Conservation Genetics of the Philippine Tarsier: Cryptic Genetic Variation Restructures Conservation Priorities for an Island Archipelago Primate

Establishment of conservation priorities for primates is a particular concern in the island archipelagos of Southeast Asia, where rates of habitat destruction are among the highest in the world. Conservation programs require knowledge of taxonomic diversity to ensure success. The Philippine tarsier is a flagship species that promotes environmental awareness and a thriving ecotourism economy in the Philippines. However, assessment of its conservation status has been impeded by taxonomic uncertainty, a paucity of field studies, and a lack of vouchered specimens and genetic samples available for study in biodiversity repositories. Consequently, conservation priorities are unclear. In this study we use mitochondrial and nuclear DNA to empirically infer geographic partitioning of genetic variation and to identify evolutionarily distinct lineages for conservation action. The distribution of Philippine tarsier genetic diversity is neither congruent with expectations based on biogeographical patterns documented in other Philippine vertebrates, nor does it agree with the most recent Philippine tarsier taxonomic arrangement. We identify three principal evolutionary lineages that do not correspond to the currently recognized subspecies, highlight the discovery of a novel cryptic and range-restricted subcenter of genetic variation in an unanticipated part of the archipelago, and identify additional geographically structured genetic variation that should be the focus of future studies and conservation action. Conservation of this flagship species necessitates establishment of protected areas and targeted conservation programs within the range of each genetically distinct variant of the Philippine tarsier.     

Successful breeding attempt of a pair of Philippine tarsier (Tarsius syrichta) in a conservation center in Bilar,Bohol, Philippines and recommendations for tarsier husbandry

The Philippine tarsier (Tarsius syrichta) belongs to the least known nocturnal primates. Tarsiers and remaining biodiversity of the Philippines are under tremendous threats from increasing human expansion, with habitat loss and illegal pet trade being the main reasons for tarsier population decline. In addition, even though the attempts were made by western and local facilities, tarsiers have not survived well in captivity. In this paper, I present an example of successful breeding of the Philippine tarsier in captive conditions but in natural climate. As the most important elements of success, I see a large amount of space provided to tarsiers, the climate similar to their natural habitat and the food resembling their natural diet. Our pair of tarsiers were joined during the mating period and held separately outside the mating period, which corresponds with their behavior in the wild and may have played a crucial role in breeding success. Eliminating stress to animals is also important. The study can provide valuable guidelines for other facilities keeping tarsiers in the Philippines and help to improve tarsiers’ welfare and in the future help to establish a viable captive population of the Philippine tarsier that will serve as a backup population and also will decrease demand on tarsiers captured from the wild.     

Isolation and characterization of 12 microsatellite loci for population studies of Sulawesi tarsiers (Tarsius spp.)

This study reports the development and characterization of the first 12 microsatellite markers for tarsiers. Nine loci were isolated from Dian's tarsier, Tarsius dianae and three from the Philippine tarsier, Tarsius syrichta. The 12 markers were used to screen 40 individuals of Dian's tarsier and 40 individuals of the Lariang tarsier, Tarsius lariang for allelic diversity. This suite of highly polymorphic microsatellites provides the first chance to genetically study parentage patterns in tarsiers.     

Strengths and Weaknesses of a Population Viability Analysis for Philippine Tarsiers (<Emphasis Type="Italic">Tarsius syrichta</Emphasis>)

