What does it do?
The rept4pop model simulates the lives of female common lizards (Zootoca vivipara).
It simulates their central-place foraging around their basking sites, offspring production and dispersal, and the survival of adults and juveniles.
This enables the model to predict the relative abundance of common lizards across a landscape.
Where does it come from?
The rept4pop model was co-created by the UK Centre for Ecology & Hydrology and Amphibian and Reptile Groups of the UK.
Rept4pop model development is led by Emma Gardner.
How does it work?
Rept4pop reads in a landcover map plus additional maps giving the locations of fine-scale habitat features (e.g. hedgerows, field margins).
It combines these with expert opinion estimates of the amount of basking opportunities and foraging resources each landcover type is expected to offer to common lizards. This allows the model to map the basking resources and map the foraging resources provided by the landscape.
The model also reads in information on the topography of the landscape and uses this to refine the basking resources map so that areas that receive more sunshine offer more basking resources than shaded areas.
It then places basking sites in the landscape, putting more in places where there are more basking resources, and initially populates these with the maximum allowed number of breeding females per basking site.
The model uses information on how far common lizards typically move away from their basking sites while foraging to work out the amount of foraging resources the female lizards would be able to gather. It assumes that common lizards spend more time foraging in nearby places and places with more foraging resources.
The model assumes that female lizards who gather more food produce more offspring.
Separate survival probabilities for adults and juveniles are then used to calculate the number of adult and juvenile females that survive to the next breeding season.
Surviving females are dispersed across the available basking sites. If the number of lizards at a basking site exceeds the allowed maximum number then any extra lizards are lost from the landscape.
The model loops round and round multiple generations to work out where common lizards would be able to survive, given the composition and configuration of habitat resources provided by the input landscape.
What knowledge does the model use?
The rept4pop model is parameterised for common lizard.
It uses:
- expert opinion on common lizard habitat preferences from a survey of 10 experts in common lizard ecology, including academic researchers, NGO staff, ecological consultants and conservation volunteers
- literature data on basking densities, litter sizes, movement ranges and survival probabilities
How do we know it works correctly?
We compared rept4pop model predictions to observations of common lizards recorded at 83 sites across Surrey by members of Surrey Amphibian and Reptile Group.
Its performance was also tested in Oxfordshire by students from the University of Sheffield and the University of Nottingham.
How has rept4pop been used?
Rept4pop’s predictions have been used by:
- volunteer surveyors to help find previous unknown common lizard populations in Northern Ireland as part of the Dragons in the Hills project.
- county ecologists investigating how common lizards might be using sites proposed for development.
We’ve also used rept4pop to:
- explore with local communities how past land use changes have affected common lizards.
- explore how future land use changes might affect common lizards, working with Defra’s national evidence teams.
Visit our pages on supporting decision-making to find out more about this work.
*4pop models 