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DIFFERENCES IN NICHE BREADTH AMONG SOME TEUTHIVOROUS MESOPELAGIC MARINE MAMMALS
Author(s) -
Whitehead Hal,
MacLeod Colin D.,
Rodhouse Paul
Publication year - 2003
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/j.1748-7692.2003.tb01118.x
Subject(s) - mesopelagic zone , nova scotia , library science , citation , geography , ecology , archaeology , biology , pelagic zone , computer science
An important issue in ecology is how species which are members of the same ecological guild differ in their use of resources (Emlen 1973, pp. 175–178). Species may use particular resources in different proportions, or, more generally, employ more or fewer resource types, so having relatively wide and narrow niche breadths, respectively. Another way of expressing this variation is from generalists, with wide niche breadths, to specialists, with narrow niches. One of the great food resources of the Earth is the cephalopod biomass of the mesopelagic and bathypelagic ocean (Clarke 1977). These animals are preyed upon by a number of deep-diving marine mammals, especially sperm whales (Physeter macrocephalus), beaked whales (family Ziphiidae), and elephant seals (Mirounga spp.). Here, we ask whether the mammalian mesopelagic cephalopod predators (which have sufficient diet information available) differ in their niche breadth. Do some use relatively more squid taxa than others? If so, why might this be? Diet in these species has been principally determined by examining the cephalopod lower beaks which accumulate in their stomachs. These beaks can be allocated to genus, and sometimes species, and a size of the original animal may be extrapolated (Clarke 1986). Thus squid beaks retrieved from the stomachs of dead or lavaged animals may be used to estimate diet (e.g., Clarke 1980). However this method possesses potential biases. These include the omission of the non