Population viability analysis (PVA) has been increasingly used to guide conservation planning for many primate species. I present an assessment of a PVA for Philippine tarsiers (Tarsius syrichta) in Corella, Bohol. The objectives were to determine 1) area requirements and 2) spatial configurations of habitat patches necessary for viable populations in Corella. I used available life history parameters and ecological data for the Philippine tarsier derived from a radiotelemetry study on 4 male and 6 female Tarsius syrichta in Corella from early March to October 1999. I used analysis of the likelihood of extinction (ALEX), a Monte Carlo simulation model that uses pseudorandom numbers to simulate a scenario involving different stochastic processes. Sensitivity analysis showed that the model output, i.e. extinction risk, was influenced by the values used for newborn, juvenile, and adult mortality but the effect of variation on adult mortality was more pronounced; a slight increase in adult mortality renders the population very unstable. Simulation of movements between habitat patches showed that addition of diffusion corridors and variation in diffusion parameters did not significantly alter the probability of extinction of the species. Models are only as useful as the data that are input, and a major weakness of this model is the lack of detailed life history and mortality data for Philippine tarsiers. Future studies should concentrate on obtaining more life history data and ecological data from additional localities. I discuss key priorities for future research that include use of alternative PVA software, a simpler modeling approach, and extensive genetic studies of different Philippine tarsier island populations.     

Population survey of the Philippine tarsier (Tarsius syrichta) in Corella, Bohol

In 1986, in response to the rapid habitat destruction throughout the archipelago, the Philippine tarsier was classified as endangered. Since that time, this tarsier has been reclassified as data deficient and more recently as near threatened despite a significant lack of information on the population density of the species. Data were collected at the Philippine Tarsier Foundation Sanctuary from June to October 2010. Population density was estimated using a modified form of the quadrat census method. A total of 55 individuals were located within the sampled area. This is equivalent to approximately 1.55 tarsiers per hectare. Ecologically, there were significantly more tarsiers found in the young secondary forest than in areas characterized as old secondary forest. Extrapolating to the entire protected area, as many as 258 tarsiers may reside in the sanctuary. The vegetation plots where tarsiers were found had substantially more trees per plot, contained trees with larger diameters, and contained slightly taller trees than did the plots where no tarsiers were observed.     

Positional behavior and social organization of the philippine tarsier (Tarsius syrichta)

This study provides preliminary data on the positional behavior and habitat use of the Philippine tarsier,Tarsius syrichta, which was studied in its natural habitat on the island of Leyte. The locomotor behavior ofT. syrichta is quite comparable to the other species of tarsiers but frequency of use of different postures and support types does seem to distinguish this species from the others.Tarsius bancanus appears to be the most specialized, using vertical clinging postures the most frequently and sitting the least;Tarsius dianae uses vertical clinging the least frequently and sitting the most, andT. syrichta is intermediate. The Philippine tarsier has a small home range similar to that ofT. spectrum. On the other hand, this species likely does not have the small family groups typical of Sulawesi tarsiers but instead uses a noyau system likeT. bancanus. This data supports some apsects ofNiemitz’s (1977) model of anatomical and behavioral specialization among tarsier species.     

Allocare in a nocturnal primate: data on the spectral tarsier, Tarsius spectrum

Non-maternal infant care in many of the small-bodied New World primate species has been hypothesized by some researchers to be related to the high infant/adult weight ratio found in these species. The spectral tarsier, Tarsius spectrum, an Old World primate, has one of the highest infant/adult weight ratios of any primate, with infants weighing between 20-33% of adult weight at birth. On the basis of the hypothesized relationship between allocare and the infant/adult weight ratio, it is predicted that the spectral tarsier will also exhibit extensive allocaretaking behaviour. The results of this study indicate that although spectral tarsiers show care by male and female subadults as well as adult males, it is extremely limited compared to the extensive allocaretaking behavior observed in New World primate species such as Aotus and Callicebus. Spectral tarsier subadult females provide substantially more allocare to infants than do subadult males or adult males. Female subadults were observed sharing food, transporting, grooming, playing, alarm calling, baby-sitting and maintaining physical contact with infants more than other age/sex classes. Although the amount of allocare exhibited by adult males and subadult males was much less than that exhibited by female subadults, the data suggest that adult and subadult male spectral tarsiers do play a small part in the care and socialization of the infant. Adult males and subadult males were both observed occasionally engaging in allocaretaking behaviors such as grooming and playing, as well as frequently patrolling and defending the territory's boundaries. The results from this study suggest that although a high infant/adult weight ratio may be a prerequisite for selection to favor extensive allocare, it is not a causal factor. Additional research is needed in order to understand better the selective pressures involved and the costs and benefits of providing allocare to subadults and adult male spectral tarsiers.     

