The odd masculinity of the dama gazelle
Please consider three trends among species of ruminants. The larger the body of the species (up to about 100 kg), the more massive the mature male tends to be relative to the adult female; the larger his horns tend to be relative to his body size; and the more conspicuous he tends to be in colouration, relative to the female. Another way of putting this: the larger the mature male is relative to the female, the more 'outsize' he seems to be in bulk, head-adornments, and showy colouration (http://www.wildlife-pictures-online.com/image-files/nyalapair1.jpg).
Because these overall trends of scaling make sense in terms of gregariousness, polygyny, and masculine rivalry, it is the exceptions that are more intriguing than the species conforming to the trends. And the dama gazelle (Nanger dama) is one such exception.
The dama gazelle has the male up to twice as massive, in full maturity, as the adult female. This is not particularly odd, because it is the largest species of antilopin bovid, a clade in which most species have the male only modestly larger than the female and the smallest species predictably have the male no larger than the female.
What is odd is that the horns of the fully mature male dama gazelle (e.g. see https://www.cokesmithphototravel.com/expedition-to-tunisia.html) are the smallest, not the largest, relative to body size among gazelles. And that his colouration, while certainly showy, is no more showy than that of the female.
Compare this with the blackbuck (Antilope cervicapra). This species is only about average in body size for a gazelle, and the male is not much larger than the female (https://www.123rf.com/photo_15739137_male-and-female-blackbuck-on-grass.html). Yet the mature male has extremely large horns while the female lacks horns altogether; and his colouration is so much showier than hers that they look like different species (https://www.downtoearth.org.in/news/wildlife-biodiversity/odisha-s-blackbucks-double-in-6-years-reveals-census-77138).
This suggests that the showy pale/dark pattern of colouration shared by the dama gazelle and the blackbuck, in which white extends so high on the figure that it catches the light and makes the animal stand out even at a distance (for dama gazelle see https://www.picfair.com/pics/011466472-endangered-dama-gazelle and https://naturerules1.fandom.com/wiki/Dama_Gazelle?file=3e2b7d460fe86e7d50d1bfec49723c12.jpg and http://awwp.alwabra.com/wp-content/uploads/2014/04/DAMA_GAZELLE_Group_Gazella_dama_ruficollis_01.jpg, has arisen for different reasons in the two species. In the dama gazelle, conspicuousness is a 'female-centred' adaptation facilitating social cohesion in general, and the male conforms to this even by keeping his horns small. By contrast in the blackbuck, conspicuousness is a 'male-centred' adaptation which tends to undermine the hiding of the inconspicuous females and juveniles from predators. In the dama gazelle, males presumably compete mainly by contests of brawn, whereas in the blackbuck males compete mainly by contests of attire and ritual fencing.
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