivorous species”. So you only should use “carnivore/s” when you refer to mammals belonging to order Carnivora. Thus, your results show that scavengers’ species were mainly “carnivores species”, i.e. red fox, cats and dogs (Figure 2B).
I hope this new explanation is useful to correct this little misunderstanding in the whole manuscript.
Statistical analysis
-The value obtained for overdispersion in the best model for urban scavengers is to low, indicating under-dispersion. I recomend to try a negative binomial GLM for scavengers and compare the results.
-This sentence “All statistical analyses were performed in the R v.3.6.1 statistical platform” has been deleted in the new version (diversity-991933-peer-review-v2). I recommend that you keep it.
Author Response
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Author Response File: Author Response.docx
Reviewer 4 Report
I think that most of my former remarks have been overlooked. So I mainly will repeat requested changes in a more concise way.
Moreover I suspect that a second referee asked for hypotheses. I totally disagree with this request. I prefer to read a paper with descriptive data than a paper with daubed hypotheses. This is my first (and possibly main concern).
- Most of hypotheses are disconnected with the introduction.
- Hypothesis 1: why do expect more published research on predators than on scavengers? How many predators / scavengers are there in the World? If you give these numbers than you can write the hypothesis.
- Hypothesis 2: you wrote lines83-84 that Magle et al. [56] already reported a bias toward developed country. You can give an hypothesis not to predict but to confirm that most studies occur in the most developed countries.
- Hypothesis 3: I didn’t read anything in the introduction suggesting a higher species richness in developed countries. Moreover I suspect that, as developed countries are located in temperate zones and less developed countries in the tropics, the species richness would be higher in the last countries (there are a lot of references on this topic). The same applies to the availability of trophic resources.
- Hypothesis 4: another hypothesis which is not linked with the introduction.
- I don’t understand why authors insist on two biomes where cities are scarce (desert and taiga). Please delete lines 193-194 in absence of comparison.
- Figure 3 is useless as it shows only six numbers that should be given in the text.
- The list of species, one of the most interesting results, must not be relegated to supplementary material contrary to poorly informative models given in table 1.
- I read that authors recorded 100 predator species in 95 papers, and 49 scavenger species in 47 papers. Ratios are quite identical. This should be written (and discussed).
- Table 1 is unnecessary. Give it as supplementary material.
- I disagree the gap detected between the articles referred to predators and scavengers (line 275) as this is the gap between the number of species.
- The first sentence of the second paragraph (line 287) should read: We confirmed the geographical bias… world [56],…’
- In the same paragraph, the most important explanation is relegated at the end (lines 298-301) when it should be the first one (line 293).
- Line 333 you write that ‘most of the species recorded in the articles are mammals and birds’. Which other groups did you expect when restricting predation and scavenging to vertebrate consumption? The only other groups are squamates and crocodilians… What is interesting in your review (and should be discussed) is the role of domestic species.
Minor comments
Delete ‘scavenging’ from key-words as this word is already in the title.
Line 41: closing bracket is missing.
Line 42: delete ‘predictable’.
Line 44: replace ‘animals’ by ‘vertebrates’.
Lines 52-53: diet is based in vegetables , fruits and berries for corvids, not for red fox with consumption of animals is not occasional as it is written.
Line 102: should read ‘species richness of carnivores’.
Lines 149 and 152: ‘added’
Lines 201-202, please give minimum – maximum instead of a mean and standard deviation (which is higher than the mean for the second one).
Lines 203-204: only two decimals for t and df and three for the p-value.
Line 218: replace ‘without identify the predators’ by ‘without identified predactors’.
Line 220: the Orders.
Lines 259-260: delete ‘devoted to study the spatio-temporal information contained in studies’.
Line 268: should read ‘know how predators and scavengers’.
Line 305: should read ‘4.3 Predator and scavenger species… ‘.
Lines 353-555: please clarify. The sentence is difficult to understand.
Author Response
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Author Response File: Author Response.docx