Identifying Primate ACE2 Variants That Confer Resistance to SARS-CoV-2

SARS-CoV-2 infects humans through the binding of viral S-protein (spike protein) to human angiotensin I converting enzyme 2 (ACE2). The structure of the ACE2-S-protein complex has been deciphered and we focused on the 27 ACE2 residues that bind to S-protein. From human sequence databases, we identified nine ACE2 variants at ACE2–S-protein binding sites. We used both experimental assays and protein structure analysis to evaluate the effect of each variant on the binding affinity of ACE2 to S-protein. We found one variant causing complete binding disruption, two and three variants, respectively, strongly and mildly reducing the binding affinity, and two variants strongly enhancing the binding affinity. We then collected the ACE2 gene sequences from 57 nonhuman primates. Among the 6 apes and 20 Old World monkeys (OWMs) studied, we found no new variants. In contrast, all 11 New World monkeys (NWMs) studied share four variants each causing a strong reduction in binding affinity, the Philippine tarsier also possesses three such variants, and 18 of the 19 prosimian species studied share one variant causing a strong reduction in binding affinity. Moreover, one OWM and three prosimian variants increased binding affinity by >50%. Based on these findings, we proposed that the common ancestor of primates was strongly resistant to and that of NWMs was completely resistant to SARS-CoV-2 and so is the Philippine tarsier, whereas apes and OWMs, like most humans, are susceptible. This study increases our understanding of the differences in susceptibility to SARS-CoV-2 infection among primates.     

Hand-raising a philippine tarsier,Tarsius syrichta

An infant female tarsier (Tarsius syrichta) weighing 20 g at birth was removed for hand-raising at 1 day of age. The infant was maintained in an incubator (32°C, 80% humidity), and fed every 2–3 hours for the first 10 days of life. The infant received a varied formula for the first 4 days. Esbilac (3.3–8.0 cc daily) was given for days 5–10. From days 11 to 67 the infant was fed 6.5–8.0 cc of formula seven times daily. A liver fortified formula was introduced on day 53. Birthweight doubled by day 41 and tripled by day 101. The animals first successful jump was observed at day 25. On day 68 she captured and ate her first live prey. Introduction to adult tarsiers began on day 60. This is the first successful hand-raising of any species of tarsier, which is a genus that reproduces poorly in captivity.     

Small,odd and old: The mysterious Tarsius pumilus is the most basal Sulawesi tarsier

In this study, we present the first genetic evidence of the phylogenetic position of Tarsius pumilus, the mountain tarsier of Sulawesi, Indonesia. This mysterious primate is the only Eastern tarsier species that occurs exclusively in cloud forests above 1800 m.a.s.l. It exhibits striking morphological peculiarities—most prominently its extremely reduced body size, which led to the common name of ‘pygmy tarsier’. However, our results indicate that T. pumilus is not an aberrant form of a lowland tarsier, but in fact, the most basal of all Sulawesi tarsiers. Applying a Bayesian multi-locus coalescent approach, we dated the divergence between the T. pumilus lineage and the ancestor of all other extant Sulawesi tarsiers to 9.88 Mya. This is as deep as the split between the two other tarsier genera Carlito (Philippine tarsiers) and Cephalopachus (Western tarsiers), and predates further tarsier diversification on Sulawesi by around 7 Myr. The date coincides with the deepening of the marine environment between eastern and western Sulawesi, which likely led to allopatric speciation between T. pumilus or its predecessor in the west and the ancestor of all other Sulawesi tarsiers in the east. As the split preceded the emergence of permanent mountains in western Sulawesi, it is unlikely that the shift to montane habitat has driven the formation of the T. pumilus lineage.     

