Response to “Resilience of harbor porpoises to anthropogenic disturbance: Must they really feed continuously?”

Wisniewska, Danuta M.; Johnson, Mark; Teilmann, Jonas; Rojano-Doñate, Laia; Shearer, J. M.; Sveegaard, Signe; Miller, Lee A.; Siebert, Ursula; Madsen, Peter T.

doi:10.1111/mms.12463

Cited by 17 publications

(14 citation statements)

References 9 publications

(20 reference statements)

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“…Higher variability of FMR in wild animals could also be related to their much more dynamic lifestyle. Wild individuals target different prey and employ varying foraging strategies (Wisniewska et al, 2016), and are exposed to different external natural and anthropogenic stressors, such as boats and other human activities (Wisniewska et al, 2018b), that may temporarily increase their metabolic rate. Additionally, we do not know whether some of our tagged animals were sick or had any breathing anomalies.…”

Section: Discussionmentioning

confidence: 99%

High field metabolic rates of wild harbour porpoises

Rojano-Doñate

McDonald

Wisniewska

et al. 2018

Journal of Experimental Biology

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Reliable estimates of field metabolic rates (FMRs) in wild animals are essential for quantifying their ecological roles, as well as for evaluating fitness consequences of anthropogenic disturbances. Yet, standard methods for measuring FMR are difficult to use on freeranging cetaceans whose FMR may deviate substantially from scaling predictions using terrestrial mammals. Harbour porpoises (Phocoena phocoena) are among the smallest marine mammals, and yet they live in cold, high-latitude waters where their high surface-tovolume ratio suggests high FMRs to stay warm. However, published FMR estimates of harbour porpoises are contradictory, with some studies claiming high FMRs and others concluding that the energetic requirements of porpoises resemble those of similar-sized terrestrial mammals. Here, we address this controversy using data from a combination of captive and wild porpoises to estimate the FMR of wild porpoises. We show that FMRs of harbour porpoises are up to two times greater than for similar-sized terrestrial mammals, supporting the hypothesis that small, carnivorous marine mammals in cold water have elevated FMRs. Despite the potential cost of thermoregulation in colder water, harbour porpoise FMRs are stable over seasonally changing water temperatures. Varying heat loss seems to be managed via cyclical fluctuations in energy intake, which serve to build up a blubber layer that largely offsets the extra costs of thermoregulation during winter. Such high FMRs are consistent with the recently reported high feeding rates of wild porpoises and highlight concerns about the potential impact of human activities on individual fitness and population dynamics.

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Section: Discussionmentioning

confidence: 99%

High field metabolic rates of wild harbour porpoises

Rojano-Doñate

McDonald

Wisniewska

et al. 2018

Journal of Experimental Biology

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“…), gobies (Gobiidae), gadoids (e.g., Atlantic cod Gadus morhua and whiting Merlangius merlangus), clupeids (e.g., Atlantic herring Clupea harengus and sprat Sprattus sprattus), and flatfish (Pleuronectiformes) (Benke et al, 1998;Gilles, 2008;Leopold et al, 2015;Andreasen et al, 2017). As small, endotherm predators living in temperate waters, harbor porpoises have limited capacity to store energy (Koopman et al, 2002) and high metabolic rates (Spitz et al, 2012;Rojano-Doñate et al, 2018); also high feeding rates were reported for wild, mainly juvenile, harbor porpoises from the Baltic Sea (Wisniewska et al, 2016(Wisniewska et al, , 2018a. If such feeding rates were generally representative for harbor porpoises (but see Hoekendijk et al, 2018), this would imply that harbor porpoises have high energetic requirements and consequently are especially vulnerable to any anthropogenic disturbance.…”

Section: Introductionmentioning

confidence: 99%

Small Cetacean in a Human High-Use Area: Trends in Harbor Porpoise Abundance in the North Sea Over Two Decades

et al. 2021

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The North Sea is one of the most heavily used shelf regions worldwide with a diversity of human impacts, including shipping, pollution, fisheries, and offshore constructions. These stressors on the environment can have consequences for marine organisms, such as our study species, the harbor porpoise (Phocoena phocoena), which is regarded as a sentinel species and hence has a high conservation priority in the European Union (EU). As EU member states are obliged to monitor the population status, the present study aims to estimate trends in absolute harbor porpoise abundance in the German North Sea based on almost two decades of aerial surveys (2002–2019) using line-transect methodology. Furthermore, we were interested in trends in three Natura2000 Special Areas of Conservation (SACs), which include the harbor porpoise as designated feature. Trends were estimated for each SAC and two seasons (spring and summer) as well as the complete area of the German North Sea. For the trend analysis we applied a Bayesian framework to a series of replicated visual surveys, allowing to propagate the error structure of the original abundance estimates to the final trend estimate and designed to deal with spatio-temporal heterogeneity and other sources of uncertainty. In general, harbor porpoise abundance decreased in northern areas and increased in the south, such as in the SAC Borkum Reef Ground. A particularly strong decline with a high probability (94.9%) was detected in the core area and main reproduction site in summer, the SAC Sylt Outer Reef (−3.79% per year). The overall trend for the German North Sea revealed a decrease in harbor porpoise abundance over the whole study period (−1.79% per year) with high probability (95.1%). The assessment of these trends in abundance based on systematic monitoring should now form the basis for adaptive management, especially in the SAC Sylt Outer Reef, where the underlying causes and drivers for the large decline remain unknown and deserve further investigation, also in a regional North Sea wide context.

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“…Secondly a cessation of echolocation activity can occur, either in CPM which is indicative of the porpoises' exploratory behavior (i.e., more clicks in a minute indicate exploring objects a shorter distances), PPM which is an indicator of porpoise presence and general use of echolocation or BPM/PPM indicative of feeding and social communication. A lowering in buzzing has been observed during the passing of noisy vessels (Wisniewska et al, 2018), while CPM and PPM was significantly reduced during wind farm construction and operation (Teilmann and Carstensen, 2012). Changes in behavior may lead to a reduction in echolocation parameters, for example when swimming at the surface, where sound propagation is reduced (van Beest et al, 2018b), if source level of the emitted echolocation clicks are reduced by the animal (Teilmann et al, 2002), or a change from pelagic to bottom feeding occur (Schaffeld et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

“…A few disturbance events are likely insignificant to the energetic status of a porpoise, but these disturbances may have fitness consequences when repeated frequently (Wisniewska et al, 2018). Porpoises are small cetaceans living in a relatively cold environment, resulting in a high demand for energy (Rojano-Donþate et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

“…Porpoise detections were aggregated into hourly values of; (i) number of porpoise clicks per minute (CPM), (ii) porpoise positive minutes (PPMs) in binary output (i.e., either no click train or at least one click train containing at least five clicks within a given minute, as defined by Clausen et al, 2018) and (iii) the ratio of minutes with high repetition rate click trains called buzzes (i.e., <15 ms between clicks) to minutes with any click train calculated per hour (BPM/PPM). Buzzing is presumed to be indicative of foraging behavior (Carlström, 2005;Todd et al, 2009;Wisniewska et al, 2016Wisniewska et al, , 2018 However, social communication is similar to buzzes and may be interpreted as feeding buzzes. One study has estimated that about 26% of all high-repetition rate click trains may be social calls and therefore not related to feeding (Sørensen et al, 2018).…”

Section: Porpoise Detectionsmentioning

confidence: 99%

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