WC is obviously biased in favor of birds, but from time to time will aim a camera at mammals, too. Including the New World Monkeys, our distant cousins and wildly diverse primates. The Howler Monkeys are the poster child for that diversity: there are about 15 species of Howler Monkeys alone. And Howlers provide another of the signature sounds of the New World tropics; at dawn and dusk, the males in a troupe of Howlers vocalize, a very loud, guttural growl that can be heard for more than three miles.
WC has only been able to photograph a few of the Howler Monkey species.
Ranging across much of central South America, the Black Howler is Near Threatened because of habitat loss, bush meat hunting and the pet trade. The species is also at risk for human diseases, including Yellow Fever.
Actually, four monkeys, two adult females and two juveniles. Named for the Rio Purus, which centers the species’ range in the easterly foothills of the central Andes, WC encountered this troupe while waiting for Macaws to arrive at a clay lick along the Madre de Dios River. This species is classified as Vulnerable, the next step up from Near Threatened.
This is primarily a Central American species, although its range includes parts of Colombia and Northwestern Ecuador as well. It’s also likely the largest of the New World Monkeys, with an adult male weighing up to 22 pounds. You can see the golden brown guard hairs on this male’s flank, the “mantle” that gives the species its name. The Golden-mantled Howler, like its Red Howler cousin, is classified as Vulnerable.
Primatologists are still sorting out whether the Black-faced Howler Monkey is a species or a subspecies of Black Howler. It’s complicated because Black Howlers start blond and get black as they age, and females remain blond or gold. There’s also another subspecies of Black Howlers called Black-and-Gold Howler monkeys. But based on habitat, WC sides with primatologists who call this a separate species. YMMV. These howlers were photographed in the Pantanal, the huge swamp in south-central Brazil. Forests there are in narrow bands along year-round water and streams. This species, of necessity, is on the ground more than other howlers, moving between galleries.
Howlers as a clade are unusual in another way: they are the only folivores, leaf-eaters, of the New World monkeys. Howlers have evolved larger molars to chew the leaves, and their intestines and intestinal flora are adapted to the low energy diet as well. And they are unique among New World monkeys in having trichromatic color vision.
This is a pitiful selection of the 15 species of howlers, let alone the dozens of subspecies. But, in fairness, they have never been a primary target of WC’s photography. Take that as evidence that the bias is real.
Wickersham's Conscience 
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