Dorota Kidawa

The effects of sex, age, season and habitat on diet of the red fox Vulpes vulpes in northeastern Poland

The diet of the red fox Vulpes vulpes was investigated in five regions of northeastern Poland by stomach content analysis of 224 foxes collected from hunters. The red fox is expected to show the opportunistic feeding habits. Our study showed that foxes preyed mainly on wild prey, with strong domination of Microtus rodents, regardless of sex, age, month and habitat. Voles Microtus spp. were found in 73% of stomachs and constituted 47% of food volume consumed. Other food items were ungulate carrion (27% of volume), other mammals (11%), birds (9%), and plant material (4%). Sex- and age-specific differences in dietary diversity were found. Adult males and juvenile foxes had larger food niche breadths than adult females and their diets highly overlapped. Proportion of Microtus voles increased from autumn to late winter. Significant habitat differences between studied regions were found. There was a tendency among foxes to decrease consumption of voles with increasing percentage of forest cover. Based on our findings, red foxes in northeastern Poland can be recognized as a generalist predators, consuming easily accessible and abundant prey. However, high percentage of voles consumed regardless of age, sex, month, or habitats may indicate red fox specialization in preying on Microtus rodents.

Body size variation of a high-Arctic seabird: the dovekie (Alle alle)

Variation in body size among subpopulations of the same species may reflect phenotypic or genetic responses to environmental gradients or geographical distance. Here, we examine geographical variation in the body size of the dovekie (Alle alle), the most numerous high-Arctic seabird. Locations of dovekie breeding sites are largely restricted to the high-Arctic zone of the Atlantic. We compared wing length, head-bill length, body mass, and a body size index of 1,076 birds from nine main colonies spanning a large part of the breeding range of the species. Results suggest morphological variation across the studied populations of dovekies, with a longitudinal increase in body size from west to east. The smallest birds breed in the western part of the population (Greenland and Jan Mayen), middle-sized individuals on Svalbard, and the largest birds (A. a. polaris subspecies) breed in the eastern part of the studied area, Franz Josef Land. Environmental (air temperature, wind speed, and sea surface temperature) and geographical (intercolonial distance) parameters were analyzed to explore potential mechanisms driving differences in body size. The body size of birds increased significantly with decreasing air temperature, but only when the two subspecies were considered. We did not find a relationship between sea surface temperature and body size of birds. Also, no close relationship was revealed between birds’ body size and the geographical distance between colonies. Whether the body size variation of dovekie can be explained by phenotypic plasticity in response to environmental conditions in wintering areas or a pattern of distance-independent gene flow between colonies remains to be explored.

Visual prey availability and distribution of foraging little auks (Alle alle) in the shelf waters of West Spitsbergen

As diving seabirds use vision underwater, it is presumed they should preferentially select sites where their preferred food items are not only abundant but also clearly visible. To test this, we studied the optical properties of the seawater in the West Spitsbergen Shelf, in combination with zooplankton abundance in the feeding grounds of the planktivorous little auks from the nearby colonies in Hornsund. We estimated the relative attractiveness of the foraging sites using a novel parameter—visual prey availability (VPAv), which relates density and proportion of the preferred food item (Calanus glacialis) of the little auk, in total zooplankton, to the optical properties of the seawater. We found a significant positive correlation between the density of foraging little auks and VPAv values. Birds chose areas where C. glacialis was both abundant and clearly visible, because of the clarity of the water and low proportion of other zooplankton species. The birds avoided foraging over the warmer Atlantic-type waters, characterised by a high abundance of zooplankton taxa mostly ignored by birds and where VPAv values were low. VPAv values could potentially also be applied to other visual planktivores for which prey preference and visual acuity are known.

The effects of loggers on the foraging effort and chick-rearing ability of parent little auks

We studied the effects of loggers attached to chick-rearing little auks (Alle alle) on their daily time budget (proportion of time spent in the colony and at sea), foraging activity (duration and proportion of long and short foraging flights), chick provisioning rate and their growth and development on Spitsbergen. We found that experimental parent birds performed shorter but more frequent long foraging flights and reduced the frequency of short foraging flights. They spent more time at the colony and reduced chick provisioning rate compared to control birds. Nestlings reared by experimental parents weighed significantly less at their middle, peak and fledging age and departed colony later than chicks of control parents. Little auks depend on energy-rich copepods associated with cold Arctic waters and are expected to face the climate-induced worsening of the foraging conditions, which may have negative impact on their time/energy budget and survival. The study may help to determine the level of extra effort little auks need to invest to breed successfully.

