Is the long‐tailed macaque at risk of extinction?

We review the evidence that long‐tailed macaques are at risk of extinction and find that papers supporting this argument present no data supporting a hypothesized decline in abundance. These papers contain numerous misrepresentations of the published literature. Long‐tailed macaques thrive in human‐altered habitats, are listed by the International Union for the Conservation of Nature as an invasive species of concern, and have shown the ability to increase by 7%–10% per year from low numbers, making the probability of extinction very low.


| INTRODUCTION
The conservation status of long-tailed macaque (Macaca fascicularis) has been a controversial subject.The International Union for the Conservation of Nature (IUCN) lists the species as an invasive species of concern (Lowe et al., 2000) since it has colonized or been introduced to several locations and expanded rapidly in such areas.
The species is now considered a threat to both native biodiversity and agriculture and is actively being controlled by culling, contraception, and translocation throughout much of its native range (Moore et al., 2023).
Another perspective presented by Gamalo et al. (2023) is that long-tailed macaques have declined in abundance and are endangered.The species has recently been upgraded to "endangered" by IUCN.Not all agree, and Professor William Laurance, one of the most respected tropical ecologists in the world, was recently quoted in Science magazine (Normile, 2023) saying, "IUCN is off-base here."Moore et al. (2023) listed long-tailed macaque as "hyper-abundant and a threat to natural ecosystems."A recent petition by the People for Ethical Treatment of Animals proposes to list the species under the US Endangered Species Act (ESA), stating this species is on track to replicate the passenger pigeon in going from highly abundant to extinct in a few generations.
However, because of its life history, no primate species may be less likely to go extinct.Its abundance is in the millions, and it is widely distributed (MacKinnon, 1986).It is more abundant in secondary forests than primary forests (MacKinnon, 1986) and is found in the highest densities near agriculture and human settlements.It has shown population growth rates of 7%-10% per annum from very small numbers when introduced (Fooden, 1995) and is listed by the Convention on International Trade in Endangered Species of Wild Fauna and Flora as an invasive species of concern (Lowe et al., 2000).Long-tailed macaques are also effectively protected from the major threats in several areas, and in Mauritius, culling has not resulted in eradication (Sussman et al., 2011).Notwithstanding these facts, a recent IUCN evaluation reclassified the species from vulnerable to endangered.Hansen et al. (2022) and Gamalo et al. (2023) also argue that this species should be listed under the ESA.The major difference between ESA listing and IUCN endangered listing is that a species can meet the IUCN criteria for endangered in several ways, such as a rate of decline or small population size.However, ESA listing is based upon an actual risk of extinction, not specific surrogates for extinction risk.
We explored the available data on the species' biology and its trends in abundance and exploitation and came to very different conclusions.We find that both Gamalo et al. (2023) and Hansen et al. (2022) present no data to support their claims of significant declines in species abundance and misrepresent published data.Neither Gamalo et al. (2023) nor Hansen et al. (2022) represent an unbiased review of the scientific literature in assessing the status and threats to the long-tailed macaque.Gamalo et al. (2023) state, "In less than three macaque generations this once ubiquitous, keystone species, who for centuries defined ecological success in anthropogenically altered habitats, where other seed dispersers, predators and prey are not able to survive, has traced an ominous population trajectory from the lower risk/near threatened (1996,2000), to least concern (2008( ), to vulnerable (2020( , 2021( ), and Endangered (2022))."This change in IUCN status has been made in the absence of any data showing the decline.Eudey (2008), Gamalo et al. (2023), Hansen et al. (2021), andHansen et al. (2022) all cite a decline of 40% in the species, from a total population of five million to a more recent total population of three million.In 2022, Hansen et al. (2022) forecast a further 50% decline in the next three generations.However, no data support these estimates when one explores the basis for these purported declines.The five million population estimate comes from a table in MacKinnon (1986) who used population estimates for Indonesia of remaining primary and secondary forests and estimated average densities in each (30 per km 2 for primary forest and 40 for secondary forest), which produced an estimate of 3.7 million individuals for Indonesia.This was then used by Fooden (1995) who added rough estimates from other countries to arrive at an estimate of the total population in 1985 of five million.

