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

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Life history strategy and ecosystem impactof a dominant small mammal herbivorein a mountain steppeKarin Nadrowski12th April 2006ContentsAcknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viiAbstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viiiZusammenfassung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x1 Introduction 11.1 Mountain steppe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Herbivores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.3 Life history strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.4 From keystone species to small mammal pest: Ecosystem impacts . . . 41.5 Situation in Mongolia and project background . . . . . . . . . . . . . . 71.6 Aim of this study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Basic Data Collection 132.1 Study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132.1.1 Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.1.2 Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162.1.3 Vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162.1.4 Higher trophic level . . . . . . . . . . . . . . . . . . . . . . . . . 182.2 Life history strategies of pikas . . . . . . . . . . . . . . . . . . . . . . . 192.3 Pikas found in the study area . . . . . . . . . . . . . . . . . . .

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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 Candidate models set . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
4.13 Model likelihoods for recapture, pooled data . . . . . . . . . . . . . . . 86
4.14 Model likelihoods for survival, pooled data . . . . . . . . . . . . . . . . 87
4.15 Model likelihoods for recapture, capture data . . . . . . . . . . . . . . . 89
4.16 Model likelihoods for survival, data . . . . . . . . . . . . . . . 90
4.17 Canditate models set for individuals from early and late litter . . . . . 93
4.18 Model likelihoods for early and late litter . . . . . . . . . . . . . . . . . 94
4.19 Pika life history traits revisited . . . . . . . . . . . . . . . . . . . . . . 102
5.1 Number of pikas captured in the summers from 2001 to 2003 . . . . . . 110
5.2 Plant species cover on sample plots . . . . . . . . . . . . . . . . . . . . 111
vLIST OF TABLES
5.3 Precipitation in the summers of 2002 and 2003 . . . . . . . . . . . . . . 111
5.4 Analysis of variance table for standing crop comparing two summers . . 114
5.5 of v table for crop species groups . 116
5.6 Signi can t e ects from the ANOVA for species groups . . . . . . . . . . 120
5.7 Production and biomass removal for a mountain steppe with burrows . 121
5.8 Ratio of burrow to steppe productivity along an altitudinal transect . . 125
5.9 Production and biomass removal along an altitudinal transect . . . . . 128
viAcknowledgements
This project could never have been nished without the help of many people, friends
and advisors and anything in between. Thank you for helping, gh ting, growing, loving,
enduring and encouraging me in so many various ways!
I am grateful to Prof. Dr. G. Miehe, Prof. Dr. R. Samjaa, Prof. Dr. R. Brandl, Dr. V. Re-
tzer, Dr. K. Wesche, Dr. J. Dauber, T. Monkhzul, R. Klug, Devlin, Carola, and Bettina
for giving scienti c advice and encouragement.
V. Retzer, K. Wesche, S. Jansen, G. Miehe, V. Clausnitzer, T. Monkhzul, R. Undrakh,
Enkhjargal, Bjambaa, Bekhee, S. Schmidt, Enkhshimek, Ojuntsetseg, Shurentsetseg,
K. and E.-O. Nadrowski and many others gave invaluable help during the organisation
of this project.
Thank you Vroni, Vayu, Ria, Lou, Gouine, Frank, Sandra, Thomas, Christina, Tatjana,
HikE, Monkhzul, Janis, Bj orn, Maike und Ines for your friendship and love.
Thanks go to the sta of the Faculty of Geography of the Philipps-University of Mar-
burg, the working-group of animal ecology in the Faculty of Biology of the University
in Marburg, the sta of the Faculty of Biology of the Mongolian University, the sta of
the GTZ-o ce in Mongolia, and the sta of the Research Center for Infectious Diseases
in Dalandzadgad.
The German Acadamic exchange, the German Science Foundation, and the Ministry
of Economic Co-operation funded this project.
Thank you Enkhjargal, Amgaa and K. Wesche for collecting plants and M. Pietsch for
drying plants in Halle, and H. von Wehrden for supplying the maps.
Thank you F. Behnsen for the drawing and pictogram of a Mongolian pika.
I’m grateful to K. Wesche, V. Retzer, and my mother for reading through the last drafts,
which greatly improved the present work.
Thanks go to the open source community. This thesis was written using the open source
Asoftwares LT X(www.latex-project.org) for typesetting, Xemacs (www.xemacs.org) asE
editor, R (www.r-project.org) for statistics and graphics, X g (www.x g.org) for some
of the gures, MARK (White and Burnham, 1999) for calculation of survival and re-
capture estimates.
I am especially thankful to my daughter Janis, who was born shortly before this study
was nished. You have brought sunshine in the winter months while I was nishing
this study and I have learned so much from you already.
viiABSTRACT
Life history strategy and ecosystem impact of a dominant small mammal
herbivore in a mountain steppe
Pikas (genus Ochotona) were suspected to possibly behave as \small mammal pests" in
the mountain steppes of the Gobi Gurvan Saikhan National Conservation Park (GGS)
in the Mongolian Gobi Altai. The park hosts rare and endangered animal species like
the snow leopard (Uncia uncia), and the argali (Ovis ammon). Additionally it is an
important rangeland for livestock of local herder families.
The present study shows that the Mongolian pika (Ochotona pallasi pricei), a sub-
species of the Pallas pika, is the dominant small mammal species in the mountain
steppes of the GGS. It outnumbered other small mammals by one order of magnitude
and outweighed them by two of them.
This study presents the rst account on trapping and observing individually marked
Mongolian pikas. It therefore presents instructions on how to capture, handle, and
observe individuals of this species. Data on capture and observation are available
2for three summers and one winter from a trapping grid of 100 100 m , including a
summer of drought. Data based on observation was more reliable in terms of encounter
success than data based on capture. Captured juveniles were discriminated from adults
using information on the development of their weight. An average adult weight was
estimated to range between 180 and 200 g.
Possible scenarios for dynamics of population densities were simulated using a sys-
tem of Leslie-matrices based on estimates for survival and reproduction of the observed
individuals. Survival rates were estimated using maximum likelihood techniques with
competing models for survival and recapture probabilities. The most parsimonious
model included e ects of population density, age, and sex on survival, while there was
no e ect of cohort a liation nor of the climatic factors season and drought. However a
classi cation of a summer and a winter season was useful to delimit age groups. Gener-
ally, adults showed higher survival rates than juveniles, females showed higher survival
rates than males, and survival declined with density. Estimates for reproduction were
based on the observations of litter number and size, resulting in a median of 3 and a
maximum of 13 juveniles per female pika.
Although simulated population densities were similar to the measured population
densities, they did not re ect the e ects of the year of drought. Population densities
were measured using pooled data from capture and observation sessions. In the study
period pika densities varied between 14.6 and 49.8 individuals per ha. Densities were
stable for most of the observed period of time, their interquartile range spanned 5.7
animals. Median density was 21.4 animals, which is less than the 28 burrows on the
trapping site. Lowest densities were reached one year after the summer of drought,
indicating a time lag of one year in the response to the drought conditions.
Comparing reproductive e ort, factors in uencing survival rates, and density dy-
namics of the Mongolian pika with other species of the genus shows that this species
exhibits traits of the group of non-burrowing pikas, which are closer to a K-type of
life history strategy than the group of burrowing pikas. Density dependent survival
indicates that burrow possession may be crucial for survival.
Ecosystem impact of the pikas was assessed studying the productivity of the burrow
habitat in comparison to steppe habitat together with the e ect of grazing by pikas and
by larger herbivores. Productivity and biomass removal was measured using exclosure
plots on burrow and steppe habitat. Burrows showed higher productivity than steppe
viii