Skull and Neck Lesions in a Long-Finned Pilot Whale (Globicephala melas): A Result of Ship Collision?

Round 1

Reviewer 1 Report

Dear authors,

I do really think your publication is in a great value, and really interesting because these animals are difficult to necropsy due to the low number of animas stranded. In addition, the technique is very interesting and I think quite novel. However, I do believe there are some issues to be amended to strength the publication.

Authors used many references from their group in a general context. I do think that the use of international references on similar topics in other parts of the world (especially Europe) will strength the publication.

See my comments below/attached file

Regards

Comments for author File: Comments.pdf

Author Response

Reviewer 1:

Dear authors,

I do really think your publication is in a great value, and really interesting because these animals are difficult to necropsy due to the low number of animas stranded. In addition, the technique is very interesting and I think quite novel. However, I do believe there are some issues to be amended to strength the publication.

Authors used many references from their group in a general context. I do think that the use of international references on similar topics in other parts of the world (especially Europe) will strength the publication.

See my comments below/attached file. Regards. We thank the reviewer for the very nice words. Yes, certainly, these whales present a challenge to necropsy due to the low number of such strandings. Regarding the references, we agree, and therefore we have now replaced two of our own references with European publications from other research groups (see below).

 

Introduction: L41-42: References 1-4. I do understand that authors would like to include references which they are authors, however, it will be better if they include references from other areas. For example, in Europe there are several countries like UK, Spain, Portugal & Italy with several publications on that. Including these references with increase the importance of obtaining information from stranded/bycatch animals worldwide. We agree, and we have now replaced two references with some European references. This has strengthened the manuscript.

 

L43: Authors are making a difference between “cheap” and “expensive” necropsies. I do think this is not a correct term. I think authors should compare between full necropsy or necropsies with a minimum sample collection. In my opinion, once a researcher is doing a necropsy it is not much more expensive to do a full necropsy than a minimum, except in terms of personnel and time resources. The expensiveness will came when the researcher need for storage facilities and sample processing. In fact, this is one of the reasons why in some countries, the necropsies have been carried out by NGOs, because they have a lot of “volunteer” personnel. Samples then are processed by institutions under the frame of different projects. Thanks for this interesting comment. We agree and have revised the introduction, so the word “cheap” is now deleted. In Denmark the necropsy is performed both by professionals and volunteers.

 

Results: L84-85. The feeding passage time in odontocetes has been considered around 2-48 hours. In my opinion, this is not a “short feeding passage time”. For example, otters regularly excrete everything within 2-4h. In fact, most of the information that we have on feeding ecology of odontocete species are obtained from stomach contents. The case of pilot whales is related to the small number of animals necropsied. In areas where animals stranded and there are teams in charge on that they reported that the species feed mainly on cephalopods (Gannon et al. 1997, Santos et al.2014), although fish can also be preyed (Whooley et al. 2015). Thanks for this relevant comment. We have now revised the text, so we no longer claim that the whale has a short feeding passage time.

L86: “no macro plastic particles were found” Corrected.

 

Discussion: L132. In my opinion, the paragraph should end after “… transportation.” And start a new paragraph with “According…”. It seems that it is another information to me. We agree. Done.

 

L143-L144: I do recommend to authors to be more specific: whales are more vulnerable to collisions when feeding and socializing. I had to read the sentence few times to understand the connection of the sentence related to the topic. Thanks for making the manuscript more readable. This is now done.

 

L144: In my opinion it will be easier to read if authors end the paragraph after the reference 13 and start a new paragraph with the “Furthermore, …”. I think that the noise impact is something different and that is why I think it will be better to separate the paragraphs. We agree. Done.

 

References: General: Authors should use references from strandings in other areas to strength the manuscript. As stated earlier, we have now added several new relevant references.

 

Figures: Fig.1. Figure legends should be possible to understand and read without the text. In the legend it is not clear the species. This information is now added.

 

Tables: T1. Table legends should be possible to understand and read without the text. In the legend it is not clear the species and where the information in coming from (e.g. necropsy). Thanks for the comment, but as response to reviewer 3, we have chosen to delete the table from the manuscript.