| EVIDENCE FOR A HISTORICAL DECLINE
The more recent population estimate of three million comes from (Fooden, 2006), who states, "Judging from limited available information, the total extant populations of the two widely distributed fascicularis-group species, M. fascicularis and Macaca mulatta, are ca.3,000,000 and 2,000,000, respectively (Fooden, 1995, p. 54;Fooden, 2000, p. 7;cf. Zhang et al., 2002, p. 20)."However, while Fooden (1995) is the source of the five million estimate, the cited page 54 makes no mention of three million, and the section of that paper on abundance ends with the five million number.
The second citation contained in Fooden (2000) is about M. mulatta, not M. fascicularis.The third citation, Zhang et al. (2002), is entitled "The primates of China" and does not mention M. fascicularis.Thus, nowhere in the cited literature is there any information on how the three million population estimate provided in Fooden (2006) was derived.Further, the serially cited claim of a population decline from five million to three million is not documented in any of the citations.Gamalo et al. (2023) states, "The ability of long-tailed macaques to utilize anthropogenic spaces makes them highly visible, creating the illusion of ubiquity even when their numbers are steeply declining inside forests and native habitats," citing Eudey (2008), Hansen et al. (2019), and Kyes et al. (2011).Eudey (2008) presents no data at all, Hansen et al. (2019) present no evidence of a downward trend, and Kyes et al. (2011) provide no estimates of abundance or trend data.
All publications claim that a "major decline" in species abundance has occurred without supporting evidence.Gamalo et al. (2023) suggest that long-tailed macaques are essentially absent from their native habitats.However, Hansen et al. (2019) estimate the density in a national park in Java at 41.4 individuals/km 2 , well above the density MacKinnon (1986) used for density in native forests (30/km 2 ).
There has been no analysis of the total abundance or the overall trend in abundance of the species.The ongoing killing and sterilization of macaques taking place near cities and agriculture suggests they are, in fact, very abundant.The lack of any trend data does not mean that declines have not occurred, but the extent of any decline or increase in abundance remains unknown.Long-tailed macaques may indeed be declining because of hunting, capture, and loss of natural habitat.But they may be increasing due to increases in secondary forests, agriculture, cities, and provisioning.However, Nuttall et al. (2022) state, "We found that gibbon, douc, PT macaque, LT macaque, langur, and peafowl showed stable or increasing population trends."Thus, Hansen et al. (2022) and Gamalo et al. (2023) misrepresent the paper's conclusions.They make no mention of several documented populations that have shown significant increases, including a sevenfold increase in 22 years in a protected area in Indonesia (Brotcorne et al., 2011).And Fooden (1995) reported a population in Sumatra increasing at a rate of 7% per year between 1972and 1986. Fooden (1995) ) also reports an introduced population on the island of Angaur in Indonesia, increasing from a few individuals to 480-600 in 75 years.Perhaps most significant to the risk of extinction is the introduction to Mauritius (thought to have occurred about 1602), where the wild population now numbers 25,000-35,000 despite culling (Sussman et al., 2011).Gamalo et al. (2023) did not cite estimates of trends in abundance in Thailand.Malaivijitnond and Hamada (2008) (Hoàng et al., 2019)," yet this reference does not mention M. fascicularis.Regarding Bangladesh, these authors state that "none found in recent surveys (pers obs)."

| EVIDENCE FOR MORE RECENT DECLINES
However, the population in Bangladesh was at the extreme of the range (Fooden, 1995) and had been found previously in very few

| CHANGES IN HABITAT
The loss of native forests worldwide is undoubtedly a threat to native biodiversity, and the most straightforward hypothesis would be that long-tailed macaques have declined in proportion to the decline in native forests.Between 1990 and 2020, according to Ritchie (2021), Indonesia lost 22% of its forest area, while across all of South East Asia (the Philippines excepted), 16% had been lost.However, these rough numbers do not distinguish between the kind of forests, and the lowland and riverine forests preferred by long-tailed macaques may have declined more.On the other hand, secondary forests, agriculture, and human-occupied areas have increased, and in those habitats, long-tailed macaques are more abundant than in native forests.Using global land-use data to calculate changes in these habitats and applying available density estimates to calculate the current population size should be possible.We are unaware that this has been attempted, nor do the published population estimates reflect this approach.

