Natural History and Morphology of Crotalus ehecatl (Serpentes: Viperidae)

Round 1

Reviewer 1 Report

In the manuscript entitled “Natural history and morphology of Crotalus ehecatl (Serpentes: Viperidae)”, the authors provided baseline data of the diet, life history and activity patterns of C. ehecatl specimens and adds to the morphological data available from previous studies. It will help to obtain a better understanding of the snake’s biology and ecology. The followings are comments that the authors need to notice.

1. Animal experiments (such as forced regurgitation) were conducting in this study, but no ethics statements are made in the manuscript (e.g., no IACUC approval no. is presented).
2. As the authors mentioned, the sample size of this study providing baseline data is small and only 13 individuals were recently sampled; some data seems highly related to previous studies (published by some of the authors). They did not detect enlarged follicles or embryos in the analyzed specimens and very little information on the reproductive cycle in both sexes were provided in this study. It would be more acceptable and contributive to publish in such journal as ‘Diversity’ if the study provides detailed reproductive data by collecting larger samples, which is important for the conservation for this species.
3. At lines 115-118, the authors used ANCOVA by log-transforming all variables, but they tested for differences in SVL and TTL between sexes with the Mann-Whitney U-tests (i.e., without transforming the variables). Why not also transforming such variables and conducting parametric testing (e.g., t-test or ANOVA) to examine the differences between sexes? When conducting ANCOVA (with SVL as the covariate), the testing variables should not be divided redundantly by SVL (i.e., TL/SVL or HL/SVL). In addition, did you find significant heterogeneity of regression slopes? When testing the homogeneity of regression slopes, the associated statistic values (i.e., the F and P values) should be presented. To meet assumptions of parametric testing, the testing results of normal distribution and homogeneity of variance (i.e., P values) should also be presented.
4. At line 174: “female” should be “females”.

Author Response

In the manuscript entitled “Natural history and morphology of Crotalus ehecatl (Serpentes: Viperidae)”, the authors provided baseline data of the diet, life history and activity patterns of C. ehecatl specimens and adds to the morphological data available from previous studies. It will help to obtain a better understanding of the snake’s biology and ecology. The followings are comments that the authors need to notice.

1. Animal experiments (such as forced regurgitation) were conducting in this study, but no ethics statements are made in the manuscript (e.g., no IACUC approval no. is presented).

RESPONSE: This part of the methodology was added as common practice applied when analyzing intestinal content and feces in live animals, however, during our study we only analyzed museum and dead specimens (road kills or sacrificed by locals). Live specimens mentioned correspond to a scientific note about diet of a C. ehecatl  individual, which was observed while it ate a rodent (Carbajal-Márquez et al. 2021), and to the specimen that was eating a quail. In both occasions, the specimens were found at the moment they captured and ingested the prey and so it was not necessary to palp the organisms or to submit a protocol for IACUC approval. We eliminated the live specimen methodology paragraph to avoid this confusioN.

 

2. As the authors mentioned, the sample size of this study providing baseline data is small and only 13 individuals were recently sampled; some data seems highly related to previous studies (published by some of the authors). They did not detect enlarged follicles or embryos in the analyzed specimens and very little information on the reproductive cycle in both sexes were provided in this study. It would be more acceptable and contributive to publish in such journal as ‘Diversity’ if the study provides detailed reproductive data by collecting larger samples, which is important for the conservation for this species.

 

RESPONSE: Intensive field sampling in recent years yielded only these 13 specimens which reflect the difficulty involved with finding this species. Regarding the comment mentioning the highly related data to other studies, we used data from a C. ehecatl scientific note published by us as well as a recollected information of C. ehecatl from L.M. Klauber´s notes.

 

As we do not have a larger sample size with which to analyze reproductive data better and since Neotropical snake copulation events are rarely documented, based on behavior, brood birth date, and activity patterns we suggest that the C. ehecatl reproductive cycle is similar to that of closely related species as well as to other Neotropical pit vipers, and it seems that this character is phylogenetically conserved. We also encourage further studies to be conducted focusing on the reproductive cycle of both sexes of this species.

 

3. At lines 115-118, the authors used ANCOVA by log-transforming all variables, but they tested for differences in SVL and TTL between sexes with the Mann-Whitney U-tests (i.e., without transforming the variables). Why not also transforming such variables and conducting parametric testing (e.g., t-test or ANOVA) to examine the differences between sexes? When conducting ANCOVA (with SVL as the covariate), the testing variables should not be divided redundantly by SVL (i.e., TL/SVL or HL/SVL). In addition, did you find significant heterogeneity of regression slopes? When testing the homogeneity of regression slopes, the associated statistic values (i.e., the F and P values) should be presented. To meet assumptions of parametric testing, the testing results of normal distribution and homogeneity of variance (i.e., P values) should also be presented.

