Patterns of blubber fat deposition and evaluation of body condition in growing southern right whale calves (Eubalaena australis)

Abstract

Marine mammals rely on blubber mainly for energy storage, buoyancy, and streamlining. Mysticetes are born with a relatively thin fat layer that grows rapidly during nursing. However, little information on blubber deposition patterns is available for baleen whale calves. We measured blubber thickness at nine body locations in 350 southern right whale (Eubalaena australis) newborn to 4–6‐month‐old calves that died on the Península Valdés (Argentina) calving ground from 2003 to 2019, to document changes in blubber thickness with growth. Additionally, we looked for differences in blubber thickness and lipid content of the outer/superficial blubber in calves that died in years with high (2003, 2005, 2007–2013) and low calf mortality (2004, 2006, 2014–2019) to test whether the former were suffering from gross nutritional stress. Blubber thickness increased at all body locations with calf length. Along the cranio‐caudal axis, blubber increased in the dorsal and ventral planes, but decreased laterally towards the peduncle, possibly to improve streamlining. We found no difference in blubber thickness and lipid content between high and low mortality years, suggesting that individuals were not undernourished. This is the first study to describe progressive increases in calf blubber during growth and contributes knowledge to right whale health and ontogeny.

Fetal growth, birth size and energetic cost of gestation in southern right whales

“…These values are very low compared to the 75.7% mean lipid concentrations measured in the outer blubber layer (dorsal‐anterior position) of dead young (<4 months old, n = 59) SRW calves in PV by Marón et al. (2021). In light of these limited data, we decided to follow the approach of Christiansen et al.…”

“…Lockyer et al (1985) presented data on tissue energy content in a 2.05 m-long fin whale fetus, which had lipid and protein concentrations of 1.2 and 10.6% (wet weight) in the blubber (midlateral position), 2.4 and 6.6% in the muscle (midlateral position), and 1.8 and 6.0% in the visceral tissues (cardiac fat), respectively. These values are very low compared to the 75.7% mean lipid concentrations measured in the outer blubber layer (dorsal-anterior position) of dead young (<4 months old, n = 59) SRW calves in PV by Marón et al (2021). In light of these limited data, we decided to follow the approach of Christiansen et al (2022), who used the mean lipid and protein concentrations from different reproductive classes of fin, sei and common minke whales (Lockyer, 1987a;Lockyer et al, 1985;Vikingsson, 1990;Vikingsson et al, 2013).…”

Histomorphological stratification of blubber of three dolphin species from subtropical waters

“…Marine mammal body composition, defined as the “ratio of blubber mass to either total body mass or lean mass” (Adamczak et al, 2021), has recently been an important tool used as a proxy for the health and condition of individuals within a population (Adamczak et al, 2021; Castrillon et al, 2017; Castrillon & Nash, 2020; Derous et al, 2020; Marón et al, 2021). Recent global trends in climate change and overfishing have raised multiple issues concerning changes in the distribution and abundance of fish stocks (Barange et al, 2018; Castrillon & Nash, 2020).…”

“…One potential factor influencing blubber histomorphology not investigated in this study is blubber lipid content. Because lipid deposition and utilization are dynamic and are involved in the response to changing environmental and physiological conditions (Marón et al, 2021), it would influence the structure and function of adipocyte cells in the different blubber layers. Future studies should also take into consideration the reproductive state of the females and the temperature range of their study area, which could potentially affect blubber histomorphology.…”

Variation of blubber thickness for three marine mammal species in the southern Baltic Sea

“…Blubber thickness is regularly used to infer the nutritional status of marine mammals ( Kauhala et al, 2019 ; Marón et al, 2021 ). However, it cannot be considered an accurate assessment of the nutritional condition of an individual as a standalone metric, since starvation processes include loss of fat (blubber thickness and lipid composition) as well as muscle mass ( IJsseldijk et al, 2019 ).…”