A package that provides some standardised methods to monitor beaver populations and predict future population dynamics.
Installation:
# install.packages(devtools)
devtools::install_github("h-a-graham/beavertools")Check out The workflow for the River Otter Catchment To see a workflow example of this package.
Here is an example of the outputs from the package. Results are from our in 2022 publication:
Graham, Hugh A., Alan Puttock, Jake Chant, Mark Elliott, Roisin Campbell‐Palmer, Karen Anderson, and Richard E. Brazier. ‘Monitoring, Modelling and Managing Beaver ( Castor Fiber ) Populations in the River Otter Catchment, Great Britain’. Ecological Solutions and Evidence 3, no. 3 (July 2022). https://doi.org/10.1002/2688-8319.12168.
This example shows the kernel density estimate for feeding signs and the derived (automated) territory locations and their classification. This enables us to make estimates of the number of territories present in the catchment over time.
River Otter Beaver Trial Forage Density
This examples shows a modelling approach to allow for the prediction of territory capacity within a catchment. Here we present two maps, one from a low minimum habitat scenario and another from a high minimum habitat scenario. We then run simulations on this to estimate the possible range of territory capacity within the catchment.
Territory Capacity Scenarios
Now that we know the territory capacity we can begin to model the population dynamics of the catchment. For the full code workflow check out beavertools/R_Otter_workflow.
By combining the known territory numbers over time we estimate the exponential growth of the population and then derive the logistic curve based on this, given a range of territory capacities which are used to estimate the asymptote.
Population Growth curve
We can then dive into this a bit more and consider how the relative/absolute growth changes with time and population density…
Population Dynamics
Finally, we can apply a range of management scenarios, where n beaver territories are removed each year starting at different times. This gives us some indication as to the level of manamgent that may be required to stabilise the population at numbers < carrying capacity.
Management Growth curves