Use of astronomy

When French scientist Louis Claude de Freycinet visited Guam in 1819 Chamorros told him that before the Spanish colonized the Marianas, Chamorros used the following calendar:

EnglishCHamoruTranslation (if known)
JanuaryTumaiguiniThis is the way, or like this
FebruaryMaimo’
MarchUmatalafTime to catch gatafe (a fish)
AprilLumuhuTime to return, or resume one’s route
MayMakmamao
JuneMananafSignifies to go on all fours, to crawl
JulySemu
AugustTenhosStormy or angry
SeptemberLumamlamSeason of lightning
OctoberFanggualo’Planting season
NovemberSumongsongSeason to repair the nets, stay in the village
DecemberUmayangganUnsettled, or weepy; season of short frequent
UmagahafTo catch shrimp

Prehistoric evidence

Freycinet also noted that an examination of Chamorro words and phrases supports the idea that the islanders were knowledgeable about astronomy and maritime arts. For instance Chamorros had names for the stars.

A cave was recently found at Liteksan (Ritidian) on the north west coast of Guam that has what is believed to be an ancient star calendar painted on the wall. University of Guam Professor Rosina Ipsing believes that the arrangement of dots on the cave wall is a calendar which divides the year into sixteen months of unequal length. The months would have been based on the movement of different constellations across the night sky. The painting has sixteen dots arranged both vertically and horizontally.

Researchers are interested in knowing how the ancient Chamorro people of the region gained their astronomical skills. The knowledge developed quite separately from that in ancient China or Europe as the Chamorro people have been settled in the Marianas for 4,000 years. The use of the stars to mark out the months rather than the moon is especially interesting in this respect.

Two other paintings in the cave show a stick-shaped human figure looking towards a constellation. In one, the figure points to the Southern Cross, in the other, to Cassiopeia. Being bright and easily identifiable, these constellations in the northern and southern sky would have been important markers. The calendar is similar to ones still used by navigators on the nearby island of Puluwat.

Explanation of months

The beginning of a month in the traditional Chamorro calendar is marked by the appearance of a star belonging to a particular group at about forty-five degrees above the horizon just before dawn in the east. The year starts with the rising of Antares and ends with the Corona Borealis.

Because different constellations occupy a greater or lesser part of the sky, the months are not of uniform length.

Ancient Chamorro petroglyphs can also be found in several places on the island of Guam. The cave drawing most well known is at Gadao’s Cave in the southern village of Inarajan. The sketches show human figures, animals, sea creatures and weapons. The colors are white, brown and black.

By Shannon J. Murphy

Editor’s note: The Department of Chamorro Affairs, government of Guam, updated the spellings to comply with the 2009 Official Chamorro English Dictionary produced and published.

For further reading

Cunningham, Lawrence J. Ancient Chamorro Society. Honolulu: The Bess Press, 1992.

Freycinet, Louis Claude de. An Account of the Corvette L’Uranie’s Sojourn at the Mariana Islands, 1819. Supplemented with the Journal of Rose de Freycinet. Translated and prefaced by Glynn Barratt. Saipan, CNMI: Commonwealth of the Northern Mariana Islands Division of Historic Preservation and the University of Guam Richard F. Taitano Micronesia Area Research Center, 2003.

Russell, Scott. Tiempon I Manmofo’na: Ancient Chamorro Culture and History of the Northern Mariana Islands. Micronesian Archaeology Survey Report No. 32. Saipan,CNMI: Commonwealth of the Northern Mariana Islands Division of Historic Preservation, 1998.