Reviewer 2 Report

Introduction

·       There is a lack of research of important literature that has been published in recent years in relation with the main issue of this paper: ship collision with whales/cetaceans.

·       The word “rotten” is referenced several times throughout the paper, the correct term is “autolysis” and should be defined by the respective level (e.g., advanced-moderate autolysis…). Similar issue with the term “beached”, correct term is “stranded”.

Materials and Methods

·       This section should be better developed. For instance, providing a summary of processing and staining techniques used for histopathologic analysis.

·       Line72-74: Furthermore, some information provided in the ‘Results’ section should have been included in this section instead. For example, sex, length, body condition, decomposition code all should have been included under ‘Materials and Methods’.

Results

·       Line 77: collision with submarine? Need to reference this statement.

·       Line 83: indicate to “See Figure 1” for further details, but I don’t see this is the right place, may be more appropriate in line 90-91?

·       Line 87: Gonad instead of genitals if refences is made to testicles.

·       Line 92-93. How lesions are described needs to be reformulated. For example; “wrecked” or  “powdered”. Better to describe properly as “multiple fractures” or “comminuted”,…

·       In general the use of the term bleeding is not the best option to describe pathological topics, it is more optimal to use hemorrhage and define the level of that (e.g., moderate/severe hemorrhage… etc)

·       Table 1: The use of “pathology” as the title of one of the columns is not correct, because there is no description of any pathology, instead lesions and findings are described. Maybe: Gross findings.

Discussion

·       Line 123. Stated that the goal is to find a forensic technique to help determine if the whale was still alive or dead at the time of collision. There is one technique to detect it histologically, that is detectable even in very decomposed carcasses. See reference:

o   Sierra E, Fernández A, Espinosa De Los Monteros A, Arbelo M, Díaz-Delgado J, Andrada M, et al. Histopathological muscle findings may be essential for a definitive diagnosis of suspected sharp trauma associated with ship strikes in stranded cetaceans. PLoS ONE. (2014) 9:2e88780. doi: 10.1371/journal.pone.0088780

·       Furthermore, the presence of fat embolism in lung microvasculature is an other tool to determine antemortem collisions (Arregui et al. 2019, 2020)

 

·       To add to this, Line 141: Reference “the importance of being able to identify the cause of death” that demonstrates again the literature review performed for this paper is very scarce and not up to date.

·       Line 118-120: Alternative hypotheses are not considered such as interactions with fishing industry or other whales, based on the statement that blunt lesions were extensive, but this is an error largely because:

o   The analyses performed are not sufficient to be able to conclude that the death was due to a ship collision, and that the lesions are truly not peri- or post mortem. Other hypotheses are not explored or researched, and are rejected outright. Also, blunt force lesions are not pathognomonic for ship strikes as they can be found in different pathological entities in small and large cetaceans.

o   Puig-Lozano et al. 2020 results showed lethal trauma in dolphins which is consistent with fisherman aggression and no net/cuts/impressions on the skin were observed.

o   Social intra-interspecific interactions when become aggressive may lead to serious injuries and/or death of the animal. Oremland 2010 supports the hypothesis of intraspecific interaction due to sexual competition in short-finned pilot whales. The prevalence of mandibular fractures increased with the length of the animal, suggesting that the animals may use their heads during fights.

§  Oremland MS, Allen BM, Clapham PJ, Moore MJ, Potter C, Mead JG. Mandibular fractures in short-finned pilot whales, Globicephala macrorhynchus. Mar Mammal Sci. (2010) 26:1–16. doi: 10.1111/j.1748-7692.2009.00334.x

o   Furthermore, killer whales striking with their snouts have been shown to produce internal injuries in other cetaceans without causing external wounds. Jefferson TA, Stacey PJ, Baird RW. A review of killer whale interactions with other marine mammals: predation to co-existence. Mam Rev. (1991) 21:151–80. doi: 10.1111/j.1365-2907.1991.tb00291.x

 

·       With regards to photos provided, associated hemorrhages are not clearly visible which in turn is a key factor considered to support the conclusion of death by ship collision (lines 122, 129). It would be recommended to include photos where hemorrhages referenced can be better observed.