Primate communication in the pure ultrasound

Few mammals-cetaceans, domestic cats and select bats and rodents-can send and receive vocal signals contained within the ultrasonic domain, or pure ultrasound (greater than 20 kHz). Here, we use the auditory brainstem response (ABR) method to demonstrate that a species of nocturnal primate, the Philippine tarsier (Tarsius syrichta), has a high-frequency limit of auditory sensitivity of ca 91 kHz. We also recorded a vocalization with a dominant frequency of 70 kHz. Such values are among the highest recorded for any terrestrial mammal, and a relatively extreme example of ultrasonic communication. For Philippine tarsiers, ultrasonic vocalizations might represent a private channel of communication that subverts detection by predators, prey and competitors, enhances energetic efficiency, or improves detection against low-frequency background noise.     

Hand‐raising a spectral tarsier (Tarsius tarsier) at the Ueno Zoological Gardens

On February 10, 2008, a newborn male spectral tarsier (Tarsius tarsier) was found on the floor of the indoor exhibit room in the Small Mammal House of the Ueno Zoological Gardens. The dam showed no signs of providing maternal care and therefore we decided to hand‐raise the infant. Its birth weight was 18.7 g. We placed the dam and infant in an incubator and gave 12.5–25% formula (for kittens), until the 145th day after birth. We limited the volume of formula intake to avoid excessive intake and to prevent diarrhea. For nutrition enrichment, we added a chicken liver homogenate to the formula 1–3 times per day. The infant was given a sunbath for 10 min on the 28th day. He showed no serious decline in health, except for diarrhea that occurred during the first few days after birth. He ate a small cricket for the first time on the 50th day and easily caught mealworms on his own on the 105th day. Gradual changes in feeding times, formula concentration, and the nutritionally enriched formula were essential for successfully hand‐raising the tarsier. Zoo Biol 30:218–224, 2011. © 2010 Wiley‐Liss, Inc.     

Inferred L/M cone opsin polymorphism of ancestral tarsiers sheds dim light on the origin of anthropoid primates

Tarsiers are small nocturnal primates with a long history of fuelling debate on the origin and evolution of anthropoid primates. Recently, the discovery of M and L opsin genes in two sister species, Tarsius bancanus (Bornean tarsier) and Tarsius syrichta (Philippine tarsier), respectively, was interpreted as evidence of an ancestral long-to-middle (L/M) opsin polymorphism, which, in turn, suggested a diurnal or cathemeral (arrhythmic) activity pattern. This view is compatible with the hypothesis that stem tarsiers were diurnal; however, a reversion to nocturnality during the Middle Eocene, as evidenced by hyper-enlarged orbits, predates the divergence of T. bancanus and T. syrichta in the Late Miocene. Taken together, these findings suggest that some nocturnal tarsiers possessed high-acuity trichromatic vision, a concept that challenges prevailing views on the adaptive origins of the anthropoid visual system. It is, therefore, important to explore the plausibility and antiquity of trichromatic vision in the genus Tarsius. Here, we show that Sulawesi tarsiers (Tarsius tarsier), a phylogenetic out-group of Philippine and Bornean tarsiers, have an L opsin gene that is more similar to the L opsin gene of T. syrichta than to the M opsin gene of T. bancanus in non-synonymous nucleotide sequence. This result suggests that an L/M opsin polymorphism is the ancestral character state of crown tarsiers and raises the possibility that many hallmarks of the anthropoid visual system evolved under dim (mesopic) light conditions. This interpretation challenges the persistent nocturnal–diurnal dichotomy that has long informed debate on the origin of anthropoid primates.     

