Lactation in whales and dolphins: evidence of divergence between baleen- and toothed-species. J. Mammary Gland Biol. 2, 205-230

Department of Zoological Research, National Zoological Park, Smithsonian Institution, Washington, DC 20008, USA.
Journal of Mammary Gland Biology and Neoplasia (Impact Factor: 4.53). 08/1997; 2(3):205-30. DOI: 10.1023/A:1026328203526
Source: PubMed

ABSTRACT Although it has been more than one hundred years since the first publication on the milks of whales and dolphins (Order Cetacea), information on lactation in these species is scattered and fragmentary. Yet the immense size of some cetaceans, and the recent evidence that another group of marine mammals, the true seals, have remarkable rates of secretion of milk fat and energy, make this group of great comparative interest. In this paper information on lactation patterns, milk composition and lactation performance is reviewed. Two very different patterns are evident. Many of the baleen whales (Suborder Mysticeti) have relatively brief lactations (5-7 months) during which they fast or eat relatively little. At mid-lactation they produce milks relatively low in water (40-53%), high in fat (30-50%), and moderately high in protein (9-15%) and ash (1.2-2.1%). From mammary gland weights and postnatal growth rates, it is predicted that their energy outputs in milk are exceptional, reaching on the order of 4000 MJ/ d in the blue whale. This is possible because pregnant females migrate to feeding grounds where they can ingest and deposit great amounts of energy, building up blubber stores prior to parturition. On the other hand, the toothed whales and dolphins (Suborder Odontoceti) have much more extensive lactations typically lasting 1-3 years, during which the mothers feed. At mid-lactation their milks appear to be higher in water (60-77%) and lower in fat (10-30%) and ash (0.6-1.1%), with similar levels of protein (8-11%). At least some odontocetes resemble primates in terms of low predicted rates of energy output and a long period of dependency of the young. However, these hypotheses are based on small numbers of samples for a relatively small number of species. Much of the available data on milk composition is of rather poor quality; for example, it is not possible to determine if milk composition changes over the course of lactation among odontocetes. Additional research on cetacean mammary glands and their secretions is needed to understand the reproductive strategies of these fascinating animals.

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    • "Long-distance migrations are a central component of the life history of many baleen whales, who give birth at low latitudes and travel to feed in the highly productive polar oceans (Oftedal 1997). However, the reproductive strategies of odontocetes and mysticetes diverge, and fasting migrations are not generally thought to be part of the odontocete life history (Oftedal 1997). "
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    ABSTRACT: Killer whales of ecotype C (Orcinus orca, TCKW) were studied in McMurdo Sound, Antarctica, during Dec 2014-Jan 2015 by dart biopsy sampling and photo-identification (photo-ID). We collected 33 dart biopsy samples including 27 samples from killer whales (26 type C, 1 type B) and 6 samples from Antarctic minke whales (Balaenoptera bonaerensis). With the exception of 7 type-B killer whales (TBKW; 5 adults, 2 calves), all killer whales sighted in the McMurdo Sound region were TCKW. By combining images from our 2013/14 and 2014/15 with an existing catalogue compiled by the Orca Research Trust ('AKWIC') and photos submitted by 'citizen scientists', we have created an expanded photo-identification catalogue for Antarctic killer whales that is scheduled to go online in 2015. Preliminary analysis of the database provides evidence for long-distance migrations of TCKW between the Ross Sea and New Zealand waters: (a) One adult female TCKW has been re-sighted in both New Zealand waters and McMurdo Sound, Antarctica; (b) a large proportion of TCKW sighted in McMurdo Sound (33-55%) bear marks caused by cookiecutter sharks that are currently assumed to be limited to north of 50°S. TCKW have also been re-sighted between years in New Zealand waters and in McMurdo Sound, with a minimum distance of 11 km between inter-annual sightings, indicating that TCKW may show seasonal site fidelity to areas of high ecological significance.
    International Whaling Commission Scientific Committee, San Diego, USA; 05/2015
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    • "Odontocetes, by comparison , are income breeders that nurse their calves over prolonged periods ranging up to several years (Tyack 1986; Oftedal 1997). Continual food consumption throughout the nursing period, along with lower rates of energy transfer (odontocete milks have less fat than mysticete milks), allow energetic demands of lactation to be distributed over a longer period (Oftedal 1997). Nevertheless, odontocete mothers must increase their daily food consumption by 32–63% over nonlactating requirements to fuel milk production (Lockyer 1981). "
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    ABSTRACT: Beluga whales (Delphinapterus leucas) have a protracted nursing period estimated to last from 6-32 months, although current estimates of beluga nursing duration are derived using approaches subject to capture bias. Recent studies have shown stable isotope profiles of dentin growth layer groups (GLGs) in marine mammal teeth serve as a reliable nursing proxy and can be used to assess individual weaning patterns. We measured stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) of dentin GLGs in teeth from eastern Canadian Arctic belugas to estimate weaning age and assess relative contributions of milk and solid food during the nursing period. δ15N declines of ~1‰ over the first 3 GLGs of most individuals were interpreted as evidence of weaning. Individual δ15N profiles indicated 15 of 27 whales were completely weaned by the end of their 2nd year, although a number of whales were weaned by the end of their 1st or 3rd year (9 and 3, respectively). Intermediate GLG2 δ15N values relative to GLGs 1 and 3 indicated most whales consumed a mixture of milk and solid food during their 2nd year, consistent with gradual weaning. Contrary to predictions based on parental care theory, nursing duration was not related to relative GLG width (used as a proxy for somatic growth) and did not differ for females and males, or among populations. δ13C variation was not a reliable indicator of nursing duration, as approximately half of the whales showed no ontogenetic δ13C patterns across GLGs deposited over the nursing period. This study provides novel life history information, which may inform beluga conservation and management decisions, and indicates belugas share prolonged nursing duration marked by individual variation observed in other odontocetes.
    Journal of Mammalogy 04/2015; 96(2):425-437. DOI:10.1093/jmammal/gyv046 · 1.84 Impact Factor
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    • "Third, energy provided from lactation was assumed to be constant in our model, although the proportion of milk constituents in cetaceans changes over time (Oftedal, 1997). In humpback whales, for example, the proportion of fat increases over the first few months of lactation, before decreasing again towards weaning (Oftedal, 1997). As we used the 4–7 month average proportion of constituents, the energetic value of milk would be greater than that of early months, and thus, the total amount of milk required to support ideal growth will be an underestimate. "
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    ABSTRACT: Whales migrate long distances and reproduce on a finite store of energy. Budgeting the use of this limited energy reserve is an important factor to ensure survival over the period of migration and to maximize reproductive investment. For some whales, migration routes are closely associated with coastal areas, exposing animals to high levels of human activity. It is currently unclear how various forms of human activity may disturb whales during migration, how this might impact their energy balance and how this could translate into long-term demographic changes. Here, we develop a theoretical bioenergetic model for migrating humpback whales to investigate the optimal migration strategy that minimizes energy use. The average migration velocity was an important driver of the total energy used by a whale, and an optimal velocity of 1.1 m s−1 was determined. This optimal velocity is comparable to documented observed migration speeds, suggesting that whales migrate at a speed that conserves energy. Furthermore, the amount of resting time during migration was influenced by both transport costs and feeding rates. We simulated hypothetical disturbances to the optimal migration strategy in two ways, by altering average velocity to represent changes in behavioural activity and by increasing total travelled distance to represent displacement along the migration route. In both cases, disturbance increased overall energy use, with implications for the growth potential of calves.
    Conservation Physiology 01/2015; 3(1):cov001-cov001. DOI:10.1093/conphys/cov001
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