Nico Lübcker

Obtaining longitudinal endocrinological data from free-ranging animals remains challenging. Steroid hormones can be extracted sequentially from non-invasively sampled biologically inert keratinous tissues, such as feathers, nails, hair and whiskers. However, uncertainty regarding the type and levels of steroids incorporated into such tissues compli...

Changes in the nutritional status of free-ranging animals have a strong influence on individual fitness, yet it remains challenging to monitor longitudinally. Nitrogen (δ15N) and carbon (δ13C) isotope values measured chronologically along the length of metabolically inert keratinous tissues can be used as a nutritional biomarker to retrospectively...

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...

The degree of dietary generalization versus specialization exhibited by populations can impact their ability to respond to changing environmental conditions. Naturally shed hair and epidermis are easily collected and may provide a suitable substrate for stable isotope analysis to assess trophic niche specialization. Whether fasting influences the i...

Income and capital breeding represent opposing ends of a continuum of reproductive strategies. Quantifying nutrient allocation to reproduction is challenging, but recent advances in compound‐specific stable isotope analysis hold promise for tracing the source of individual compounds allocated to reproduction. Here, we describe a novel approach of u...

The Southern Ocean is a major sink of anthropogenic CO2 and an important foraging area for top trophic level consumers. However, iron limitation sets an upper limit to primary productivity. Here we report on a considerably dense late summer phytoplankton bloom spanning 9000 km2 in the open ocean of the eastern Weddell Gyre. Over its 2.5 months dura...

Tracing how free-ranging organisms interact with their environment to maintain water balance is a difficult topic to study for logistical and methodological reasons. We use a novel combination of triple-oxygen stable isotope analyses of water extracted from plasma (δ¹⁶O, δ¹⁷O, δ¹⁸O) and bulk tissue carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes of feat...

The distribution, density and percentage contribution of pack ice seals during ship-board censuses in the marginal sea ice zone beyond the Lazarev Sea in spring 2019 are presented. Adult/juvenile crabeater seals ( n = 19), leopard seals ( n = 3) and Ross seals ( n = 10) were sighted during 582.2 nm of censuses along the ship’s track line in the are...

Can the carbon and nitrogen isotope values of offspring be used as a proxy for their mother’s diet? Using foetal physiology to interpret bulk tissue and amino acid δ15N values Supplementary Materials.

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...

Understanding the underlying ecological factors that affect the distribution patterns of organisms is vital for their conservation. Cephalopods such as giant warty squids Moroteuthopsis longimana are important in the diets of marine predators, including grey-headed albatrosses Thalassarche chrysostoma , yet our understanding of their habitat and tr...

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 P...

ABSTRACT: Insight into the trophic ecology of marine predators is vital for understanding their ecosystem role and predicting their responses to environmental change. Juvenile southern elephant seals (SES) Mirounga leonina are considered generalist predators within the Southern Ocean. Although mesopelagic fish and squid dominate their stomach lavag...

Prey selection for models: A Bayesian statistical mixing modelling approach was used for the dietary reconstruction, using the Stable Isotope Analysis in R (SIAR v. 4.2) package (Parnell et al. 2010). The SIAR method utilises a tissue-and species-specific trophic discrimination factor (TDF) to adjust prey isotopic values to the isotopic values obta...

Herein, we demonstrate how southern elephant seals whiskers can provide fine-scale dietary data. We used the isotopic data contained in the whiskers segments to quantify the contribution of crustaceans to the diet of juvenile southern elephant seals at Marion Island, in the Southern Ocean.

The alien invasive silver carp Hypophthalmichthys molitrix established a self-sustaining feral population in an oligotrophic impoundment, Flag Boshielo Dam, in South Africa. The ability of this population to persist in a dam with low algal biomass (median annual suspended chlorophyll a = 0.08 µg l⁻¹), and limited access to rivers considered large e...

Stable isotopes provide a powerful, indirect approach to assess the trophic ecology of individuals on a spatial and temporally integrated basis (especially when combined with telemetry). However, using stable isotopes requires accurate, species-specific quantification of the period of biomolecule deposition in the sampled tissue. Sequentially sampl...

Diet seems to be a key factor driving diversity and isolation among killer whale populations. Killer whales at Marion Island, Southern Ocean, have been observed preying on seals and penguins but are also know to depredate Patagonian toothfish from longline fishing vessels. However, their diet is poorly known especially when they occur offshore. We...

Predicting the potential geographical distribution and spread of non-native species is of major concern to ecologists. Silver carp Hypophthalmichthys molitrix, ranked as one of the world’s 100 worst invasive species, were introduced into South Africa in 1975, but the potential spread of this invader has not yet been addressed, despite recent studie...

Pansteatitis (yellow fat disease) is ubiquitous in the free‐ranging population of Oreochromis mossambicus from Loskop Reservoir ( LR ), South Africa. The disease is nutritionally mediated and associated with a diet high in polyunsaturated or rancid fats, frequently of fish origin. While piscivory has never been reported in dietary studies of O. mos...

Nile crocodile (Crocodilus niloticus) mass mortality events in the Olifants River between the Letaba River confluence in South Africa and Lake Massingir in Mozambique have been attributed to pansteatitis: a disease that affects fat depots of the animals. The disease is also found in sharptooth catfish (Clarias gariepinus) in the same area, and the...