Mindoro is the seventh largest island in the Philippines, located off the south-western coast of Luzon and northeast of Palawan and politically divided into two provinces: Occidental Mindoro and Oriental Mindoro. All our observations originate from the vicinity of Barangay Udalo, Municipality of Abra de Ilog, Province of Occidental Mindoro. The total observation area, locally known as Munting Buhangin, consists of 14.52 ha (145,200 m²) of privately-owned real estate, subdivided into eighty residential lots and several common areas with currently fourteen finished vacation houses of various styles and sizes (Fig. 1).

Figure 1. 

Map of the Philippines indicating the position of the records of V. bangonorum. Base maps: Open Street Map and data from http://srtm.csi.cgiar.org.

Ridges with a maximum height of 155 m elevation form natural boundaries to the east, south and west; the northern border is an approximately 700-metre-long rocky coast interspersed with four beaches and coves (Suppl. material 1: fig. S1). This shoreline is closely fronted by a long stretch of coral reefs and forms part of the Verde Island Passage (or Verde Island Marine Corridor), internationally hailed as the “Center of the Center of Marine Biodiversity” (Carpenter and Springer 2005). There is no direct road access, hence no motorised traffic within this area. To protect the natural surroundings with its inhabiting wildlife, trespassing and harmful activities, including all forms of hunting, plant/fruit collection, littering, logging and kaingin (slash-and-burn), are prohibited and privately monitored within the boundaries of Munting Buhangin. Approximately three-quarters of the area has remained undisturbed since 1998, resulting in a partly very dense secondary tropical lowland forest with areas of semi-closed canopy.

Dominant flora includes members of the Dipterocarpaceae, other native non-hardwood tree and shrub species, vining plants (Anamirta sp.) and climbing ferns (Lygodium sp.) and old fruit trees (Mangifera indica, Cocos nucifera) (Suppl. material 1: fig. S2). Typical beach vegetation includes species of Barringtonia, Terminalia, Caesalpinia and Ipomoea (Primavera and Sadaba 2012).

No rivers or creeks run through the property. The only constant freshwater source is a small oval-shaped drip-catch basin of approximately 100 cm × 50 cm with a maximum depth of only 5 cm, located above one of the beaches at 31 m elevation close to the eastern boundary. Especially during the dry season, there are gatherings of Cane Toads (Rhinella marina) and other amphibian species. These may provide easy prey for lizards and snakes (Suppl. material 1: fig. S3).

Our report is based on citizen-science data, contributed mainly by the co-author and collected over eleven years from 2011 to 2022. Each animal observed was photographed or video recorded; the summary includes only clearly identified records. We selected 29 clear and identified examples to represent sightings of the lizards during this period (Table 1).

We then mapped out the area, based on the sightings of Varanus bangonorum. Depending on the contributor, the use of recording equipment varied, mostly Panasonic DMC-TZ8 and TZ71, lately Sony RX10 IV and occasionally cell phone camera (Realme C11). We also verified the geographical coordinates of the sighting localities by using a hand-held navigator Garmin GPSmap 62s and added our corresponding field notes as a short reference (Table 1; 1–29). Coordinates and elevation for other points of interest are additionally included, for example, water sources and traps (Table 1; 30–32).

We gathered information, particularly on the local hunting methods, through informal interviews with local community members from Udalo (Tagalog) and Latag (Iraya). The interviews conducted were not standardised. The interviews did not last long, the basic questions being about the observation of monitor lizards in given locations and the attitude of the local population towards them and potential threats.

All photo- and video-graphic evidence is based on chance encounters within Munting Buhangin. We did not handle lizards for any purpose other than rescue and release (Table 1; 7, 9, 12, 13).

These lizards are diurnal, leading a mixed life between terrestrial and arboreal habitats. On 18-09-2021, we observed a young individual resting and sleeping for more than 12 hours overnight, approximately two metres above the ground. It did not seek shelter from the continuous heavy rainfall (Fig. 2A, Table 1; 20 and 21). The lizards also chose higher vegetation for basking on tree trunks at three to six metres height (Fig. 2B, Table 1; 8, 18, 21, Suppl. material 1: fig. S4).

Figure 2. 

A. A juvenile specimen is sleeping on a shrub (Plumeria sp.) in a characteristic position- holding the branch close to the body, with four limbs and a tail along the tree trunk on the night of 18 September 2021 at 23:52 h.; B. Adult monitor lizard (Table 1; 18) basking on a palm tree trunk (Cocos nucifera). Photographs by Michaela S. Webb.

The by-far largest (estimated SVL of more than 50 cm) monitor lizard was observed for several minutes while foraging for rodents (Muridae). Using alternate movements of the front legs for digging, it expanded a hole in the ground in a slightly sloped area (Table 1; 16). Throughout this activity, the lizard constantly remained alert by frequently withdrawing its head from the hole, looking around and flicking its tongue (Suppl. material 2). This specimen’s impressive size was visible when it finally ran off with a captured rodent in its snout.

The catching of the notorious invasive Cane Toads (Rhinella marina) was most frequently observed (Suppl. material 3). The same adult animal, distinguished by its remaining neck snare, was sighted three weeks earlier within the same observation area (Table 1; 22). The third and last encounter happened six months later when this individual was observed roaming around in a different location, still wearing the remains of the neck sling (Fig. 3, Table 1; 25).

Figure 3. 

Adult lizard carrying a hunted Cane Toad (Rhinella marina) (12-02-2022). The same individual was observed six months later (27-07-2022). Photographs by Gerlyn D. Aguirre (left), Nhayume A. Bandico (right).

We observed a young specimen catching and chewing on a large insect, likely a member of the order Coleoptera (Table 1; 5, Suppl. material 1: fig. S5). The unusual observation was when, after seeing the observer, the lizard squatted and then excreted faeces before disappearing into the undergrowth. A closer examination of the faeces showed chitinous insect parts’ remains, suggesting that some insects’ exoskeleton cannot be completely digested, confirming insectivorous behaviour amongst young individuals (Table 1; 29, Suppl. material 1: fig. S6).

Before description of the Mindoro endemic species Varanus bangonorum in 2014 (Welton et al. 2014), we observed the public trading of monitor lizards during occasional visits to Puerto Galera (a neighbouring municipality in the Province of Oriental Mindoro) between 1998 and 2002: animals were bound and hung alive from tree limbs by the roadside (Brgy. Sto. Niño; main road from Balatero pier to town proper).

The last encounter (on 16-06-2016) with a captive monitor lizard happened on the verge of departure from Balatero pier by private outrigger boat (banka) back to Munting Buhangin. We observed a person with a monitor lizard on a “leash” (a string looped around the neck) while walking with the lizard along Balatero beach. After some difficult discussions, he finally agreed to part with the animal in exchange for PHP 200 (Table 1; 7, Suppl. material 1: fig. S7).

The hunting of local Monitor Lizards is seasonal during dry months. It is done by setting different kinds of simple, yet very effective traps hidden within leaf-littered grounds. Foot and neck snares are being used to trap the lizards (e.g. Suppl. material 1: figs S8–S10). Depending on location and positioning, empty traps may be challenging to detect by the untrained eye unless the string used as a snare is of bright colour. In 2022, we successfully destroyed more than thirty traps on the Western and Eastern sloping borders at Munting Buhangin (Fig. 4, Table 1; 31 and 32).

Figure 4. 

On 27-02-2022 remains of a strangled juvenile Bangon Monitor Lizard (Varanus bangonorum) were discovered and removed; all traps were destroyed and snares were collected. The western slope, Munting Buhangin. Photographs by Michaela S. Webb.