Biological and Conservation Aspects of Otter Mortality: A Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript is well writen and organised. The topic is within the scope of the journal and the article is interresting and original. The idea for the review is rather smart and the manuscript has a high potential for citation. On that basis I will recomend acception, but after majour revision, as the text have to be restructured.

Introduction: The introduction includes important topics like distribution, conservation status and diet, but did not provided data on the migration biology of otters.  As migrations are actually among the main risks for mortality in these species, some information have to be provided. There are no data on the habitat ranges of the otter species. This is important because some species have rather large individual ranges.

Main comments:

Line 88: It is somehow awkward to reduce 850 results to only 33. As this is the only paragraph in Material and method section, it has to be revised and the "non-specific working" searching terms have to be explained. The 700 titles obviously did not concerned otters and that means that the search with the use of the provided key words was not effective. Were some of these key words used in combinations? There is a lack of analisys of how many otter specimens were object of these 33 articles.

Line 137 Table 1: please remove "and" after "drowning" and explain what do you mean under that term. The drawning has to be forced by some factors...(see also Line 140). How to understand terms like "Unknown", "Nutritional disorders" and "Natural causes"? In line 143 the causes "sharka attacks" and "infections" were combined under "Natural causes". This is rather confusing. The authors may will to provide more detailed paragraph on the selection and grouping of the Mortality causes in the Mterial and Method section.   

Line 178-179: This sentence belongs to the introduction.

Line 243: The authors stated that the fights are "not very common", but at the end of the parragraph they provide information about 10 cases of death due to such fights and this is a significant number.

Line 296-298: The sentence have to be revised!

Line 324-329: This paragraph is confusing... Indead, Europe, North and South America seem to contribute to the field, however data from Africa and Asia are completelly lacking. Even data from Japan are lacking, where the Otter is a folklor symbol. This topic has to be adressed more clearly. 

Conclusion: I am not convinced by the first five sentences of this paragraph. The data are not enough for such conclusions and for several species there are no data at all. The geographic limitatrion of the data is also not suportive for the first part of the conclusion.

Figure 2. I am not sure how this picture will be published in the end version of the manuscript, but within the .pdf file the figure is not usable. The information is not clear, the letters are too small, the color coading is unclear, some sections are not even indexed. The picture hase to be restiled to become more reader friendly.

 

Comments on the Quality of English Language

I am not a native speaker, but as I can judge the language is according the scientific standards. However, I have the feeling that some corrections of the literature style may help the text to be improved (see the text of Lines 148 to 153; Line 212: "aquatic otter"?; "two distinct environments, aquatic and marine"). In this relation I propose corrections to be provided by a natiuve speaker.

Author Response

The manuscript is well writen and organised. The topic is within the scope of the journal and the article is interresting and original. The idea for the review is rather smart and the manuscript has a high potential for citation. On that basis I will recomend acception, but after majour revision, as the text have to be restructured.

Introduction: The introduction includes important topics like distribution, conservation status and diet, but did not provided data on the migration biology of otters.  As migrations are actually among the main risks for mortality in these species, some information have to be provided. There are no data on the habitat ranges of the otter species. This is important because some species have rather large individual ranges.

Author answer: Information regarding migration biology and ranges was added.

Line 88: It is somehow awkward to reduce 850 results to only 33. As this is the only paragraph in Material and method section, it has to be revised and the "non-specific working" searching terms have to be explained. The 700 titles obviously did not concerned otters and that means that the search with the use of the provided key words was not effective. Were some of these key words used in combinations? There is a lack of analisys of how many otter specimens were object of these 33 articles.

Author answer: thank you for the comment, yes it is true that only with the works at first many results appear that were not related to mortality but to other studies. We authors did again the section material and methods using the combination of words, to provide a realistic number.

Line 137 Table 1: please remove "and" after "drowning" and explain what do you mean under that term. The drawning has to be forced by some factors...(see also Line 140). How to understand terms like "Unknown", "Nutritional disorders" and "Natural causes"? In line 143 the causes "sharka attacks" and "infections" were combined under "Natural causes". This is rather confusing. The authors may will to provide more detailed paragraph on the selection and grouping of the Mortality causes in the Mterial and Method section.  

Author answer: after "drowning" it was a word that was missing and was added to the table again. The author is the material and methods description explain better the different categories on mortality. Natural causes was changed to Infectious diseases.

Line 178-179: This sentence belongs to the introduction.

Author answer:  sentence removed

Line 243: The authors stated that the fights are "not very common", but at the end of the parragraph they provide information about 10 cases of death due to such fights and this is a significant number.

Author answer:  first sentence eliminated.

Line 296-298: The sentence has to be revised!

Author answer:  revised.

Line 324-329: This paragraph is confusing... Indead, Europe, North and South America seem to contribute to the field, however data from Africa and Asia are completelly lacking. Even data from Japan are lacking, where the Otter is a folklor symbol. This topic has to be adressed more clearly.

Author answer:  revised.

