Comparative Studies of Life History Strategies in Cetaceans
Date Issued
2008
Date
2008
Author(s)
Huang, Shiang-Lin
Abstract
Studies of life histories, figuring the detail schedule of growth, reproduction and longevity of life, stand on the central role of biology and provide valuable information for effective resource conservation and management. Many life history traits are not independent of each other and are bound together by three major trade-offs between life span and reproduction, between extant and future reproductive success, and between quantity and quality of offspring. These trade-offs finally form the fast-slow continuum of life history strategy, the r- and K-strategy selection. To find the association between the evolution of life history and ecological-ethological adaptation in different organisms, the comparative analysis by multivariate statistical methods provide an insight into evolution patterns of life history. etaceans are top marine predators and many of them face grave conservative challenges in their long-term survival. Some difficulties in making solid conservation policies arise from the deficiency of detailed cetacean life history traits (LHT) that can illustrate the most critical stage in life. The most solid way to obtain the first-hand LHT is to follow the fate of individuals and record the size and age at different status of growth. The alternative method to reliably extrapolate the LHT of undocumented species without any lethally specimen collecting is to use the potential allometric relationships between LHT. At present study, we seek to clearify the LHT interactions in cetaceans. Then we will propose the reliable expressions in the allometry of cetacean LHT. We particularly focus on the estimation of Ax, which has been one of the most difficult one LHT to be obtained by long-lived tracing or massively collecting dead oldest cetaceans.y reviewing published data, we explored the correlation in life history traits by general linear model. After removing confounding and unrelated factors, longevity (Ax) was primarily determined by the asymptotic length (Lx) and age at sexual maturity (Am): Ax = 0.962Lx0.435Am0.463, or Ax = 1.795Lx0.487 when Am is not available. We then calculated the lifetime fecundity as expected daughters per female per lifetime and the intrinsic rate of population increase. In the 47 documented species, most baleen whales deliver less than 10 daughters whereas most toothed cetaceans deliver less than 5 daughters in their whole lives and should be considered as extreme K-species when considering their conservation plans. Even a tiny change in rmax can be sensitive to over-exploitation. The unusual high rmax for migratory Balaenopteridae and Eschritidae may suggest compensation effect to past over-exploitation. The presented estimates of rmax in cetaceans can be used for estimating more precisely the quota of potential biological removal, which has been another critical criterion in management of incidental takes of cetacean. In addition, we proposed a generalized expression to estimate the effective population size, which has been another critical base for conservation management.he comparative study of life history variation reveals the interactions between organisms and their external environment and offers more predictive and quantitative guidance in conservation but quite limited in cetaceans. By principle component analysis, 90.75% life history variation could be explained by the body size and the reproduction factors. By the jackknife correctness from discriminant analysis, cetacean phylogeny itself had only 29.2% correct classification with family. With further ecological implications, 5 major niches of life history patterns in cetaceans are generalized with an average of 95.2% correctness. The Niche 1 concerns the long migratory and interrupted feeding lifestyle; Niche 2 – low ambient temperature waters; Niche 3 - socially cohesive behavior system; Niche 4 – open and pelagic waters; Niche 5 – shallow and warm waters and perhaps high mortality. The differences of fitness among cetaceans were presented on their lifetime fecundity and intrinsic population growth rate with high lifetime reproduction for Niche 1, 4, 5 while low for Niche 2, 3 and highest intrinsic population growth rate for Niche 1, 5 while lowest for Niche 3. The generalization of five life history patterns strongly links the paraphyletic convergence with ecological differentiation and potentially offers more predictive and quantitative guidance for the conservation of cetaceans.
Subjects
allometry
cetaceans
life history strategy
conservation, biodiversity
SDGs
File(s)![Thumbnail Image]()
Loading...
Name
ntu-97-D90225009-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):2cf631ff1405a01c0a2b78015f438b7d