Comparative Studies of Life History Strategies in Cetaceans 鯨類生活史策略的比較研究 Shiang-Lin Huang 1 , Lien-Siang Chou 1 , I-Hsun Ni 2 1: Institute of Ecology and Evolution Biology, NTU 2: Department of Environmental Biology and Fisheries Science, NTOU.
Comparative Studies of Life History Strategies in Cetaceans鯨類生活史策略的比較研究Shiang-Lin Huang1, Lien-Siang Chou1, I-Hsun Ni21: Institute of Ecology and Evolution Biology, NTU2: Department of Environmental Biology and Fisheries Science, NTOU
Life history studies provide valuable information for effective resource conservation and management. Cetaceans are top marine predators and many of them face grave conservative challenges. Some difficulties in making solid conservation policies arise from the deficiency of detailed cetacean life history that can illustrate the most critical stage in life. By reviewing published literatures, this study (1)explored the interactions in life history traits, (2)estimated the reproduction potential, and (3)generalized the potential patterns of life history in cetaceans. In life history traits, longevity (Ax) was primarily determined by the asymptotic length (Lx) and age at sexual maturity (Am): Ax = 0.962Lx0.435Am0.463. The estimation of cetaceans’ reproduction potential showed that most baleen whales deliver less than 10 daughters (R0) whereas most toothed cetaceans deliver less than 5 daughters, which should be considered as extreme K-species in conservation. The estimates of intrinsic rate of increase (rmax) can be used for estimating more precisely the quota of potential biological removal, another critical criterion in management of cetacean.
The comparative study of life history variation reveals the interactions between organisms and their external environment. By principle component analysis and discriminant analysis, 5 major types of life history in cetaceans are generalized. The Type 1 concerns the long migratory lifestyle; Type 2 – low ambient temperature waters; Type 3 - socially cohesive behavior system; Type 4 – open and pelagic waters; Type 5 – shallow and warm waters and high mortality. The differences of fitness among cetaceans show high lifetime reproduction for Types 1, 4, 5 while low for Types 2, 3 and highest intrinsic population growth rate for Types 1, 5 while lowest for Type 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.