On the interplay between hypothermia and reproduction in a high arctic ungulate

For free-ranging animals living in seasonal environments, hypometabolism (lowered metabolic rate) and hypothermia (lowered body temperature) can be effective physiological strategies to conserve energy when forage resources are low. To what extent such strategies are adopted by large mammals living under extreme conditions, as those encountered in the high Arctic, is largely unknown, especially for species where the gestation period overlaps with the period of lowest resource availability (i.e. winter). Here we investigated for the first time the level to which high arctic muskoxen (Ovibos moschatus) adopt hypothermia and tested the hypothesis that individual plasticity in the use of hypothermia depends on reproductive status. We measured core body temperature over most of the gestation period in both free-ranging muskox females in Greenland and captive female muskoxen in Alaska. We found divergent overwintering strategies according to reproductive status, where pregnant females maintained stable body temperatures during winter, while non-pregnant females exhibited a temporary decrease in their winter body temperature. These results show that muskox females use hypothermia during periods of resource scarcity, but also that the use of this strategy may be limited to non-reproducing females. Our findings suggest a trade-of between metabolically driven energy conservation during winter and sustaining foetal growth, which may also apply to other large herbivores living in highly seasonal environments elsewhere.publishedVersio

Predicting global killer whale population collapse from PCB pollution

This research was supported by grants to J.-P.D. from the Canadian National Science and Engineering Research Council (NSERC) (PGSD3-443700-2013) and Aarhus University’s Graduate School and Science and Technology (GSST) and Department of Bioscience; and by funding from the Danish DANCEA program (MST-112-00171 and MST-112-00199); the Defra, Scottish and Welsh Governments (for CSIP/SMASS/CEFAS); and the Icelandic Research Fund (i. Rannsóknasjóður; grant no. 120248042). B.M. was supported by funding from NERC (grant no. SMRU 10001). This paper is a contribution from the BONUS BALTHEALTH project, which has received funding from BONUS (Art. 185), funded jointly by the EU, Innovation Fund Denmark, Forschungszentrum Jülich GmbH, German Federal Ministry of Education and Research (grant no. FKZ 03F0767A), Academy of Finland (decision no. 311966), and Swedish Foundation for Strategic Environmental Research.Killer whales (Orcinus orca) are among the most highly polychlorinated biphenyl (PCB)–contaminated mammals in the world, raising concern about the health consequences of current PCB exposures. Using an individual-based model framework and globally available data on PCB concentrations in killer whale tissues, we show that PCB-mediated effects on reproduction and immune function threaten the long-term viability of >50% of the world’s killer whale populations. PCB-mediated effects over the coming 100 years predicted that killer whale populations near industrialized regions, and those feeding at high trophic levels regardless of location, are at high risk of population collapse. Despite a near-global ban of PCBs more than 30 years ago, the world’s killer whales illustrate the troubling persistence of this chemical class.PostprintPeer reviewe

Le Poète, Ou Mémoires D'Un Homme De Lettres : écrits par lui-même

[Pierre Jean-Baptiste Desforges]Vorlageform der Veröffentlichungsangabe: A Hambourg : Chez Les Principaux Libraire

Maternal Transfer and Long-Term Population Effects of PCBs in Baltic Grey Seals Using a New Toxicokinetic–Toxicodynamic Population Model

