Thomas Ruf
Research Institute of Wildlife Ecology, University of Veterinary Medicine Vienna
Title
Optimization of energy turnover in mammals exposed to fluctuating resources:case studies
Abstract
I am interested in how mammals adjust their energy expenditure to fluctuations in environmental resources,
and how physiological constraints shape life-history tactics.
In this talk, I will present data from four case studies on marmots, hares, wild boar, and edible dormice.
Hares and marmots are both examples for how mammals adjust their "metabolic machinery" i.e., the size of
alimentary organs to variable energy demands (e.g. costs of lactation) and seasonally changing food
availability. Both species show a high degree of phenotypic plasticity "inside the body", that is, up- and
downregulation of the size of their gastrointestinal tract, with energetic effects that have been
underestimated in the past.
However, we hypothesize that in hares, the time required to upregulate nutrient processing organs during
lactation may limit maximum energy turnover. Our preliminary results from ongoing experiments on this
question support this "central limitation" hypothesis.
Wild boar and edible dormice experience another type of fluctuations in food resources, in addition to
seasonal changes. Both species are "pulsed resource consumers", specialized on exploiting the occasional
mast fructification of trees such as beech and acorn. We found that in wild boar this has led to highly
flexible life history tactics with rapid shifts along a slow-fast continuum as environmental conditions
change rapidly from year to year. Leslie-matrix models and elasticity analyses indicate that these shifts
have a strong impact on population dynamics (and on sensible management measures for this species).
Edible dormice on the other hand, are able to predict mast seeding, and restrict reproduction to years
with high food supply. This leads to entire populations either reproducing or skipping reproduction in
each year. This pattern enabled us to uncover a strong tradeoff between reproductive costs and future
survival which is not masked by variation in individual fitness.
Education
| 1986
| MS Biology, Phillips University Marburg, Germany
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| 1992
| Dr. rer. nat.; Phillips University Marburg, Germany
Thesis: Energetics of daily torpor in Djungarian hamsters. Advisor: Gerhard Heldmaier
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| 1992 - 1993
| Feodor-Lynen Research fellowship of the Alexander von
Humboldt Foundation at Kent State University (USA)
Research on reproductive adjustments in photoperiodically responsive and nonresponsive deer mice.
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| 1993 - 1996
| University Assistant at the Department of Biology,
University of Marburg, Germany
Research on reproductive energetics an seasonal adaptation in European small rodents.
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| 1996 - 2001
| University Assistant, Research Institute of Wildlife Biology, University of Veterinary Medicine Vienna
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| 2001 to present
| Associate Professor, Research Institute of Wildlife Biology, University of Veterinary Medicine, Vienna
Research on seasonal adaptation, energetics of reproduction, and population dynamics in various mammals.
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Recent relevant projects
- FWF project "Costs and benefits of changes in organ size in Alpine Marmots (Marmota marmota)" (2002-2004).
- FWF project "Physiological limits to maximum energy turnover in mammals" (2005 –2007).
Recent relevant publications
- Hackländer K., Tataruch F. and Ruf T. (2002) The effect of dietary fat content on lactation energetics in the European hare (Lepus europaeus). Physiologicial and Biochemical Zoology 75: 19-28
- Hume I. D., Beiglböck C., Ruf T., Frey-Roos F., Bruns U., and Arnold W. (2002) Seasonal changes in morphology and function of the gastrointestinal tract of free-living alpine marmots (Marmota marmota). Journal of Comparative Physiology B: 197-297
- Bieber C., and Ruf T. (2005) Population dynamics in the wild boar Sus scrofa: Ecology, elasticity of growth rate, and implications for the management of pulsed resource consumers. Journal of Applied Ecology, in press
- Ruf T., Fietz J., Schlund W., and Bieber C. (2005) High survival in poor years: life history tactics adapted to mast seeding in the edible dormouse. Ecology, in press
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