| EVALUATION OF THREATS: EXPORTS, PEST CONTROL
There is no question that many long-tailed macaques are being culled or sterilized due to negative interactions with humans.Data from the Malaysian Wildlife Department annual report (Department of Wildlife and National Parks Peninsular Malaysia, 2018) estimates that 53,687 were culled in Malaysia in 2018.The same reports for 2017-2021 show an average number culled at the same general level.That is certainly a large number of animals.Still, there is no evidence that these removals cannot be sustained since the abundance is higher in secondary forests, near agriculture, and cities.The persecution may reflect higher abundance rather than nonsustainable killing.If indeed the populations are in decline, then as abundance declines, there would be less human conflict, and the need for culling would be reduced.Since such persecution does not occur on a large scale in Buddhist Thailand, even if the species went locally extinct in much of Indonesia and Malaysia, there is no scenario in which they would go extinct in Buddhist Bali and Thailand.
We can estimate what level of exploitation would be sustainable by simply looking at the rate of increase in unexploited populations.Fooden (1995) reported that the population in Sumatra increased at a rate of 7% per year between 1972 and 1986, and another population increased at a rate of 10%.Using the undocumented three million as a total population size and a 7% intrinsic rate of increase, the annual sustainable number killed or removed would be 210,000 individuals.
Compared to the scale of culling in Malaysia, the number of longtailed macaques exported for medical purposes, shown in table 1 of Gamalo et al. (2023), is distinctly lower.Excluding China and Mauritius, which are not within the native range of long-tailed macaques, the average annual exports are 16,378.This level of exports seems sustainable even if these individuals came from wild populations, which is unlikely.But if we assume that all these animals came from the wild and that there are only one million free-living individuals, the number of exported individuals is still within the number of sustainable removals.

| HOW MIGHT EXTINCTION OCCUR?
Long-tailed macaques could go extinct if all individuals were drawn out of forest habitat to be near cities and agriculture, where they would be eliminated as pests.Even if that did occur over large areas, at some point, the population size would be low enough that they would no longer be pests, and either the population would rebuild as it has been documented to occur where they were not persecuted, or the populations would come to an equilibrium with respect some level of removals.The idea that the rate of removals would not decline if the number of macaques in human-used areas declined dramatically seems improbable.Even more improbable is that the last macaques would choose to move out of the native and secondary forests to be shot or trapped.Further, this scenario would require that the many areas where long-tailed macaques are protected would no longer be protected.Gamalo et al. (2023) present the recent IUCN Red List assessment and the ESA petition submission as cumulative evidence for establishing high extinction risk.However, closer examination shows that data do not support the recent IUCN species classifications.While it is not the intent for IUCN criteria to be applied based on unstructured expert opinion (Collen et al., 2016), in the absence of data, only opinion remains.And there was no indication that a structured approach to eliciting expert judgment (Hemming et al., 2018) was followed by Gamalo et al. (2023) or Hansen et al. (2022).

| CONCLUSIONS
The ESA petition is a reformatted version of the most recent IUCN assessment (Hansen et al., 2022) and is not a separate determination or regulatory finding.Thus, the petition cannot be considered an independent line of evidence because it contains the same flaws as the IUCN assessment.In their current forms, the recent IUCN assessment and ESA petition are unreliable substitutes for an independent empirical assessment of extinction risk.
In summary, the abundance of long-tailed macaques may have declined, but none of the published literature cited to support the IUCN listing as endangered presents any data to support the hypothesized decline, nor does the literature establish that the species is at risk of becoming extinct.What is needed are better data and evidence-based management of removals and culling.
Gamalo et al. (2023) contain many misrepresentations of published papers and impute content to the papers that cannot be found in the text.The only time series of abundance given by Gamalo et al. (2023) is a statement that there has been a 50% decline between 2010 and 2020 in a National Park in Cambodia, citingNuttall et al. (2022).
said, "For these reasons, the population of long-tailed macaques [in Thailand] has increased 5-10 folds compared with 15 years ago."Gamalo et al. (2023) say with reference to Viet-Nam that "[r] ecent publications from Vietnam indicate a dramatic decline in group sizes and local extirpations Lao, Gamalo et al. (2023) say "In Lao PDR, the remaining number of individuals has declined precipitously; a recent survey estimated only 500 remaining individuals, a reduction of almost 400% in the last 10 years, with possibly only one subpopulation remaining that has not hybridized with rhesus macaques (M.mulatta) (pers.obs.Phaivanh Phiapalath, 2021; Hamada et al., 2011)."However, Hamada et al. (2011) estimate the total population size in Lao "lies with the range of 420-4200."No trend estimates are presented in this publication.Assuming the 500 individual estimate comes from the undocumented personal observation, then an estimate of 500 lies within the range estimated by Hamada et al. (2011).