Unusual hunting and feeding behaviour of polar bears on Spitsbergen

Prolonged chasing of an adult reindeer ( Rangifer tarandus ) by a polar bear ( Ursus maritimus ) was observed both on land and in the sea, in Magdalenefjorden, northwest Spitsbergen. Polar bears were also observed catching black guillemot ( Cepphus grylle ) in the sea in northwest Spitsbergen and feeding on chicks in the arctic tern ( Sterna paradisea ) colony in Hornsund, southwest Spitsbergen. While feeding on seabird species is unsurprising, the prolonged chasing of adult reindeer is unusual for polar bear hunting behaviour. The few documented cases of polar bear hunting reindeer consist of either surprising and killing resting/sleeping prey or stalking and a short rapid chase of the reindeer. Our observations describe new feeding habits of polar bears that may be in response to decreasing seal availability due to shrinking sea-ice cover in the Arctic.

Influence of primary reproductive investments on blood biochemistry, leukocyte profile, and body mass in a small Arctic seabird

ABSTRACT Growing evidence indicates that producing eggs may constitute a considerable cost of reproduction. If female parental care, which in many species exceeds male performance, is added to these initial costs, it may be concluded that females contribute more to reproduction than males. However, this additional burden on females should reduce their survival and skew the usually equal sex ratio, but this is generally not the case. A resolution of this apparent paradox requires studies estimating the parental investments of both sexes at different stages of breeding, with particular focus on the initial reproductive stage. In the present study, egg composition and its energetic value was estimated in the Dovekie (or Little Auk, Alle alle), a seabird exhibiting bi-parental care except for the end of the chick-rearing period, when the female deserts the brood while the male continues the feeding and escorts the chick during fledging. Condition estimates (size-adjusted body mass and several hematological and biochemical parameters, including concentrations of hemoglobin, glucose, cholesterol, and triglycerides, as well as the leukocyte profile) were also examined in both sexes during the prelaying, laying/relaying, and chick-rearing periods. The egg composition and its energy content indicate that the energetic demands of egg production are not as high as previously assumed, and the non-resource–based costs in females seem to be similar to those experienced by males during the mating period (nest site and/or paternity guarding). However, it was also found that females had lower body mass than males throughout the whole breeding season, suggesting overall female-biased costs of reproduction despite very similar parental performance. This suggests that females are more susceptible to the negative effects of reproduction. If so, their earlier brood desertion may be a response to the additive costs of parental investments.

Variation in faecal corticosterone metabolites in an Arctic seabird, the Little Auk (Alle alle) during the nesting period

Glucocorticoids participate in the control of whole body homoeostasis and an organism’s response to stress. Corticosterone, which is the principal glucocorticoid in birds, has been shown to increase in response to different energetic demands and perturbations that individuals have to cope with. In this study, a non-invasive method to examine the corticosterone secretion by measuring faecal corticosterone metabolites (FCM) has been established for an Arctic seabird, the Little Auk (Alle alle). A group-specific immunoassay was successfully validated for adults and chicks using an adrenocorticotropic challenge test. Then, FCM levels were investigated under different energetic and physiological demands, determined by weather conditions, week of chick rearing in adults, and age in chicks. The amount of rainfall had no effect on FCM levels in adults, whereas it negatively affected FCM levels in chicks. There was no variation in FCM concentrations among weeks of chick rearing in adults. In chicks, the FCM levels increased with age. Moreover, chicks with higher FCM levels had lower body mass and fledged later than chicks with lower FCM levels. This study demonstrates that environmental stress such as poor weather conditions can trigger significant changes in corticosterone levels in seabird chicks. Furthermore, the results indicate that corticosterone may be involved in the physiological and behavioural adjustments necessary for successful fledging and post-fledging survival.

New Insights into the Microbiota of the Svalbard Reindeer Rangifer tarandus platyrhynchus

Svalbard reindeer (Rangifer tarandus platyrhynchus) is a non-migratory subspecies of reindeer inhabiting the high-arctic archipelago of Svalbard. In contrast to other Rangifer tarandus subspecies, Svalbard reindeer graze exclusively on natural sources of food and have no chance of ingestion of any crops. We report the use of a non-invasive method for analysis of fecal microbiome by means of sequencing the 16S rDNA extracted from the fecal microbiota of R. tarandus platyrhynchus from a small, isolated population in Hornsund, South Spitsbergen National Park. Analyses of all samples showed that 99% of the total reads were represented by Bacteria. Taxonomy-based analysis showed that fecal bacterial communities consisted of 14 phyla. The most abundant phyla across the population were Firmicutes and Bacteroidetes, and those phyla jointly accounted for more than 95% of total bacterial sequences (ranging between 90.14 and 98.19%). Specifically, Firmicutes comprised 56.53% (42.98–63.64%) and Bacteroidetes comprised 39.17% (34.56–47.16%) of the total reads. The remaining 5% of the population reads comprised of Tenericutes, Cyanobacteria, TM7, Actinobacteria, Proteobacteria, Verrucomicrobia, Elusimicrobia, Planctomycetes, Fibrobacteres, Spirochaetes, Chloroflexi, and Deferribacteres. Differences in the fecal bacteria composition between particular reindeer were not statistically significant which may reflect the restricted location and similar diet of all members of the local population.

