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  • 1. Boström, Jannika
    et al.
    Fransson, Thord
    Henshaw, Ian
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Kullberg, Cecilia
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Åkesson, Susanne
    Autumn migratory fuelling: a response to simulated magnetic displacement in juvenile wheatears, Oenathe oenathe2010In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 64, no 11, p. 1725-1732Article in journal (Refereed)
    Abstract [en]

    Recent experiments exposing migratory birds to altered magnetic fields simulating geographical displacements have shown that the geomagnetic field acts as an external cue affecting migratory fuelling behaviour. This is the first study investigating fuel deposition in relation to geomagnetic cues in long-distance migrants using the western passage of the Mediterranean region. Juvenile wheatears (Oenanthe oenanthe) were exposed to a magnetically simulated autumn migration from southern Sweden to West Africa. Birds displaced parallel to the west of their natural migration route, simulating an unnatural flight over the Atlantic Ocean, increased their fuel deposition compared to birds experiencing a simulated migration along the natural route. These birds, on the other hand, showed relatively low fuel loads in agreement with earlier data on wheatears trapped during stopover. The experimental displacement to the west, corresponding to novel sites in the Atlantic Ocean, led to a simulated longer distance to the wintering area, probably explaining the observed larger fuel loads. Our data verify previous results suggesting that migratory birds use geomagnetic cues for fuelling decisions and, for the first time, show that birds, on their first migration, can use geomagnetic cues to compensate for a displacement outside their normal migratory route, by adjusting fuel deposition.

  • 2. Cresswell, Will
    et al.
    Lind, Johan
    Stockholm University, Faculty of Science, Department of Zoology.
    Kaby, Ulrika
    Stockholm University, Faculty of Science, Department of Zoology.
    Quinn, John
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Does an opportunistic predator preferentially attack nonvigilant prey?2003In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 66, no 4, p. 643-648Article in journal (Refereed)
    Abstract [en]

    The dilution effect as an antipredation behaviour is the main theoretical reason for grouping in animals and states that all individuals in a group have an equal risk of being predated if equally spaced from each other and the predator. Stalking predators, however, increase their chance of attack success by preferentially targeting nonvigilant individuals, potentially making relative vigilance rates in a group relatively important in determining predation compared with the dilution effect. Many predators, however, attack opportunistically without stalking, when targeting of nonvigilant individuals may be less likely, so that the dilution effect will then be a relatively more important antipredation reason for grouping. We tested whether an opportunistically hunting predator, the sparrowhawk, Accipiter nisus, preferentially attacked vigilant or feeding prey models presented in pairs. We found that sparrowhawks attacked vigilant and feeding mounts at similar frequencies. Our results suggest that individuals should prioritize maximizing group size or individual vigilance dependent on the type of predator from which they are at risk. When the most likely predator is a stalker, individuals should aim to have the highest vigilance levels in a group, and there may be relatively little selective advantage to being in the largest group. In contrast, if the most likely predator is an opportunist, then individuals should simply aim to be in the largest group and can also spend more time foraging without compromising predation risk. For most natural systems this will mean a trade-off between the two strategies dependent on the frequency of attack of each predator type.

  • 3.
    Fransson, Thord
    et al.
    Naturhistoriska Riksmuseet.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Johansson, Patrik
    Sveriges geologiska undersökningar.
    Kullberg, Cecilia
    Stockholm University, Faculty of Science, Department of Zoology.
    Lind, Johan
    Stockholm University, Faculty of Science, Department of Zoology.
    Valllin, Adrian
    Stockholm University, Faculty of Science, Department of Zoology.
    Magnetic cues trigger extensive refuelling2001In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 414, p. 35-36Article in journal (Refereed)
  • 4.
    Hedlund, Johanna S. U.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Kullberg, Cecilia
    Stockholm University, Faculty of Science, Department of Zoology.
    Fransson, Thord
    Long-term phenological shifts and intra-specific differences in migratory change in the willow warbler Phylloscopus trochilus2015In: Journal of Avian Biology, ISSN 0908-8857, E-ISSN 1600-048X, Vol. 46, no 1, p. 97-106Article in journal (Refereed)
    Abstract [en]

