Costs of infant carrying in common marmosets, Callithrix jacchus: an experimental analysis

In callitrichids (marmosets and tamarins), not only the mother but also the father and older offspring (helpers) living in the group take part in infa nt carrying. As a measure of the costs of infant carrying in callitrichids, we measured the distance individual common marmosets were able to leap wit hout carrying infants and when carrying infants of different weight. We fou nd a significant negative correlation between carrying weight and the dista nce marmosets could leap. A weight of 65 g (the combined weight of newborn twins) reduced the leaping ability by an average of 17%. We conclude that i nfant carrying in callitrichids entails significant behavioural costs that can be expected to have great impact on their life in the field, especially on foraging and predator avoidance, that is, behaviours that incorporate l eaping ability. (C) 2001 The Association for the Study of Animal Behaviour.