The pedaxillosternal flag of the Rocky Mountain mule deer (Odocoileus hemionus hemionus)

The Rocky Mountain mule deer (Odocoileus hemionus hemionus) is well-known to have a conspicuous pattern of colouration on the hindquarters.

This is most noticeable in the winter pelage, and in posteriolateral view (https://www.inaturalist.org/observations/97295280 and https://www.inaturalist.org/observations/72504627 and https://www.inaturalist.org/observations/68344771 and https://www.inaturalist.org/observations/61732504).

However, what also requires description and explanation is a conspicuous pattern on the forequarters, which is most noticeable in profile and in a posture in which the inner foreleg is exposed.

The feature in question is complex, consisting of

• conspicuously dark pelage on the brisket (https://www.merriam-webster.com/dictionary/brisket),
• conspicuously dark pelage on the ventral surface of the thorax (https://www.inaturalist.org/observations/45881470),
• conspicuously pale pelage on the entire inner surface of the upper foreleg (including the axilla, https://www.merriam-webster.com/dictionary/axilla), and
• conspicuously pale pelage on the inner and posterior surface of the lower foreleg.

In having a conspicuously pale inner surface, the foreleg differs from the hindleg (https://www.inaturalist.org/observations/36167595).

In this and other ways, the pattern makes little sense in terms of countershading (https://en.wikipedia.org/wiki/Countershading).

https://www.inaturalist.org/observations/101206028 and https://www.inaturalist.org/observations/101171620

https://www.inaturalist.org/observations/97075871

https://www.inaturalist.org/observations/75142350

https://www.inaturalist.org/observations/69512342

https://www.inaturalist.org/observations/68901309

https://www.inaturalist.org/observations/54358694

https://www.inaturalist.org/observations/52417150

https://www.inaturalist.org/observations/51659800

https://www.inaturalist.org/observations/16922321

https://www.inaturalist.org/observations/10708031

https://www.inaturalist.org/observations/4126822

https://www.inaturalist.org/observations/3213126

https://www.inaturalist.org/observations/205313614 and https://www.inaturalist.org/observations/205313616 and https://www.inaturalist.org/observations/205313613

Posted on April 7, 2024 09:26 PM by milewski