Comoros Wildlife Expedition 168312: Tracking Endemics Across Four Volcanic Islands

Expedition 168312 was a six-week intensive wildlife survey conducted between March 12 and April 23, 2024, across the four islands of the Comoros archipelago. Led by the University of Réunion’s Centre de Recherches Océan Indien (CROI) in partnership with the Comorian Ministry of Environment and the International Union for Conservation of Nature (IUCN), the expedition deployed eight field biologists, two GIS specialists, and three local guides fluent in Shikomori and French. Using Garmin GPSMAP 66i units, bioacoustic recorders (Wildlife Acoustics Song Meter Mini), and camera traps (Reconyx HyperFire 2 HF2X), the team documented 27 endemic vertebrate species—including 14 birds found nowhere else on Earth—and confirmed the continued presence of the critically endangered Anjouan scops owl (Otus capnodes) at three previously unverified sites. This report details methodology, findings, conservation implications, and on-the-ground realities of fieldwork in one of the world’s most isolated and understudied island ecosystems.

The Archipelago: Geology, Isolation, and Evolutionary Crucible

The Comoros archipelago comprises four main islands—Grande Comore (Ngazidja), Anjouan (Nzwani), Mohéli (Mwali), and Mayotte (Maore)—situated in the Mozambique Channel between northern Madagascar and eastern Mozambique. Though politically fragmented—with Mayotte administered by France since 2011—the islands share a volcanic origin and deep evolutionary history. Each island emerged independently via hotspot volcanism between 5.2 million years ago (Mayotte) and just 500,000 years ago (Grande Comore). This staggered emergence created sequential colonization windows, resulting in a ‘stepping-stone’ speciation pattern now recognized as one of the clearest natural laboratories for allopatric divergence in the Indian Ocean.

Grande Comore hosts Mount Karthala, an active shield volcano standing 2,361 meters above sea level—the highest point in the archipelago. Its last eruption occurred in May 2007, depositing over 12 cm of ash across 70 km² of montane forest. Anjouan features the rugged Moya Massif, where primary cloud forest persists at elevations between 900–1,400 m. Mohéli’s terrain is dominated by limestone karst and lowland rainforest, while Mayotte’s older geology supports deeper soils and more diverse plant communities, including 112 endemic vascular plant species—nearly double Grande Comore’s count.

Island Age and Endemic Richness Correlation

A strong inverse correlation exists between island age and avian endemism: younger islands harbor higher proportions of endemic birds due to rapid adaptive radiation post-colonization. Mayotte, at 5.2 Ma, hosts 5 endemic bird species; Anjouan (3.8 Ma) has 8; Mohéli (2.5 Ma) has 9; and Grande Comore (0.5 Ma), despite its size, supports 11 endemic birds—including the iconic Comoro blue pigeon (Alectroenas sganzini) and the nearly flightless Comoro thrush (Turdus bewsheri). This pattern reflects both time-for-speciation constraints and repeated founder effects across dispersal barriers.

Field Methodology: Precision Surveying Across Terrain Gradients

Expedition 168312 employed stratified random sampling across elevation bands: coastal (0–200 m), mid-elevation forest (200–800 m), montane cloud forest (800–1,400 m), and subalpine scrub (1,400–2,000 m). At each site, teams established 500-meter linear transects aligned perpendicular to slope contours. Biologists walked transects at 1.2 km/h, recording all vertebrate sightings and vocalizations using standardized IUCN protocols. Each transect was surveyed twice daily—dawn (05:30–07:30) and dusk (17:00–19:00)—to maximize detection of crepuscular species like the Anjouan scops owl and Mohéli bulbul (Hypsipetes moheliensis).

Camera trap grids covered 120 km² total, with Reconyx HyperFire 2 units spaced 250 m apart in a hexagonal lattice. Units were set at 0.4 m height, angled 15° downward, and programmed to capture 3-second video clips triggered by PIR sensors with 30-second cooldown. Battery life averaged 142 days per unit (using Energizer Ultimate Lithium L91 cells), though 17% required mid-expedition replacement due to high humidity (>92% RH) and salt corrosion near coastal zones. Audio monitoring used Wildlife Acoustics Song Meter Mini devices sampling at 44.1 kHz/16-bit, deployed at 200-m intervals along transects and calibrated with NIST-traceable sound pressure level meters (Brüel & Kjær Type 2250).

Local Knowledge Integration

Three Comorian field guides—Abdallah Mzé, Salima Said, and Youssouf Cheikh—provided irreplaceable ecological intelligence. Mzé, a lifelong resident of Mtsangamouji village on Anjouan, identified 19 distinct call variants of Otus capnodes, enabling acoustic differentiation between territorial males and roosting pairs. Said, trained by the NGO Action pour la Protection des Oiseaux à Mayotte (APO-M), led teams to three undocumented roost caves in Mohéli’s Tsararano Gorge—sites inaccessible without knowledge of seasonal river crossings and limestone fissure access points. Their contributions reduced survey time by 38% and increased detection probability for cryptic species by 52%, per occupancy modeling (PRESENCE v4.3.1).

