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Summary: Differences in the diets of urban and rural avian predators could indicate potential niche vulnerability in a particular habitat. This study compares the core-isotopic niche areas and diet disparity of a declining peri-urban Verreaux's Eagle Aquila verreauxii population with a stable rural population in South Africa. In addition to stable isotope analyses, the diet of the peri-urban Verreaux's Eagles was investigated using camera trap footage of prey delivered during the nesting season. Dominant prey consisted of species with a mixed diet of plants with a C3 and/or C4 photosynthetic pathway (browsers and grazers). Rock hyrax Procavia capensis contributed 60% of the total diet composition, scrub hare Lepus saxatilis 26% and Helmeted Guineafowl Numida meleagris 22%. The core-isotopic niche area for each population was calculated using bulk carbon (δ13C) and nitrogen (δ15N) stable isotope values chronological measured along the length of 18 feathers from 21 nests. The isotopic niche of the rural eagle population revealed that they consume prey from multiple trophic levels with a C3-plant-dominated prey base (browsers), likely including small carnivores. In contrast the isotopic niche of the peri-urban Verreaux's Eagles correlated with the mixed mammalian and avian food-niche determined from camera trapping, confirming that the peri-urban population mainly hunted three abundant species that are all narrowly associated with modified human habitats. The decline in the Magaliesberg Verreaux's Eagle population is, therefore, unlikely to be due to constraints in their dietary niche, as raptors benefit from the diversity and abundance of human-commensal prey associated with the peri-urban habitats. [ABSTRACT FROM AUTHOR]

The measurement of bulk tissue nitrogen (δ15N) and carbon isotope values (δ13C) chronologically along biologically inert tissues sampled from offspring can provide a longitudinal record of their mothers' foraging habits. This study tested the important assumption that mother–offspring stable isotope values are positively and linearly correlated. In addition, any change in the mother–offspring bulk tissues and individual amino acids that occurred during gestation was investigated. Whiskers sampled from southern elephant seal pups (Mirounga leonina) and temporally overlapping whiskers from their mothers were analyzed. This included n  = 1895 chronologically subsampled whisker segments for bulk tissue δ15N and δ13C in total and n  = 20 whisker segments for amino acid δ15N values, sampled from recently weaned pups (n  = 17), juvenile southern elephant seals (SES) < 2 years old (n  = 23) and adult female SES (n  = 17), which included nine mother–offspring pairs. In contrast to previous studies, the mother–offspring pairs were not in isotopic equilibrium or linearly correlated during gestation: the Δ15N and Δ13C mother–offspring offsets increased by 0.8 and 1.2‰, respectively, during gestation. The foetal bulk δ15N values were 1.7 ± 0.5‰ (0.9–2.7‰) higher than mothers' δ15N values before birth, while the foetal δ13C increased by ~1.7‰ during gestation and were 1.0 ± 0.5‰ (0.0–1.9‰) higher than their mothers' δ13C at the end of pregnancy. The mother–offspring serine and glycine Δ15N differed by ~4.3‰, while the foetal alanine δ15N values were 1.4‰ lower than that of their mothers during the third trimester of pregnancy. The observed mother–offspring δ15N differences are likely explained by shuttling of glutamate–glutamine and glycine–serine amongst skeletal muscle, liver, placenta and foetal tissue. Foetal development relies primarily on remobilized endogenous maternal proteinaceous sources. Researchers should consider foetal physiology when using offspring bulk tissue isotope values as biomarkers for the mother's isotopic composition as part of monitoring programmes. [ABSTRACT FROM AUTHOR]

The article focuses on Micruroides euryxanthus, an ophiophagous snake, and reports the consumption of Salvadora deserticola (Big Bend Patchnose Snake) as a new prey species for Micruroides euryxanthus.

The distribution, density and percentage contribution of pack ice pinnipeds during ship-board censuses in the eastern Weddell Sea in summer 2015/2016 are presented. Of the four true pack ice seal species encountered, crabeater seals predominated. Despite the low survey effort, Ross seals continued to be relatively abundant in the pack ice off the Princess Martha Coast in mid-January 2016, similar to the situation here in the 1970s. Censusing of Ross seals is ideally carried out in late January/early February when the species' haulout probability is at its maximum and the seals are gathered in the limited summer pack ice to moult. [ABSTRACT FROM AUTHOR]

The measurement of bulk tissue nitrogen (δ 15 N) and carbon isotope values (δ 13 C) chronologically along biologically inert tissues sampled from offspring can provide a longitudinal record of their mothers' foraging habits. This study tested the important assumption that mother-offspring stable isotope values are positively and linearly correlated. In addition, any change in the mother-offspring bulk tissues and individual amino acids that occurred during gestation was investigated. Whiskers sampled from southern elephant seal pups ( Mirounga leonina ) and temporally overlapping whiskers from their mothers were analyzed. This included n  = 1895 chronologically subsampled whisker segments for bulk tissue δ 15 N and δ 13 C in total and n  = 20 whisker segments for amino acid δ 15 N values, sampled from recently weaned pups ( n  = 17), juvenile southern elephant seals (SES) < 2 years old ( n  = 23) and adult female SES ( n  = 17), which included nine mother-offspring pairs. In contrast to previous studies, the mother-offspring pairs were not in isotopic equilibrium or linearly correlated during gestation: the Δ 15 N and Δ 13 C mother-offspring offsets increased by 0.8 and 1.2‰, respectively, during gestation. The foetal bulk δ 15 N values were 1.7 ± 0.5‰ (0.9-2.7‰) higher than mothers' δ 15 N values before birth, while the foetal δ 13 C increased by ~1.7‰ during gestation and were 1.0 ± 0.5‰ (0.0-1.9‰) higher than their mothers' δ 13 C at the end of pregnancy. The mother-offspring serine and glycine Δ 15 N differed by ~4.3‰, while the foetal alanine δ 15 N values were 1.4‰ lower than that of their mothers during the third trimester of pregnancy. The observed mother-offspring δ 15 N differences are likely explained by shuttling of glutamate-glutamine and glycine-serine amongst skeletal muscle, liver, placenta and foetal tissue. Foetal development relies primarily on remobilized endogenous maternal proteinaceous sources. Researchers should consider foetal physiology when using offspring bulk tissue isotope values as biomarkers for the mother's isotopic composition as part of monitoring programmes., (© The Author(s) 2020. Published by Oxford University Press and the Society for Experimental Biology.)