Life history strategy and ecosystem impact of a small mammal herbivore in a mountain steppe [Elektronische Ressource] / Karin Nadrowski

Informations

• Publié par: philipps-universitat_marburg
• Publié le: 01 janvier 2006
• Nombre de lectures: 23
• Langue: English
• Poids de l'ouvrage: 4 Mo

Extrait

Life history strategy and ecosystem impact
of a dominant small mammal herbivore
in a mountain steppe
Karin Nadrowski
12th April 2006Contents
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
Zusammenfassung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x
1 Introduction 1
1.1 Mountain steppe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Herbivores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Life history strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 From keystone species to small mammal pest: Ecosystem impacts . . . 4
1.5 Situation in Mongolia and project background . . . . . . . . . . . . . . 7
1.6 Aim of this study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2 Basic Data Collection 13
2.1 Study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1.1 Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.1.2 Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.1.3 Vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.1.4 Higher trophic level . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.2 Life history strategies of pikas . . . . . . . . . . . . . . . . . . . . . . . 19
2.3 Pikas found in the study area . . . . . . . . . . . . . . . . . . . . . . . 25
2.4 Grid trapping and observation . . . . . . . . . . . . . . . . . . . . . . . 26
2.4.1 Capture site and burrow characteristics . . . . . . . . . . . . . . 26
2.4.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.4.3 Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.4.4 Captured species and biomass of small mammals . . . . . . . . 30
2.4.5 Welfare considerations in trapping and handling pikas . . . . . . 32
2.4.6 Capture and observation success . . . . . . . . . . . . . . . . . . 34
2.4.7 To trap or not to trap? Comparing trapping with observation . 35
2.5 Parasites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
2.6 Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
2.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3 Estimating Density 47
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.2 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
iCONTENTS
4 Life history 57
4.1 Age structure and life tables . . . . . . . . . . . . . . . . . . . . . . . . 57
4.1.1 From weight to age . . . . . . . . . . . . . . . . . . . . . . . . . 58
4.1.2 Seasonal development of age structure . . . . . . . . . . . . . . 69
4.1.3 Cohort life tables . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.1.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
4.2 Modelling survival rates . . . . . . . . . . . . . . . . . . . . . . . . . . 79
4.2.1 Modelling background . . . . . . . . . . . . . . . . . . . . . . . 79
4.2.2 Survival rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
4.2.3al of early and late litter . . . . . . . . . . . . . . . . . . 92
4.2.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
4.3 Reproduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
4.4 Population dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
4.5 Discussing life history strategy . . . . . . . . . . . . . . . . . . . . . . . 101
4.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
5 Ecosystem impact 109
5.1 Production and biomass removal . . . . . . . . . . . . . . . . . . . . . . 109
5.2 Pika densities on regional scale . . . . . . . . . . . . . . . . . . . . . . 124
5.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
6 General Discussion 133
6.1 Life history strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
6.2 Ecosystem impact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
6.3 Further research needs . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
References 143
Curriculum vitae 155
iiList of Figures
2.1 Location of the Gobi Gurvan Saikhan National Conservation Park . . . 14
2.2 Map of the study area comprising the Duund and Zuun Saikhan . . . . 14
2.3 Picture on the south facing slope of the Saikhan . . . . . . . . . 15
2.4 of the research camp . . . . . . . . . . . . . . . . . . . . . . . . 16
2.5 Walther-Lieth diagrams of two climatic stations within the park . . . . 16
