Meeting Abstract

P2.23  Monday, Jan. 5  Conservation biology of Verreaux’s sifaka (Propithecus verreauxi verreauxi): Prospective and retrospective perturbation analyses. LAWLER, RR*; CASWELL, H; Boston University; Woods Hole Oceanographic Institution rlawler@bu.edu

In this study, we employ two separate analyses in order to understand how population growth rate (pgr) responds to changes in the population’s vital rates (rates of survival, growth, and fertility). Prospective analyses are commonly used to inform management decisions and ask the question: how would pgr change, given a change in one or more of the vital rates? Retrospective analyses examine how variation in pgr is expressed as a function of the (co)variation of the vital rates. This type of analysis can reveal how year-to-year variation in growth, survival, and fertility contributes to variation in pgr. Our prospective analysis was achieved by developing a time-invariant, five-stage matrix model using 17 years of data collected on a wild population of Verreaux’s sifaka. Using this matrix model, we calculated sensitivity and elasticity values that capture the prospective dependency of how pgr would change, given a change in a vital rate. Our retrospective analysis draws from matrix models developed from the first half and last half of the 17-year dataset. From these matrices, we decompose variation in pgr into contributions from the variation in the vital rates. Our results show that pgr is most sensitive to transitions into maternity, and less dependent on survival and growth of reproductively immature animals. We also find that variation in survivorship of mothers contributes the largest amount to variation in pgr. Our results suggest that the long-term viability of the sifaka population depends on recruitment of females into motherhood and is less dependent on the survival of pre-reproductive females.