"Sensitivity Analysis": Sea Turtles

Submitted by mmorales on Mon, 2006-10-16 11:01. |

Using the realistic life history parameters for sea turtles given below. Calculate R0 for the following scenarios:

  1. Increase survivorship of eggs/hatchlings to 1.0.
  2. Absolute increase of 0.1 in juvenile survivorship.
  3. Absolute increase of 0.1 in survivorship of breeders.
Class Ages (x) Age-Specific Survivorship (gx) Fecundity (mx)
Eggs/Hatchlings <1 0.6747 0
Juveniles 1-15 0.7308 0
Sub-Adults 16-21 0.7425 0
Novice Breeders 22 0.8091 127
Mature Breeders 23-54 0.8091 80

Although this assignment won't be graded, I encourage you to come to class Wednesday with your answers. Below is the R code for the spotted owl example which you can use as a template.

## Age-specific survivorship
## Note total age classes = 20, i.e., from 0-19
g0 <- .26
g1 <- .94
gx <- c(g0, rep(g1,17), 0)   # One less gx value than age classes!

## Function to convert gx to lx
gx2lx <- function(gx) {
  lx <- vector()
  lx[1] <- 1
  for(i in 1:length(gx)) lx[i+1] <- lx[i]*gx[i]
  lx
}

## Survivorship schedule
lx <- gx2lx(gx)

## Fecundity
m1 <- .07
m2 <- .21
m3 <- .68
mx <- c(0, m1, m2, rep(m3,17))

## Visualize lifetable
data.frame(lx,mx)

## Calculate R0
R0 <- sum(lx*mx)

» mmorales's blog