Macaques as Seed Dispersal Agents in Asian Forests: A Review

Long-Tailed Macaque (Macaca fascicularis) Contraception Methods: A Systematic Review

The contraception-based approach to wildlife management is a humane and effective alternative to population control methods. Wildlife management only has a few conventional ways to control overpopulation, such as culling, translocation, poisoning, and allowing natural death. Nevertheless, these methods usually have short-term, lethal, and unethical effects. The present systematic review aims to review the knowledge on contraception reported in long-tailed macaques as an alternative to population control. We obtained 719 records from searching CABI, PubMed, ScienceDirect, and Scopus electronic databases. After the screening and selection process, according to PRISMA guidelines, 19 articles that met the eligibility criteria were chosen. Of the 19 articles, 15 were studies on female long-tailed macaque contraception methods (six (6) hormonal and nine (9) non-hormonal). We analyzed four (4) selected articles on male Cynomolgus monkey contraception methods (two (2) hormonal and two (2) non-hormonal). One of the nine (9) articles on female long-tailed macaque contraception reports negative results. Furthermore, only two (2) studies used free-ranging long-tailed macaques as test subjects, while seventeen (17) tested on captive ones. The challenges of long-tailed macaque contraception identified in this review were the effectiveness of the contraceptive, the administration route, the economic feasibility, the distinction between captive and free-ranging Cynomolgus macaques, the choice of permanent or reversible contraception, the capability of contraceptive use for population control, and the lack of studies on the free-ranging long-tailed macaque. Notwithstanding the literature gap on long-tailed macaque contraception for population control, long-tailed macaque contraception exhibits potential as an alternative method to culling long-tailed macaque. Future research should address these obstacles to support the long-tailed macaque contraception as an alternative population control method.

Feeding ecology of free-ranging long-tailed macaques in East Java, Indonesia: Relationship with human food availability

Food availability is an important factor affecting the feeding strategies of animals. Primate species living in habitats with high human activity have the potential to employ unique strategies to utilize human food resources. This study describes the feeding ecology of provisioned free-ranging long-tailed macaques (Macaca fascicularis) inhabiting Alas Purwo National Park, East Java, Indonesia. The activity budgets, dietary compositions, vertical usage, and ranging patterns of macaques were recorded between October 2021 and March 2022, and their relationships with the number of visitors (a proxy of human food availability) were examined. The macaques consumed more human food (mean ± SD: 53.9 ± 25.6%) than natural food (43.8 ± 25.5%), followed by unidentified food (2.3 ± 6.3%). Human food has several effects on the behavioral ecology of macaques, including reduced movement and increased social activity in response to the number of visitors, decreased consumption of natural food, frequent use of the ground and subcanopy strata, and decreased home range when the number of visitors increases. Thus, the relative importance of human food has substantially changed the essential behavioral ecology of provisioned macaque troops. Understanding the behavioral plasticity of macaques, particularly their responses to anthropogenic effects, could guide and contribute to the formulation of conservation policies and management plans.

Foraging Strategies of Invasive Macaca fascicularis may Promote Plant Invasion in Mauritius

The effectiveness of seed dispersal by frugivorous primates may vary between seasons and plant species, depending on foraging strategies. We investigated how foraging strategies of an invasive frugivorous primate (the long-tailed macaque, Macaca fascicularis) affect seed dispersal effectiveness (SDE) between native and invasive plants in Mauritius’ native remnant forests. By collecting behavioural data on a group of partially habituated macaques via scan sampling from December 2019 until December 2020 (mean 19.2 ± SD 7.3 hours per month), we investigated seasonal patterns in diet, home range, and fruit availability to identify foraging strategies and determine fruit preference. We simultaneously assessed SDE for invasive vs native plants by quantifying native and invasive fruits consumed or dropped intact by macaques during feeding bouts (n = 114). Macaques fed increasingly on ripe invasive fruits and less on other food items as fruit availability increased, due to preference for invasive fruits and disproportionate availability of invasive vs native fruits. When fruit became scarcer, macaques had larger home ranges, increasingly fed on scarce unripe native and invasive fruits, and expanded their diet by eating orchard crops, indicating use of energy-maximizing strategies. Macaques consumed more native than invasive fruits when unripe and commonly destroyed seeds of native fruits, indicating higher SDE for invasive vs native plants. Higher discard rates of unripe compared to ripe fruits further reinforced these differences in SDE. Our results highlight potential facilitation of plant invasion by an invasive primate, due to foraging strategies shaped by the availability of invasive fruits.

The Influence of Seed Characteristics on Seed Dispersal Early Stages by Tibetan Macaques

