A review of the macaque contraceptive programme in Hong Kong

Abstract

Macaques are the most widely distributed non-human primates on Earth. Taking advantage of their high adaptability, they occupy a huge variety of habitats and climates, and adapt to a wide variety of diets. The astonishing flexibility also allows them to survive outside their natural range. Macaques are very valuable to the ecosystem and human society, they had provided numerous benefits in ecological, economic, scientific and cultural aspects. However, high adaptability has led them to cause nuisance problems in many places. Different management measures such as translocation and population control were implemented around the world. Feeding ban and contraceptive programme were used in Hong Kong. This study aimed to review the effects of the macaque contraceptive programme on macaques by studying (1) the population dynamics of macaques with emphasis on age group structure and birth rate, and (2) the ecological assessment of macaques with emphasis on activity budget and feeding ecology. Data were collected on three troops with sterilization treatment and three troops without. Age group structure was studied by conducting a population survey and comparing results of the two treatment groups. Birth rate data was retrieved and calculated from population survey results in previous reports. Macaque behaviours were studied by conducting an activity budget using the interval scanning method. Feeding ecology was studied by identifying the plant species consumed by the macaques during the observation study. The overall birth rate dropped from 59.13% in 2009 to 32.86% in 2018. The age group structure had a significant shift in the proportion of immatures to adult females. The proportion of adult females in sterilized troops were higher by around 20% and the proportion of immatures was lower by around 25%. Also, non-sterilized troops shared similar age group structure as data in 2008, suggesting that the programme was successful in limiting the population growth in macaques. A total of 5,934 behavioural observation points were collected during 24.35 hours of observation study. The percentage of grooming behaviour per hour was 46.10% for sterilized macaque group while that for non-sterilized macaque group was 12.69%. The percentage of grooming behaviour in all sterilized macaque troops were significantly higher than each of the non-sterilized macaque troop, implying that grooming helped macaques to maintain their social bonding within the troop. The results indicated that the programme had effect some changes to the macaque behaviours. However, more researches were needed to determine whether aggressive behaviour became more frequent after sterilization. A total of 12 plant species were seen consumed by macaques during this study. Despite proofing effective in controlling the population of macaques, the contraceptive programme should extend the operation area closer to areas with nuisance problems. The feeding ban should be maintained together with the education programme to further discourage visitors from feeding wild animals, and thus preventing further changes in macaques’ behaviour and movement range. Researches should be carried out on the influences of anthropogenic activities on macaques’ behaviour. In addition, the goal of the macaque contraceptive programme and the long-term effects should be reviewed.