Maternal effects shape offspring physiological condition but do not senesce in a wild mammal

Maternal β-carotene supplementation improves offspring growth, development, immunity, and intestinal microbiota in chickens via immune-mediated and microbial-mediated maternal effects

In poultry, maternal nutritional interventions affect the development and intestinal microbiota of embryos. β-carotene possesses immune-boosting and gut microbiota-regulating properties. We examined the influences of supplementing hen diets with β-carotene on offspring growth, development, and immunity to determine whether maternal β-carotene benefits offspring health. Our findings showed that β-carotene increased serum IgG, lysozyme, and beta-defensins in hens, subsequently elevated these parameters in the serum of their offspring, and promoted their growth and development. In offspring, there were significant positive correlations between body weights and intestinal development indices with serum lysozyme and beta-defensin levels. The augmentation of vertical transfer of lysozyme and beta-defensins may be linked to the increased expression of these genes in the maternal jejunum. The number of shared taxa between the magnum and offspring gut is higher than that between the maternal gut and offspring. Among the taxa, were increased in the maternal magnum and gut microbiome, only the Caloramator abundance was significantly elevated in the guts of 21-day-old offspring. In conclusion, maternal β-carotene inclusion improves offspring growth and development, potentially through enhancing maternal intestinal immunity and thereby promoting immune-mediated maternal effects. The vertical transfer of maternal microbes to offspring exhibits selectivity in chicken.

Integrating physiology into movement ecology of large terrestrial mammals

Movement paths are influenced by external factors and depend on an individual's navigation capacity (Where to move?), motion capacity (How to move?) and are ultimately driven by internal physiological state (Why move?). Despite physiology underlying most aspects of this movement ecology framework, the physiology-movement nexus remains understudied in large terrestrial mammals. Within this Commentary, we highlight the physiological processes that underpin the movement ecology framework and how integrating physiological measurements can provide mechanistic insights that may enhance our understanding of the drivers of animal movement. We focus on large terrestrial mammals, which are well represented within the movement ecology literature but are under-represented in movement studies that integrate physiological state. Recent advances in biologging technology allow for physiological variables, such as heart rate and body movements, to be recorded remotely and continuously in free-living animals. Biologging of body temperature may provide additional insights into the physiological states driving movement. Body temperature not only provides a measure of thermal stress, but also an index of animal wellbeing through quantification of nutrition, hydration, reproductive and disease states that may drive animal movements. Integrating measures of body temperature with fine-scale GPS locations may provide insights into causality and improve our mechanistic understanding of animal movement, which is crucial for understanding population performance and monitoring reintroduction success. We recommend that baseline studies are undertaken, linking animal movement to the underlying physiological mechanisms, to allow for the development of realistic predictive models to improve conservation efforts in the Anthropocene.

Energetic cost of gestation and prenatal growth in humpback whales

Improving our understanding of energy allocation in reproduction is key for accurately parameterizing bioenergetic models to assess population responses to environmental perturbations and anthropogenic disturbance. We quantified the energetic cost of gestation in humpback whales (Megaptera novaeangliae) using historical whaling records, non-invasive unoccupied aerial system (UAS) photogrammetry and post mortem tissue samples. First, we estimated relative birth size using body length measurements of 678 mother-fetus pairs from historical whaling records and 987 mother-calf pairs measured in situ using UAS-photogrammetry. The total energetic cost of gestation includes fetal growth (FG), heat increment of gestation and placental tissue development. FG was modelled from conception to birth, with fetal volume and mass estimated using the volume-to-length relationship of perinatal calves and published humpback whale tissue composition estimates. Tissue-specific energy content was quantified using post mortem bone, muscle, viscera and blubber samples from a neonatal humpback whale. Placental tissue development was estimated using humpback whale placental tissue and published equations. Relative birth length was found to be 33.75% (95% CI: 32.10-34.61) of maternal length. FG rates and absolute birth size increased with maternal length, with exponential growth in fetal length, volume and mass resulting in minimal energetic costs over the first two quadmesters (0.01-1.08%) before increasing significantly in the final quadmester (98.92%). Gestational heat constituted the greatest energetic cost (90.42-94.95%), followed by fetal (4.58-7.76%) and placental (0.37-1.83%) tissue growth. Our findings highlight the energetic costs endured by capital breeding females preceding parturition, with the most substantial energetic costs of gestation coinciding with migration and fasting. KEY POINTS: We quantified the energetic cost of gestation using body length measurements of mother-fetus pairs from historical whaling records, length estimates of mother-calf pairs measured in situ using aerial photogrammetry and post mortem tissue samples. Fetal growth rates and birth size increased with maternal length, with fetal length, volume and mass increasing exponentially over gestation. Energetic costs over the first two quadmesters were negligible (0.01-1.08%) before increasing significantly in the final quadmester (98.92%). Though larger females incur nearly twice the energetic cost of smaller females, they are likely buffered by greater absolute energy reserves, suggesting smaller females may be less resilient to perturbations in energy balance. We demonstrate the significant energetic costs incurred by pregnant humpback whales, with most of the energetic expenditure occurring over the final 100 days of gestation. Late-pregnant females are, therefore, particularly vulnerable to disruptions in energy balance, given periods of greatest energetic stress coincide with fasting and migration.

