Covariates

SURPH probabilities can be modeled as a function of two types of covariates:

1. Group Covariates.
2. Individual Covariates.

Group Covariates

Group covariates are factors that affect one or more of the populations as a whole. Examples are ambient temperature, sex, and h abitat type. There are two varieties of group covariates:

1. Time-invariant group covariates that are the same from one sampling occasion to the next. The user defines the value of a time-invariant group covariate for each population. An example might be the sex of the individuals in the populations.
2. Time-variant group covariates are allowed to change from one sampling occasion to the next. The user defines the value of a time-variant group covariate for each period of each population. An example might be the average temperature for each period.

Individual Covariates

The Individual covariates apply to each individual. Examples include body length and body weight. The user specifies the value of an individual covariate for each individual.

The nature of the relationship between the covariates and the resulting SURPH probabilities is defined by the link function.