Phylogenetic affinities of tarsier in the context of primate Alu repeats

Related genomes tend to be colonized by the same or similar repetitive sequence elements. Analysis of these elements provides useful taxonomic information. We have sequenced Alu repeats from tarsier and compared them with those from strepsirhine prosimians (lemurs, sifaka, and galago) and the human genome. Tarsier elements cluster with Alu subfamilies from the human lineage. The oldest subfamily in tarsier and the most abundant human subfamilies share an RNA secondary structure motif which is absent both in the earliest dimeric Alu Jo and in the strepsirhine elements. These findings are consistent with the view that tarsiers form a sister clade with anthropoides rather than with other prosimians. Alu repeats in tarsier genome are relatively old, which indicates a dramatic slowdown or even an arrest of these elements' amplification about 20 Myr ago.     

Introducing an innovative semi‐captive environment for the Philippine tarsier (Tarsius syrichta)

In response to demands for research, captive breeding, and tourism, a semi‐captive environment was created for the Philippine tarsiers (Tarsius syrichta) in Corella, Bohol, Philippines. The 7600‐m² enclosure was continuous with the surrounding habitat, and utilized a unique predator control fence design and a lighting system to attract nocturnal insects. During 2 years of observation, the locations of over 500 tarsier sleeping sites were recorded. Tarsiers were found to prefer dense, low‐level vegetation in secondary forests, with perching sites averaging 2 m above the ground. Up to 10 tarsiers were observed within the enclosure at one time, which is a high density compared to densities based on home‐range estimates for wild tarsiers in the vicinity of the study site. In addition, the tarsiers were observed to be more social than previously reported. Zoo Biol 24:101–109, 2005. © 2005 Wiley‐Liss, Inc.     

Predation experiments on infant spectral tarsiers (Tarsius spectrum)

In this paper, I investigate how mother and infant spectral tarsiers, Tarsius spectrum, respond to the presence of potential predators. I conducted this study at Tangkoko Nature Reserve in Sulawesi, Indonesia, from June to November 1999. I exposed 2 infants to 3 types of potential predators (large models of birds of prey, large rubber snakes and the vocalizations of large birds of prey) for a total of 18 nights. Infants moved a greater distance from their parked location when exposed to rubber snakes (1.8 m) compared to nights when they were not exposed to potential predators (0.23 m). On the other hand, when large bird of prey models were placed near the parked infant, the infant did not move from its parked locale (0.05 m). Parked infants repeatedly gave alarm calls in response to the presentation of all potential predator types. When an infant produced an alarm call following the presentation of a potential predator, the mother responded with her own alarm call approximately 88% of the time. However, when an infant produced an inappropriate alarm call, the mother responded with her own alarm call only 19% of the time. These results suggest that spectral tarsier infants use alarm calls to ask questions about the things they encounter in their environment. Infants and mothers both produced a twittering alarm call in response to the bird of prey models, whereas they both produced a harsh loud call 3 times in rapid succession in response to the presence of the rubber snakes.     

Associations between adult spectral tarsiers

While anecdotal observations of gregarious behavior in nocturnal prosimian primates are common, most anthropologists continue to refer to them as solitary, perhaps based on the assumption that the occasional social interactions observed via ad libitum methods represent random chance encounters and not patterned social interactions. In this paper, I test the null hypothesis that nocturnal encounters between spectral tarsier (Tarsius spectrum) group members, outside of the sleeping tree, are the result of chance. Three male‐female pairs were radio‐collared and observed over a 4‐month period, using continuous focal animal sampling at the Tangkoko Nature Reserve (Sulawesi, Indonesia). Using Waser's random gas model, I found that spectral tarsiers spent more time in proximity to other group members than expected by chance, given the size of their home range and nightly path length. Adult group members spent 11% of the night in physical contact and an additional 17% of the night within a 10‐m radius of one another. Spectral tarsiers were also observed to significantly increase the amount of time spent foraging when located less than 10 m from another group member. Individuals foraging in proximity to another adult group member had lower insect capture rates compared to individuals who were not foraging in proximity to another adult group member. If living in a group is costly to these tarsiers' foraging efficiency, then why don't they actively avoid one another when foraging? One situation in which it might benefit tarsiers to be gregarious is high predation pressure. Preliminary results suggest that predation pressure by snakes may be the most likely factor selecting for the tarsiers to forage in proximity. Am J Phys Anthropol 128:74‐83, 2005. © 2005 Wiley‐Liss, Inc.     