 

RESPONSE: Statistical analyses were modified considering these and the other reviewer´s comments, including the use of parametric tests and avoiding the redundant HL and TL division by the SVL.

 

4. At line 174: “female” should be “females”.

 

RESPONSE: This was corrected, thank you for noticing it.

Reviewer 2 Report

The authors seek to provide details on aspects of the biology of a poorly understood snake species. They invested considerable effort to obtain the data, and did a commendable job in analyzing the data and putting it together in a paper. Yes, the data are sparse, which the authors acknowledge, but they deserve the light of day. Given the intent of the special issue, I feel the manuscript is highly desirable, and recommend acceptance. However, it is going to need a fair bit of revision, for which I'm supplying a marked-up manuscript with many suggestions, the large majority of which are relatively minor.

There is one major issue, nevertheless, that I feel should be addressed. The authors really should consider scrapping the use of SVL as the covariate in measuring sexual body component dimorphism, and instead reanalyze the data using the geometric mean of the three body measures, which should be the least-biased measure of overall body size. As I explained in a comment on the marked manuscript, SVL (which most everyone uses incorrectly as the covariate) is primarily a measure of trunk size, which is almost certainly female-biased due to maternity selection for larger clutches. The female bias in SVL leads to male bias in head size, as they are two parts of a whole. Please take a look at these two references, which address the issue in more detail, and consider re-running the analyses:

Johnson and Hayes (2020), An improved approach to measuring sexual dimorphism in snakes: Morphological variation in the Bahamian Racer (Cubophis vudii vudii). Reptiles & Amphibians, 27(2), 137-146.

Cochran, C. 2019. Variation in morphology, diet, and venom composition in Crotalus pyrrhus. Unpublished Ph.D. dissertation, Loma Linda University, Loma Linda, Calilfornia, USA.

On a personal note, I want to encourage the authors to continue their good work. And I don't mind signing my name to this review.

- William K. Hayes, Loma Linda University

Comments for author File: Comments.pdf

Author Response

The authors seek to provide details on aspects of the biology of a poorly understood snake species. They invested considerable effort to obtain the data, and did a commendable job in analyzing the data and putting it together in a paper. Yes, the data are sparse, which the authors acknowledge, but they deserve the light of day. Given the intent of the special issue, I feel the manuscript is highly desirable, and recommend acceptance. However, it is going to need a fair bit of revision, for which I'm supplying a marked-up manuscript with many suggestions, the large majority of which are relatively minor.

There is one major issue, nevertheless, that I feel should be addressed. The authors really should consider scrapping the use of SVL as the covariate in measuring sexual body component dimorphism, and instead reanalyze the data using the geometric mean of the three body measures, which should be the least-biased measure of overall body size. As I explained in a comment on the marked manuscript, SVL (which most everyone uses incorrectly as the covariate) is primarily a measure of trunk size, which is almost certainly female-biased due to maternity selection for larger clutches. The female bias in SVL leads to male bias in head size, as they are two parts of a whole. Please take a look at these two references, which address the issue in more detail, and consider re-running the analyses:

Johnson and Hayes (2020), An improved approach to measuring sexual dimorphism in snakes: Morphological variation in the Bahamian Racer (Cubophis vudii vudii). Reptiles & Amphibians, 27(2), 137-146.

Cochran, C. 2019. Variation in morphology, diet, and venom composition in Crotalus pyrrhus. Unpublished Ph.D. dissertation, Loma Linda University, Loma Linda, Calilfornia, USA.

RESPONSE: We sincerely appreciate the time that the reviewer took to mark our manuscript, all the suggestions were considered as they greatly improved it, and all the modifications were marked on the document, figures, and tables.

We appreciate the suggestion made about using the geometric mean instead of the SVL as the alternative covariant. However, this was the only suggestion we did not follow completely in our revision of the paper. And we decided to maintain the used analyses with slight modifications suggested by the reviewer for the following reasons: 1. to avoid discarding specimens that don´t have complete data and with this reduce our already limited sample size, 2. to avoid altering our results and in turn our interpretation of these, 3. to keep our work as comparable as possible to other studies on Neotropical rattlesnakes and other snakes (including works by the reviewer). Nonetheless, we acknowledge the utility of this new approach and will consider including these analyses in future studies with larger sample sizes.

 

On a personal note, I want to encourage the authors to continue their good work. And I don't mind signing my name to this review.

