Survival implications of the development of behavioural responsiveness and awareness in different groups of mammalian young

Abstract

This paper focuses on the development of behaviours that are critical for the survival of newborn and juvenile mammals of veterinary and wider biological interest. It provides an updated, integrated and comparative analysis of how postnatal maturation of sensory, motor and perceptual capacities support and constrain behavioural interactions between mammalian young and the mother, any littermates and the environment. Young that are neurologically exceptionally immature, moderately immature and mature at birth are compared, and include, for example, marsupial joeys, rodent pups and ruminant offspring. Mothers in these three groups exhibit distinctive patterns of birthing and postnatal care behaviours. To secure survival of the young, maternal care must compensate for behavioural inadequacies imposed by the limited sensory capacities the young possess at each stage. These sensory capacities develop in a predictable sequence in most mammals such that before birth the sequence progresses to an extent that parallels the degree of neurological maturity reached at birth. The extent of neurological maturity is likewise reflected in how long it takes after birth for the necessary brain circuit connectivity to develop sufficiently to support cortically based cognitive modulation of behaviour. This takes several months, days-to-weeks or minutes-to-hours in young that are, respectively, neurologically exceptionally immature, moderately immature, or mature at birth. Once achieved, cognitive awareness confers a high degree of behavioural flexibility that allows the young to respond more effectively to the unpredictability of their postnatal environments. It is shown that the onset of this cognitively based flexibility in the young of each group coincides with their first exposure to a variable environment that requires such behavioural flexibility.

KEY WORDS:

• Neurological development
• sensory capacities
• mother–young interactions
• cognitive awareness
• flexible behavioural responsiveness
• newborn survival challenges

Acknowledgements

We particularly thank Dr Tamara Diesch (Consultant, Stokes Valley, New Zealand) for most helpful contributions to this paper. In addition we record our appreciation to Professors Laura Bennet (University of Auckland), Craig Johnson (Massey University) and David Morton (University of Birmingham, UK), Associate Professor George Bates (Wilson College, PA, USA) and Dr David Bayvel (International Animal Welfare Consultants Limited, New Zealand) for helpful discussion, MAF Biosecurity New Zealand (now the Ministry for Primary Industries) for partial financial support, Corrin Hulls (Massey University) for invaluable practical help during the preparation of the manuscript, and two anonymous referees for their constructive comments on the submitted manuscript.

Notes

*Non-peer-reviewed