02555nas a2200505   4500000000100000008004100001260001500042100002600057700001600083700001700099700002400116700001700140700001600157700001700173700001600190700001900206700001700225700001400242700001500256700001400271700001700285700001600302700001800318700002200336700002300358700001700381700001800398700001800416700002200434700001700456700001600473700002100489700002400510700002500534700001700559700001900576700002200595700002000617700002100637245013600658856005500794300001300849490000700862520118000869       2024                            d  c2024-05-241 aAndré L. Koch Liston1 aXueying Zhu1 aTran V. Bang1 aPhaivanh Phiapalath1 aTanvir Ahmed1 aSabit Hasan1 aSajib Biswas1 aShimul Nath1 aToufique Ahmed1 aKurnia Ilham1 aNgwe Lwin1 aCain Agger1 aSuzuki Ai1 aEmeline Auda1 aEva Gazagne1 aJan F. Kamler1 aMilou Groenenberg1 aSarah Banet-Eugene1 aNeil Challis1 aNicole Leroux1 aPablo Sinovas1 aVanessa H. Muñoz1 aSusan Lappan1 aZaki Zainol1 aValeria Albanese1 aAthanasia Alexiadou1 aDaniel R. K. Nielsen1 aAnna Holzner1 aNadine Ruppert1 aElodie F. Briefer1 aAgustin Fuentes1 aMalene F. Hansen00aA model for the noninvasive, habitat-inclusive estimation of upper limit abundance for synanthropes, exemplified by M. fascicularis  uhttps://www.science.org/doi/10.1126/sciadv.adn5390  aeadn53900 v103 aAccurately 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.