Estimate Calf-Cow Ratio.

bbr_calf_cow_ratio(
  x,
  adult_female_proportion = 0.65,
  sex_ratio = 0.5,
  variance = "bootstrap",
  year_start = 4L
)

Format

The return object has these columns:

PopulationName: Population name
Year: Year sampled
estimate: Calf-Cow ratio estimate
lower: Confidence limit
upper: Confidence limit
groups: Groups sampled
female_calves: Estimated female calves
females: Estimated adult females

Arguments

x: A data frame that has recruitment data.
adult_female_proportion: Assumed or estimated proportion of females in the population used to assign unknown sex caribou. Values must be between 0 and 1. Can be set to 0 to exclude unknown sex caribou from recruitment estimates. The default is set at 0.65.
sex_ratio: Sex ratio of caribou at birth used to assign calves and yearlings as male or female. Sex ratio is defined as the proportion females at birth. Values must be between 0 and 1. The default is set at 0.5.
variance: Estimate variance using "binomial" or "bootstrap". The default is set as "bootstrap".
year_start: A whole number between 1 and 12 indicating the month of the start of the caribou (i.e., biological) year. By default, April is set as the start of the caribou year.

Value

A data frame. The columns are listed in the format section.

Details

x needs to be formatted in a certain manner. To confirm the input data frame is in the right format you can use the bbd_chk_data_recruitment function. See the vignette("methods", package = "bbouretro") for the equations used in this function.

User’s can input the assumed proportion of females in the population (to estimate females from adult caribou that have unknown sex) as well as sex ratio at birth.

Examples

calfcow_est <- bbr_calf_cow_ratio(
  bboudata::bbourecruit_a,
  adult_female_proportion = 0.65,
  sex_ratio = 0.5,
  variance = "binomial"
)
calfcow_est <- bbr_calf_cow_ratio(
  bboudata::bbourecruit_a,
  adult_female_proportion = 0.60,
  sex_ratio = 0.65,
  variance = "bootstrap"
)