Marmoset
One of the smallest monkeys, and one of the few with claws rather than nails, because it gouges bark for gum. Twins are the usual birth, not the exception.
Photo by Bart van Dorp, CC BY 2.0
Overview
Marmosets have claws instead of nails, on every digit except the big toe, and chisel shaped lower incisors they use to gouge holes in bark. That is not a curiosity, it is the animal's job description: they are gum feeders, and when other food is short they can spend up to 70 percent of their time working trees for exudate.
A common marmoset is 12 to 15 centimetres in the body with a tail twice that again, and weighs 300 to 360 grams. Twins are the normal birth rather than the exception, and a pair of newborns can come to 40 percent of the mother's body weight. Groups run from 2 to 13, and care by males and older siblings is not a nicety, it is described as necessary for the infants to survive.
Temperament
A marmoset alone is a marmoset in trouble. This is a cooperatively breeding primate whose entire social structure is a family unit doing shared work, and single housing is the standard failure in captivity.
They are diurnal, loud, and they mark with scent constantly. Hand reared animals frequently develop behaviour that does not resolve, because the thing they missed was not handling, it was being raised by a group. Nothing in an adult marmoset's behaviour is trainable in the way a dog's is.
Care and grooming
Gum is the sticking point. A diet of fruit and insects without a gum source leaves an animal doing the thing it evolved to do with nothing to do it on, and captive diets need a proper exudate substitute plus the right vitamin D3, since deficiency disease in captive marmosets is well documented.
They are small, fast and delicate, and they need a primate vet. Their teeth are working tools and dental problems follow directly from the wrong diet.
Living and exercise
Tall, warm, and never on its own. Height, branches at varied angles and gouging substrate to work on, which is the closest thing to real enrichment this species has.
Primates carry the heaviest legal restrictions of anything on this shelf. Several US states ban private primate ownership outright and others require permits, and in England a licence is now required to keep one. Check what applies where you are before anything else.
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