Executive Overview
In the realm of modern zoological medicine, the line between veterinary science and wildlife conservation is razor-thin. When Masaya, a 15-year-old critically endangered roloway monkey (Cercopithecus diana roloway), developed a debilitating, golf-ball-sized mass on her foot at Chester Zoo, her future—and potentially that of her species—hung in the balance. Faced with a pathological mystery that had eluded definitive diagnosis for years, a multidisciplinary medical team took a calculated, high-stakes gamble: they executed a pioneering, complex limb-sparing surgery that had never before been documented in this specific primate species.
Today, that gamble has yielded a double triumph. Not only has Masaya fully recovered and retained full mobility of her foot, but she has also recently given birth to a healthy, inquisitive female infant named Lagertha—named after the legendary Viking warrior queen.
This landmark case represents far more than a routine veterinary success story. It is a masterclass in cross-institutional collaboration, bringing together the frontline animal husbandry expertise of Chester Zoo with the advanced diagnostic and surgical infrastructure of the University of Liverpool’s Small Animal Teaching Hospital. More importantly, against the bleak backdrop of a species teetering on the brink of extinction—with fewer than 2,000 individuals remaining in the wild across Ghana and the Ivory Coast—every successful birth within a managed European Endangered Species Programme (EEP) serves as an invaluable lifeline.
This comprehensive report details the chronological unfolding of Masaya’s ordeal, explores the intricate veterinary procedures that saved her limb, contextualizes the broader geopolitical and environmental threats facing roloway monkeys, and highlights the profound implications of Lagertha’s birth for global biodiversity preservation.
Detailed Chronology: From Mysterious Lameness to Surgical Breakthrough
Years of Elusive Pathology
Masaya’s medical journey at Chester Zoo, where she arrived in 2023, was complicated from the outset by a persistent, confounding foot issue. For months, zoo veterinarians observed intermittent lameness and localized swelling that resisted standard therapeutic interventions.
Veterinary teams at the zoo’s Animal Health Centre executed a battery of diagnostic procedures, including targeted X-rays, high-resolution ultrasounds, and multiple tissue biopsies. Yet, despite these exhaustive efforts, the underlying etiology of the lesion remained shrouded in medical ambiguity. The pathology did not present as a classic tumor, nor did it neatly align with standard infectious profiles.
As time progressed, veterinary hypotheses coalesced around the likelihood of a deep-seated, chronic abscess—potentially seeded by a historic injury from a foreign body, such as a sharp thorn embedded during foraging behavior in her native habitat or early enclosure life. By early 2025, however, conservative management had reached its limits. The swelling escalated dramatically, expanding to the size of a golf ball, compromising tissue integrity, and threatening to force a catastrophic medical decision: full amputation of the foot.
The Road to Liverpool: Advanced Diagnostics
Recognizing that standard in-house options were exhausted, Chester Zoo’s veterinary staff made the unprecedented decision to transport the high-value primate off-site to a specialized academic medical facility.
The logistical choreography required for such a transfer cannot be overstated. Transporting a wild, critically endangered primate requires rigorous biosecurity protocols, precise anesthetic planning, and psychological stress mitigation.
Charlotte Bentley, Veterinary Officer at Chester Zoo’s Animal Health Centre, reflected on the operation’s unique logistics:
"It’s not every day you take a monkey to vet school. We had to bring everything she might need, from anesthesia equipment to medications and specialized thermal blankets to maintain her core body temperature throughout the transit and diagnostic phases."
Upon arrival at the University of Liverpool’s Small Animal Teaching Hospital, Masaya underwent advanced Computed Tomography (CT) imaging. The CT scan provided unprecedented three-dimensional visualization of the mass, mapping its exact margins relative to the delicate skeletal structures, tendons, and vascular pathways of the foot.
The Pioneering Operation
Armed with precise anatomical mapping from the CT scan, a combined team of zoo veterinarians and university surgeons formulated an aggressive, limb-sparing surgical intervention.
Rachel Burrow, a veterinary surgeon and lecturer at the University of Liverpool who assisted with both the initial CT imaging and the subsequent theater procedures, noted the unusual nature of the patient:
"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 companion animals like 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."
Literature reviews conducted by the surgical team confirmed that no documented medical precedent existed for performing this exact tumor-resection and limb-preservation procedure on a roloway monkey. The margin for error was vanishingly small. A miscalculation could sever critical blood supply or nerve pathways, resulting in necrosis and rendering amputation unavoidable anyway.
With meticulous precision, the surgical team excised the golf-ball-sized mass while meticulously dissecting around healthy surrounding tissue. Their efforts paid off: the operation was an unmitigated success. Masaya retained all but one of her digits, preserving the biomechanical integrity of her foot and paving the way for a remarkable recovery.
