Humanity has doubted the intelligence of Elephants in the same way that they doubted the intelligence of Cetaceans. The same is true for the Elephants doubting the Humans for similar reasons to the Cetaceans. However, when the communication barrier was finally surmounted, Humanity was unimpressed.
Some of them had been literally talking to dolphins for subjective centuries, and in the dolphins' own language. Getting Elephants to communicate with Humans in the local Terran dialect wasn't all that special. Nevertheless, Elephants were recognised, like Pigs, as another Deathworlder cogniscent species.
The fact that one used to farm another for nutrition is something many Humans prefer to sweep under the rug. The Pigs, for the record, are willing to declare that all things being equal, their ancestors were perfectly willing to eat Humans at every given opportunity. Both species have acknowledged the other as being very tasty indeed and strains of culture-grown flesh are available for interested parties. The fact that there is one obligatory herbivore among the number of Terra's intelligent species has been something of a relief amongst many Havenworlders.