What does it do?
The add4pop model simulates the lives of female European adders (Vipera berus).
It simulates their central-place foraging around their hibernacula, as well as offspring production, survival and dispersal.
This enables the model to predict the relative abundance of adders across a landscape.
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Where does it come from?
The add4pop model was co-created by the UK Centre for Ecology & Hydrology and Amphibian and Reptile Groups of the UK.
Add4pop model development is led by Emma Gardner and Becky Turner.
How does it work?
Add4pop 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 hibernating resources and foraging resources each landcover type is expected to offer to adult and juvenile adders. This allows the model to map the hibernating 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 hibernating resources map so that areas that receive more sunshine offer more hibernating resources than shaded areas.
It then places hibernacula in the landscape, putting more in places where there are more hibernating resources, and initially populates these with the maximum allowed number of breeding female adders per hibernaculum.
The model uses information on how far adult adders typically move away from their hibernation sites while foraging to work out the amount of foraging resources the female adders would be able to gather. It assumes that adders spend more time foraging in nearby places and places with more foraging resources.
The model assumes that female adders who gather more food produce more offspring.
It then calculates the amount of foraging resources the juvenile adders would be able to gather using information on how far away from their hibernacula birthing adders are likely to leave their young. It assumes that juveniles who gather more foraging resources are more likely to survive to adulthood.
Surviving juvenile females are dispersed across the available hibernacula. If the number of adders at a hibernating site exceeds the allowed maximum number then any extra adders are lost from the landscape.
The model loops round and round multiple generations to work out where adders 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 add4pop model is parameterised for European adder.
It uses:
- expert opinion on adder habitat preferences from a survey of 17 experts in adder ecology, including academic researchers, NGO staff, ecological consultants and conservation volunteers
- literature and field data on hibernacula densities, litter sizes, movement ranges and survival probabilities
How do we know it works correctly?
We compared add4pop model predictions to the number of adders recorded at 257 sites by volunteers taking part in the Make the Adder Count survey.
How has add4pop been used?
We’ve used add4pop to:
- explore with local communities how past land use changes have affected adders.
- help citizen scientists identify areas to survey for adders
- help agencies, land managers and conservation volunteers identify areas for habitat creation
- explore the likelihood of adders recolonising habitats
- explore whether adder populations might be limited by other unmodelled factors such as climate or public pressure
Visit our pages on supporting decision-making to find out more about this work.
*4pop models 