Supporting Context & Metrics: The Roloway Monkey Crisis
Ecological Profile and Geographic Distribution
To fully grasp the significance of Masaya’s survival and Lagertha’s birth, one must examine the perilous status of the roloway monkey (Cercopithecus diana roloway) within the global ecosystem.
Native to the upper Guinea forest zone of West Africa—primarily restricted to fragmented forest patches in Ghana and the Ivory Coast—roloway monkeys are arboreal, highly social primates characterized by their striking white beards, chestnut backs, and contrasting black coats. They play a crucial ecological role as seed dispersers within their native rainforests, helping to maintain forest regeneration and biodiversity.
However, their specialized ecological requirements make them exceptionally vulnerable to anthropogenic pressures. According to assessments by the International Union for Conservation of Nature (IUCN), fewer than 2,000 mature individuals now survive in the wild.
Drivers of Decline: Deforestation and Bushmeat Poaching
The precipitous decline of the roloway monkey is driven by two primary, interrelated crises:
- Habitat Destruction: West Africa has experienced some of the highest rates of deforestation globally. Agricultural expansion (particularly for cocoa and palm oil production), logging, and mining have fragmented the continuous canopy forests upon which roloway monkeys depend, isolating populations and restricting genetic flow.
- Bushmeat Poaching: Despite legal protections across their range, roloway monkeys are heavily targeted by commercial bushmeat hunters. Because of their conspicuous appearance and vocal nature, they are easily located, making them prime targets for illegal hunting.
The Role of Managed Breeding Programs
With wild populations facing near-term extinction risks, zoological institutions serve as vital demographic and genetic arks. Chester Zoo is one of only two institutions in the United Kingdom housing roloway monkeys, placing an immense operational responsibility on its animal management and veterinary teams.
Masaya is formally integrated into the European Endangered Species Programme (EEP). EEPs utilize sophisticated studbook management and genetic tracking to maximize genetic diversity within captive populations, ensuring that if wild populations collapse entirely, robust, genetically healthy insurance populations are maintained to facilitate potential future reintroductions.
Within this framework, every birth is a quantified victory. Lagertha is Masaya’s third daughter, cementing the mother’s status as a foundational matriarch within the European population.
Official Statements and Expert Perspectives
The convergence of advanced veterinary medicine and conservation success has generated widespread acclaim across the scientific and zoological communities.
Reflecting on the psychological and physical recovery of the patient, Zoe Edwards, Primate Keeper at Chester Zoo, offered detailed insights into Masaya’s maternal competence post-surgery:
"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."
The functional interdependence of the limb-sparing surgery and successful infant rearing cannot be overstated. Primate motherhood is physically demanding; mothers must constantly cradle, groom, and transport clinging infants while navigating complex, three-dimensional arboreal environments. Had Masaya undergone a full amputation, her ability to navigate ropes, branches, and vertical structures while balancing an infant would have been severely compromised, potentially endangering the newborn or forcing human intervention.
Charlotte Bentley emphasized the emotional and professional satisfaction of the inter-institutional partnership:
"She’s been an absolute trooper all the way through, and I’m just glad we were able to do something for her."
Future Outlook: Hope for a Fragile Legacy
As the dust settles on this extraordinary medical intervention, the daily life at Chester Zoo’s primate enclosure has returned to a vibrant, watchful normalcy.
Lagertha, whose moniker honors the fierce independence and resilience of a Viking queen, now represents a living symbol of resilience in modern conservation biology. Visitors and researchers alike can observe her clinging securely to her mother’s chest, exploring the enrichment structures of the habitat alongside four other members of the roloway monkey troop.
Looking Ahead: Research, Replication, and Resilience
The success of Masaya’s surgery opens new horizons for zoo-academic partnerships. By proving that complex orthopaedic and soft-tissue limb-sparing surgeries can be safely and successfully performed on endangered exotic species, the University of Liverpool and Chester Zoo have established a new clinical benchmark. This case study will undoubtedly be integrated into veterinary curricula and shared across global zoological networks, providing a practical roadmap for veterinarians facing similar pathological dilemmas in other rare taxa.
However, veterinary triumphs in controlled environments cannot blind the global community to the sobering reality outside zoo gates. While captive breeding programs successfully safeguard genetic lines, the ultimate salvation of the roloway monkey depends entirely on systemic habitat preservation, enhanced anti-poaching enforcement, and community-based conservation initiatives within Ghana and the Ivory Coast.
For now, inside the secure boundaries of Chester Zoo, Masaya and Lagertha offer a compelling reminder of what is possible when advanced science, dedicated animal husbandry, and unwavering conservation commitment intersect. In the fragile struggle against extinction, every saved foot—and every newborn life—counts.
