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Katrin Stapput

Publications and source records attributed to Katrin Stapput.

7 recordsLinked to original sources
PubMed2006

Avian magnetic compass: fast adjustment to intensities outside the normal functional window.

To determine how fast birds can adapt to magnetic intensities outside the normal functional window of their magnetic compass, we tested migratory birds in a magnetic field of 92,000 nT, twice the intensity of the local geomagnetic field at the test site in Frankfurt a.M., Germany. In the local field, robins showed a significant preference of their southerly migratory direction, whereas in the 92,000-nT field, they were initially disoriented. However, when the birds were preexposed to 92,000 nT for 1 h before being tested, they were able to orient under this intensity, and their behavior did not differ from that in the geomagnetic field. These data show that birds require only a short time to adjust to magnetic intensities, which they cannot spontaneously use for orientation. Interpreting these findings in view of the radical pair model (Ritz et al. 2000), this means that they can learn rather quickly to interpret novel activation patterns on their retina.

Animal Migration↗
PubMed2005

Two different types of light-dependent responses to magnetic fields in birds.

A model of magnetoreception proposes that the avian magnetic compass is based on a radical pair mechanism, with photon absorption leading to the formation of radical pairs. Analyzing the predicted light dependency by testing migratory birds under monochromatic lights, we found that the responses of birds change with increasing intensity. The analysis of the orientation of European robins under 502 nm turquoise light revealed two types of responses depending on light intensity: under a quantal flux of 8.10(15) quanta m(-2) s(-1), the birds showed normal migratory orientation in spring as well as in autumn, relying on their inclination compass. Under brighter light of 54.10(15) quanta m(-2) s(-1), however, they showed a "fixed" tendency toward north that did not undergo the seasonal change and proved to be based on magnetic polarity, not involving the inclination compass. When birds were exposed to a weak oscillating field, which specifically interferes with radical pair processes, the inclination compass response was disrupted, whereas the response to magnetic polarity remained unaffected. These findings indicate that the normal inclination compass used for migratory orientation is based on a radical-pair mechanism, whereas the fixed direction represents a novel type of light-dependent orientation based on a mechanism of a different nature.

Animal Migration↗
PubMed2005

The sea-finding behavior of hatchling olive ridley sea turtles, Lepidochelys olivacea, at the beach of San Miguel (Costa Rica).

Newly hatched olive ridley sea turtles (Lepidochelys olivacea) were tested for their directional preferences in a sand-filled circular arena in total darkness. Hatchlings that had crawled about 5 m on the beach, toward the sea preferred the southwesterly direction that would have brought them to the water line, whereas hatchlings that had been denied this experience headed eastward, a direction of unclear origin. These data suggest that a short crawl across the natural beach can set the direction in which the young turtles subsequently move. The crawling experience was sufficient to acquire the compass course that they later follow, probably with the help of a magnetic compass, not only in the water, but already while still on land.

Animals↗
PubMed2004

Magnetic compass orientation of migratory birds in the presence of a 1.315 MHz oscillating field.

The radical pair model of magnetoreception predicts that magnetic compass orientation can be disrupted by high frequency magnetic fields in the Megahertz range. European robins, Erithacus rubecula, were tested under monochromatic 565 nm green light in 1.315 MHz fields of 0.48 microT during spring and autumn migration, with 1.315 MHz being the frequency that matches the energetic splitting induced by the local geomagnetic field. The birds' responses depended on the alignment of the oscillating field with respect to the static geomagnetic field: when the 1.315 MHz field was aligned parallel with the field lines, birds significantly preferred northerly directions in spring and southerly directions in autumn. These preferences reflect normal migratory orientation, with the variance slightly increased compared to control tests in the geomagnetic field alone or to tests in a 7.0 MHz field. However, in the 1.315 MHz field aligned at a 24 degrees angle to the field lines, the birds were disoriented in both seasons, indicating that the high frequency field interfered with magnetoreception. These finding are in agreement with theoretical predictions and support the assumption of a radical-pair mechanism underlying the processes mediating magnetic compass information in birds.

Animal Migration↗
PubMed2004

Visual lateralization and homing in pigeons.

The aim of our study was to analyse the components of visual lateralization in pigeon homing, a large-scale spatial task. In a series of 13 releases, birds were tested as binocular controls or monocularly with the right or left-eye covered. Occlusion of either eye had a significant effect on initial orientation and homing performance. Vanishing bearings were deflected to the side of the open eye, vanishing intervals were longer, and homing speed was reduced. These parameters were affected to a different degree. Initial orientation was markedly lateralized, with birds using their right-eye deviating less from the mean of control birds and showing significantly less variance. One minute after release, the deviation and variance were similarly large in both monocular groups. However, while the right-eyed birds improved their performance until leaving the release site, the left-eyed birds failed to do so. Vanishing intervals were similar in both monocular groups, but homing speed was reduced to a lesser extent in pigeons using the right-eye. The degree of lateralization varied across different releases, but superiority of the right-eye/left hemisphere prevailed. Lateralization did not depend on familiarity with the release site. This suggests that the crucial processes involved the eyes, but did not depend on visual memory of landscape features at the release site. Results reveal, for the first time, asymmetries of directional orientation as an essential component of lateralized homing performance. As likely mechanisms we suggest hemispheric differences in magnetic compass orientation and in the adjustment to optic flow.

Age Factors↗
PubMed2004

Light-dependent magnetoreception in birds: interaction of at least two different receptors.

Passerine migrants require light from the blue-green part of the spectrum for magnetic compass orientation; under yellow light, they are disoriented. European robins tested under a combination of yellow light and blue or green light showed a change in behavior, no longer preferring their seasonally appropriate migratory direction: in spring as well as in autumn, they preferred southerly headings under blue-and-yellow and northerly headings under green-and-yellow light. This clearly shows that yellow light is not neutral and suggests the involvement of at least two types of receptors in obtaining magnetic compass information, with the specific interaction of these receptors being rather complex.

Animal Migration↗