Venezuelan migrants often have a quick answer when asked to name the most difficult stretch of their eight-country journey to the U.S. border, and it's not the dayslong jungle trek through Colombia and Panama with its venomous vipers, giant spiders and scorpions. It's Mexico.

"In the jungle, you have to prepare for animals. In Mexico, you have to prepare for humans," Daniel Ventura, 37, said after three days walking through the Darien Gap and four months waiting in Mexico to enter the U.S. legally using the government's online appointment system, called CBP One. He and his family of six were headed to Fort Atkinson, Wisconsin, where he has a relative.

Mexico's crackdown on immigration in recent months — at the urging of the Biden administration — has hit Venezuelans especially hard. The development highlights how much the U.S. depends on Mexico to control migration, which has reached unprecedented levels and is a top issue for voters as President Joe Biden seeks reelection.

Arrests of migrants for illegally crossing the U.S.-Mexico border have dropped so this year after a record high in December. The biggest decline was among Venezuelans, whose arrests plummeted to 3,184 in February and 4,422 in January from 49,717 in December.

While two months do not make a trend and illegal crossings remain high by historical standards, Mexico's strategy to keep migrants closer to its border with Guatemala than the U.S. is at least temporary relief for the Biden administration.