Argument is saying Deers have some spots. Then it is says there could be ecological reason for the same.
Conclusion: They must be acting as a signal.
To strengthen we must specify something that proves the dotes are used as a signal.
A. Exceptional size and vigor also mark the subspecies of deer characterized by the best-defined dots :
Additional Info. IRRELEVANT.B. Grazing animals with a coat of uniform color may be harder to spot than spotted deer in certain tall grasses.
Other Animals are OFS.C. A temporary change of color easily can be perceived by the other members of the species, marking a visual signal in the most prevalent species of deer. :
There is no temporary change of color . Rather bright spots are permanent.D. Deers respond much faster to moving shapes that have dots than they do to moving shapes that are otherwise identical but without dots. :
WOW. So, dots are helping in someway. Hence, supporting out conclusion.E. Deers give several kinds of vocal signals than do similar species such as horses. :
Horses are OFS.