Puerto Rican Boa

A characteristic of the species is the irregular parietal scales. It can grow to some 1.9 m (6.2 ft), with 261 to 271 ventral scales and 67 to 75 caudal scales, according to Stejneger in 1904, who only knew of at least twelve specimens at the time. The colours of the three live specimens he knew of were variable; two he describes as "bistre" (deep, dark, grayish brown), the other as "chestnut" with a darker colour near the tail, the first had a darker ventral surface, the second he describes as "slate" coloured, and the last had a lighter slate-brown underside with the ventral scales having paler edges. The first was patterned with seventy to eighty indistinct dusky cross bars consisting of a row of spots, these cross bars increasing in width to the end of the snake; in the second these patterns were much more distinct, with the crossbars having pale centres but being outlined in blackish colour, the lateral spots being so aligned as to form a blackish line in the front third of its body, but in the last snake there was little evidence of patterning with only a few scattered and obscure darkish spots on its sides. The iris he describes as "silvery gray clouded with dusky". It grows to 1.8–2.7 m (5.9–8.9 ft) in total length.

Similar species. …

It is found in wooded and rocky places in the foothills. It is more common in the northwest and in the karst regions which are found along the northern coast of the island.

The boa feeds by seizing the prey in its jaws, wrapping several coils around it, and then constricting until the prey has suffocated. The prey is then swallowed headfirst. The feeding habits of the very young are unknown. However, locals claim they eat small lizards, other small vertebrates and some insects. This species is a sit-and-wait predator as opposed to an active hunter of prey. It is a nocturnal, terrestrial hunter which is not found often in trees. The dissections of 72 snakes from the West Indies show that while young boas of the genus Epicrates feed primarily on anoles, mature boas (with the exception of Epicrates gracilis) feed for some 60% on mammals combined, which distinguishes them ecologically from the other three genera of snakes on the island. Birds constitute some 10% of the diet. The rest of the prey items are composed of Anolis lizards and a very small number of frogs. They also prey on much larger-sized prey than the other snakes. Half of the mammals are non-native species of mice (Mus) and rats (Rattus), it is suspected that the original prey was other small mammals such as Nesophontes, Brotomys and Isolobodon before the introduction of these species. Bats constitute the other half. Newborn snakes may possibly feed on geckos. …

The specific epithet inornatus is from the Latin negation of ornatus, meaning 'adorned', thus the boa is 'unadorned'.