Saitoti Petro, a tall, slender 29-year-old is marching with four other young men who belong to a pastoralist people called the Maasai. Beneath the folds of his thick cloak, he carries a sharpened machete.
Only a few years ago, men of Petro's age would most likely have been stalking lions to hunt them – often, to avenge cattle that the big cats had eaten.
And so he's joined an effort to protect lions, by safeguarding domestic animals on which they might prey.
Petro is one of more than 50 lion monitors from communities on the Maasai steppe who walk daily patrol routes to help shepherds shield their cattle in pasture, with support and training from a small, Tanzanian nonprofit called African People & Wildlife.
Over the past decade, this group has also helped more than a thousand extended households to build secure modern corrals made of living acacia trees and chain-link fence to protect their livestock at night.
This kind of intervention is, in a way, a grand experiment.
The survival of lions - and many other threatened savannah species, from cheetahs to giraffes to elephants - likely depends on finding a way for people, livestock and wild beasts to continue to use these lands together, on the plains where the earliest humans walked upright through tall grass.
Across Africa, the number of lions has dropped by more than 40 percent in two decades, according to data released in 2015 by the International Union for Conservation of Nature, putting lions on the list of species scientists consider "vulnerable" to extinction.
A young male lion yawns as he wakes up in Tanzania's Tarangire National Park.
They have disappeared from 94 percent of the lands they used to roam in Africa, what researchers call their "historic range."
The biggest reason for lion's retreat is that their former grasslands are being converted into cropland and cities. Losing habitat is the top risk to wildlife in Africa and globally. But on open savannahs where lions still roam, poaching for body parts and revenge killings are the next most significant threats.
Lions are respected as worthy adversaries in Maasai culture. Anyone who harms more than nine is said to be cursed. But avenging the death of a prize cow wins respect, like dueling to avenge a lost family member.
And what happens here in Tanzania will help determine the fate of the species; the country is home to a more than a third of the roughly 22,500 remaining African lions, according to data from researchers at the University of Oxford.
Maasai tribesmen hang out in the village of Loibor Siret, Tanzania.
There's some evidence that recent steps taken to mitigate conflict are working.
Although protecting animals in pasture is a trickier challenge, the lion monitors helped to defuse 14 situations in 2017 that might have led to lion hunts, according to records collected by African People & Wildlife.
Within a study area monitored by the nonprofit Tarangire Lion Project, the monthly count of lions hit a low of around 120 lions in fall 2011 - down from about 220 lions in 2004.
But the population started to recover in 2012, reaching more than 160 lions by 2015.
Wildlife refuges are sometimes not a sufficient answer - at least for species that require large ranges.
Associated Press