As the lioness wearily raises her head from a parched acacia thicket, safari guide Daniel seizes the opportunity to count the number of whiskers tapering beneath her fleshy-pink nose.
He grabs a tatty notebook from the dashboard of our dusty Toyota Land Cruiser and thumbs through pages of childlike lion sketches. After some deliberation, he confidently identifies the lioness as Madala, while behind her rests a male, Naserein. Even without his characteristic flowing crown - an adaptation to this hot, dry environment - the predator still looks majestic.
Daniel pulls out a smartphone to take a picture and record our co-ordinates. A guide for the Sasaab Lodge, he's one of 20 trained lion watchers operating in the Samburu National Reserve in Northern Kenya, close to the Equator, where we're currently bumping through arid, thorny, sun-scorched plains in search of big cats.
After every sighting, Daniel inputs data into a custom-made app, which he'll then transmit to a central information bank once we have Wi-Fi connection back at the lodge. It's all part of a drive to monitor the number of lions in Samburu and increase a population that is currently under threat.
Arguably the most iconic of safari's Big Five headliners, there are currently 32,000 lions in Africa - a drop of 90% since 1975, according to statistics from National Geographic. In Kenya, the birthplace of safari, there are fewer than 2,000 lions, and Kenya Wildlife Service estimates 100 were lost last year.
Although overshadowed by the appalling decimation of elephants and rhino by poaching, the plight of Africa's lions is now receiving deserved attention. "People expect to see a lion on safari; if they don't they'd be surprised," says Mickey Carr-Hartley who, along with his wife Tanya, owns Sasaab and three other properties in The Safari Collection portfolio.
In Samburu, the couple is supporting the work of inspirational conservationist Shivani Bhalla, who is passionately working to raise both the profile and population of Africa's big cats through her project Ewaso Lions, and guests at Sasaab are invited to learn about her work. She is also responsible for the Lion Watch initiative and the phone app Daniel and his colleagues now use.
I meet the 36-year-old Kenyan in her "office", a huddle of simple canvas tents in the Westgate Community Conservancy, which borders with the Samburu National Reserve. A plan for the week ahead is scribbled on a white board which hangs from a tent pole, while an old, battered laptop is flipped open on the camp table, although there's no internet connection available.
An Oxford graduate who originally came to Samburu for her PhD, Shivani has been camping here for the past eight years. Her slight frame and bookish appearance cast her as the archetypal scientist, but get her on the subject of predators and she becomes wildly animated.
She pulls out a faded and slightly blurry Kodak print of a cheetah, a snap she proudly tells me she took in this very area when she was eight years old. It sparked a passion which has led to her being awarded a Whitley Award for conservation and being named an emerging explorer by National Geographic.
Shivani highlights community conflict as the main threat to lions and much of her work involves educating the 600 Samburu families in Westgate about the importance of wildlife. Habitat destruction and overgrazing has led to a significant drop in lions' prey, meaning many now target the pastoral community's precious livestock.
But by teaching people about the value of wildlife and the money it brings through tourism, along with methods to protect livestock, she has helped raise the number of Samburu lions from 11 in 2007 to a present count of 40.
"And for the first time we've noticed that lions in the reserve are starting to roar, a sign they feel safe," she tells me with relief.
We're joined by Letoya, a 20-year-old Samburu warrior whose tall, lithe body arches like a bow as he leans in the tent doorway. His sleek, braided hair is pasted with ochre, and he wears a body armour of colourful beadwork. As part of her Warrior Watch programme, Shivani has trained him and 13 others to become wildlife guardians, monitoring lion behaviour and troubleshooting any problems in the community.
In the past, Letoya, like many of his peers, regarded lions as a nuisance. "But now I am coming to like them, and I understand they bring me money," he says with calm conviction. "I want them to be with us for a very long time."
Shivani recalls an incident last September when Loirish, a lion Letoya was responsible for, was shot in the nearby Kalama Conservancy after killing 10 camels in three months. "Letoya sat next to the dead body for three hours. He couldn't say a word."
Guests at Sasaab Lodge can make donations to Ewaso Lions but even by staying in the Westgate Conservancy, where the lodge pays a lease to the Samburu people, they are supporting wildlife and community.
The nine luxurious tents on the banks of the Ewaso Nyiro River are a world apart from Shivani's simple set-up. An infinity pool and spa overlook the shallow water where elephants cross, and open-sided stone bathrooms offer the chance to shower by starlight.
I fall asleep to the sound of a grunting Verreaux's eagle owl and baboons barking like an agitated pack of dogs; in the morning I awake to find dik-diks (who look like Bambis shrunk on a 90-degree wash cycle) truffling on my front lawn, and weaver birds dressing their pendulous nests that hang from acacia trees like rough-hewn baubles.
In the past, only government officials would visit this part of Kenya and subsequently villages are unaffected by mass tourism. To my relief, a trip to a local manyatta (homestead) is far from being a contrived circus show.
Their shoulders waning under the 5kg weight of elaborate beaded collars, which they even sleep in at night, women set about household tasks such as milking goats, cleaning pots with ostrich feathers and keeping fires lit inside their dark, dung-plastered homes.
Almost 40% of children in the conservancy now go to school, and Sasaab regularly donates funds to the Ngutuk Ongiron primary school and clinic. Shivani also works with the Safari Collection's excellent in-house community and conservation manager Ali Allport on projects to introduce children to wildlife, which they intend to roll out in the company's Solio property in Laikipia and Sala's Camp in the Masai Mara.
Set up in 1970, Solio holds the mantle for being Africa's most successful rhino breeding reserve, but on my visit to the lodge, set within Kenya's first private conservancy in a valley between Mount Kenya and the Aberdare Mountains, I spend time with a number of lions. I share an hour with three 18-month-old cubs who tumble and play-flight in the long grass, doing their best to aggravate their remarkably composed father. It's the first of many sightings.
It's a similar story in the Mara, further south-west, where the annual wildebeest migration serves as an open buffet for lions who are otherwise haphazard hunters. Bellies bloated, they lick their paws, leaving discarded carcasses for vultures to feast on.
During other months, however, numbers are lower. Nic Elliot, project director for the Mara Lion Project, says in the past five years lions have changed their behaviour and become more shy, mainly as a result of conflict with local Maasai communities. Yet despite all the problems, he still rates Kenya as the best place in Africa to see - and hear - lions.
As I lie in bed that night in Sala's Camp, in a quiet corner of the Masai Mara Reserve close to the Tanzanian border, I'm certain I hear a gruff, rolling roar. It could be thunder, but I very much hope it's a lion.
TRAVEL FACTS - KENYA
:: Sarah Marshall was a guest of The Safari Collection (www.thesafaricollection.com) who offer a seven-night package (two nights at Solio Lodge, three nights at Sasaab and two nights at Sala's Camp) from 5,250 US dollars per person (two sharing) on an all-inclusive basis. Includes all transfers, internal flights, park and conservation fees, game drives, sundowners and bush picnics.
:: Kenya Airways (www.kenya-airways.com; 020 8283 1818) fly daily from Heathrow to Nairobi from £732.96 return. The airline also offers connections through KLM's regional UK departures via Amsterdam to connect with daily services to Nairobi from Amsterdam.