    Climate change can influence many aspects of avian phenology and especially migratory shifts and changes in breeding onset receive much research interest in this context. However, changes in these different life-cycle events in birds are often investigated separately and by means of ringing records of mixed populations. In this long-term study on the willow warbler Phylloscopus trochilus, we investigated timing of spring and autumn migration in conjunction with timing of breeding. We made distinction among individuals with regard to age, sex, juvenile origin and migratory phase. The data set comprised 22-yr of ringing records and two temporally separated data sets of egg-laying dates and arrival of the breeding population close to the ringing site. The results reveal an overall advancement consistent in most, but not all, phenological events. During spring migration, early and median passage of males and females became earlier by between 4.4 to 6.3 d and median egg-laying dates became earlier by 5 d. Male arrival advanced more, which may lead to an increase in the degree of protandry in the future. Among breeding individuals, only female arrival advanced in timing. In autumn, adults and locally hatched juvenile females did not advanced median passage, but locally hatched juvenile males appeared 4.2 d earlier. Migrating juvenile males and females advanced passage both in early and median migratory phase by between 8.4 to 10.1 d. The dissimilarities in the response between birds of different age, sex and migratory phase emphasize that environmental change may elicit intra-specific selection pressures. The overall consistency of the phenological change in spring, autumn and egg-laying, coupled with the unchanged number of days between median spring and autumn migration in adults, indicate that the breeding area residence has advanced seasonally but remained temporally constant.

  • 5.
    Hedlund, Johanna S. U.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Sjösten, Frida
    Sokolovskis, Kristaps
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Point of no return – absence of returning birds in the otherwise philopatric willow warbler Phylloscopus trochilus2017In: Journal of Avian Biology, ISSN 0908-8857, E-ISSN 1600-048X, Vol. 48, no 3, p. 399-406Article in journal (Refereed)
    Abstract [en]

    The return of individual birds to a specific area in successional years, i.e. philopatry, is a remarkable behavioural trait. Here we report on the remarkably reversed: the complete absence of returning individuals of a migratory passerine with otherwise pronounced philopatry. At a high latitude study site in Abisko (68°32ʹN, 18°80ʹE) in northern Sweden none of the banded adult willow warblers Phylloscopus trochilus returned to breed 2011–2014. This is in stark contrast to all other reports in the literature and also to our two southern study sites (at 56°56ʹN, 18°10ʹE and at 58°94ʹN, 17°14ʹE) where 18–38% of adults returned. We investigated this aberrant pattern found in Abisko by analysing three parameters known to influence philopatry; nest predation, breeding success and breeding density, and predicted that absence of philopatry should co-occur with low breeding success, low breeding density and/or high nest predation. The results did not corroborate this, except that breeding density was lower at Abisko (49–71 pairs km–2) than at the southern sites (106 pairs km–2, 101 pairs km–2). Instead, we suggest the hypothesis that the absence of philopatry is caused by an influx of southern, dispersal-prone individuals deploying another breeding strategy and that this intra-specific range expansion is enabled by milder climate and low population density.

  • 6.
    Henshaw, Ian
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Fransson, Thord
    Swedish Museum of Natural History, Bird Ringing Centre.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Jenni-Eiermann, Susanne
    Swiss Ornithological Institute.
    Kullberg, Cecilia
    Stockholm University, Faculty of Science, Department of Zoology.
    Information from the geomagnetic field induce changes in corticosterone secretion in a migratory birdManuscript (Other academic)
  • 7.
    Henshaw, Ian
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Fransson, Thord
    Naturhistoriska riksmuseet, Ringmärkningscentralen.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Jenni-Eiermann, Susanne
    Swiss ornithological Institute.
    Kullberg, Cecilia
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Information from the geomagnetic field triggers a reduced adrenocortical response in a migratory bird2009In: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 212, p. 2902-2907Article in journal (Refereed)
    Abstract [en]

    Long-distance migrants regularly pass ecological barriers, like the Sahara desert, where extensive fuel loads are necessary for a successful crossing. A central question is how inexperienced migrants know when to put on extensive fuel loads. Beside the endogenous rhythm, external cues have been suggested to be important. Geomagnetic information has been shown to trigger changes in foraging behaviour and fuel deposition rate in migratory birds. The underlying mechanism for these adjustments, however, is not well understood. As the glucocorticoid hormone corticosterone is known to correlate with behaviour and physiology related to energy regulation in birds, we here investigated the effect of geomagnetic cues on circulating corticosterone levels in a long-distance migrant. Just as in earlier studies, juvenile thrush nightingales (Luscinia luscinia) caught during autumn migration and exposed to the simulated geomagnetic field of northern Egypt increased food intake and attained higher fuel loads than control birds experiencing the ambient magnetic field of southeast Sweden. Our results further show that experimental birds faced a reduced adrenocortical response compared with control birds, thus for the first time implying that geomagnetic cues trigger changes in hormonal secretion enabling appropriate behaviour along the migratory route.

