A critically endangered roloway monkey named Masaya recently gave birth to a daughter named Lagertha, months after undergoing a complex surgery that saved her foot from amputation. The operation was performed by a team of veterinarians and surgeons from the University of Liverpool's Small Animal Teaching Hospital. Masaya, a 15-year-old roloway monkey living at Chester Zoo, had developed a golf-ball-sized mass on her foot and was facing the possibility of losing the limb. The medical team could find no previous examples of the same procedure being performed on a roloway monkey. The surgery was successful, allowing Masaya to keep all but one of her toes. Lagertha is Masaya's third daughter, making the birth especially valuable for a species facing an uncertain future. According to the International Union for Conservation of Nature (IUCN), fewer than two thousand roloway monkeys remain in the wild. Their natural range includes Ghana and the Ivory Coast, where the animals are threatened by both habitat destruction and poaching. Because the species is so rare, the health and reproductive success of individual animals such as Masaya can have wider importance. She is part of the European Endangered Species Programme, a coordinated breeding effort designed to help safeguard the species from extinction. Masaya's foot problems began before the operation and had repeatedly troubled her since she arrived at Chester Zoo in 2023. Veterinarians carried out X-rays, ultrasounds and biopsies, but the underlying cause remained difficult to determine. They eventually suspected that Masaya had a persistent abscess, possibly caused by an old injury from a thorn. By 2025, the swelling had become worse. Zoo staff decided Masaya needed more detailed imaging and transported her to Liverpool for a CT scan. Rachel Burrow, a veterinarian and lecturer at the University of Liverpool, helped with both Masaya's CT scan and the subsequent operation. She said: "This was the last chance to save Masaya's foot before amputation. Working with primates is completely different from my usual patients, who are typically cats and dogs, and it was a real privilege to care for such a rare animal. It's great to see the surgery was a success - she's comfortable, active, and using the limb well." Zoe Edwards, primate keeper at Chester Zoo, said: "Masaya is a very experienced mum and she's parenting magnificently. Lagertha is only a few weeks old and is very dinky, but already curious about the roloway monkey habitat and inquisitive about us. The fact Masaya's foot has healed so well is a huge relief. If she'd had an amputation, we'd have been left with real questions about whether she could hold her offspring or continue with her normal behaviors." Masaya has since recovered well, and her new daughter is thriving alongside her. Lagertha, whose name comes from a Viking queen, can now be seen with Masaya and four other monkeys at Chester Zoo.