Quantifying the energy stores of capital breeding humpback whales and income breeding sperm whales using historical whaling records

Abstract

Cetacean energy stores are known to vary according to life history, reproductive status and time of year; however, the opportunity to quantify these relationships is rare. Using a unique set of historical whaling records from Western Australia (1952–1963), we investigated energy stores of large cetaceans with differing life histories, and quantified the relationship between total body lipid and length for humpback whales (Megaptera novaeangliae) (n = 905) and sperm whales (Physeter macrocephalus) (n = 1961). We found that total body lipid increased with body length in both humpback and sperm whales, consistent with size-related energy stores. Male humpback whales stored 2.49 kl (15.6 barrels) (31.9–74.9%) more lipid than male sperm whales of equivalent length, to fuel their annual migration. Relative lipid stores of sperm whales (males) were constant throughout the year, while those of humpback whales varied with reproductive class and sampling date. Pregnant female humpback whales had higher relative energy stores than non-pregnant females and males (26.2% and 37.4%, respectively), to fuel the energy demands of gestation and lactation. Those that reached the sampling site later (en route to their breeding grounds) carried higher lipid stores than those that arrived earlier, possibly reflecting individual variation in residency times in the Antarctic feeding grounds. Importantly, longer pregnant females had relatively larger energy stores than the shorter pregnant females, indicating that the smaller individuals may experience higher levels of energetic stress during the migration fast. The relationships we developed between body lipid and length can be used to inform bioenergetics and ecosystem models when such detailed information is not available.

Income and capital breeding in males: energetic and physiological limitations on male mating strategies

“…As a consequence, for capital breeders, lipids (and possibly proteins) are the only possible energy sources for species with extended breeding seasons (e.g. Irvine et al, 2017). However, where breeding seasons are short, capital breeders can have no appreciable fat stores (e.g.…”

“…Resource distribution will also play a similar role for males. For example, there is spatial separation between breeding and feeding sites in capital-breeding humpback whales (Megaptera novaeangliae), but not in sperm whales (Physeter microcephalus; Irvine et al, 2017). Similarly, spring peepers start to breed early in the year, before insect prey is available; spring peepers therefore need to build capital stores of energy before they overwinter (Wells and Bevier, 1997).…”

Anthropogenic disturbance in a changing environment: modelling lifetime reproductive success to predict the consequences of multiple stressors on a migratory population

“…These results highlight the importance of body size (i.e. the volume of reserves that can be accumulated; Irvine et al 2017) as a way to buffer stochastic and periodic variability in the environment (Lindstedt and Boyce 1985, Millar and Hickling 1990, Costa 1993 while sustaining high costs of reproduction (Christiansen et al 2018). In concert with many other recognized benefits of large size, such as a low mass-specific metabolic rate (White et al 2009) and an efficient cost of transport (Williams 1999), this could have acted as an evolutionary force driving the development of the large sizes of baleen whales (Brodie 1975, Slater et al 2017).…”

Humpback Whale Movements and Behavior in Response to Whale-Watching Vessels in Juneau, AK

“…Humpback whales migrate to Southeast Alaska from low latitude breeding grounds and are reliably present from May to September (Lopez and Pearson, 2017). Acquiring nutrients and energy on the Alaskan feeding grounds is essential for body maintenance and preparation for migration to low-latitude breeding grounds where humpback whales fast due to limited prey availability (Irvine et al, 2017).…”