- William K. Hayes, Loma Linda University

RESPONSE: Again, many thanks for the great review and the extremely useful suggestions, we really appreciated them.

Reviewer 3 Report

The  manuscript covers interesting aspects of the natural history and biology of a rattlesnake species in central Mexico. This study uses traditional methods represents the kind of paper that is very valuable but unfortunately published rarely in the current scientific landscape.

The authors did a good job in utilizing all available specimens and information of a relatively rare snake species.

Aside from the comments and edits I provide in the attached PDF file I have two general comments:

(1) acknowledging how difficult it can be to get specimens of rare snake species I like to emphasize that statistics are based on the number of subjects (n). There is a danger to overvalue statistical results even if the actual n for a sample group is pretty low and observations are more anecdotal than statistically supported. The authors mention that their sample size is relatively low but I think this should be more reflected throughout the conclusion section.

(2) the English language in the manuscript needs to be edited throughout. The authors switch from active to passive voice in several instances, there are numerous missing or superfluous words throughout the manuscript. I do not think the common name of the rattlesnake species needs to be mentioned as often as it is. Sentences are often too long and need to be shortened. In short, rigorous language editing throughout the manuscript will improve the quality by a lot in order to have a more clear and readable paper.

I sincerely hope the authors can attend to these aspects and get this interesting paper published.

Comments for author File: Comments.pdf

Author Response

The  manuscript covers interesting aspects of the natural history and biology of a rattlesnake species in central Mexico. This study uses traditional methods represents the kind of paper that is very valuable but unfortunately published rarely in the current scientific landscape.

The authors did a good job in utilizing all available specimens and information of a relatively rare snake species.

Aside from the comments and edits I provide in the attached PDF file I have two general comments:

(1) acknowledging how difficult it can be to get specimens of rare snake species I like to emphasize that statistics are based on the number of subjects (n). There is a danger to overvalue statistical results even if the actual n for a sample group is pretty low and observations are more anecdotal than statistically supported. The authors mention that their sample size is relatively low but I think this should be more reflected throughout the conclusion section.

RESPONSE: Many thanks for calling our attention to this weakness. We emphasized the relatively small sample size that reflects the rarity of the species and the difficulty that is involved in studying it in the field, and although our results should be taken with some caution, they are similar to others of other Neotropical and general snakes.

(2) the English language in the manuscript needs to be edited throughout. The authors switch from active to passive voice in several instances, there are numerous missing or superfluous words throughout the manuscript. I do not think the common name of the rattlesnake species needs to be mentioned as often as it is. Sentences are often too long and need to be shortened. In short, rigorous language editing throughout the manuscript will improve the quality by a lot in order to have a more clear and readable paper.

RESPONSE: Suggested modifications were made to the manuscript and we did a thorough review of the English language. 

There was only one part where we did not follow the reviewer’s suggestions, which is the naming of squamation characters in the methodology, and we did it so to keep homogeneity with the description of C. ehecatl and to avoid confusion with the way banding patterns were mentioned in that description.

 

I sincerely hope the authors can attend to these aspects and get this interesting paper published.

RESPONSE: Your comments and edits in the marked pdf were very helpful to improve the manuscript, we thank you for your time making them. 

Round 2

Reviewer 1 Report

At lines 375, 399, 435, 450, and 485, several “**ulminates” are misspelled.

At lines 383, “12ulmin” is misspelled.

Author Response

Many thanks for noticing this, those instances of culminates were changed in our last save by the autocorrect feature in my computer without us realizing. We changed all those instances and made sure that the last version is without those errors.

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper is much improved. I don't have the time to read it as thoroughly as I did the first draft, for which I shared extensive suggestions, but I trust the highly capable editor(s) to work with the authors on cleaning up some lingering English grammar issues. Here are a few small items I did pick up on:

Lines 112-113 - What is meant by "when at least one side of the specimen was present." 

Lines 351-353 - The sentence remains a bit awkward in that it fails to make clear that the rodents and bird are *prey* reported for C. d. durissus.

Lines 365-368 - Crotalus atrox is another primarily rodent feeder (Beavers, R. A. (1976). Food habits of the western diamondback rattlesnake, Crotalus atrox, in Texas (Viperidae). The Southwestern Naturalist, 503-515.)

Line 399 - 13ulminates?!

At this point I see no need to review at another draft. I'm looking forward to seeing the final version.

-WKH

Author Response

Many thanks for the second round of reviews, some of the spotted mistakes were introduced by the autocorrect feature in our last save, but we changed back all of them to the right spelling "culminatus" and made sure that they stayed corrected in the last version.

We reworded the three instances that were confusing or awkwardly written, thanks for spotting them.