Female body condition affects foetal growth in a capital breeding mysticete

Abstract

Summary1. Understanding how female body condition (FBC) influences foetal development, and hence offspring production, is fundamental for our understanding of species reproductive physiology and life history. 2. We investigated the effects of FBC on foetus growth in common minke whales. Pregnant minke whales were sampled around Iceland during the summer feeding seasons between 2003 and 2007 and the length and weight of their foetuses were measured. FBC was modelled as the relative difference between measured blubber volume and the average expected blubber volume of individual whales. Generalized linear models were used to test the effect of FBC on foetus length, while accounting for the daily growth in foetus size through gestation, as well as other covariates. 3. Foetus length increased curvilinearly through the study period at an average rate of 0Á964 cm day À1 (SE = 0Á138). The effect of FBC on foetal length was nonlinear, showing an almost linear positive relationship for females in poorer body condition (FBC < 0), which levelled off at better body conditions (FBC > 0). 4. The curvilinear relationship between FBC and foetus growth was confirmed by fitting a generalized additive model and by running separate analyses on two subsets of data separating females in poorer and better condition. 5. Our findings suggest that females that are in poorer body condition reduce their energetic investment in their foetus proportionately to their condition, most likely to help maintain a high survival probability. That foetus length did not increase for females in better body condition suggests that females have an upper limit on the amount of energy they will or can invest in their foetus. Reducing the size at birth by reducing the gestation period is also unlikely, because the reproductive cycle of balaenopterids is strongly linked to their seasonal migration between feeding grounds and breeding grounds. This study is the first to demonstrate that FBC can affect foetus growth in a capital breeding mysticete.

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

“…Interestingly, our body lipid–length equations illustrate that the longer pregnant females stored relatively more energy than the shorter pregnant females, thus having more energy to transfer to their offspring [13]. Maximizing energy stores is critical for capital breeders, who must trade off their own body condition to maximize offspring survival [17,67]. Maternal energy stores have been shown to influence fecundity [68], fetal growth [67], weaning mass [69,70] and, thus, ultimately survival [70,71].…”

“…Maximizing energy stores is critical for capital breeders, who must trade off their own body condition to maximize offspring survival [17,67]. Maternal energy stores have been shown to influence fecundity [68], fetal growth [67], weaning mass [69,70] and, thus, ultimately survival [70,71]. Large maternal energy stores enable longer fasting periods for the mothers [72,73], which in turn provide calves with a thermoregulatory benefit of longer duration in the warm waters of their breeding areas [15].…”

Linking Behavior to Vital Rates to Measure the Effects of Non‐Lethal Disturbance on Wildlife

“…From this we can estimate the relative body condition of an impacted female, FBC Imp (%) (Christiansen et al . ): …”

Cytochrome P450 isozyme protein verified in the skin of southern hemisphere humpback whales (Megaptera novaeangliae): Implications for biochemical biomarker assessment

“…The challenge remains in valance these two factors. For a more accurate index it have been advocate that in addition to morphometry measurements, parameters such as age or reproductive class, the day in the feeding season or the stage of the annual reproductive cycle, year and sex, that play a fundamental role in blubber variation, should be consider in the index (Boyd et al, 2010a;Christiansen et al, 2014). The need to include these parameters is especially evident if one takes into account that body mass can change for different reasons other than change in lipid content (Boyd et al, 2010a).…”

“…This correlation with energy reserves is extended to offspring viability and survival. Early-term abortion as well as adverse outcomes for fetal growth, neonatal mass, weaning mass and calf body condition are just some of the end-points studied which have been correlated with maternal energy reserves (Atkinson and Ramsay, 1995;Christiansen et al, 2016;Christiansen et al, 2014;Knowlton et al, 1994).…”