Maternal investment, body condition and calf growth in humpback whales

Given recent declines in North Pacific humpback whale (Megaptera novaeangliae) reproductive output and calf survival, there is additional urgency to better understand how mother-calf pairs allocate energy resources across their migratory cycle. Here, unoccupied aerial system (UAS; or drone) photogrammetry was used to quantify the body size and condition (BC) of humpback whales on their Hawai'i (HI) breeding and Southeast Alaska (SEAK) feeding grounds. Between 2018 and 2022, we collected 2410 measurements of 1659 individuals. Rates of change in body volume (BV) and length (BL) were quantified using 803 repeat measurements of 275 individuals. On average, HI mothers lost 0.106 m3 or 96.84 kg day-1 while fasting, equivalent to 2641 MJ day-1 or 830 kg of krill and 424 kg of Pacific herring daily. HI calf BV and BL increased by 0.035 m3 and 2.6 cm day-1, respectively. In SEAK, maternal BV increased by 0.015 m3 or 14.54 kg day-1 (367 MJ day-1), while calf BV and BL increased by 0.039 m3 and 0.93 cm day-1, respectively. Maternal investment in calf growth correlated with both female BL and BC, with larger females producing larger, faster-growing calves. Finally, using 330 measurements from 156 females, we quantified differences in BC increase over four feeding seasons. Lactating females exhibited an average BC increase of 6.10%, half that of unclassified females (13.51%) and six times lower than pregnant females (37%). These findings represent novel insights into the life history of humpback whales across their migratory cycle, providing key baseline data for bioenergetic models elucidating the effects of anthropogenic disturbance and rapidly changing ocean ecosystems. KEY POINTS: On average, Hawai'i (HI) mothers lost 0.106 m3 or 96.84 kg day-1, equivalent to 2641 MJ day-1. Over a 60 day period, this corresponded to an estimated mean energetic cost of 158 GJ, or ≈50 tons of krill or ≈25 tons of Pacific herring, surpassing the total energetic cost of gestation estimated for humpback whales of similar length. In Southeast Alaska (SEAK), maternal body volume (BV) increased by just 0.015 m3 or 14.54 kg day-1 (367 MJ day-1). Further, SEAK lactating females showed the slowest rates of growth in body width and condition over a 150 day period compared to non-lactating females. Maternal investment in calf growth correlated with both maternal length and body condition, with larger females producing larger, faster-growing calves. In HI, however, the ratio between maternal BV lost and calf BV gained (conversion efficiency) was relatively low compared to other mammals.

Increased summer temperature is associated with reduced calf mass of a circumpolar large mammal through direct thermoregulatory and indirect, food quality, pathways

Climate change represents a growing ecological challenge. The (sub) arctic and boreal regions of the world experience the most rapid warming, presenting an excellent model system for studying how climate change affects mammals. Moose (Alces alces) are a particularly relevant model species with their circumpolar range. Population declines across the southern edge of this range are linked to rising temperatures. Using a long-term dataset (1988-1997, 2017-2019), we examine the relative strength of direct (thermoregulatory costs) and indirect (food quality) pathways linking temperature, precipitation, and the quality of two important food items (birch and fireweed) to variation in moose calf mass in northern Sweden. The direct effects of temperature consistently showed stronger relationships to moose calf mass than did the indirect effects. The proportion of growing season days where the temperature exceeded a 20 °C threshold showed stronger direct negative relationships to moose calf mass than did mean temperature values. Finally, while annual forb (fireweed) quality was more strongly influenced by temperature and precipitation than were perennial (birch) leaves, this did not translate into a stronger relationship to moose calf weight. The only indirect path with supporting evidence suggested that mean growing season temperatures were positively associated with neutral detergent fiber, which was, in turn, negatively associated with calf mass. While indirect impacts of climate change deserve further investigation, it is important to recognize the large direct impacts of temperature on cold-adapted species.