Endemic Avifauna: The Heartbeat of Island Identity

Expedition 168312 confirmed viable populations of all 14 Comorian endemic birds, but with alarming distribution shifts. The Comoro olive bee-eater (Merops superciliosus) showed a 41% range contraction since the 2012 CROI baseline, retreating exclusively to protected forest patches above 1,100 m on Anjouan. Meanwhile, the Mayotte drongo (Dicrurus waldenii) expanded its range into degraded agricultural edges—a behavioral adaptation likely driven by insect prey abundance in pesticide-free cassava fields.

Most consequential was the rediscovery of the Anjouan scops owl. Previously known from only five historical specimens collected between 1875 and 1953, and presumed possibly extinct after no verified records between 1998 and 2021, the expedition recorded 17 individuals across three sites: the Cirque de Moya (1,280 m), the slopes of Mt. Ntringui (1,040 m), and a limestone cave system near Sada (890 m). Vocalizations were captured at peak amplitude of 78 dB SPL at 1 m distance—distinctly lower than the closely related Madagascar scops owl (Otus rutilus), which averages 86 dB. Genetic samples (feathers and fecal swabs) were collected under permit #COM-ENV-2024-168312-BD and will be sequenced at the Wellcome Sanger Institute.

• Comoro blue pigeon: 1,820 individuals estimated across Grande Comore’s montane forests (95% CI: 1,540–2,100)
• Mohéli bulbul: 3,240 individuals, concentrated in lowland forest fragments >10 ha in size
• Anjouan brush-warbler (Nesillas longicaudata): 487 individuals, all within 14 km² of Moya Massif’s core zone
• Comoro fody (Foudia eminentissima): 11,300 individuals—highest density recorded in secondary growth near Mitsamiouli

Conservation Status Updates

IUCN Red List assessments were updated following expedition data. The Anjouan scops owl moved from Data Deficient to Critically Endangered (CR B1ab(iii)+2ab(iii)) due to an estimated extent of occurrence of just 24 km² and ongoing habitat degradation. The Comoro thrush shifted from Endangered to Vulnerable after confirming stable populations in Karthala’s upper slopes, where 86% of remaining habitat falls within the recently expanded Parc National de Karthala (established January 2024, covering 21,400 ha). However, the Mohéli bulbul remains Endangered, with 62% of its population confined to a single 4.3 km² forest remnant threatened by illegal rosewood logging.

Mammalian and Herpetofaunal Discoveries

While avian endemism dominates Comorian conservation narratives, Expedition 168312 yielded critical insights into understudied mammal and reptile lineages. Camera traps recorded 216 independent detections of the Comoro rousette (Rousettus obliviosus), a fruit bat endemic to Anjouan and Mohéli. Roost counts revealed colony sizes averaging 287 bats (range: 42–731), with 83% of roosts located in lava tubes—geological features increasingly compromised by quarrying for construction aggregate. A newly documented behavior involved synchronized dawn departures timed precisely to first light, suggesting photoperiod sensitivity previously unrecorded in pteropodids.

Three lemur species were confirmed: the Anjouan dwarf lemur (Cheirogaleus andysabini), the Mohéli mouse lemur (Microcebus mamiratra), and the critically endangered Mayotte lemur (Eulemur fulvus mayottensis). Genetic analysis of fecal samples confirmed M. mamiratra is genetically distinct from its closest relative, M. griseorufus of Madagascar, with 4.7% mitochondrial cytochrome b divergence—exceeding thresholds for full species designation. All three lemurs exhibited nocturnal activity peaks between 22:00–02:00, aligning with peak insect abundance measured via CDC light traps (John W. Hock model 512).

Marine and Coastal Interfaces: Where Land Meets Ocean

Though primarily terrestrial, Expedition 168312 included coordinated marine surveys along 37 km of coastline using snorkel transects and drone-based reef mapping. DJI Mavic 3 Multispectral drones flew pre-programmed grid missions at 25 m altitude, capturing NDVI and chlorophyll-a indices across fringing reefs. Analysis revealed 68% coral cover on uninhabited islets like Choza off Mohéli, versus just 29% on reefs adjacent to villages with untreated wastewater discharge (e.g., Nioumachoua, Grande Comore). The critically endangered hawksbill turtle (Eretmochelys imbricata) was documented nesting at seven sites—four new locations confirmed, including a 120-m stretch of black-sand beach on Anjouan’s southern coast where nest density reached 3.2 nests per 100 m.

Coastal bird surveys recorded 14 seabird species, including the regionally significant red-footed booby colony on Mayotte’s offshore islet of Pamanzi—home to 1,280 breeding pairs, the largest known aggregation in the western Indian Ocean. GPS tracking of five individuals via Lotek Wireless ST-12 tags showed foraging radii averaging 47 km, with dives reaching maximum depths of 18.3 m (recorded by SeaTag-MOD sensors). These data directly informed the 2024 expansion of Mayotte’s Marine Protected Area (MPA) network, adding 22,000 ha of pelagic foraging corridors.

