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ULM - Unified Life Models
Warning : This page is outdated. The last version of ULM can be downloaded on the ULM website.

Population Dynamics Modelling
Version 5 - January 2016

The ULM computer program (Legendre & Clobert 1995, Ferrière & al. 1996) has been designed to study a large panel of population dynamics models, for research or teaching purposes :

  • Ecology
  • Management, conservation biology
  • Deterministic and stochastic discrete time dynamical systems
Download ULM

ULM is distributed free of charge. Users are under their own responsibility.


After installation, the ULM directory should contain :

  • ULM program ulm.exe
  • example model files *.ulm
  • reference manual ulmref.pdf
How to run ULM ?
  • Double-click on any model file *.ulm. Select program c :\ulm\ulm.exe to open the file
  • ULM will then be run with files *.ulm as input
  • Click compile to process the file, and run to run the model
  • For detailed informations consult ulmref.pdf
How does ULM work ?

Models are described in a text file according to a reduced declaration language, close to the mathematical formulation. The program is run with the model file as input, and the system can be studied interactively by means of simple commands, producing convenient graphics and numerical results. The kernel of ULM is a symbolic evaluator. Stochastic models are handled via Monte Carlo simulation.

What can be modeled ?
  • any species life cycle graph (matrix models) (Caswell 1989, 2000)
  • inter- and intra-specific competition, density dependence (non linear systems)
  • environmental stochasticity (Tuljapurkar 1990) (random processes)
  • demographic stochasticity (branching processes)
  • metapopulations, migrations (coupled systems)
Which results ?
  • population trajectories, distributions
  • growth rate, population structure, generation times
  • sensitivities to changes in parameters, fitness landscape
  • probability of extinction, quasi-extinction, extinction times
  • lyapunov exponents, bifurcation diagrams


Caswell H. 1989. Matrix Population Models. Sinauer Associates Inc., Sunderland, MA, USA.

Caswell H. 2001. Matrix Population Models. Second edition.

Ferrière R, F Sarrazin, S Legendre & J-P Baron. 1996. Matrix population models applied to viability analysis and conservation : Theory and practice with ULM software. Acta OEcologica 17:629-656.

Legendre S & J Clobert. 1995. ULM, a software for conservation and evolutionary biologists. Journal of Applied Statistics 22:817-834.

Legendre S, J Clobert, AP Møller & G Sorci. 1999. Demographic stochasticity and the social mating system in the process of extinction of small populations : The case of passerines introduced to New Zealand. American Naturalist 153:449-463.

Tuljapurkar S. 1990. Population Dynamics in Variable Environments. Lecture Notes in Biomathematics, Springer Verlag, Germany.

Schoener TW, J Clobert, S Legendre & DA Spiller. 2003. Life-history models of extinction : A test with island spiders. American Naturalist 162:558-573.

Legendre S. 2004. Influence of age structure and mating system on population viability. In Evolutionary Conservation Biology (Ferrière R, U Dieckmann & D Couvet eds.), Cambridge University Press, pp. 41-58.

Author : Stéphane Legendre, formerly at
Laboratoire d’Ecologie
Ecole Normale Supérieure
46 rue d’Ulm
75230 Paris Cedex 05

Jean Clobert, Régis Ferrière, Frédéric Gosselin, Jean-Dominique Lebreton, François Sarrazin.