Catanduanes is situated on the easternmost edge of
Luzon: 13.3 to 14.1 degrees north latitudes and between 124.1 and 124.3 degrees east longitudes. The island bounded on the west by the
Maqueda Channel, on the south by
Lagonoy Gulf, and on the north and east by the
Philippine Sea. Several small islands comprise the province. Its aggregate land area totals approximately . The coastlines, that stretch to almost , are jagged with many bays. The topography of Catanduanes Island is rugged and mountainous, becoming more pronounced towards the central portion of the island. Less than 10 percent of the land area has a slope gradient under 8%, mostly fractured and narrow strips of plains located along the coastal areas where most of the inhabitants are settled. The highest mountain peak is in Boctot, located between the municipalities of
Virac and
San Miguel with an elevation of above sea level. It is the premier mountain range with broadly spread
old-growth forests and watershed which exerts widespread influence over its immediate environs that include the municipalities of Virac,
Bato, and San Miguel. Other prominent mountain forms include the ranges: Obi in
Caramoran, Cagmasoso in
San Andres, and the Summit and Magsumoso ranges within the
Viga and
Gigmoto areas. The lowlands include the Virac Plain, Viga Plain, San Andres Plain and the Bato River Flood Plain. The coastal municipalities with limited lowland agricultural areas are
Pandan and Caramoran. The more extensive lowlands are found in the southern parts of the province. The largest coastal plain is the contiguous wetlands of Viga,
Panganiban and
Bagamanoc over which lies the widest area of rice paddies and
nipa mangroves. The province is mostly rugged and mountainous terrain. Its slope characteristics are 13% gently sloping to undulating, 1% classified rolling to hilly, 2% very hills and mountains, 47% level to very gently sloping, 32% steep hills and mountainous, and 5% undulating to rolling. Ten of the eleven municipalities of the province is situated along the coastal fringes, over which locate its mostly fractured plains. The only landlocked municipality is San Miguel with its
poblacion (
town center) sitting in a location entirely devoid of flatlands. The majority of the built-up areas occupy zones that are classified as flat to rolling.
Flora and Fauna The island is a
biodiversity hotspot. Its
rainforests are home to the
Philippine brown deer,
flying foxes, and other endemic bat species,
warty pigs,
civets,
cobras, giant
pythons,
monitor lizards,
sailfin lizards and other endemic animals. Exotic bird species such as the Philippine
hornbill,
rail, parrot,
bittern,
egret,
pheasant,
coot,
lapwing,
plover,
Philippine duck,
quail,
owl,
oriole,
kingfisher,
swiftlets and many more are also found. A record of "Philippines Birding Trip Reports" has found massive bird species in several parts of the island such as the watershed and timberland forests reserve in Gigmoto where scattered deer populations are also usually reported. The
Catanduanes bleeding-heart (
Gallicolumba luzonica rubiventris) had experienced over-exploitation in the late 20th century. Although most forests are still intact, this species has suffered overhunting, making it very rare and is believed to be near extinction or already extinct as its last reported specimen was collected in 1971. The
southern giant slender-tailed cloud rat (
budkon/
bugkon), which is found only in Catanduanes and the southern half of
Luzon Island, is still widely reported. It is critically endangered as humans hunt them for food and to some extent, as pets. In mainland Luzon, sightings of the creature are already rare while in
Marinduque, it is generally considered extinct. Inventory of the
entomological fauna on the island has been conducted by various scientific institutions. A survey that was submitted to the national museum has revealed interesting species in the forest reserve of Gigmoto and Pandan. A total of 2,000 entomological specimens and its allies were collected compromising 323 species under 45 genera and 50 families. The
Catanduanes narrow-mouthed frog (
Kaloula kokacii), an
arboreal amphibian found only in Catanduanes and some parts of Bicol, enjoys its diversity but is being carefully monitored. Another
endemic amphibian
Hylarana similis is found only in Catanduanes and Luzon islands. The published research by Brown and Siler in the Journal of Biogeography (2013) actually reported this species in the forests of Gigmoto. One of the very recent species found in Catanduanes and portions of the Bicol region is the new loam-swimming
skink, a legless reptile with its assigned scientific name
Brachymeles makes. The
dipterocarp forest also harbors numerous tropical plant species including the threatened species of
pitcher plants and
rafflesia as well as endemic banana varieties. Many highly economical hardwood trees such as
yakal,
apitong,
palosapis, and
molave are still found in the central forests through local reports indicate that these species are already threatened. Mangrove forests exist in several coastal areas but the largest locations are in Banquerohan (Viga-Panganiban), Agoho in San Andres, and Batalay in Bato. The Catanduanes reefs harbor many endangered and threatened types of mollusks such as
giant Triton,
cowries,
abalone,
cone snails,
conches, octopuses,
squids, and
nautiluses. Marine mammals are also reported to frequent on its eastern coasts such as species of dolphins and whales, which appear from March to June. Many edible marine algae such as
caulerpa,
valonia, and
turbellaria also grow abundantly on its rough coasts. The island is nestled in the very beginning of the
Kuroshio Current, a sea current that runs through the eastern Philippines, Taiwan, and Japan. Tuna migration, which is at its peak in the months of April and May, can be seen in the Maqueda channel.
Dugongs were once known to swim on Catanduanes coasts, but this event is already becoming extremely rare. The Catanduanes coast is one of the best spots for the
flying fish population; a flying fish can attain its fullest size in Catanduanes which may weigh .
Rabbitfish Siganus sp., a type of reef fish is one of the most heavily exploited marine tropical fish in Catanduanes. Its fry that comes out in shallow coasts during the breeding season (March–May) is fished in large volumes. Approximately 10 million rabbitfish fries are caught annually. This natural event supplies food for many people but its ecological impact can be devastating. Nature advocates started to strengthen their campaign for an eco-dialogue for this matter.
Sea cucumbers are also abundant in many islets of the eastern coasts facing the Philippine Sea.
Palumbanes (province satellite group of islands) has beaches with fine yellowish-white sand. It is also one of the most biodiverse marine zones on the island. However, coral reef exploitation has been severely inflicted for the last 10 years on its waters. The local government and some sectors are already undergoing efforts to revive Palumbanes Island by building artificial reefs and employing fishing regulations.
Rivers •
Maygñaway River, drains into the
Philippine Sea Weather and climate Without a pronounced dry season, precipitation is distributed fairly well throughout the year becoming wetter in the last quarter into the early months of the first quarter, when tropical disturbances and monsoon winds especially the
Northeast Monsoon (
Amihan) bring in heavy rains. Other months are characterized by short periods of dryer days and fine weather, except in July and August when the dry and gusty southwest monsoon winds intensify. Catanduanes's geographical position has it lying completely exposed to the
Philippine Sea. Therefore, it is known as "Land of the Howling Winds" because it is frequently visited by tropical cyclones. ==Administrative divisions==