MEPS prepress abstract  -  DOI:

Maternal body size and condition determine calf growth rates in Southern right whales

Fredrik Christiansen*, Fabien Vivier, Claire Charlton, Rhianne Ward, Alicia Amerson Stephen Burnell, Lars Bejder


ABSTRACT: The cost of reproduction is a key parameter determining a species’ life history strategy. Despite exhibiting some of the fastest offspring growth rates among mammals, the cost of reproduction in baleen whales is largely unknown since standard field metabolic techniques cannot be applied. We quantified the cost of reproduction for Southern right whales (Eubalaena australis) over a three-month breeding season. We did this by determining the relationship between calf growth rate and maternal rate of loss in energy reserves, using repeated measurements of body volume obtained from Unmanned Aerial Vehicle photogrammetry. We recorded 1,118 body volume estimates from 40 female and calf pairs over 40-89 days. Calves grew at a rate of 3.2cm day-1 (SD=0.45) in body length and 0.081m3 day-1 (SD=0.011) in body volume, while females decreased in volume at a rate of 0.126m3 day-1 (SD=0.036). The average volume conversion efficiency from female to calf was 68% (SD=16.91). Calf growth rate was positively related to the rate of loss in maternal body volume, suggesting that maternal volume loss is proportional to the energy investment into her calf. Maternal investment was, in turn, determined by her body size and condition, with longer and more rotund females investing more volume into their calves compared to shorter and leaner females. Lactating females lost on average 25% of their initial body volume. This study demonstrates the considerable energetic cost that females face during the lactation period and highlights the importance of sufficient maternal energy reserves for reproduction in this capital breeding species.