Implements a type 2 functional response to the availability of three resources: blood hosts (\(B\)), aquatic habitats (\(Q\)), and sugar (\(S\)).
$$\sigma = \sigma_X \left( \frac{\sigma_Q Q}{1+\sigma_Q Q} + \frac{\sigma_B B}{1+\sigma_B B} + \frac{\sigma_S S}{1+\sigma_S S} \right)$$
Usage
# S3 method for class 'type2'
F_sigma(t, xds_obj, s)