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Introduction

Scale counts have long been used to enable us to differentiate between visually similar species. In order to produce an accurate scale count we first need to be able to identify each of the scales by both name and location.

The body of a ratsnake can be split into 3 clearly defined areas. The head, the body and the tail. Each area comprises of different scale types.

The head is broken up into approx 20 scales. In the table below you can find the various scale names along with variations on the names and a number corresponding to a label on the images following the table.
Scale Name
Alternate name/s
Label No.
     
Rostral   1
Inter-nasal # 2
Pre-frontal # 3
Frontal # 4
Supra-ocular # 5
Parietal # 6
Temporal   7
Mental   8
Lower labial Infralabial 9
Anterior Chin shield Anterior Sub-lingual 10
Posterior Chin shield Posterior Sub-lingual 11
Ventral   12
Pre-nasal Nasal 13
Post-nasal Nasal 14
Loreal Frenal 15
Pre-ocular   16
Sub-ocular 2nd preocular/presubocular 17
Upper Labial Supralabial * 18
Post-ocular   19
* Some of which may have contact with the eye.
# These are the nine plates associated with ‘ratsnake’ species, they are shared with over half of all colubrids however. It is therefore more useful to compare the scales in profile to the snakes head for identification.




Scale name Alternate name/s Image number
     
Ventral Belly 12
Dorsal   20
Anal Plate   21
Subcaudal    
Tip   23


The main body and tail comprise of very few scales in comparison to the head so I have incorporated these areas into a single image.


While identifying the scales, it may be a simple enough job when using a picture, it can often be very time consuming and hard work when using a live specimen. One of the main problems is that every animal is different so while the scales are usually in the same place they can often be aligned slightly differently. In order to help solve this problem you can find the definitions of each scale below.
Rostral This scale is found at the front of the snakes head on the top jaw. It is connected to the inter-nasal, pre-nasal and first upper labials.
Inter-nasal. These scales are the first connected pair that can be found on the head, travelling backwards from the rostral scale. They connect with the rostral, a pre-frontal and pre-nasal scales.
Pre-frontal. These connected scales also come in a pair located between the inter-nasal pair and the frontal scale. They connect with the inter-nasal, frontal, supra-ocular, post nasal and loreal scales.
Supra-ocular. This pair of scales are located on either side of the frontal scale, directly above the eyes. They are connected to the frontal, pre-ocular, post-ocular and parietal scales.
Frontal. This large single scale can be found between the supra-ocular scales. It is connected to the supra-ocular, pre-frontal and parietal scales. It is often the largest single scale on the head
Parietal. These are the last head scales to be found on the top of the head before starting the scales of the body when working from the front. They are connected to the temporals, frontal, supra-ocular and dorsal scales.
Temporal. These are the last scales to be found on the side of the head before starting the scales of the body when working from the front. They are connected to the parietal, post-ocular and upper labial scales.
Mental. This scale mirrors the rostral scale only this is found on the bottom jaw. Located at the front of the bottom jaw it is connected to the lower labials.
Lower labial. These scales follow the jaw line on the lower jaw from the mental scale to the back of the jaw. They are connected to the mental and chin shield scales.
Chin shield. These scales can be found on the underside of the head. They are paired twice around the mental groove. The first or anterior chin shields are connected to the mental and lower labial scales along with the posterior chin shields. The second or posterior chin shields are connected to the lower labials as well as the anterior chin shields. They are the last head scales on the base before the body scales begin.
Ventral. These scales follow the length of the body from close to the chin shields right down to the anal plate. They are one of the most common scales on a snake with only the dorsal scales being higher in quantity. They are connected to the dorsal scales and anal plate.
Pre-nasal. These can be found in front of the nostril. They are connected to the rostral, inter-nasal, post-nasal and upper labial scales.
Post-nasal. These can be found behind the nostril. They are connected to the pre-frontal, loreal and upper labial scales.
Loreal. Located between the post-nasal and pre-ocular scales they are also connected to the pre-frontal and upper labial scales. On some species they are also connected to a frenocular scale.
Frenocular. Although not shown in the above images this scale can sometimes be found between the loreal and pre-ocular scales.
Pre-ocular. These scales are located adjoining the front of the eye. They are connected to the loreal, sub-ocular and supra-ocular scales.
Sub-ocular. Located directly below the eye, these scales are connected to the upper labial and post-ocular scales.
Upper labials These scales follow the jaw line in the same way as the lower labials and are connected to the mental scale and chin shields.
Post-ocular. These scales are found at the rear of the eye and connected to the supra-ocular, temporal and upper labial scales.
Dorsal. These are the most common scales to be found on the snake. They are found on the back and sides of the snakes’ body.
Anal plate. This scale is often split into 2 scales that cover the cloaca. It is here the body ends and the tail begins. They are connected to the ventral and sub-caudal scales.
Tip. This final scale signifies the end of the animal and is connected to the sub-caudal scales. It caps the end of the tail.
Sub-caudal. These either come in pairs (as shown in the above image) or are single scales that follow the tail from the anal plate through to the end of the animal at the tip.


In order to complete an accurate scale count of the body and tail scales it is important to know where to start and finish and, in the case of the dorsal scales, where they are taken. If you look on the underside of a snakes head you will see the posterior chin shields. There is then a small gap filled by smaller scales followed by wider scales that then follow down the base of the snake. To count ventral scales you start at the first of the wider scales and continue all the way down the body until, but not including, the anal plate. The sub-caudal scales are started straight after the anal plate. If the sub-caudal scales are divided then you count in pairs all the way to, but not including, the tip scale. The dorsal scales are counted in three places, one head length behind the head, one in the middle of the body and one head length in front of the anal scale. The results are displayed in that order. There are 2 different methods of collecting these scale counts that result in the same number. Both methods are shown to the left


Scale counts are an integral part of the herpetology hobby. Hopefully this article has gone some way to explaining what and where the various scales are. Using this information combined with brief descriptions on how to take the three main scale counts you will now be able to confidently take and pass on scale counts.
This site has information on the following genera of Ratsnakes ... Spilotes, Spalerosophis, Ptyas, Zamenis, Elaphe, Rhinechis, Senticolis, Pseudelaphe, Pantherophis, Bogertophis, Orthriophis, Gonyosoma, Oreocryptophis, Oocatochus, Euprepiophis, Coelognathus, Archelaphe