 

·       Lines 128-131. Strong statements are made based on several factors and lesions, but none of them could be considered pathognomonic for vessel strike, nor indeed  “the lack of other patho-anatomical diagnosis” because it is not as robust as it should be in this case, for that it is essential to rule out other possible causes of death. Therefore, we should always perform differential diagnoses. Furthermore, that the animal was in an area of high maritime traffic, is a risk of collision but we can’t assume this the cause of death. 

 Conclusions

·       I agree with the statement about the need and importance to perform complete necropsies, but need to highlight the importance that these are conducted by veterinarians with ample pathology experience with support from experienced pathologists to perform histopathology analyses. 

 

·       We need to be cautious when making diagnoses of causes of death.  To be able to draw conclusions, these need to be backed with robust evidence. Similarly, knowledge of diagnostics tools described in the literature is key to be able to make diagnostic statements about the death of cetaceans – if not we risk making erroneous claims that can difficult the development of measures against a specific threat.

Author Response

Reviewer 2:

Introduction: There is a lack of research of important literature that has been published in recent years in relation with the main issue of this paper: ship collision with whales/cetaceans. We thank the reviewer for raising this issue and have now added extra references.

• The word “rotten” is referenced several times throughout the paper, the correct term is “autolysis” and should be defined by the respective level (e.g., advanced-moderate autolysis…). Similar issue with the term “beached”, correct term is “stranded”. We agree. The words “rotten” is replaced with “autolysis” and have been defined. The word “beached” is replaced with “stranded”.

Materials and Methods: This section should be better developed. For instance, providing a summary of processing and staining techniques used for histopathologic analysis. This has now been performed.

• Line72-74: Furthermore, some information provided in the ‘Results’ section should have been included in this section instead. For example, sex, length, body condition, decomposition code all should have been included under ‘Materials and Methods’. Thanks for pointing this out - this information have now been removed from results to the material and method section.

Results:  Line 77: collision with submarine? Need to reference this statement. Thanks for this comment. There have only been anecdotal descriptions of possible collisions between whales and submarines (e.g. a description in The New York Times, October 7^th, 1959), so we have decided to delete “submarine” here.

• Line 83: indicate to “See Figure 1” for further details, but I don’t see this is the right place, may be more appropriate in line 90-91? Yes, that is correct. This has now been corrected.
• Line 87: Gonad instead of genitals if refences is made to testicles. This is now changed.
• Line 92-93. How lesions are described needs to be reformulated. For example; “wrecked” or  “powdered”. Better to describe properly as “multiple fractures” or “comminuted”. Done.
• In general the use of the term bleeding is not the best option to describe pathological topics, it is more optimal to use hemorrhage and define the level of that (e.g., moderate/severe hemorrhage… etc). This have been changed everywhere in the manuscript, except in the “Simple summary”, where we consider that “bleeding” should be kept.
• Table 1: The use of “pathology” as the title of one of the columns is not correct, because there is no description of any pathology, instead lesions and findings are described. Maybe: Gross findings. Thanks for the comment. However, based on a comment from reviewer 3, we have decided to delete Table 1 from the manuscript. The findings are already described in the text.

 

Discussion

• Line 123. Stated that the goal is to find a forensic technique to help determine if the whale was still alive or dead at the time of collision. There is one technique to detect it histologically, that is detectable even in very decomposed carcasses. See reference: Sierra E, Fernández A, Espinosa De Los Monteros A, Arbelo M, Díaz-Delgado J, Andrada M, et al. Histopathological muscle findings may be essential for a definitive diagnosis of suspected sharp trauma associated with ship strikes in stranded cetaceans. PLoS ONE.(2014) 9:2e88780. doi: 10.1371/journal.pone.0088780. Furthermore, the presence of fat embolism in lung microvasculature is another tool to determine antemortem collisions (Arregui et al. 2019, 2020)
  We thanks very much for these information. They are now included in the manuscript.
• To add to this, Line 141: Reference “the importance of being able to identify the cause of death” that demonstrates again the literature review performed for this paper is very scarce and not up to date.
  We thanks for the comments and the references. We have added these and revised the manuscript.
  
