Elsevier

Animal Behaviour

Volume 173, March 2021, Pages 1-7
Animal Behaviour

Slow learning of feeding skills in a nocturnal extractive forager

https://doi.org/10.1016/j.anbehav.2020.12.015Get rights and content

Highlights

  • Javan slow lorises show ontogenetic changes of difficult to eat foods.

  • Javan slow lorises co-feed in pairs and groups on gum, insects and nectar.

  • Lorises achieve adult diet after sexual maturity, dispersing a year later.

A long developmental period in animals is often needed to learn skills for adult reproduction and survival, including feeding behaviour. The nocturnal Javan slow loris, Nycticebus javanicus, is unusual in that it consumes a specialized diet of difficult to extract resources, as well as disperses up to a year after sexual maturity. Here, we examined the ontogeny of its feeding behaviour to understand whether learning to feed on difficult resources, including by co-feeding, is related to delayed dispersal. We collected feeding and proximity data on developing and adult wild slow lorises at a long-term field site in Cipaganti, West Java from 2012 to 2018. To determine whether acquisition of insects, exudates, nectar and flowers varied by age, we ran logistic generalized additive mixed models. We found that intake of insects and exudates occurred significantly more in the early stages, and feeding on nectar significantly more in the later stages, of development. Co-feeding occurred for all food types, with insects showing the most co-feeding events during early development, and co-feeding on exudates remaining high throughout development. Social learning via co-feeding is a potentially important factor in transmission of dietary information from older individuals, including siblings and parents, to young slow lorises. Differences between immature and adult diets levelled off after sexual maturity and before average dispersal. Together these factors suggest that the period required to learn to forage on difficult items could help explain the delayed dispersal patterns seen in mammals with similar foraging strategies.

Section snippets

Data Collection

From April 2012 until December 2018, we observed free-ranging Javan slow lorises in an agroforest environment on Mount Puntang, near the village of Cipaganti (7°6′6″-7°7′S and 107°46′–107°46′5″E) in West Java, Indonesia. The open nature of this habitat allows for a relatively clear view of animals when they are not in dense vegetation, and it is possible for animals to see each other across open fields at distances up to 50 m. The main foods of this population are exudates, floral nectar,

Results

The dietary composition, not weighted by the food intake, throughout ontogeny revealed differences in diet between age categories (Table 2). Infants/juveniles consumed the highest percentage of insects, whereas in the adult diet this percentage was almost halved. Gum comprised the highest percentage of the diet in all age classes, although it decreased slightly in adults. The percentage of nectar and flowers in the diet increased with age, with adults having the highest values. Leaves were

Discussion

The foraging and feeding experiences animals have early in life can have lasting implications for adult preferences, fitness and survivorship (Altmann, 1998; Hauser, 1993; Slagsvold & Wiebe, 2007). Here we have shown that the nocturnal Javan slow loris displays ontogenetic shifts in diet, which are potentially related to physical and social factors, including the conveyance of dietary information through co-feeding behaviour (Galef Jr & Giraldeau, 2001). Given that the dietary stabilization

Acknowledgments

We thank Indonesian RISTEK (22/TKPIPA/FRP/SMXI/2011, 1007/IPH,1/Ks02/IV/2014, 1008/IPH.1/KS02/IV/2014, 386/SIP/FRP/E5/Dit.KI/XI/2017, 147/SIP/FRP/E5/DitKIV/2018, S/476/E5/E5.4/SIP/2020) and the regional Perhutani and BKSDA for authorizing the study and our field team D. Bergin, E. Brown, F. Cabana, R. Cibabuddthea, C. Marsh, S. McCabe, Y. Nazmi, A. Nunur, R. O'Hagan, K. Reinhardt, J. Rode, D. Rustandi, M. Sigaud, D. Spaan and A. Zaelany. We also thank three anonymous referees and the editor for

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