All frugivorous monitors are highly secretive, and rarely seen through chance encounters. Varanus olivaceus is no different, and in fact has been documented spending several days at a time in the tops of fruiting trees, decending to the ground only to move to the next tree.
Varanus olivaceus was the first frugivorous monitor species known to science. It has a greenish-gray dorsal ground color, overlain with darker transverse bands on the neck, body, limbs, and tail. Ventral coloration is gray to grayish-green or yellow, overlain with a variable number of dark brown or black longitudinal gular stripes.
Despite having been considered extinct for nearly 150 years, in the past several decades Varanus olivaceus has been documented throughout its proposed range. This species has the largest distribution among frugivorous monitors, but remains characterized as vulnerable
Varanus olivaceus is designated as a CITES Appendix II species. This taxon is not currently threatened by extinction, but may become so unless trade or other factors are closely monitored.
Varanus olivaceus is very similar to its closest relative V. bitatawa, and has a slightly more robust head, but with less robust body and limbs. This species generally has a gray to olive ground color, overlain by dark brown to black solid transverse bands on the neck, body, limbs, and tail (most prominent in juveniles, becoming less discernible with age); head coloration often lightest anteriorly, often transitioning to a predominantly yellow-green color in labial region. Ventral coloration generally a uniform grayish-green, grayish yellow, or olive, overlain with conspicuous dark gray to black longitudinal gular stripes.
Varanus olivaceus is known from southern Luzon Island (Bicol Peninsula), as well as Polillo and Catanduanes islands. The northern extent of this species' distribution is limited to the southern portion of the Sierra Madre Mountain Range.
As with the other two species of frugivorous monitors, Varanus olivaceus is a predominately arboreal species, spending vast amounts of time in the canopies of fruiting trees. During dry periods, it can be expected to transition to a more terrestrial lifestyle in search of a preferred secondary food source, snails.
The specific epithet is likely derived from the olive-green ground color often exhibited by this species.
Luzon Pleistocene Aggregate Island Complex
Varanus olivaceus is a forest obligate (as with its closest relatives V. mabitang and V. bitratawa), and is heavily dependent upon unfragmented lowland and mid-elevation forests with sufficient stands of fruiting Pandanus, Canrium, or Ficus trees.
Varanus olivaceus would most likely be confused with its closest relative, V. bitatawa, but can be distinguished from that species by the presence of dark colored dorsal bands.
Varanus olivaceus is considered a forest obligate, requiring relatively large tracts of intact habitat. Specifically, the protection of habitat which includes dense populations of this species' prefered fruiting trees (Pandanus and Ficus) will be essential for maintaining this species in the future.
The most severe threat to this species is likely habitat loss or degradation, although collection for the pet trade and for bush meat are additional likely threats.
