Estimated Total Numbers:

West Indian Manatee (Trichechus manatus )¹ 1,000
Jaguar (Panthera onca)² 600-1,000
Howler Monkey (Alouatta pigra)³ 10,000+
American Saltwater Crocodiles (Crocodylus acutus)⁴ 1,000
Morelets Crocodiles (Crocodylus moreletii)⁵ 8,800

________________________
Sources
¹ Belize Coastal Zone Management Authority, 2012
² Alan R. Rabinowitz, 1991; some more recent estimates suggest the number of jaguars in Belize has declined
³ Reliable estimates of howler monkeys in all of Belize have not been found, although the population in the Baboon Sanctuary reportedly has grown to about 6,000, while the population near Monkey River is believed to have declined from over 11,000 to about 1,500 following Hurricane Iris in 2001
⁴ Platt & Thorbjarnarson, 2000 (population estimate excludes hatchlings)
⁵ Comisión Nacional para el Conocimiento y Uso de la Biodiversidad, Mexico, 2005 (population of all ages)

--Lan Sluder

Update: I'm told that a better current estimate (by the Panthera organization) of the jaguar population in Belize is 750, although the population is divided into two areas. About 500 in a single contiguous area is said to be a sustainable population.

Biodiversity: Number of Flora and Fauna Species Found in Belize
(Estimates vary depending on the source and date1)

Birds 575-625
Amphibians 36-37
Reptiles 106-110
Snakes 59-60
Turtles 13
Mammals 145-152
Butterflies 1,000
Moths 900-1,000
Fish (Salt & Freshwater) 630-640
Sharks 22
Vascular Plants 3,750-4,000
Native Trees 700

1 Perhaps the best overall source on Belize’s biodiversity is the report Compilation of Information on Biodiversity in Belize by Jan C. Meerman, 2005.

--Lan Sluder