Leonardo DiCaprioWhen you're Leonardo DiCaprio and you tweet about causes dear to your heart, you get results. In response to the actor's tweet about a rare and endangered porpoise, Mexican President responded directly to the "Titanic" star.

DiCaprio tweeted on May 11 that "the vaquita is the most endangered marine mammal in the world" and urged his 17.5 million followers to "take action."

"I welcome @LeoDiCaprio and @World_Wildlife's concern regarding the Vaquita Marina," President Pena Nieto wrote in his first series of tweets about the issue. "@Mexico has focused all its efforts to prevent the extinction of this species."

Per Reuters, populations of the vaquita, a small snub-nosed porpoise, have dropped sharply in recent years. That's because of extensive gillnet fishing in the Gulf of California for shrimp and totoaba (a delicacy in Asia).

Although Mexico imposed a two-year ban on gillnet fishing in the vaquita's habitat in 2015, critics say the ban needs better enforcement.

According to Viva Vaquita, a group dedicated to saving the porpoise, the vaquita population was estimated to be less than 50 in January 2017. July 8 is "International Save the Vaquita Day" if you want to get involved.

DiCaprio is well known for his environmental activism. He joined the April Washington D.C. Climate Change March with a sign that read "Climate Change is Real." He also stars in and produced the documentary "Before the Flood," about the impact of global warming around the world.