Chaetodon lunula can reach a length of 20 cm (nearly 8 in).These large butterflyfishes have an oval outline, with a pattern of ascending oblique reddish stripes on the flanks and black and white bands over the face and eyes, similar to the "raccoon" mask (hence the common name). They show a black spot on the caudal peduncle and oblique yellow stripes behind the head. They have 10-14 dorsal spines and 3 anal spines.
Halfmoon Butterflyfish's facts
The oval-shaped raccoon butterflyfish can reach a length of nearly 8 inches. In addition to its striking black and white bands over the face and eyes, it has a pattern of reddish stripes on the flanks. They also have a noticeable black blotch at the base of the tail fin — meant to look like an eye to confuse their predators— and oblique yellow stripes behind the head.
The raccoon butterflyfish is generally not aggressive toward other fish, except their not big fans of lionfish and triggerfish. When those two show up, the raccoon butterfly can get feisty and territorial.
They prefer seaward reefs and shallow reef flats of lagoons, and like hanging out anywhere up to 90 feet or so.
Halfmoon Butterflyfish's Behavior & Ecology
This species prefers seaward reefs and shallow reef flats of lagoon, at a depth of over 30 m.
Halfmoon Butterflyfish's Feeding
Chaetodon lunula is a nocturnal species that usually lives in small groups. Adults feed mainly on nudibranchs and small invertebrates, but also on algae and coral polyps.
Halfmoon Butterflyfish's Reproduction
Butterflyfishes are egg-scatterers, releasing their gametes to the whims of surface currents cued by moon and tides. Larval young develop through a strange armored “tholichthys” stage as pelagic plankton, settling down (hopefully) as miniature adults. Like most other chaetodonts, the raccoon species are indistinguishable sexually.
Halfmoon Butterflyfish's Relationship with Humans
It is traded in aquarium fishery.
Halfmoon Butterflyfish habitat
This species is found in lagoons and on outer reefs where it is most commonly observed in rocky areas, either slopes or in the inter-tidal zone (especially juveniles). Animals occur singly, paired, or in small aggregations. Favoured food items include nudibranchs, tubeworm tentacles, coral polyps and algae (G.R. Allen pers. comm. 2006). It rarely feeds on live corals (Pratchett 2005), but has exhibited a decline in abundance from 1979 to 2003 at Moorea (Berumen and Pratchett 2006).
Halfmoon Butterflyfish threats
There appear to be no major threats to this species.