Pampas deer (Ozotoceros bezoarticus), a cervid counterpart to a combination of reedbuck (Redunca) and oribi (Ourebia)

Ozotoceros bezoarticus ( and





Publicado el octubre 8, 2022 09:33 TARDE por milewski milewski


Redunca (bovid) and Ozotoceros (cervid) do share similar/convergent degrees of external traits/patterns. Of course, this is just postulation, but could it be, that perhaps Odocoileus/direct chrono genera of Odocoileus, are the ancestor(s) of Ozotoceros? They look stunningly similar, to the Odocoileus, even as they’re more related to Mazama?

Publicado por paradoxornithidae hace casi 2 años


I agree that, of all the South American deer other than Odocoileus virginianus itself (which has penetrated quite deeply into this continent), Ozotoceros bezoarticus is the one most resembling O. virginianus.

The main differences seem to be in body size and the proportional size of the tail.

At about 25 kg average body mass for adult females, O. bezoarticus is smaller than the smallest subspecies of O. virginianus (about 30 kg). It is also smaller than any species of reedbuck (Redunca fulvorufula, about 30 kg).

So, diminution is an important aspect of the evolution of O. bezoarticus, relative to both ancestral Odocoileus and ecologically comparable Redunca.

The proportional diminution of the tail in O. bezoarticus is understandable in view of the plasticity of the size of the tail in Odocoileus. This has brought the size of the tail in O. bezoarticus towards that in Redunca redunca. However, a considerable difference remains, in not only in the proportional size of the tail, but also its colouration and activation as a caudal flag.

Redunca redunca:

Ozotoceros bezoarticus:

The tail and hindquarters of O. b. leucogaster resemble those of Ourebia montana (body mass about 15 kg) as much as those of Redunca:

They also resemble those of some individuals of Odocoileus hemionus columbianus:

However, most individuals of the latter have the tail longer than in O. bezoarticus:

Publicado por milewski hace casi 2 años
Publicado por milewski hace casi 2 años

One of the best illustrations of juvenile in Ourebia montana cottoni/masakensis:

Publicado por milewski hace casi 2 años

Is there any particular reason, why the tail is diminutive, particularly, in the above, aforementioned taxa (that fir the reduced tail criterion) of ruminants? Even the related (via the Odocoileini tribe/clade) Odocoileus genus doesn’t display such a trait, as seen here (, I am pondering on the implications of these features.

Publicado por paradoxornithidae hace casi 2 años


The photo-pair you linked shows the almost unbelievable evolutionary plasticity of the caudal flag/hindquarters bleeze in Odocoileus.

Odocoileus hemionus is thought to have evolved recently from Odocoileus virginianus, and the two species remain able to interbreed. However, the pattern on the hindquarters is almost unrecognisably different, in conjunction with the tail no longer being flagged in O. hemionus hemionus.

One reason why, in cervids, the tail becomes small, is reduction of surface area in cold climates. This seems to explain the relatively small tail in O. hemionus hemionus to some extent.

However, this explanation would not apply to O. bezoarticus.

So, the diminution of the tail in O. bezoarticus (25 kg), relative to both ancestral Odocoileus and ecologically analogous Redunca, is one of the puzzling aspects of the pampas deer. It suggests convergence with Ourebia montana (15 kg) as much as Redunca redunca (35 kg).

So, a fair 'working model' for O. bezoarticus seems to be that it is the ecological counterpart for a combination of Redunca redunca ( and Ourebia montana (

This would make sense, given how widespread these two spp. of bovids are in African savannas. However, the sexual dimorphism in the growth of head-adornments remains different in cervid vs bovid.

Coming back to your question re the tail: O. bezoarticus would seem to have a diminutive tail for the same reasons that Ourebia, Raphicerus, and Madoqua have diminutive tails. What could that reason be?

Publicado por milewski hace casi 2 años

excellent images, such subtle, but distinct, differences.

Publicado por paradoxornithidae hace casi 2 años

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