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Patterns of Heloderma

Patterns of Heloderma

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Patterns of Gila Monsters: unique and fascinating
The "traditional" separation of Heloderma suspectum into the two distinct subspecies H. suspectum suspectum and H. suspectum cinctum was based on patterns and distribution (see map!). This no longer valid. The difference in mtDNA expression (mitrochondrical base sequence divergence) of individuals from the most northern and nearly most southern populations (Hermosillo, Sonora, Mexico) with a distance of 650 Miles differ only by 0,5%. The banded reticulate dichotomy does not portray geographic pattern that normally indicate distinct subspecies (Ref. 1,18,53).
There is a tendency to believe that specimens of the northern distribution area are more banded and lighter in color, although dark speciems (coloration like Hermosillo) were collected in southern Utah. If bands partially break up they form large yellow/orange areas which could be evenly dotted in between the bands (formally H. s. cinctum). Gila Monsters out of the more southern range might expose more reticulate (e.g. dotted bands) patterns (Ref. 2). The impression is that of a reticulated pattern. Independent from their origin, all hatchlings show a banded pattern (Ref. 2). The most impressive change happens within the first six months after hatching. The patterns on their heads do not undergo significant changes while reaching maturity.

Changes of patterns

Uniform pattern of hatchling Pattern changes of Heloderma suspectum of the southern distribution area after 6 month Pattern changes of Heloderma suspectum of the southern distribution area after 6 month Pattern changes of Heloderma suspectum of the southern distribution area after 6 month
Uniform pattern of hatchling Pattern changes of Heloderma suspectum of the southern distribution area after 6 month Pattern changes of Heloderma suspectum of the southern distribution area after 12 month Pattern changes of Heloderma suspectum of the southern distribution area after 24 month
Examples of pattern changes of Heloderma suspectum of the southern distribution area:
Photographs of four of my own captive born hatchlings and their growth rate at 6,12 and 24 month.
 
Uniform pattern of hatchling of the central distribution area Pattern changes in Heloderma suspectum of the central distribution area after 6 month Pattern changes in Heloderma suspectum of the central distribution area after 12 month Pattern changes in Heloderma suspectum of the central distribution area after 24 month
Uniform pattern of hatchling of the northern distribution area Pattern changes in Heloderma suspectum of the northern distribution area after 6 month Pattern changes in Heloderma suspectum of the northern distribution area after 12 month Pattern changes in Heloderma suspectum of the northern distribution area after 24 month
Examples of pattern changes of Heloderma suspectum of the central distribution area:
Photographs of four of my own captive born hatchlings and their growth rate at 6,12 and 24 month.
 
Uniform pattern of hatchling of the central distribution area Pattern changes in Heloderma suspectum of the central distribution area after 6 month Pattern changes in Heloderma suspectum of the central distribution area after 12 month Pattern changes in Heloderma suspectum of the central distribution area after 24 month
Uniform pattern of hatchling Pattern changes of Heloderma suspectum of the northern distribution area after 6 month Pattern changes of Heloderma suspectum of the northern distribution area after 12 month Pattern changes of Heloderma suspectum of the northern distribution area after 24 month
Examples of pattern changes in Heloderma suspectum of the northern distribution area:
Photographs of three US imported specimens at hatching and their growth rate at 6,12 and 24 month.


 
Additionally, their photographs document weight gain, growth in length (SVL) and total length. An adult Gila Monster will grow from two to three millimeters per year up to the end of it's life  (ref. 1).
 

Examples of patterns of the ventral scales

Ventral pattern of Heloderma suspectum of the southern distribution area. (ARIZONA border to MEXICO) Ventral pattern of Heloderma suspectum of the southern distribution area. (ARIZONA border to MEXICO) Ventral pattern in central distribution area (central ARIZONA) Ventral pattern in northern distribution area (NEVADA, UTAH and northern ARIZONA)

Ventral pattern of Heloderma suspectum of the southern distribution area. (ARIZONA border to MEXICO)

Ventral pattern in central distribution area (central ARIZONA) Ventral pattern in northern distribution area (NEVADA, UTAH and northern ARIZONA)


When you observe the colours of the flat ventral scales, it becomes apparent that the number of patterns with dark scales diminish on the way to the northern distribution area. In other words, the more north in this distribution area the more lighter colour the scales will be. Former areas of black scales will turn into small bands with narrow yellow bands in the middle.


Examples of Tail Patterns


Patterns of tails in southern distribution area Patterns of tails in southern distribution area Patterns of tails in central distribution area Patterns of tails in northern distribution area
Patterns of tails in southern distribution area Patterns of tails in central distribution area Patterns of tails in northern distribution area

The photographs show the tails of individuals from the southern distribution area. Their yellow bands have partially dark bands within. The black bands are free from other colors.  Gila Monsters from the central area of distribution tend to have black bands with yellow dots and the yellow bands have black markings. In the northern distribution area, the tails are more commonly plain coloured , alternating with black and yellow bands.

The depicted examples of areal patterns are representative for most individuals. There are also integrates and totally different patternd specimens in every area of distribution. Further irritation arises because hatchlings very often have totally different coloration and patterns like their parents.Specimens of the same clutch sometimes look so different that they are not recognized as siblings.

Pattern variations within families Pattern variations within families Pattern variations within families Pattern variations within families
Pattern variations within families Pattern variations within families Pattern variations within families Pattern variations within families


Examples of different patterns of the head of Heloderma suspectum:

Patterns of the head of Heloderma suspectum Patterns of the head of Heloderma suspectum Patterns of the head of Heloderma suspectum Patterns of the head of Heloderma suspectum
In "contrast" to the change of body patterns, the patterns of the head are very consistent. A field biologist or a keeper will be able to easily identify different specimens still after years (Ref. 34, 52).

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