  
• Line 118-120: Alternative hypotheses are not considered such as interactions with fishing industry or other whales, based on the statement that blunt lesions were extensive, but this is an error largely because: - The analyses performed are not sufficient to be able to conclude that the death was due to a ship collision, and that the lesions are truly not peri- or post mortem. Other hypotheses are not explored or researched, and are rejected outright. Also, blunt force lesions are not pathognomonic for ship strikes as they can be found in different pathological entities in small and large cetaceans. We thanks the reviewer for this comment. We agree that we cannot reject these many possibilities, and we have now further emphasized this in the manuscript.

     Puig-Lozano et al. 2020 results showed lethal trauma in dolphins which is consistent with fisherman aggression and no net/cuts/impressions on the skin were observed. Thanks, this has been added to the manuscript now.

    Social intra-interspecific interactions when become aggressive may lead to serious injuries and/or death of the animal. Oremland 2010 supports the hypothesis of intraspecific interaction due to sexual competition in short-finned pilot whales. The prevalence of mandibular fractures increased with the length of the animal, suggesting that the animals may use their heads during fights.. Oremland MS, Allen BM, Clapham PJ, Moore MJ, Potter C, Mead JG. Mandibular fractures in short-finned pilot whales, Globicephala macrorhynchus. Mar Mammal Sci. (2010) 26:1–16. doi: 10.1111/j.1748-7692.2009.00334.x. Many thanks, this important information has been added to the manuscript now.

   Furthermore, killer whales striking with their snouts have been shown to produce internal injuries in other cetaceans without causing external wounds. Jefferson TA, Stacey PJ, Baird RW. A review of killer whale interactions with other marine mammals: predation to co-existence. Mam Rev. (1991) 21:151–80. doi: 10.1111/j.1365-2907.1991.tb00291.x Thanks, this has also been added to the manuscript now.

• With regards to photos provided, associated hemorrhages are not clearly visible which in turn is a key factor considered to support the conclusion of death by ship collision (lines 122, 129). It would be recommended to include photos where hemorrhages referenced can be better observed. We agree, but we are sorry, we do not have better photos. However, one photo is replaced with a little better one, and we furthermore a photo from muscles of the neck region has been included in Figure 1.
• Lines 128-131. Strong statements are made based on several factors and lesions,but none of them could be considered pathognomonic for vessel strike, nor indeed  “the lack of other patho-anatomical diagnosis” because it is not as robust as it should be in this case, for that it is essential to rule out other possible causes of death. Therefore, we should always perform differential diagnoses. Furthermore, that the animal was in an area of high maritime traffic, is a risk of collision but we can’t assume this the cause of death. Thanks for the comment. We agree that we cannot be sure what causes these lesions, and that the high maritime traffic in these areas are causing collision. These aspects are discussed in the manuscript, and we have pointed out the uncertainties more clear now.

 Conclusions

• I agree with the statement about the need and importance to perform complete necropsies, but need to highlight the importance that these are conducted by veterinarians with ample pathology experience with support from experienced pathologists to perform histopathology analyses. Thanks for the comment. In Denmark we are a team of veterinarians, biologist and conservators working with whale strandings and necropsies. There are no financial possibilities that the work can be carried out exclusively by veterinarians who is specialized in whale necropsy. As far as possible, a veterinarian always participates in the necropsy (also in this case). The veterinarians all have other task, however, the histological examinations are carried out by dedicated veterinarians. We have now shortly added the importance including veterinarians in the full necropsy work in the discussion section.

