“LA BESTIA” (“The Beast”) still trundles along the length of Mexico, from Guatemala to the United States. But the infamous freight train has fewer people perched on its roof and clinging to its sides. Since last month the Mexican authorities have been cracking down on Central American migrants clambering on board; their ranks have dwindled from hundreds to dozens on each journey.

“We have an obligation to stop the migrants getting on the train, because the train is a danger to them,” said Humberto Mayans, the head of Mexico’s new migrant programme. Mr Mayans has cited the risks of travellers losing their lives or limbs from falling off the train when exhausted, or being pushed off by the gangs who prey on those aboard.

Such dangers are horribly real. But for all the rhetoric about protecting migrant rights, the government’s tougher policies are motivated more by pressure from the United States to tackle a rise in the number of unaccompanied child migrants coming north from Honduras, El Salvador and Guatemala. Around 66,000 unaccompanied minors were detained at the border with the United States between last October and the end of August, an 88% increase on the same period in the previous year.

As well as cracking down on La Bestia, the new Mexican programme includes raids on flophouses along the route north, as well as more checkpoints on roads near the border with Guatemala. The numbers of unaccompanied minors making it to the United States have fallen sharply in recent weeks: detentions at the border have declined from over 10,000 in June to 3,100 in August. A similar pattern exists in the number of families being detained.

A six-billion-peso ($500m) modernisation plan seeks to ensure that La Bestia never recovers its role as the route of choice for the poorest migrants. The plan includes replacing large stretches of track so that trains can go faster, making them more difficult to board. Vehicles will run ahead of the trains and send back information about what lies ahead, including migrants who remain willing to risk the jump.

Campaigners argue that such measures are aggravating the risks. They say migrants will rely more heavily on people-smugglers, leaving them even more vulnerable to extortion by corrupt officials and to abuse, kidnapping and murder by criminal gangs who promise safe passage at a price. “Nobody in their right mind would want the migrants to be getting on the train,” says Friar Tomás González, who runs a shelter close to the tracks in the southern city of Tenosique. “But this policy is increasing the dangers they face.”

The friar complains that the measures are designed to calm a political storm in the United States rather than to deal with the root causes of the exodus from Central America. Shelters echo to stories of rampant gang violence and poverty back home that make the risks of the northbound journey tolerable. Cutting off La Bestia may deter some from making the journey, not all.