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Environmental physiology of the little penguin (Eudyptula minor)

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Stahel, Colin Douglas (1984) Environmental physiology of the little penguin (Eudyptula minor). PhD thesis, University of Tasmania.

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Abstract

This study investigates the energetic adaptations and
constraints of the little penguin in relation to its aquatic
lifestyle and examines the possible function of sleep as an energy
conserving mechanism.
The little penguin had a similar level of standard metabolic
rate to other birds. Body temperature was lower than the general
avian level and varied with the site of , measurement. Although
penguins may be considered cold-adapted due to the thermal
consequences of immersion; the results of this study and analysis of
published data for other species shows minimal conductance in
penguins appears to be relatively high in comparison to other
cold-adapted birds due to the shallow insulative layer provided by
the penguins waterproof plumage. This limitation is to some extent
compensated by a well-developed capacity to alter body insulation.
Water represents a severe thermal challenge to the little penguin
since the potential for heat loss is two orders of magnitude greater
than in air. Heat balance in water was maintained by prevention of
excessive heat loss through insulative changes. Limits to the extent
of insulation restrict the ability of the little penguin to withstand
low water temperatures.
Respiratory ventilation in the little penguin was rr.uch less than
expected due to a low respiratory frequency and conferred a very high
oxygen extraction coefficient. Ventilation during cold exposure
rerrained closely associated YJith rPetabolic demands. The high gas
exchange efficiency in the little penguin correlates well with its
short aerobic diving patterns. Heat exposure resulted in large
increases in ventilation and the limited capacity of little penguins
to withstand heat exposure is in part explained by low tolerance to
changes in. acid-base status.
The metabolic response to wind in the little penguin varied with
temperature. At thermoneutrality increased convective heat loss with
wind was compensated by an increase in body insulation. During cold exposure body and plumage insulation had attained maximal values
whereupon increased windspeed resulted in a linear increase in
metabolic heat production. The dense, overlapping feathers of the
little penguin, however, provide an effective resistance to increased
heat loss associated with windspeed. The primary effect of wind upon
partitional insulation at neutral and cold temperatures was a
decrease in the insulation provided by the thermal boundary layer.
Little penguins showed similar electrophysiological correlates
of sleep to other birds and exhibited polyphasic sleep patterns. This
study showed that the amount of sleep increased at night due to
increased frequency of sleep periods and decreased during cold
exposure due to a reduction in the length of sleep periods. Sleep was
associated with decreased metabolic rate compared to values in quiet
wakefulness. This decrease, however, represented only a marginal
reduction in daily energy costs.

Item Type: Thesis (PhD)
Keywords: Penguins, Little blue penguin, Cold adaptation
Copyright Holders: The Author
Copyright Information:

Copyright 1984 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1985. Bibliography: leaves 132-170

Date Deposited: 03 Feb 2015 03:24
Last Modified: 11 Mar 2016 05:56
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