Human Dimensions of Conservation

Expedition 168312 conducted structured interviews with 142 households across 17 villages. Over 78% reported direct reliance on forest resources for medicinal plants (notably Psychotria comorensis bark for hypertension treatment) and bushmeat (primarily fruit bats and small lemurs). Yet 92% expressed willingness to participate in community-led patrols if compensated at ≥$12 USD/day—the minimum wage threshold validated by the World Bank’s 2023 Comoros Poverty Assessment. Two pilot programs launched during the expedition: the ‘Guardians of Moya’ initiative on Anjouan, training 18 villagers in SMART (Spatial Monitoring and Reporting Tool) patrolling, and the Mohéli Eco-School Curriculum, integrating local ecology into grade 5–8 science modules developed with UNESCO’s Regional Office for Southern Africa.

Logistical Realities and Field Challenges

Operational constraints shaped every aspect of the expedition. No commercial flights connect the islands; inter-island transport relied on Air Comores’ ATR 42-500 aircraft (capacity: 48 passengers), with scheduled service limited to three weekly rotations per route. Delays averaged 4.2 hours per leg due to weather and maintenance—on March 28, a mechanical issue grounded the Mohéli–Anjouan flight for 36 hours, forcing reallocation of camera traps via chartered speedboat (Zodiac Pro 4.7 m, powered by Yamaha 60 HP engine). Power reliability was inconsistent: only 32% of surveyed villages had grid electricity, necessitating solar-charged power stations (Goal Zero Yeti 1500X) for data processing.

Health logistics were equally demanding. Malaria incidence in rural Comoros remains 2.4 cases per 1,000 person-days (Ministry of Health 2023 surveillance data), requiring strict adherence to WHO-recommended chemoprophylaxis (atovaquone-proguanil). Two team members contracted dengue fever in late March, treated at Hôpital de Moroni’s newly upgraded tropical disease wing—equipped with Abbott ID NOW diagnostic platforms capable of detecting NS1 antigen within 15 minutes. Water purification relied on Sawyer MINI filters (0.1 micron pore size), tested daily against ISO 16266:2021 standards for E. coli removal efficiency.

1. Daily caloric intake averaged 3,120 kcal, sourced 68% from local staples: banana, manioc, and fish
2. Team members carried 12.7 kg average field load: GPS, audio gear, batteries, water, and first aid
3. Communication relied on Iridium 9555 satellite phones; average signal latency: 1.8 seconds
4. GPS accuracy averaged ±2.3 m (with SBAS correction), critical for microhabitat mapping
5. Temperature extremes ranged from 19.4°C (montane Anjouan, pre-dawn) to 34.7°C (coastal Mohéli, midday)

Policy Implications and Forward Pathways

Data from Expedition 168312 directly informed three national policy actions ratified in June 2024. First, the Comorian government approved Decree No. 2024-021, establishing the Anjouan Scops Owl Sanctuary—a 1,840-ha protected zone encompassing all three confirmed roost sites and buffer corridors. Second, the Ministry of Environment adopted the ‘Island Endemism Index’ (IEI), a quantitative metric weighting species uniqueness, population size, and threat exposure—now embedded in environmental impact assessment guidelines for infrastructure projects. Third, Mayotte’s Prefecture enacted Ordinance No. 2024-044 restricting aggregate quarrying within 500 m of known lava tube roosts, citing Expedition 168312’s geospatial risk modeling.

Long-term monitoring infrastructure is now operational: 42 permanent bioacoustic nodes (Wildlife Acoustics SM4 units) are installed across priority sites, streaming encrypted data to the CROI server in Saint-Denis via Starlink terminals. Real-time alerts trigger automated SMS notifications to park rangers when calls of Otus capnodes or Microcebus mamiratra exceed threshold frequencies. Funding for this network comes from the Global Environment Facility’s Small Grants Programme ($217,000 committed) and the European Union’s BIOPAMA initiative.

Expedition 168312 did not merely document biodiversity—it mapped vulnerability with surgical precision. It proved that the Anjouan scops owl persists not as a relic but as a dynamic, adaptable species clinging to microrefugia in a rapidly changing landscape. It demonstrated that local ecological knowledge, when formally integrated with high-resolution technology, produces conservation intelligence far exceeding what either approach achieves alone. And it affirmed that the Comoros remain not a biological footnote, but a frontline laboratory where extinction trajectories can still be altered—through science rigorously applied, partnerships respectfully forged, and policies decisively enacted. The next phase—Expedition 168313—launches October 2024, focusing on soil invertebrate endemism and fungal symbionts in montane orchids. Field notes from that mission will build directly on the spatial frameworks, acoustic libraries, and community trust established during these six foundational weeks on Ngazidja, Nzwani, Mwali, and Maore.