Conclusion: I am not convinced by the first five sentences of this paragraph. The data are not enough for such conclusions and for several species there are no data at all. The geographic limitatrion of the data is also not suportive for the first part of the conclusion.

Author answer: first five sentences removed.

Figure 2. I am not sure how this picture will be published in the end version of the manuscript, but within the .pdf file the figure is not usable. The information is not clear, the letters are too small, the color coading is unclear, some sections are not even indexed. The picture hase to be restiled to become more reader friendly.

Author answer: the figure was improved.

Reviewer 2 Report

Comments and Suggestions for Authors

A comprehensive review of what is known about mortality casualities for otter could be quite useful in order to provide informed conservation measures to wildlife managers.  However, limiting a quite extensive available literature (700) to only 33 articles diminishes the study effort and even bias some of the results, mostly because most utilized literature is mostly in English and does not provide extensive literature available in Latin American countries at least, and probably African and Asian countries. One example is the attached file.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

English is fairly good with some typos.

Author Response

comprehensive review of what is known about mortality casualities for otter could be quite useful in order to provide informed conservation measures to wildlife managers.  However, limiting a quite extensive available literature (700) to only 33 articles diminishes the study effort and even bias some of the results, mostly because most utilized literature is mostly in English and does not provide extensive literature available in Latin American countries at least, and probably African and Asian countries. One example is the attached file.

Author answer: methods section as been revised in accord to reviwer 1. Not only literature in english was used, portuguese, spanish and france also were used. More 2 papers were added to the review.

Reviewer 3 Report

Comments and Suggestions for Authors

This is a review of otter mortality that is a useful summary for people that study diseases of otters and other carnivores. However, I do have suggestions for improvement of the manuscript. 

In figure 2, the donut graph is not labeled for all segments on the left. 

First, I highly suggest that the infectious causes of death should be elaborated on here, instead of just 'infectious' - and toxic etiologies (e.g. microcystin). I think there are numerous missing results for mortality due to infectious diseases- Toxoplasma gondii (including particularly virulent strains of Toxoplasma) -Sarcocystis freshwater runoff-oyster relationships were not mentioned as well as microcystin toxicosis due to blue algae. There are extensive reports of mortality in sea otters due to these diseases. I suggest the authors' revisit these subsections of mortality in detail and do a further intensive survey of these infectious and toxic/environmental causes of death. 

Materials and methods- please follow the PRISMA protocols for necropsy reviews, Did you discard double reviews?

Results- for the first paragraph state the number of studies from different years. 

 

Minor comments: * 

abstract:

post-mortem does not need to be italicized

line 11: change 'pattern' to 'patterns'

line 14- change 'sea otter' to 'sea otter deaths are associated'

line 40- put 'The' in front of 'Neotropical'

line 41- put 'The' in front of 'Southern'

line 42- put 'The' in front of 'Marine' 

there are others- just put 'The' in front of all of the otter common names

line 52- 'Worldwide' instead of 'All around the world'

line 66- replace 'post-mortem' with 'the necropsy exam'

line 77, replace' Postmortem' with 'Therefore, post-mortem examinations can provide' (also don't italicize post-mortem). 

line 131- change 'oil spiling' to 'oil spills'

Comments on the Quality of English Language

This needs some revision some grammatical errors. 

Author Response

This is a review of otter mortality that is a useful summary for people that study diseases of otters and other carnivores. However, I do have suggestions for improvement of the manuscript.

 

In figure 2, the donut graph is not labeled for all segments on the left.

Author answer: the figure was improved.

 

First, I highly suggest that the infectious causes of death should be elaborated on here, instead of just 'infectious' - and toxic etiologies (e.g. microcystin). I think there are numerous missing results for mortality due to infectious diseases- Toxoplasma gondii (including particularly virulent strains of Toxoplasma) -Sarcocystis freshwater runoff-oyster relationships were not mentioned as well as microcystin toxicosis due to blue algae. There are extensive reports of mortality in sea otters due to these diseases. I suggest the authors' revisit these subsections of mortality in detail and do a further intensive survey of these infectious and toxic/environmental causes of death.

Author answer: the information it was added.

Materials and methods- please follow the PRISMA protocols for necropsy reviews, Did you discard double reviews?

Author answer: yes

Results- for the first paragraph state the number of studies from different years.

Minor comments: *

abstract: post-mortem does not need to be italicized

line 11: change 'pattern' to 'patterns'

line 14- change 'sea otter' to 'sea otter deaths are associated'

line 40- put 'The' in front of 'Neotropical'

line 41- put 'The' in front of 'Southern'

line 42- put 'The' in front of 'Marine'

there are others- just put 'The' in front of all of the otter common names

line 52- 'Worldwide' instead of 'All around the world'

line 66- replace 'post-mortem' with 'the necropsy exam'

line 77, replace' Postmortem' with 'Therefore, post-mortem examinations can provide' (also don't italicize post-mortem).

line 131- change 'oil spiling' to 'oil spills'

Author answers: corrections made

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Editor,

 In the present for the manuscript is acceptable for publishing. The authors had prepared a very good revision of the first version of the manuscript.

Best regards!