 

·       We need to be cautious when making diagnoses of causes of death.  To be able to draw conclusions, these need to be backed with robust evidence. Similarly, knowledge of diagnostics tools described in the literature is key to be able to make diagnostic statements about the death of cetaceans – if not we risk making erroneous claims that can difficult the development of measures against a specific threat. We totally agree on that, and we therefore not conclude that the whale was striked by a ship or that the traumatic event caused its dead.

Reviewer 3 Report

Review of Animals 1816682, “Skull and neck lesions in a long-finned pilot whale (Globicephala melas): A result of ship collision?,” by Altrup et al.

 

This is a simple manuscript. I wholeheartedly agree with the authors’ conclusion that necropsies should be thorough rather than cursory, and that they should include examination of internal tissues (dissection pluashistology/toxicology if possible). I think that nearly everyone who reads this paper would already agree that vessel traffic and ship strikes are a major threat to all cetaceans, but the information presented here helps to make that case.

 

I agree it is most likely that this animal died due to ship strike, but the authors can’t be certain of that, at least with the information provided here. I have observed broken bones that were presumed to have occurred by impact with whale flukes or collisions/fighting with other animals, and although that is less likely, it (and other such causes) cannot be ruled out here, especially in the absence of other data.

 

I also agree it is likely that this pilot whale was alive before the impact, but it is too bad that the authors were unable to provide the histological or erythrocyte results to conclusively determine that the whale was alive when the trauma was inflicted (instead of the damage occurring post mortem). Unfortunately, the circumstances did not allow for this to happen.

 

The necropsy results presented in Table 1 are nice but they really have nothing to do with a potential ship strike. They provide no information that a ship strike either did or did not occur, with the sole exception of the first entry (muscle and bones).

 

Photograph C of Figure 1 does not show much except a piece of bone. It is inconclusive with regard to a ship strike. Are there no photos of the “powder” of broken bones that are described? Also, the blue letters (A-C) are difficult to see against the dark background; I would use white or a lighter color. More importantly, I hope the authors can find better photos to show, or more results from the muscle or blood work. There is not much to go on here.

 

The writing is OK in this simple manuscript but should be improved. It seems as if there was not a careful proofreading. I have listed below some (but not all) of the obvious mistakes, many of which could probably be found by copy editors.

 

In conclusion, this is a short and simple manuscript that provides some evidence (unfortunately, no definitive evidence) of a possible ship strike, which is itself not really a remarkable occurrence. The main point—that necropsy evaluation must include detailed examination of internal organs and tissues—is important, but also fairly obvious.

 

Minor comments:

Line 20: Please explain what is meant by “insertions.” Incisions?

Line 20: The clause that begins with “Multiple fractured bones” is a fragment but not a complete sentence, as it lacks a verb. You could say “There were multiple…” or something like that.

Line 24: replace “having” with “with”

Line 27: revealed, not reveal (always report in past tense)

Line 31: I am not sure what you mean by “almost powdered sure rounded.” Please rewrite with clarity.

Line 44: exclusive, not exclusively

Line 45: the case with (not of)

Line 49: “stroked by” is not the proper way to say this (hit by?)

Line 53: insert comma after “occur”

Line 69: a few?

Line 84: change comma before “however” to a period or semicolon

Line 93: “powdered” is an odd verb in English. Turned to powder? Pulverized? Please explain better…

Line 96: Why is the entire new paragraph here indented?

Line 122; delete comma after vertebrae

Line 123: simpler to write “Our goal was to use a…”

Line 142: delete comma

Line 143: please explain what “facing the surface” means. At the surface?

Line 162: and that this collision immediately caused?

Line 162: This shows?

Author Response

Reviewer 3

This is a simple manuscript. I wholeheartedly agree with the authors’ conclusion that necropsies should be thorough rather than cursory, and that they should include examination of internal tissues (dissection pluashistology/toxicology if possible). I think that nearly everyone who reads this paper would already agree that vessel traffic and ship strikes are a major threat to all cetaceans, but the information presented here helps to make that case. Thanks, and we agree on that. We hope that this manuscript will remind readers of the importance of thorough necropsies of stranded whales.

