Long-term community-based monitoring of tamaraw Bubalus mindorensis on Mindoro Island, Philippines S HINYA I SHIHARA ,R ODEL M. B OYLES ,H ISASHI M ATSUBAYASHI A RNEL N. DEL B ARRIO ,M ERBEN R. C EBRIAN ,A IKO I SHIDA ,R OSALINA M. L APITAN E UFROCINA P. A TABAY ,L IBERTADO C. C RUZ and Y UKIO K ANAI

The Critically Endangered tamaraw Bubalus mindorensis is endemic to Mindoro Island, Philippines, and little is known of its ecology. During 2006-2011 we used community-based monitoring to examine the population status and ecology of tamaraw in the species' core habitat of Mount Iglit-Baco National Park. Each year, for 5 consecutive days at the end of the dry season, trained local volunteers and rangers or project staff were allocated to 18 vantage points in the study area (c. 160 km 2 ). Tamaraw were categorized as adult (.5 years), juvenile (2-5 years) or calf (,2 years), and sexed when possible. During the study period the population was 239-314 (mean 271), with no significant fluctuations in age structure (percentage of adults, juveniles and calves: 57.8, 21.0 and 21.3%) or estimated adult female reproductive rates (29.1%). In adults, but not in juveniles, the sex ratio was biased towards females (1: 1.86 ,P , 0.01). Bulls were often solitary (32.2% of sightings), whereas the majority of cows (94.7%) formed small groups of 2-12 individuals of different ages, with or without bulls (53.4 and 46.6%, respectively). These results demonstrate that the population remained relatively stable, maintaining a constant age structure and reproductive rate, and that long-term community-based monitoring was effective for quantitative characterization of the tamaraw's social behaviour, which is critical for conservation and management of the species.