2.6 Gradient of soil pro les along an altitudinal transect . . . . . . . . . . 17
2.7 Picture of burrow sampling plots . . . . . . . . . . . . . . . . . . . . . 18
2.8 of the Mongolian and the Daurian pika . . . . . . . . . . . . . . 21
2.9 Distribution of the Daurian pika . . . . . . . . . . . . . . . . . . . . . . 21
2.10 of the Pallas pika . . . . . . . . . . . . . . . . . . . . . . . 22
2.11 Map of burrows and trap locations on the trapping site . . . . . . . . . 27
2.12 Mongolian pikas encountered by capture or observation . . . . . . . . . 36
2.13 Parasite load during the year . . . . . . . . . . . . . . . . . . . . . . . 41
2.14 Movement distances within two years . . . . . . . . . . . . . . . . . . . 43
2.15 Movement and between sample sessions . . . . . . . . 44
3.1 Density estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
4.1 Weight structure of captured pikas . . . . . . . . . . . . . . . . . . . . 60
4.2 Average weight determined by growth curves . . . . . . . . . . . . . . . 62
4.3 Growth curve from maximum growth rates . . . . . . . . . . . . . . . . 63
4.4 Discriminating juveniles from adults . . . . . . . . . . . . . . . . . . . . 64
4.5 Predictions for age class composition . . . . . . . . . . . . . . . . . . . 65
4.6 Comparing growth of O. pallasi pricei, rufescens, curzoniae . . . . . . . 67
4.7 Cohort survival based on capture and observation . . . . . . . . . . . . 70
4.8al based on . . . . . . . . . . . . . . . . . . . . . 70
4.9 Cohort survival based on capture for three summers . . . . . . . . . . . 71
4.10 Probabilities for two encounter histories . . . . . . . . . . . . . . . . . . 79
4.11 Survival rates depending on density, sex, and age . . . . . . . . . . . . 88
4.12al rates for individuals from early and late litter . . . . . . . . . 95
4.13 Reproductive state during the year . . . . . . . . . . . . . . . . . . . . 97
4.14 Trajectories for the numbers of males over females . . . . . . . . . . . . 101
4.15 Two pikas gh ting over territories . . . . . . . . . . . . . . . . . . . . . 101
5.1 Hierarchical design of the exclosure experiment . . . . . . . . . . . . . 112
5.2 Estimates for standing crop based on habitat, time, and pika grazing . 115
5.3 for crop predicted by species group . . . . . . . . . 119
5.4 Pika burrow densities for di eren t livestock densities and altitudes . . . 127
iiiLIST OF FIGURES
ivList of Tables
2.1 Precipitation in the summer months from 2000 to 2003 . . . . . . . . . 15
2.2 Standing crop along an altitudinal transect . . . . . . . . . . . . . . . . 17
2.3 Rare and endangered animal species in the GGS . . . . . . . . . . . . . 18
2.4 Life history traits of Ochotona daurica and O. pallasi . . . . . . . . . . 24
2.5 Habitat preference of pallasi pricei and O. daurica . . . . . . 26
2.6 Date, duration, and reference area of sample sessions . . . . . . . . . . 29
2.7 Species captured on the trapping site . . . . . . . . . . . . . . . . . . . 31
2.8 Ochotona pallasi pricei captured and observed on the trapping site . . 34
2.9 Accuracy of identi cation by capture and observation . . . . . . . . . . 37
2.10 Length and regularity of encounters by capture and observation . . . . 38
2.11 Information gained by additional observation . . . . . . . . . . . . . . . 39
2.12 by capture . . . . . . . . . . . . . . . . . 40
3.1 Abundance and density predicted by di eren t estimators . . . . . . . . 50
3.2 Movement distances based on capture and observation . . . . . . . . . 52
4.1 Median weights for all capture sessions . . . . . . . . . . . . . . . . . . 61
4.2 Individuals used to construct a growth curve for maximum growth rate 63
4.3 Predicted cohort strengths based on winter and growth criteria . . . . . 64
4.4 Age structure at the end of the summers 2000-2002 . . . . . . . . . . . 71
4.5 Cohort Life Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
4.6 Life Tables for all sexes . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.7 Life Tables for litter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
4.8 Propabilities to observe four di eren t encounter occasions . . . . . . . . 80
4.9 Number of animals used for modelling . . . . . . . . . . . . . . . . . . 82
4.10 Parameter coding for pooled data, using the most reliable information . 83
4.11 P coding for capture data, spanning three summers . . . . . . 84
4.12