I agree it is most likely that this animal died due to ship strike, but the authors can’t be certain of that, at least with the information provided here. I have observed broken bones that were presumed to have occurred by impact with whale flukes or collisions/fighting with other animals, and although that is less likely, it (and other such causes) cannot be ruled out here, especially in the absence of other data. Thanks for this comment. We agree, and this is also why we do not draw a foolproof conclusion in the manuscript. We have now added a discussion of alternative explanations for the lesions.

I also agree it is likely that this pilot whale was alive before the impact, but it is too bad that the authors were unable to provide the histological or erythrocyte results to conclusively determine that the whale was alive when the trauma was inflicted (instead of the damage occurring post mortem). Unfortunately, the circumstances did not allow for this to happen. Thank you for this comment. Yes, we are also sorry that we were not able to safely conclude whether the whale was dead or alive at the time of the traumatic incident.

The necropsy results presented in Table 1 are nice but they really have nothing to do with a potential ship strike. They provide no information that a ship strike either did or did not occur, with the sole exception of the first entry (muscle and bones). The intention with Table 1 was to give an overview of the necropsy findings – both them relevant to the ship strike and the other pathological findings. But since these information are already summarized in the text, we have chosen to delete the table here. 

Photograph C of Figure 1 does not show much except a piece of bone. It is inconclusive with regard to a ship strike. Are there no photos of the “powder” of broken bones that are described? Also, the blue letters (A-C) are difficult to see against the dark background; I would use white or a lighter color. More importantly, I hope the authors can find better photos to show, or more results from the muscle or blood work. There is not much to go on here. We agree. We have revised Figure 1, but as we have no really good photos, it was not possible to illustrate the observed skull lesions more clearly. Instead the neck lesion is now illustrated, and the skull lesions illustrated with a slightly better photo and the figure legend is revised. The blue letters (A-C) is replaced with white letters (A-D).

The writing is OK in this simple manuscript but should be improved. It seems as if there was not a careful proofreading. I have listed below some (but not all) of the obvious mistakes, many of which could probably be found by copy editors. Thanks for the list with obvious mistakes (they are now all corrected – see below). We have also reviewed the manuscript together with an English-proficient professional.

In conclusion, this is a short and simple manuscript that provides some evidence (unfortunately, no definitive evidence) of a possible ship strike, which is itself not really a remarkable occurrence. The main point—that necropsy evaluation must include detailed examination of internal organs and tissues—is important, but also fairly obvious. Thanks for the review.

Minor comments:

Line 20: Please explain what is meant by “insertions.” Incisions? It is corrected to “incisions” now.

Line 20: The clause that begins with “Multiple fractured bones” is a fragment but not a complete sentence, as it lacks a verb. You could say “There were multiple…” or something like that. It is now corrected as suggested.

Line 24: replace “having” with “with” Done.

Line 27: revealed, not reveal (always report in past tense) Done.

Line 31: I am not sure what you mean by “almost powdered sure rounded.” Please rewrite with clarity. The text is revised now.

Line 44: exclusive, not exclusively Corrected now.

Line 45: the case with (not of) Corrected now.

Line 49: “stroked by” is not the proper way to say this (hit by?) Corrected now.

Line 53: insert comma after “occur” Done.

Line 69: a few? Yes, this has now been corrected.

Line 84: change comma before “however” to a period or semicolon. We have changed comma to semicolon.

Line 93: “powdered” is an odd verb in English. Turned to powder? Pulverized? Please explain better… Thanks, this has now been changed to “pulverized into small fragments”.

Line 96: Why is the entire new paragraph here indented? Sorry, it was a formatting error and has now been fixed.

Line 122; delete comma after vertebrae Done.

Line 123: simpler to write “Our goal was to use a…” Thanks, this is now done.

Line 142: delete comma Done.

Line 143: please explain what “facing the surface” means. At the surface? Yes, it is better with “at the surface”, so the text has been revised.

Line 162: and that this collision immediately caused? Yes, we have now revised the text as suggested.

Line 162: This shows? Corrected.