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| 2. |
- Allander, K
(författare)
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The effects of an ectoparasite on reproductive success in the great tit: a 3-year experimental study
- 1998
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Ingår i: CANADIAN JOURNAL OF ZOOLOGY-REVUE CANADIENNE DE ZOOLOGIE. - : NATL RESEARCH COUNCIL CANADA. - 0008-4301. ; 76:1, s. 19-25
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The effects of ectoparasites on host reproductive success have been studied in a variety of bird species. Most of these studies concern either colonial or hole-nesting birds, which have been suspected of being particularly susceptible to parasites because
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| 3. |
- Angerbjörn, Anders, et al.
(författare)
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Factors Influencing Winter Food Choice by Mountain Hares (Lepus-Timidus L) on Swedish Coastal Islands
- 1987
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Ingår i: Canadian Journal of Zoology. - : Canadian Science Publishing. - 0008-4301 .- 1480-3283. ; 65:9, s. 2163-2167
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Tidskriftsartikel (refereegranskat)abstract
- In mainland areas, mountain hares seem unable to survive on a single browse species. However, mountain hares on islands off the west coast of Sweden rely almost entirely on a plain heather diet during winter. Herein, we give as a possible explanation for this phenomenon that the high concentration of sodium in the heather in the coastal areas can buffer the high sodium excretion otherwise observed in hares feeding on heather under experimental conditions. Furthermore, hares selected heather with the highest nitrogen and phosphorus contents. We argue that the pattern of food choice exhibited by the hares in the coastal area is to be expected in homogenous habitats where hares rely on one dominant food species. In heterogenous habitats, the possibility of food selection on a nutritional level is to a considerable extent overridden by effects of digestibility and concentration of secondary compounds in the different food plants available.
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| 4. |
- Arnemo, Jon, et al.
(författare)
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Effects of different doses of medetomidine and tiletamine-zolazepam on the duration of induction and immobilization in free-ranging yearling brown bears (Ursus arctos)
- 2012
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Ingår i: Canadian Journal of Zoology. - 0008-4301 .- 1480-3283. ; 90, s. 753-757
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Tidskriftsartikel (refereegranskat)abstract
- We compared anesthetic protocols with different doses of tiletamine-zolazepam (TZ) combined with medetomidine (M) for 288 yearling brown bear (Ursus arctos L., 1758) immobilizations with the objective of finding a combination of doses that would provide fast induction with a duration of anesthesia long enough to minimize the need for administering additional drug. The duration of induction time and immobilization was dose-dependent. Increasing the M dose resulted in significantly shorter induction times and a lower probability of giving supplemental drugs. Increasing the TZ dose prolonged duration of anesthesia. For yearling brown bears in Scandinavia, captured shortly after den emergence in April and May, we recommend total dart doses of 1.0-1.66 mg M/dart, plus 62.5-125 mg TZ/dart, depending on the individual requirements for the length and depth of anaesthesia.
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| 5. |
- Arzel, C., et al.
(författare)
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A flyway perspective of foraging activity in Eurasian Green-winged Teal, Anas crecca crecca
- 2007
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Ingår i: Canadian Journal of Zoology. - 0008-4301 .- 1480-3283. ; 85:1, s. 81-91
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Tidskriftsartikel (refereegranskat)abstract
- Time-activity budgets in the family Anatidae are available for the wintering and breeding periods. We present the first flyway-level study of foraging time in a long-distance migrant, the Eurasian Green-winged Teal, Anas crecca crecca L., 1758 ("Teal"). Behavioral data from early and late spring staging, breeding, and molting sites were collected with standardized protocols to explore differences between the,sexes, seasons, and diel patterns. Teal foraging activity was compared with that of the Mallard, Anas platyrhynchos L., 1758 and Northern Shoveler, Anas clypeata L., 1758, and the potential effects of duck density and predator-caused disturbance were explored. In early spring, foraging time was moderate (50.5%) and mostly nocturnal (45%). It increased dramatically in all three species at migration stopovers and during molt, mostly because of increased diurnal foraging, while nocturnal foraging remained fairly constant along the flyway. These patterns adhere to the "income breeding" strategy expected for this species. No differences between the sexes were recorded in either species studied. Teal foraging time was positively correlated with density of Teal and all ducks present, but negatively correlated with predator disturbance. Our study suggests that Teal, in addition to being income breeders, may also be considered as income migrants; they find the energy necessary to migrate at staging sites along the flyway.
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| 6. |
- Arzel, C., et al.
