Fast Fact Attack: Endangered Species No. 77 – The Northern Brown Howler


Brown howler monkey (Alouatta guariba)

Photographer – Peter Schoen

“We are living on the planet as if we have another one to go to”
Terry Swearingen

If you have ever been lucky enough to have heard a howler monkey calling in the wild, you will know how it got its name.  Arguably one of the loudest animals on the planet, they can be heard up to three miles away through the dense jungle.  Alexander von Humboldt said about howler monkeys, “their eyes, voice, and gait are indicative of melancholy”.  The howlers in this clip may not be of the sub-species guariba guariba, but the sound is typical of the species in general.  And, believe me, this is not something you need to take you by surprise in the dark.

The International Union for Conservation of Nature (IUCN) lists most of these sedentary, arboreal howler monkeys (fifteen species) as threatened, due to human activities such as ceaseless hunting for bush meat, and habitat loss and degradation.  But, for the most part, the howlers are still fairly plentiful, with the exception of the Mexican howler (Alouatta palliata mexicana – a sub-species of the mantled howler) and today’s highlighted species, the northern brown howler (Alouatta guariba guariba).  They have both suffered to the point of being driven to near extinction.

Howler monkeysHowler monkeys are a large and inexpensive source of protein.  One monkey could easily feed a family of four.  And, they are slow and docile, which makes them easy prey.  Then, there are the usual illegal logging activities and other forms of human encroachment that we see everywhere across the globe.  The locations change, but the threats remain the same.

Howlers are not only large themselves, but they are also among the largest of the New World monkeys.  They range in bodily height from two to three feet.  Added to that, they have extremely long, prehensile tails which can measure anything from three feet to an astounding three times the size of the monkey itself.  This tail is invaluable to the New World monkeys.  They use it to travel through the branches and can wrap it round and swing freely to pluck leaves and fruit with their hands.

Another helpful augmentation of the howlers is their incredibly keen sense of smell. They have short stumpy, round noses which Howler monkey (Alouatta guariba) in Santa Maria de Jetiba, Brazil.can sniff out nourishment (the nostrils have sensory hairs inside) at over two to three miles.  Possibly no coincidence that they can be heard that far away as well.

A further adaptation is the molars, specially designed to shear through tougher leaves.

But, it doesn’t end there.  These marvellous monkeys are also blessed with trichromatic colour vision, which is thought to have developed in the species to allow selection of the very best leaves available.

One last staggering attribute is, of course, that voice.  A combination of large throat with specialised vocal chords and larynx produces a whole range of growls, barks, howls and roars.  This ability is unique to the howler species.

Howler monkeys are slow-moving folivores.  They spend most of the daylight hours relaxing in the trees.  The rest of their time is shared between eating, travelling and grooming. They move quadrupedally along the tops of branches, using their hands and their long, strong tails.  They live in groups of four or five.  Occasionally there are more. One dominant male usually rules the troop.

Baby howler monkey at the Sloth Sanctuary, Costa Rica by Jonathan LeyHowler monkeys do not have a specific breeding season, but females are only able to produce offspring every twenty-two months.  One infant will be born as a result of the liaison, after a gestation period of six months.  Most infants are weaned at one year, and reach maturity at five years (male) and approximately three and a half years (female).

The species, brown howler monkey (Alouatta guariba), lives in forests in south-eastern Brazil and far north-eastern Argentina.  There are two sub-species; today’s featured northern brown howler (Alouatta guariba guariba), listed as ‘critically endangered’, and the southern brown howler (Alouatta guariba clamitans) listed as ‘of least concern’.

Habitat
Sub-montane, montane and lowland forests.
Where
Brazil:  The Northern brown howler is confined to a small area north of the  Rio Jequitinhonha.  The Jequitinhonha flows through the Brazilian state of Minas Gerais.
What they eat
Mature leaves, though younger leaves are preferred.  Mature fruit is also an important part of the diet.  And, they will also eat, buds, flowers, and nuts.
Threats
Hunting and  deforestation, hunting being the larger threat as they are ale to  survive in small fragments of forest if they are left alone by hunters.  They are both susceptible to, and carriers of, disease.
Status: Critically Endangered
The Northern brown howler (Alouatta guariba guariba), is listed on the  IUCN Red List of Threatened Species  as Critically Endangered.  It has been on the critical list since 1996.  It is also protected by  Cites Appendix 11.  Little over two hundred of the species still survive in the wild.  I have been unable to find any record of Northern howler monkeys being kept in zoos, either in captive breeding programs or as an attraction.

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Howler monkey at risk of extinction because of stress

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Fast Fact Attack: Endangered Species No. 44 – The Cotton-top Tamarin


Cotton-top tamarin clinging to tree

Photo: William T Hornaday

Description
The cotton-top tamarin was declared endangered in 1973;  and in 1974 it became illegal to export them.  Prior to that, these endearing little monkeys were subjected to years of torment.  Exported to the United States by the tens of thousands, they were used for long-term biomedical research.  Notwithstanding that mass depletion of the species, they were also highly sought after, and taken, by zoos and pet traders.

Closely related to humans, the cotton-top tamarin was found to spontaneously develop a highly prevalent idiopathic colitis resembling human ulcerative colitis.  Four out of five animals died or were euthanised after a disease course of two to ten days.  [1]  Having lost most of my own family to cancer, I never fail to see, and always fully appreciate, the need for a wide range of research. However, this use, or rather misuse, of animals was unforgivable. It’s hard to imagine the horror of it all.  All international trade has long since been banned, but now the species faces other risks  –  again created by man.

The cotton-top tamarin is a New World monkey.  As you can imagine, it’s pretty rare. Tamarins are monomorphic, arboreal and diurnal.  They are instantly recognisable by the long white chine from forehead to shoulders.  They have mutated claws on all digits and only two molars on either side of the jaw.  Startlingly, they weigh no more than a pound. They live in groups ranging from one to nineteen, though the more common size would be three to nine.  They are highly intelligent, with their language showing signs of some grammatical structure.

The cotton-top tamarin has a monogamous breeding system.  Gestation lasts about one hundred and forty days, followed by the birth of twins.  Females produce twice a year.

Habitat
Tropical rainforests, secondary forests and open woodlands; up to altitudes of four hundred metres.
Where
Northwest Colombia
What they eat
Insects, fruit, sap, small birds, lizards, and eggs.
Threats
Deforestation:  Most of its habitat, 98% over the last decade, has been lost to farming, expansion of human settlements and fuel.
Status: Critically Endangered
The cotton-top tamarin  (Saguinus oedipus) is listed on the  IUCN Red List of Endangered Species  as Critically Endangered.  It is also listed on CITES Appendix I.  Various non-profit making organisations are helping in their own way.  Nature reserves have been set up to help maintain populations.  The species has been legally protected in Colombia since 1969.

“Because the heart beats under a covering of hair, of fur, feathers, or wings, it is, for that reason, to be of no account?”
Jean Paul Richter