For comparison, see deep hip and tail dissections of a ferret, a rabbit, and a tree shrew.

Function:

The fox's tail can be used in communication, in conjunction with posture and facial expression. A tail tucked between the pelvic limbs is a show of submission, while a lifted or horizontal tail may indicate aggression. Contentment is displayed through lateral wagging of the tail [1].

The tail is also constantly used for balance in locomotion. All muscles in the tail are synchronized to keep the tail stable, and counteract cyclic torques while galloping. The tail flexor (dorsal) and extensor (ventral) muscles are responsible for maintaining the positioning of the tail [2].

While many other mammals that possess tails also use them for communication, and to a smaller degree for balance, their musculature often does not have the same degree of development as that found in the fox. Rabbits and deer, for example, have the ability to elevate their tails as a sign of danger, but their tail musculature does not allow the same degree of lateral motion as the fox, nor is it as long relative to body size, preventing it from playing a significant role in locomotion.

Dissection:

The spinalis, semispinalis, and longisssimus muscles extend from the body wall to the proximal tail. The spinalis muscle's tendons extend from the muscle belly at the caudal end of the body to the distal aspect of the tail. The muscle bellies of the tail muscles run the length of the tail, but are thickest at the proximal end. The tail is divided into left and right ventral, and left and right dorsal, bundles of tendons.

The dorsal muscle of the tail is the sacrocaudalis dorsalis muscle, a posterior extension of the multifidus muscle. It is used for extension of the tail. On the ventral surface of the tail is the sacrocaudalis ventralis medialis muscle, used for flexion of the tail. The right and left sacrocaudalis ventralis lateralis muscles are on the lateral aspects of the tail, and produce a side-to-side, wagging motion. These ventral muscles originate from undifferentiated hypaxial muscles at the caudal end of the body. This undifferentiated muscle mass is homologous to the musculature found in shark tails [3].

Sources:

1. Alderton, David. 1994. Foxes, Wolves, and Wild Dogs of the World. Facts on File,
New York.

2. Wada N, Hori H, and Tokuriki M. 1993. Electromyographic and kinematic studies of tail movements in dogs during treadmill locomotion. J Morphology. 217(1):105-113.

3.Romer, Alfred Sherwood. 1962 .The Vertebrate Body. Third Edition. W.B. Saunders Company, Philadelphia and London. 627 pp

Links

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to mammalian deep hip and tail