(författare)
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A flyway perspective of foraging activity in Eurasian Green-winged Teal, Anas crecca crecca
- 2007
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Ingår i: Canadian Journal of Zoology. - : National Research Council of Canada. - 0008-4301 .- 1480-3283. ; 85:1, s. 81-91
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Tidskriftsartikel (refereegranskat)abstract
- Time-activity budgets in the family Anatidae are available for the wintering and breeding periods. We present the first flyway-level study of foraging time in a long-distance migrant, the Eurasian Green-winged Teal, Anas crecca crecca L., 1758 ("Teal"). Behavioral data from early and late spring staging, breeding, and molting sites were collected with standardized protocols to explore differences between the,sexes, seasons, and diel patterns. Teal foraging activity was compared with that of the Mallard, Anas platyrhynchos L., 1758 and Northern Shoveler, Anas clypeata L., 1758, and the potential effects of duck density and predator-caused disturbance were explored. In early spring, foraging time was moderate (50.5%) and mostly nocturnal (45%). It increased dramatically in all three species at migration stopovers and during molt, mostly because of increased diurnal foraging, while nocturnal foraging remained fairly constant along the flyway. These patterns adhere to the "income breeding" strategy expected for this species. No differences between the sexes were recorded in either species studied. Teal foraging time was positively correlated with density of Teal and all ducks present, but negatively correlated with predator disturbance. Our study suggests that Teal, in addition to being income breeders, may also be considered as income migrants; they find the energy necessary to migrate at staging sites along the flyway.
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| 7. |
- Backström, Tobias, et al.
(författare)
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Short-term stress: effects on cortisol levels and carotenoid spots in Arctic char (Salvelinus alpinus)
- 2016
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Ingår i: Canadian Journal of Zoology. - : Canadian Science Publishing. - 0008-4301 .- 1480-3283. ; 94, s. 707-712
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Tidskriftsartikel (refereegranskat)abstract
- Earlier studies have shown that the carotenoid pigmentation in Arctic char (Salvelinus alpinus (L., 1758)) is connected to stress responsiveness. These studies also suggested that the pigmentation is dynamic and can change quickly. Therefore, we wanted to investigate the effect of a short-term stressor on the number of carotenoid spots before and after certain time intervals after the stressor. Individuals were exposed to a net-restraint stressor for 1 min and then assigned a recovery time of either 0, 1, 2, 8, or 24 h. Photographs were taken before the stressor and after the recovery time to count carotenoid spots and to look at the relative changes over time. Behaviour during the stressor and cortisol levels after the assigned recovery time were evaluated. We found that the change in spottiness, measured as the ratio of spots after and before the stressor, changed with recovery time on the right side but not on the left side. Furthermore, left-side spots were correlated with struggling activity. Thus, carotenoid pigmentation seems to be lateralized, with more static spots on the left side connected to stress responsiveness, whereas spots on the right side seem to be more dynamic.
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| 8. |
- Ball, John
(författare)
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Seasonal differences in the relative importance of specific phenolics and twig morphology result in contrasting patterns of foraging by a generalist herbivore
- 2013
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Ingår i: Canadian Journal of Zoology. - : Canadian Science Publishing. - 0008-4301 .- 1480-3283. ; 91, s. 338-347
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Tidskriftsartikel (refereegranskat)abstract
- The co-evolved relationship between the chemical composition of plants and herbivory is fundamental in understanding diet selection of herbivores and their impacts on plants and ecosystems. However, the impact of plant secondary chemistry on mammalian herbivory is not fully understood. We investigated seasonal influences of phenolics with low molecular weight (e.g., flavonoids, salicylates) and plant morphology of the tea-leaved willow (Salix phylicifolia L.) on moose (Alces alces (L., 1758)) foraging. We analysed the relationship of different phenolic compounds in twigs and browsing in winter, and in leaves and the degree of leaf stripping in summer, and the role of plant morphology. In winter, higher concentrations of phenolics, e.g., myricetin-related compounds (belonging to the flavonoids), had a negative impact on herbivory by moose. This impact was not associated with a single compound but instead seemed to be more a result of synergistic or additive effects of different compounds. In contrast, the models for summer browsing showed a pronounced effect of plant morphology. Our analyses reveal differences in the relative importance of phenolics of low molecular weight and plant morphology on diet selection between seasons. These findings are relevant for understanding feeding decisions and mechanisms deterring mammalian herbivores known for shaping the vegetation on the ecosystem level.
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| 9. |
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| 10. |
- Brännäs, Eva, et al.
(författare)
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Density-dependent Effects of Prior Residence and Behavioural Strategy on Growth of Stocked Brown Trout (Salmo trutta)
- 2004
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Ingår i: Canadian Journal of Zoology. - : Canadian Science Publishing. - 0008-4301 .- 1480-3283. ; 82:10, s. 1638-1646
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Tidskriftsartikel (refereegranskat)abstract
- When animals face temporally periods of strong intraspecific competition, prior residency, available resources, and their competitive abilities in terms of size and behavioural strategy affect their chances of survival. Density, individual size, and behavioural strategy had the strongest effect on growth. The mean growth rate of both resident and intruding brown trout (Salmo trutta L., 1758) decreased with increasing density, and the largest individuals were the most successful ones independently of the density of prior residency. An aggressive behavioural factor was beneficial at the lowest and intermediate densities, whereas a nonaggressive behavioural factor was beneficial at higher densities. Prior residency had no overall significant effect on growth, as the effect was highly density-dependent. The difference in growth rate between introduced and resident individuals was significant only at high density and low food abundance per individual. The intruders had a significantly lower growth rate at high densities and fewer individuals had a high growth rate. These results suggest that stocking fish at densities exceeding the carrying capacity of the habitat results in fewer individuals that are able to compete for resources than if fewer individuals were stocked. Brood stock can then be used in a more efficient way.
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