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Diet, spatial ecology and energetics of echidnas: the significance of habitat and seasonal variation

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Sprent, JA (2012) Diet, spatial ecology and energetics of echidnas: the significance of habitat and seasonal variation. PhD thesis, University of Tasmania.

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Abstract

The ant- and termite-eating echidna is a solitary, monotreme mammal with a highly
seasonal life history. I investigated several aspects of the seasonal energetics and ecology
of free-ranging echidnas: the role of leptin in the annual mass cycle, seasonal and habitat
effects on diet, the relationship between home range size and habitat quality, and the
effect of habitat on the siting of echidna latrines.
The echidna has a large seasonal variation in fat stores, which reach their maximum prior
to hibernation. I hypothesised that the hormone leptin would have the same role in the
echidna as in eutherian hibernators, i.e. that there would be a direct relationship between
body mass and plasma leptin that would change to allow pre-hibernatory fattening. I
found significant seasonal variations in plasma leptin, with the highest levels occurring in
hibernation and in females during mating. The lowest levels were found in males after the
reproductive period. Rather than the expected strong positive relationship between
adiposity and plasma leptin I found a weak negative relationship, similar to that in
reptiles and birds.
To determine if there was any significant seasonal variation in diet associated with prehibernatory
fattening I investigated diet using scat and stable isotope analysis. Echidna
scats consisted largely of ants and the larvae of pasture cockchafer beetles. There was
significant seasonal variation in percent occurrence of larvae, but not in the ant species
found in scats or in the stable isotopic composition of echidna plasma. Although there
was no difference in the prey items that contributed most to scat contents of animals
living in different habitats, stable isotope analysis of blood showed a highly significant
effect of habitat type on δ15N.
Female echidnas showed a significant negative relationship between the proportion of
woodland habitat and home range size, whereas there was no such relationship for males,
which had significantly larger home ranges. My data suggest that female home range is
scaled to available resources, while male home range is probably scaled to maximise
access to females.
The role of latrines and their relationship to habitat was examined by a detailed survey of
part of the field site, where many echidna home ranges were known to overlap. Latrines
were located more frequently in scrub than in pasture or thick bush and the highest
frequency of latrines occurred where there were two home ranges that overlapped.
Latrines may be important in the spatial organisation of echidnas.

Item Type: Thesis (PhD)
Keywords: echidna - diet - leptin - homerange - latrine - seasonal variation
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Date Deposited: 17 Aug 2012 04:42
Last Modified: 11 Mar 2016 05:53
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