There are numerous ecological and evolutionary implications for the ability of frugivores to predate on fruits and consume or disperse their seeds. Tibetan macaques, which are considered important seed predators, typically feed on fruits or seeds. However, systematic research into whether they have a seed dispersal function is still lacking. Endozoochory allows seeds to disperse over greater distances by allowing them to remain in the animal’s digestive tract. Consumption of fruit may not imply effective seed dispersal, and the physical characteristics of seeds (e.g., size, weight, specific gravity, etc.) may influence the dispersal phase’s outcome. We conducted feeding experiments with three captive Tibetan macaques (Macaca thibetana) and nine plant seeds to determine the influence of seed characteristics on Tibetan macaques’ early stages of seed dispersal. The results revealed that the percentage of seed destruction (PSD) after ingestion was 81.45% (range: 15.67−100%), with the PSD varying between plant species. Among the three passage time parameters, the transit time (TT) (mean: 18.8 h and range: 4−24 h) and the time of seed last appearance (TLA) (mean: 100.4 h and range: 48−168 h) differed significantly between seed species, whereas the mean retention time (MRT) (mean: 47.0 h and range: 32−70.3 h) did not. In terms of model selection, PSD was influenced by seed size, weight, volume, and specific gravity; TT was influenced by seed-to-shell investment rate, weight, volume, and specific gravity; and TLA was influenced only by seed size. These findings imply that seeds with a smaller size, specific gravity, volume, and greater weight pass more easily through the monkeys’ digestive tracts. Particularly, seeds with a mean cubic diameter (MCD) of <3 mm had a higher rate of expulsion, larger volume, and weight seeds pass faster, while smaller remained longer. Tibetan macaques, as potential seed dispersers, require specific passage time and passage rates of small or medium-sized seeds. Larger and heavier seeds may be more reliant on endozoochory. Tibetan macaques have the ability to disperse seeds over long distances, allowing for gene flow within the plant community.

The role of lemur seed dispersal in restoring degraded forest ecosystems in Madagascar

Anthropogenic disturbances lead to the degradation or destruction of tropical forests, with negative consequences for flora, fauna, and local people. Restoration plantings may compensate these impacts, but time and financial expenditures are high. Thus, priority is often given to plantations of a few introduced species that have little value for conservation. Animal seed dispersal may diversify and accelerate regeneration of restoration plantings, thereby lowering their costs. We studied seed dispersal quantity and quality of crowned lemurs (Eulemur coronatus) in a highly degraded forest in northern Madagascar, conducting behavioural observations and germination experiments and describing dispersed plant species’ characteristics. Crowned lemurs were highly frugivorous, dispersing a large number of seeds and plant species. While there were negative effects of gut passage on germination, the positive effects of pulp removal outweighed these, resulting in an overall positive effect on regeneration. Our study confirmed that effects of gut passage are dependent on the dispersed plant species. We found 20 plant species, including three threatened with extinction, whose only dispersers in Oronjia seem to be crowned lemurs. We conclude that lemurs play important roles in protecting plant species and maintaining healthy ecosystems through seed dispersal, and that E. coronatus is a key species in this respect. In addition, if lemurs were included in restoration, they would disperse a diversity of plant species that cannot be matched by conventional restoration plantings. Their influence would facilitate the regeneration of some, but not all plant species. Negative effects, like the spread of invasive species through seed dispersal by lemurs, must also be considered.

Roadside monkeys: anthropogenic effects on moor macaque (Macaca maura) ranging behavior in Bantimurung Bulusaraung National Park, Sulawesi, Indonesia

A growing body of research focuses on how anthropogenic factors affect the behavior and ecology of primates and their ecosystems. Infrastructural development, such as roads, is an increasingly pervasive anthropogenic impact that destroys primate habitat, affects the distribution and dispersal of primates, and facilitates human-primate interactions. At our field site in Bantimurung-Bulusaraung National Park, Sulawesi, Indonesia, a major road bisects the habitat of the endangered moor macaque (Macaca maura). Beginning in 2015, we observed a behavioral shift by our main study group: they began spending more time along the road foraging in trash pits and waiting for provisions from vehicles. Our objective in this study was to examine how access to anthropogenic foods has affected the group's ranging behavior by comparing ranging data collected before (2010-2011) and after the shift (2016-2017). In contrast to what we expected, home ranges were significantly larger and daily travel distance was significantly longer after the shift compared to before. As predicted, mean distance to the road decreased after the shift. These results likely reflect the irregular and spatially dispersed nature of provisioning at this site. The macaques appear to be attracted to the road because it presents opportunities to obtain palatable and energy-dense foods. Our results indicate that moor macaques are able to flexibly adjust their ranging behavior in response to anthropogenic impacts. However, given the risks of being in proximity to roads and humans, management of this emerging human-macaque interface is needed.

Reliability of macaques as seed dispersers

Seed dispersal is an ecological process crucial for forest regeneration and recruitment. To date, most studies on frugivore seed dispersal have used the seed dispersal effectiveness framework and have documented seed-handling mechanisms, dispersal distances and the effect of seed handling on germination. In contrast, there has been no exploration of "disperser reliability" which is essential to determine if a frugivore is an effective disperser only in particular regions/years/seasons or across a range of spatio-temporal scales. In this paper, we propose a practical framework to assess the spatial reliability of frugivores as seed dispersers. We suggest that a frugivore genus would be a reliable disperser of certain plant families/genera if: (a) fruits of these plant families/genera are represented in the diets of most of the species of that frugivore, (b) these are consumed by the frugivore genus across different kinds of habitats, and (c) these fruits feature among the yearly staples and preferred fruits in the diets of the frugivore genus. Using this framework, we reviewed frugivory by the genus Macaca across Asia to assess its spatial reliability as seed dispersers. We found that the macaques dispersed the seeds of 11 plant families and five plant genera including at least 82 species across habitats. Differences in fruit consumption/preference between different groups of macaques were driven by variation in plant community composition across habitats. We posit that it is essential to maintain viable populations of macaques across their range and keep human interventions at a minimum to ensure that they continue to reliably disperse the seeds of a broad range of plant species in the Anthropocene. We further suggest that this framework be used for assessing the spatial reliability of other taxonomic groups as seed dispersers.