Infant marmosets are reared on site within their family group where the family are able to do this successfully. In captivity, larger litter sizes (for example triplets) are more frequent and some marmoset families are not able to successfully rear triplets. Optimal family group welfare is maintained, where appropriate, by euthanasia of some infants to reduce litter size down to a number that the family can rear. The decision to reduce litter size is made on a case by case basis, under veterinary supervision. It would not be appropriate to hand rear marmoset infants away from their families (on site or anywhere else) as their physical and psychological welfare needs could not be met in these circumstances.