Empirical evidence has shown that historical exposure of polychlorinated biphenyls (PCBs) to Baltic grey seals not only severely affected individual fitness, but also population growth rates and most likely caused the retarded recovery rate of the depleted population for decades. We constructed a new model which we term a toxicokinetic–toxicodynamic (TKTD) population model to quantify these effects. The toxicokinetic sub-model describes in detail the bioaccumulation, elimination and vertical transfer from mother to offspring of PCBs and is linked to a toxicodynamic model for estimation of PCB-related damage, hazard and stress impacts on fertility and survival rates. Both sub-models were linked to a Leslie matrix population model to calculate changes in population growth rate and age structure, given different rates of PCB exposure. Toxicodynamic model parameters related to reproductive organ lesions were calibrated using published historical data on observed pregnancy rates in Baltic grey seal females. Compared to empirical data, the TKTD population model described well the age-specific bioaccumulation pattern of PCBs in Baltic grey seals, and thus, the toxicokinetic parameters, deduced from the literature, are believed to be reliable. The model also captured well the general effects of PCBs on historical population growth rates. The model showed that reduced fertility due to increased PCB exposure causes decreased vertical transfer from mother to offspring and in turn increased biomagnification in non-breeding females. The developed TKTD model can be used to perform population viability analyses of Baltic grey seals with multiple stressors, also including by-catches and different hunting regimes. The model can also be extended to other marine mammals and other contaminants by adjustments of model parameters and thus provides a test bed in silico for new substances. CC BY 4.0© 2022, The Author(s)© 2022 Springer Nature Switzerland AG. Part of Springer Nature.Published: 15 October 2022Open access funding provided by University of Skövde. Funding was provided by Viltforskningsanslaget, Swedish Environmental Protection Agency (2021-00028) and the BONUS program BaltHealth (Art. 185). Mauritsson was partially supported by the Swedish research council, grant/award number 2018-05523. The authors declare that no other support were received during the preparation of the manuscript.</p

High Mercury levels: are Arctic seals “what” or “where” they eat?

In contrast to other regions of the world or even sympatric terrestrial species, Arctic marine predators continue to accumulate increasing levels of Mercury (Hg) in their tissues. Hg bioaccumulation in Arctic seals may be linked to their particular life style, or to their extreme physiological adaptations, such as a short period of lactation with very fatty milk. The present study aimed at assessing how dietary resources and hunting distribution influence Hg exposure in Arctic true seals, through the integration of isotopic tracers with Hg levels. Indeed stable Carbon, Nitrogen and Sulfur isotope ratios can be successfully used to study species’ ecology and indicate potential contamination sources. For this reason hair was sampled from free-ranging hooded seal Cystophora cristata (Cc, n = 25) and harp seal Phoca groenlandicus (Pg, n = 36) in the pack ice of the Greenland Sea (near Jan Mayen). Stable isotope ratios were acquired via Isotope Ratio – Mass Spectrometry and used to model stable isotope niches (Standard Ellipses Areas; SEAs). Iterative Bayesian estimations were used to calculate the % of overlap between the ellipses. Total-Hg (T-Hg) concentrations were measured via Atomic absorption spectroscopy. The Cc δ15N-δ13C SEA (3.02‰2) was larger than that of Pg (2.64‰2) in 69% of model runs and did not overlap (22%). This may reflect Cc wide migrations down to warmer sub-Arctic waters compared to Pg that have an exclusively Arctic distribution. Moreover, while Cc hunt for a variety of bentho-pelagic prey (e.g., halibut, redfish, cod and squid) during long dives down to 1000m, Pg feed mostly on pelagic schooling fish between 100 and 400m of depth. The Cc δ15N-δ34S SEA (21‰2) was also larger than that of Pg (16‰2) in 85% of model runs; but this time the ellipses overlapped considerably (52%). Indeed both species presented two distinct groups along the δ34S axis: the most 34S enriched group included adult individuals, while the 34S depleted one included juveniles. This may result from the shallower hunting behavior of juvenile seals and their reliance on ice food webs. Finally, the larger migratory patterns and deep feeding behavior of Cc seem to determine significantly higher levels of T-Hg levels in this species (3.2±3.6 µg g-1) with respect to Pg (1.7±0.9µg g-1; U = 322, P = 0.01), as a consequence of (1) the higher number of Hg sources in sub-Arctic waters and (2) Hg remobilization from the sea bottom and its uptake by benthic food webs.SODYMARS (FRIA scholarship