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Massey University Li:J;ary Palmerston North
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Ecology and behaviour of the Mahoenui Giant weta (Deinacrida nov. sp.)
A thesis presented in partial fulfilment of the requirements for the degree of Masterate of Science in Ecology at Massey University.
Grace Elizabeth Richards
1994
Plate 1 A female Mahoenui weta displaying the threat posture
ABSTRACT
Basic information about the ecology of Mahoenui weta (Deinacrida nov. sp.) is provided from captive and field studies. Transmitters, betalights and capture- recapture were used to track movements and activity. Weta have a three year lifecycle with three main age groups present thoughout the year. Two colour morphs were present (brown and yellow); 15% of males and 27% of females were yellow morph. Mortality rate decreased with age; 80% died between instars 1 and 6, 40% died between instars 7 - 9. Mild overt agonistic behaviour was observed. Courtship behaviour was simple and females played a passive role. Mating took from 1 to 14 hours and often included multiple copulations. Weta were more active in summer than winter and adults were active for longer periods than juveniles. Activity patterns in captivity were similar to those in the field. Most weta remained within a small area (1 - 3 m3) for much of their lives and often returned to rest in the same place on successive days. Large gorse ( Ulex europaeus) bushes with little or no goat browsing were preferred whereas isolated bushes and small and heavily browsed gorse was less favoured. Weta are generalist feeders. Those reared on gorse and pasture plants had low mortality (1 died out of 9) and gained weight more steadily than weta reared on native vegetation (9 died out of 11). Mahoenui reserve provides suitable food and shelter and affords some protection against predators.
However the possible destruction of the gorse habitat by fire or disease still poses a major threat to the weta population.
iii
ACKNOWLEDGEMENTS
I wish to thank my supervisors Dr Murray Potter and Dr Ian Stringer for their input and assistance; Judy Redfearn for her invaluable typing skills; my fiance Cameron Redfearn for his assistance and enthusiasm in my field work; Dean Strange my co-worker at Mahoenui reserve; and all the others whose interest in my work was most supportive throughout the course of my research.
TABLE OF CONTENTS:
(Page)
Title page
Abstract iii
Acknowledgements iv
Table of Contents v
List of Tables vii
List of Figures vii
List of Plates viii
CHAPTER ONE General Introduction 1
CHAPTER TWO Study Area 4
CHAPTER THREE General Methods 9
3.1
Locating and measuring weta9
3.2
Collection of Mahoenui weta9
3.3
Maintaining Mahoenui weta9
3.4
Nocturnal Study of Mahoenui weta13
3.5
Statistical Analysis16
CHAPTER FOUR Development, Morphology and Lifecycle of
Mahoenui weta 18
Introduction
19
Methods
20
Results
4.1
Mahoenui weta eggs21
4
.2 Colouration24
4.3
Sex Ratio25
4.4.1
Number of instars and size range of instars25
4.4.2
Growth rates27
4.4
.3 Weight change28
4.5
lnstar estimation28
4.6.1
Duration of stadia38
4.6.2
Longevity of adults38
4.6.3
Overwintering40
4
.7.1 lnstars present during four seasons43
4.7.2
Lifecycles of Mahoenui weta48
4.7.3
Lifespan of Mahoenui weta50
4.8
Mortality of Mahoenui weta50
Discussion
53
CHAPTER FIVE Behaviour of Mahoenui weta in captivity
and at Mahoenui reserve 60
Introduction
61
Methods
62
Results
5.1
Cannibalism62
5.2
Ecdysis63
5.3
Damage and regeneration of appendages67
v
Discussion CHAPTER SIX
5.4 5.5 5.6 5.7
Introduction Methods Results 6.1
6.2 Discussion CHAPTER SEVEN
Introduction Methods Results 7.1
7.2
7.3 Discussion CHAPTER EIGHT
Introduction Methods Results 8.1
Discussion CHAPTER NINE CHAPTER TEN
Appendices References
8.2 8.3 8.4
Defence Aggression
Courtship and copulation Oviposition
Mahoenui weta activity time budgets
Nocturnal activity Activity levels
Habitat choice and movement of Mahoenui weta
Nocturnal habitat choice and movement of Mahoenui·weta
Diurnal habitat use and daily movement of Mahoenui weta
Locating eggs
(Page)
69 72 75 79 83 90
91 92 92 93 113
117 118 120 124 131 139 141
Diet of Mahoenui weta 147
148 149
Diet preference 151
Diet of Mahoenui weta at Mahoenui reserve 154
Gorse feeding trials 156
Comparison between Mahoenui weta fed
exotic and native plants 157
163
Conclusions 166
Application of my research to the management and conservation of the Mahoenui weta 170
173 181
LIST OF TABLES:
{Page) {Page)
Table 4.1 21 Table 5.5 74
Table 4.2 22 Table 5.6 75
Table 4.3 23 Table 5.7 77
Table 4.4 24 Table 5.8 80
Table 4.5 26 Table 5.9 81
Table 4.6 26 Table 6.1 112
Table 4.7 33 Table 7.1 130
Table 4.8 33 Table 7.2 131
Table 4.9 39 Table 7.3 132
Table 4.10 39 Table 7.4 138
Table 4.11 41 Table 7.5 138
Table 4.12 42 Table 8.1 152
Table 4.13 51 Table 8.2 153
Table 5.1 66 Table 8.3 153
Table 5.2 68 Table 8.4 156
Table 5.3 71 Table 8.5 162
Table 5.4 74
LIST OF FIGURES:
Figure 2.1 6 Figure 6.10 106
Figure 2.2 7 Figure 6.11 107
Figure 3.1 11 Figure 6.12 108
Figure 3.2 12 Figure 6.13 109
Figure 4.1 29 Figure 6.14 110
Figure 4.2 30 Figure 6.15 111
Figure 4.3 32 Figure 7.1 123
Figure 4.4 34 Figure 7.2 123
Figure 4.5 35 Figure 7.3 125
Figure 4.6 36 Figure 7.4 126
Figure 4.7 45 Figure 7.5 126
Figure 4.8 46 Figure 7.6 128
Figure 4.9 47 Figure 7.7 128
Figure 4.10 49 Figure 7.8 129
Figure 4.11 49 Figure 7.9 129
Figure 5.1 82 Figure 7.10 134
Figure 6.1 97 Figure 7.11 134
Figure 6.2 98 Figure 7.12 135
Figure 6.3 99 Figure 7.13 135
Figure 6.4 100 Figure 7.14 137
Figure 6.5 101 Figure 7.15 137
Figure 6.6 102 Figure 8.1 155
Figure 6.7 103 Figure 8.2 159
Figure 6.8 104 Figure 8.3 161
Figure 6.9 105
vii
LIST OF PLATES:
Plate 1 Plate 2.1 Plate 2.2 Plate 3.1 Plate 3.2 Plate 4.1 Plate 4.2 Plate 7.1 Plate 7.2
(Page)
ii 8 8 17 17
52 52
140 140
