Philippine native-oak acorn refers to the nuts of Lithocarpus species — true oaks native to Philippine forests. They’re called survival food because they’re edible but need processing to remove tannins.
Basic definition
A hard-shelled nut with a woody cup or "cap" at the base, produced by trees in the genus Lithocarpus, family Fagaceae. Not a true Quercus oak, but closely related.
Taxonomy
Kingdom: Plantae
Order: Fagales
Family: Fagaceae — beech/oak family
Genus: Lithocarpus Blume
Common PH species: L. coopertus "katigbi", L. ovalis "palosapis nut", L. luzoniensis, L. jordanae "hayupag"
Francisco Manuel Blanco first listed several under Quercus in Flora de Filipinas, later moved to Lithocarpus.
What it looks like
Nut: 2-4 cm long, ovoid to round. Hard brown shell when mature, green when young
Cupule: Scaly woody cap covering 1/3 to 1/2 of the nut, like a beret. This is the dead giveaway it’s an acorn
Tree: Medium to large forest trees, 15-30m tall. Leaves are leathery, simple, alternate. Found in upland primary/secondary forests, Luzon to Mindanao
Why it’s “survival food”
Tannins: Raw acorns are very bitter and astringent. High tannin content can cause nausea and constipation if you eat them unprocessed. Not a casual snack like barobo.
Processing needed: Traditionally leached to make edible:
Local names
Katigbi, hayupag, palosapis nut, ulayan. Name changes per region and species.
Barobo vs Acorn — survival context
Barobo Solanum ferox: Eat immediately. Sweet-tart. No prep. Kid’s roadside snack.
PH oak acorn: Requires work. Bitter raw. Only worth it if you need calories and have time/fire/water. That’s why it’s “survival” grade.