Because animals, in all my experience, naturally have no names in which we - the collective we that is - know by human terms, I chose an apt descriptor. All sabertooth cats have a highly specific mechanism of predation, which is exsanguination by use of the namesake canine teeth, and thus all are "red in tooth". So too is it a reference to the work of Lord Alfred Tennyson, who merely popularized the phrase in the work In Memoriam.