Octavio Fuentes, the organization's executive director, said the October total stood out because the group's highest monthly counts historically fall in June and July, when desert temperatures peak.

"When I saw the number of 12, it was anomalous because usually October isn't as high," Fuentes said. "Our highest numbers are in June, July historically, of course, because of the heat."

July remains the deadliest month recorded so far this year, with 19 recoveries, Fuentes said. In all, the remains of 101 migrants have been found in Arizona's desert since January, including 38 on federal land, according to the group.

Fuentes said 10 of the remains found in October were estimated to be six to eight months old, while the most recent discovery was about five weeks old — a reminder that many deaths go undiscovered for months in the remote corridors where migrants travel.

The October figures come as Humane Borders raises alarms about the loss of federal authorization for a dozen of its water stations. Federal agencies declined to renew permits for the sites, ending a 25-year arrangement that had allowed the group to place water in some of the desert's most dangerous stretches.

"We had water stations with the National Park Service, Bureau of Land Management and Fish and Wildlife," Fuentes said. "That's where our water stations were at recently, but were removed."

It is too early to determine whether the removal of the stations played a role in any of the deaths recorded over the past month, and Fuentes did not draw a direct causal link. But the timing has heightened concern among volunteers and supporters, who note that the stations were positioned on federal land where migrants are known to travel and where natural water sources are scarce.

Humane Borders says roughly 70 percent of its water stations remain in operation in other parts of the desert. A petition calling on federal agencies to restore the permits has gathered more than 1,000 signatures.

The group's water stations have long been a subject of debate in Arizona, where border enforcement, humanitarian aid and public-lands policy intersect. Supporters describe the stations as a basic lifeline that prevents heat-related deaths; critics have argued they can encourage unauthorized crossings. Federal land managers have not publicly detailed their reasons for declining the renewals.

For residents of border communities and for the families of missing migrants, the October numbers add urgency to an annual toll that has remained stubbornly high. Humane Borders volunteers say they will continue searching for remains and maintaining the stations that remain permitted, while pressing for the federal authorizations to be restored before next summer's heat.

"Our highest numbers are in June, July," Fuentes said, "and that's when we need every station we can get."