TAPACHULA, Mexico (AP) — About 1,500 migrants formed a new caravan Wednesday in southern Mexico, hoping to walk or catch rides to the U.S. border. The migrants are mainly from Central and South America. Some say they are hoping to reach the United States before Donald Trump’s inauguration in January, saying they think it might be more difficult after that. They started out walking from the city of Tapachula, near the border with Guatemala, where thousands of migrants are stranded because they do not have permission to cross further into Mexico. What are migrant caravans? Migrant caravans began forming in 2018, and they became a final, desperate hope for poorer migrants who do not have the money to pay smugglers. If migrants try to cross Mexico alone or in small groups, they are often either detained by authorities and sent back to southern Mexico, or worse, deported back to their home countries. In that sense, there is safety in numbers: it is hard or impossible for immigration agents to detain groups of hundreds of migrants. So police and immigration agents often try to pick off smaller groups, and wait for the main body of the caravan to tire itself out. Usually the caravans stop or fall apart within 150 miles (250 kilometers). What are the obstacles? There is no safety in numbers, however, against threats, extortion or abduction by drug cartels in Mexico, which have become heavily involved in migrant trafficking. The cartels charge migrants or their smugglers for permission to cross their territories along the border. Migrants walk through Tapachula, Chiapas state, Mexico, Wednesday, Nov. 20, 2024, hoping to reach the U.S. border. (AP Photo/Edgar H. Clemente) In addition, the gangs often kidnap migrants, hold them in terrible conditions or torture them until they call relatives to send money for their release. The biggest obstacle, though, is the searing heat, dehydration and distance: it is over 1,100 miles (1,780 kilometers) from Tapachula to the nearest border crossing at Matamoros, across from Brownsville, Texas. And that is the shortest, but also one of the most dangerous routes. It would mean 16 days of straight walking even for an adult with no rest stops; many of the migrants come with their children. Why do they come? Since migrants usually cannot find work to support themselves in Tapachula, most of the foreigners trapped there are desperate to leave. Some feel a sense of urgency, hoping to reach the border before Trump's Jan. 20 inauguration. 4,000 migrants headed for US, trying to beat Trump to the punch “It is going to be more difficult, that's why we are going in hopes of getting an appointment quicker so we are able to cross before he (Trump) takes office,” said Yotzeli Peña, 23, a migrant from Venezuela. “That would be easier.” Weren't there changes to keep caravans from forming? This year, in a bid to stop people from gathering at the border to claim asylum, the U.S. government expanded areas where migrants can apply online for appointments to enter the United States to a large swath of southern Mexico. Migrants pause on the shoulder of a road, on the outskirts of Tapachula, Chiapas state, Mexico, Wednesday, Nov. 20, 2024, during their journey to the U.S. border. (AP Photo/Edgar H. Clemente) The CBP One cellphone app was instituted to make asylum claims more orderly. About 1,450 appointments are made available daily, encouraging migrants to get an appointment before they show up at the border. But the service was only available in northern and central Mexico. Fear of mass deportations spreads in immigrant communities By extending the app south to Tapachula, officials hoped it would stem the rush north. But some migrants still want to be close to the border so that if they do get one of the cherished appointments, they can get to it quickly and not risk missing it. Trump has promised to end the app, reduce legal pathways to the U.S. and organize mass deportations. Do they ever reach the border? The biggest caravans formed in 2018 and 2019, and back then Mexican officials helped out some of the migrants by arranging buses to border cities, but that created a backlash in those communities. Groups from those original caravans did eventually reach the border. In caravans since then, most participants have sought out as many hitch-hiking or paid rides as they can, and often swarm empty trucks to hitch a ride on empty freight platforms. But that has become much harder as Mexican authorities discouraged buses, taxis and trucks from stopping to pick up migrants. In recent years, authorities have eventually offered temporary transit permits to dissolve the caravans.