Temporary pools are not `enemy-free'

Temporary pools are traditionally considered as refuges where the conspicuous anostracans are protected from predation. While this is true for the size-selective predation by fish, there is compelling evidence that invertebrate predation is an important biotic stress regulating temporary pool communities. In rock pools in southeastern Botswana, we studied the impact of some suspected invertebrate predators on populations of the freshwater anostracan Branchipodopsis wolfi by means of observations and manipulative experiments. In a survey of 45 pools, the relationship between B. wolfi natural population sizes and the abundance of suspected predators were never negative for turbellarians and mosquito larvae. When dragonfly larvae, notonectids or tadpoles were present, the anostracan populations were generally non-existent or very small. In enclosure experiments with turbellarians, there was a significant effect of predation within one hour of the start; the average daily predation rate was about 1/4 anostracan per turbellarian. Anostracans from a pool with few turbellarians were slightly less vulnerable than those from a turbellarian-rich pool. Furthermore, there was an indication of males being predated on more than females. With dragonfly larvae and notonectids, the predation effect was marked with all six anostracans in an experiment eaten in less than one day by a single predator (predation rate: about one anostracan every 2 h per predator). In a behavioral study, both sexes of B. wolfi avoided swimming above sediment that held more turbellarians than the open patches; there was no evidence for chemical communication with respect to this behavior.     

Direct and Indirect Impacts of Raptor Predation on Lemurs in Southeastern Madagascar

I calculated rates of predation by 2 species of diurnal raptors, Polyboroides radiatus and Accipiter henstii, on the lemur community of Ranomafana National Park, Madagascar from 2700 h of observation and 470 prey deliveries at 7 nests of each hawk species. The 2 hawks consumed 7 of 12 lemurs found in the park region, with a body mass of 63–3500 g and including diurnal and nocturnal species of all group sizes. Calculations of predation rates indicate that raptor predation is a significant cause of mortality for lemur populations relative to other causes. Minimum rates of predation by Polyboroides radiatus and Accipiter henstii on Microcebus rufus, Cheirogaleus major, Avahi laniger, Hapalemur griseus, Eulemur fulvus rufus, Eulemur rubriventer, and Varecia variegata resulted in the raptors removing of 1–21% of the population per yr, similar to other rates of predation on primates documented in the literature. Modeling of lemur populations under varying levels of raptor predation pressure that I calculated found that one may attribute 3–17% of adult, juvenile, and infant mortality for nocturnal lemurs and 2–66% of adult, juvenile, and infant mortality for diurnal lemurs to diurnal raptor predation. Raptor predation may significantly depress intrinsic growth rates and carrying capacity of Avahi laniger, Hapalemur griseus, Eulemur fulvus rufus, Eulemur rubriventer, and Varecia variegata owing to their low fecundities, long life spans, and long age to sexual maturation. Nocturnal lemurs may best avoid predation by diurnal raptors by exhibiting a solitary lifestyle and cryptic antipredator tactics, whereas, diurnal lemurs benefit less by increasing group size than by using specific antipredator tactics.     

Interactions between a wild Bornean orang-utan and a Philippine slow loris in a peat-swamp forest

All documented orang-utan–loris interactions have been from Sumatra, where lorises were opportunistically preyed upon by orang-utans. In this paper, we describe two accounts of the Bornean orang-utan (Pongo pygmaeus wurmbii) interacting with the Philippine slow loris (Nycticebus menagensis). The interactions were by two adolescent female orang-utans. No attempts to catch the loris were observed on either occasion. Neither interaction was hostile. During the second observation, which was more detailed, we considered the behaviour to be play rather than aggression or attempted predation. Based upon the lack of interest from the adult females during these rare encounters, we propose that the behaviour represents play or non-aggressive exploration rather than predation.