DNA extracted from faeces as a source of information about endemic reindeer from the High Arctic: detection of Shiga toxin genes and the analysis of reindeer male-specific DNA

DNA extracted from faeces may be a valuable source of information about the animal itself, as well as its microflora. An isolated reindeer population from Svalbard (Rangifer tarandus platyrhynchus) was tested for the presence of Shiga toxin encoding genes in the collected faecal samples. Even though the reindeers were not interacting with any other ruminants, which are considered to be a major reservoir of Shiga toxin containing bacteria, the stx1 gene was detected in 9 out of 10 tested samples, and the stx2 subtype c was found in five tested samples. This is an exceptionally high proportion, especially in the case of stx1, when compared to those observed in semi-domesticated or wild cervid populations in less remote locations. Distribution of the investigated genes in a small, local population indicates a different pattern of transmission, which seems to favour bacteria carrying the stx1 genes over those carrying the stx2 genes. The overall high percentage of animals with microbiota containing the stx genes suggests an important role of these genes in such an extreme environment for either hosts or their gut bacteria. Additionally, male-specific DNA found in the faeces was isolated in order to establish a given animal’s sex. PCR based on two pairs of primers, DBY7 and DBY8 gave the expected length of product characteristic for Y chromosome. The results of molecular sexing were consistent with field observations.

Parent-offspring interactions in a long-lived seabird, the Little Auk (Alle alle) : begging and provisioning under simulated stress

AbstractLong-lived seabirds are good models to study the mechanisms that mediate the parent–offspring interactions. Contrary to studies under natural conditions, experimental manipulations allow us to assess the birds’ reactions in a short time period. We used the stress hormone corticosterone as an independent experimental factor to simulate the stress reaction, to examine changes in the behaviour of Little Auk chicks and parent birds. In the first experiment, we hypothesised that after enhancement of the corticosterone level Little Auk (Alle alle) chicks intensify their begging performance and attain a higher pre-fledging body mass than the control chicks. In the second experiment, we hypothesized that parent Little Auks with an increased corticosterone level feed their chicks less frequently and spend less time at the colony than their untreated partners and the control birds. We also expected that chicks with one parent implanted with corticosterone fledge later and with a lower body mass than chicks of two untreated parents. The obtained results supported the above hypotheses. We demonstrated that modification of begging performance in Little Auks constitutes an adaptive mechanism that guards against the decrease in the chicks’ body condition during stressful periods. Even though the provisioning rate in Little Auks can be regulated according to the chick’s needs (expressed by the intensity of the begging display), it appears that adult birds regulate their provisioning strategy primarily according to their body state. The results suggest that parent Little Auks under stressful conditions will decrease their parental effort and redirect the available energy towards self-maintenance. The study provides novel insights into the behaviour of long-lived alcids using an experimental approach on free-living birds.ZusammenfassungEltern-Nachwuchs Interaktionen bei einem langlebigen Seevogel, dem Krabbentaucher (Alle alle): Betteln und Versorgen bei simuliertem Stress Langlebige Meeresvögel eignen sich gut, um Mechanismen der Eltern-Nachwuchs Interaktion zu untersuchen. Im Gegensatz zu Studien unter natürlichen Bedingungen erlauben experimentelle Manipulationen, die unmittelbare Reaktion der Vögel zu messen. Wir verabreichten das Stresshormon Kortikosteron zur Simulierung einer Stressreaktion und, um Verhaltensänderungen bei Eltern- und Jungtieren zu beobachten. Die Hypothese im ersten Experiment war, dass Küken mit erhöhtem Kortikosteronspiegel ihr Bettelverhalten intensivieren und schwerer werden als die Kontrolltiere. Im zweiten Experiment postulierten wir, dass Eltern mit erhöhtem Kortikosteronspiegel ihren Nachwuchs seltener füttern und weniger Zeit in der Kolonie verbringen als ihre unbehandelten Partner bzw. Kontrolltiere. Wir erwarteten auch, dass Küken von Paaren, in denen ein Elternteil mit einem Kortikosteronpellet implantiert war, später schlüpfen und dabei leichter sind als Küken von unbehandelten Eltern. Die Ergebnisse unserer Experimente unterstützten unsere Hypothesen. Wir konnten zeigen, dass die Modifikation des Bettelverhaltens beim Krabbentaucher ein adaptiver Mechanismus ist, der einer Verschlechterung der Verfassung während Stressperioden entgegenwirkt. Obwohl die Versorgungsrate beim Krabbentaucher entsprechend dem Bedürfnis der Küken (ausgedrückt durch die Intensität des Bettelverhaltens) reguliert werden kann, scheinen erwachsene Vögel ihre Versorgungsstrategie primär nach ihrer Körperverfassung auszurichten. Die Ergebnisse legen nahe, dass Krabbentaucher in Belastungssituationen ihre elterliche Fürsorge reduzieren und die verfügbare Energie in Richtung Selbsterhalt umlenken. Die Studie liefert neue Einsichten in das Verhalten langlebiger Alken unter Verwendung eines experimentellen Ansatzes bei freilebenden Vögeln.