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

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 3 mo 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 un manned aerial vehicle photogrammetry. We recorded 1118 body volume estimates from 40 female and calf pairs over 40 to 89 d. Calves grew at a rate of 3.2 cm d −1 (SD = 0.45) in body length and 0.081 m 3 d −1 (SD = 0.011) in body volume, while females decreased in volume at a rate of 0.126 m 3 d −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 in vestment was 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 over the 3 mo breeding season. 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.

Unoccupied aerial system assessment of entanglement in Northwest Atlantic gray seals (Halichoerus grypus)

“…, Rhodes and Spiegel 2017, Christiansen et al . ). While UAS may cause visual and acoustic disturbance of marine mammals, especially pinnipeds that rest on land, if maintained above altitudes where behavioral responses are observed, UAS surveys can be performed without major disturbance (Pomeroy et al .…”

Challenges of collecting blow from small cetaceans

“…Remotely piloted aircraft (e.g., drones) are increasingly being used as the platform of choice to monitor wildlife in many different circumstances (Linchant et al 2015, Gonzalez et al 2016 and have enabled the collection of data that were previously difficult if not impossible to collect. In studies of marine mammals, drones have been used with thermal imaging to assess populations (Seymour et al 2017), determine body condition and identify individual whales (Dawson et al 2017, Christiansen et al 2018, count dugongs (Hodgson et al 2013) and pinnipeds (McIntosh et al 2018), acquire photographic images to estimate population size (Colefax et al 2018, Hodgson et al 2018, record behavior (Goebel et al 2015, Fiori et al 2017, Torres et al 2018, and collect blow samples from whales (Pirotta et al 2017, Dom ınguez-S anchez et al 2018. The collection of biological samples is of particular interest, as drones are potentially a noninvasive tool with minimal impact on the animals (Christiansen et al 2016).…”

Foraging rates of ram‐filtering North Atlantic right whales

“…Here, they obtain food with high energy density (Davies, Vanderlaan, Smedbol, & Taggart, ; Michaud & Taggart, ), which allows rapid accumulation of energy over a short period of time. The energy acquired during a foraging season facilitates the growth of dependent calves, the energetic recovery of lactating females (Christiansen et al, ; Miller, Best, Perryman, Baumgartner, & Moore, ; Miller et al, ) and the storage of energy for future demands. Accumulated lipid stores are required to sustain individuals during prolonged fasting migrations, are critical for successful calving and nurture (Christiansen et al, ), and can buffer against effects from human stressors, including unanticipated energetically costly life‐history events such as entanglement (van der Hoop, Corkeron, & Moore, ).…”

“…Here, they obtain food with high energy density (Davies, Vanderlaan, Smedbol, & Taggart, 2015;Michaud & Taggart, 2007), which allows rapid accumulation of energy over a short period of time. The energy acquired during a foraging season facilitates the growth of dependent calves, the energetic recovery of lactating females (Christiansen et al, 2018;Miller, Best, Perryman, Baumgartner, & Moore, 2012;Miller et al, 2011) and the storage of energy for future demands.…”

“…Accumulated lipid stores are required to sustain individuals during prolonged fasting migrations, are critical for successful calving and nurture (Christiansen et al, 2018), and can buffer against effects from human stressors, including unanticipated energetically costly life-history events such as entanglement (van der Hoop, Corkeron, & Moore, 2016).…”