A model for the noninvasive, habitat-inclusive estimation of upper limit abundance for synanthropes, exemplified by M. fascicularis.

Accurately estimating population sizes for free-ranging animals through noninvasive methods, such as camera trap images, remains particularly limited by small datasets. To overcome this, we developed a flexible model for estimating upper limit populations and exemplified it by studying a group-living synanthrope, the long-tailed macaque (Macaca fascicularis). Habitat preference maps, based on environmental and GPS data, were generated with a maximum entropy model and combined with data obtained from camera traps, line transect distance sampling, and direct sightings to produce an expected number of individuals. The mapping between habitat preference and number of individuals was optimized through a tunable parameter ρ (inquisitiveness) that accounts for repeated observations of individuals. Benchmarking against published data highlights the high accuracy of the model. Overall, this approach combines citizen science with scientific observations and reveals the long-tailed macaque populations to be (up to 80%) smaller than expected. The model's flexibility makes it suitable for many species, providing a scalable, noninvasive tool for wildlife conservation.

Unmanned aerial vehicles (UAVs) with thermal infrared (TIR) sensors are effective for monitoring and counting threatened Vietnamese primates.

Monitoring the population size of threatened primate species with minimal disturbance is becoming an outstanding requirement for conservation and wildlife management. Drones with thermal infrared (TIR) and visible spectrum (RGB) imaging are increasingly used to survey arboreal primates, but ground-truthing is still required to assess the effectiveness of drone-based count estimates. Our pilot study aims to assess the ability of a drone with both TIR and RGB sensors to detect, count, and identify semi-wild population of four endangered species of langurs and gibbon in the Endangered Primate Rescue Center (EPRC) in northern Vietnam. We found that TIR imagery enabled higher detection rates compared to RGB imagery and obtained an accurate count with the TIR only after four drone flights. We could identify langurs species based on thermal signature at a flight height of 50 m from the ground level (max tree height = 15 m), via size and shape of the body. With TIR imagery, we were able to record inconspicuous behaviors such as foraging and play. While some individuals initially showed flight or avoidance behaviors when the drone was sighted, these behaviors decreased or were absent on following drone surveys. Our study suggests that monitoring and precisely counting langur and gibbon species populations could be successful with the use of thermal drones only.

CoFee-L: A Model of Animal Displacement in Large Groups Combining Cohesion Maintenance, Feeding Area Search and Transient Leadership.

In the tropics, the conservation of tree species is closely linked to that of animals, as a large proportion of trees are zoochoric and therefore rely on the movement of animals to disperse their seeds in order to increase the chances of the survival of progeny and to allow migration in the face of climate change. Research into the prediction of animal movements is therefore critical but has so far focused only on particular features of collective behavior. In contrast, we included the concepts of cohesion maintenance, feeding area search and transient leadership in a single model, CoFee-L, and tested it to simulate the movement of a wild-ranging troop of primates (Macaca leonina). We analyzed and compared observations and simulations with a statistical physics tool (mean squared displacement) and with histograms and χ2 (for the step length and turning angle distributions). CoFee-L allowed us to simulate the physical properties of the troop's center of mass trajectory as well as the step length and angle distributions of the field data. The parametrization of CoFee-L was rather straightforward, as it was sufficient to fix a set of parameters easily observable in the field and then to adjust the values of four parameters that have biological meaning.

Northern pigtailed macaques rely on old growth plantations to offset low fruit availability in a degraded forest fragment.

Space-use and foraging strategies are important facets to consider in regard to the ecology and conservation of primates. For this study, we documented movement, ranging, and foraging patterns of northern pigtailed macaques (Macaca leonina) for 14 months in a degraded habitat with old growth Acacia and Eucalyptus plantations at the Sakaerat Biosphere Reserve in northeastern Thailand. We used hidden Markov models and characteristic hull polygons to analyze these patterns in regard to fruit availability. Macaques' home range (HR) was 599 ha and spanned through a natural dry-evergreen forest (DEF), and plantation forest. Our results showed that active foraging increased with higher fruit availability in DEF. Macaques changed to a less continuous behavioral state during periods of lower fruit availability in DEF, repeatedly moving from foraging to transiting behavior, while extending their HR further into plantation forest and surrounding edge areas. Concomitantly, macaques shifted their diet from fleshy to dry fruit such as the introduced Acacia species. Our results showed that the diet and movement ecology adaptations of northern pigtailed macaques were largely dependent on availability of native fruits, and reflected a "high-cost, high-yield" foraging strategy when fresh food was scarce and dry fruit was available in plantation forest. Conversely, wild-feeding northern pigtailed macaque populations inhabiting pristine habitat approached a "low-cost, low-yield" foraging strategy. Our results outline the effects of habitat degradation on foraging strategies and show how a flexible species can cope with its nutritional requirements.

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.

Cultural flies: Conformist social learning in fruitflies predicts long-lasting mate-choice traditions.

Despite theoretical justification for the evolution of animal culture, empirical evidence for it beyond mammals and birds remains scant, and we still know little about the process of cultural inheritance. In this study, we propose a mechanism-driven definition of animal culture and test it in the fruitfly. We found that fruitflies have five cognitive capacities that enable them to transmit mating preferences culturally across generations, potentially fostering persistent traditions (the main marker of culture) in mating preference. A transmission chain experiment validates a model of the emergence of local traditions, indicating that such social transmission may lead initially neutral traits to become adaptive, hence strongly selecting for copying and conformity. Although this situation was suggested decades ago, it previously had little empirical support.

Foraging strategies underlying bird egg predation by macaques: A study using artificial nests.

Bird egg predation is widespread in non-human primates. Although nest predation is often described as opportunistic, little is known about foraging strategies and nest detection in primates. Since it is the prevalent cause of nest failure in the tropics, birds select nest sites within specific microhabitats and use different nest types to increase nesting success. Identifying the nests targeted by the northern pigtailed macaques (Macaca leonina), an omnivorous cercopithecine species, and known nest predator, will shine light on nest foraging strategies in primates. The aim of this research was to reveal if nest predation is a selective or opportunistic feeding behavior. We studied, using artificial nests and camera traps, the influence of nest type (open-cup vs. cavity), microhabitat (i.e., understory density, canopy cover, canopy height, ground cover, and presence vs. absence of thorns and lianas), and nest height, on nest predation by a troop of northern pigtailed macaques in the Sakaerat Biosphere Reserve (Thailand), a degraded environment. In our study, macaque predation on artificial nests was high; out of the 200 nests that were set up, 112 were plundered by macaques. Although predation rates decreased with nest height, nest type, and microhabitat had no significant effect on predation by macaques. Nest detectability and accessibility did not affect predation rates. Macaques actively searched for nests in different microhabitats, suggesting that nest predation by this primate might be considered a selective feeding behavior in this degraded habitat. Consequently, nest predation by this primate might have important conservation implications on the population dynamics of forest-dwelling bird species. Behavior observation methods, such as instantaneous scan sampling, may underestimate nest predation by primates, a furtive and cryptic behavior.