  • 8.
    Henshaw, Ian
    et al.
    Uppsala universitet.
    Fransson, Thord
    Naturhistoriska riksmuseet, ringmärkningscentralen.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Kullberg, Cecilia
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Geomagnetic field affects spring migratory direction in a long distance migrant2010In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 64, no 8, p. 1317-1323Article in journal (Refereed)
  • 9.
    Henshaw, Ian
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Fransson, Thord
    Swedish Museum of Natural History, Bird Ringing Centre.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Kullberg, Cecilia
    Stockholm University, Faculty of Science, Department of Zoology.
    Simulated geomagnetic displacement affects spring migratory direction in a long distance migrantManuscript (Other academic)
  • 10.
    Henshaw, Ian
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Fransson, Thord
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Lind, Johan
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Centre for Cultural Evolution.
    Vallin, Adrian
    Stockholm University, Faculty of Science, Department of Zoology.
    Kullberg, Cecilia
    Stockholm University, Faculty of Science, Department of Zoology.
    Food intake and fuel deposition in a migratory bird is affected by multiple as well as single-step changes in the magnetic field2008In: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 211, p. 649-653Article in journal (Refereed)
    Abstract [en]

    Recent studies have shown that migratory thrush nightingales (Luscinia luscinia) experimentally treated with multiple changes of the magnetic field simulating a journey to their target stopover area in northern Egypt, increased fuel deposition as expected in preparation to cross the Sahara desert. To investigate the significance of food intake on the body mass changes observed, in the work described here we analysed food intake of the nightingales under study in those earlier experiments. Furthermore, to study whether a single change in the magnetic field directly to northern Egypt is sufficient to provide information for fuelling decisions, we performed a new experiment, exposing thrush nightingales trapped in Sweden, directly to a magnetic field of northern Egypt. Our results show that an experimentally induced magnetic field of northern Egypt, close to the barrier crossing, triggers the same response in fuel deposition as experiments with multiple changes of the magnetic field simulating a migratory journey from Sweden to Egypt, suggesting that migratory birds do not require successive changes in field parameters to incorporate magnetic information into their migratory program. Furthermore, irrespective of experimental set up (single or multiple changes of the magnetic field parameters) increase in food intake seems to be the major reason for the observed increase in fuelling rate compared with control birds, suggesting that geomagnetic information might trigger hormonal changes in migratory birds enabling appropriate fuelling behaviour during migration.

  • 11.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Tovetorps Forskningsstation2011In: Sörmlandsbygden 2012 / [ed] Margareta Elg, Nyköping: Österbergs & Sörmlandstryck , 2011, p. 49-66Chapter in book (Other (popular science, discussion, etc.))
  • 12. Jonsson, Bengt Gunnar
    et al.
    Laikre, Linda
    Stockholm University, Faculty of Science, Department of Zoology.
    Götmark, Frank
    Ryman, Nils
    Stockholm University, Faculty of Science, Department of Zoology.
    Almered Olsson, Gunilla
    Björk, Lars
    Ebenhard, Torbjörn
    Hjältén, Joakim
    Ihse, Margareta
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Milberg, Per
    Nilsson, Sven G.
    Smith, Henrik
    Wramner, Per
    Skogspolitiken hotar biologiska mångfalden2008Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    DN Debatt Måndag 14 april 2008

  • 13.
    Kullberg, Cecilia
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Henshaw, Ian
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Johansson, Patrik
    Sveriges Geologiska Undersökning.
    Fransson, Thord
    Naturhistoriska Riksmuseet.
    Fuelling decisions in migratory birds: geomagnetic cues override the seasonal effect.2007In: Proceedings of the Royal Society of London B, Vol. 274, no 1622, p. 2145-2151Article in journal (Refereed)
    Abstract [en]

    Recent evaluations of both temporal and spatial precision in bird migration have called for external cues in addition to the inherited programme defining the migratory journey in terms of direction, distance and fuelling behaviour along the route. We used juvenile European robins (Erithacus rubecula) to study whether geomagnetic cues affect fuel deposition in a medium-distance migrant by simulating a migratory journey from southeast Sweden to the wintering area in southern Spain. In the late phase of the onset of autumn migration, robins exposed to the magnetic treatment attained a lower fuel load than control birds exposed to the ambient magnetic field of southeast Sweden. In contrast, robins captured in the early phase of the onset of autumn migration all showed low fuel deposition irrespective of experimental treatment. These results are, as expected, the inverse of what we have found in similar studies in a long-distance migrant, the thrush nightingale (Luscinia luscinia), indicating that the reaction in terms of fuelling behaviour to a simulated southward migration varies depending on the relevance for the species. Furthermore, we suggest that information from the geomagnetic field act as an important external cue overriding the seasonal effect on fuelling behaviour in migratory birds.

  • 14.
    Kullberg, Cecilia
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Kaby, Ulrika
    Stockholm University, Faculty of Science, Department of Zoology.
    Lind, Johan
    Stockholm University, Faculty of Science, Department of Zoology.
    Impaired flight ability prior to egg laying: A cost of being a capital breeder2005In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 19, no 1, p. 98-101Article in journal (Refereed)
    Abstract [en]
    • 1To investigate flight ability in captive Zebra Finches during reproduction we compared change in escape take-off ability and wing load of reproducing females with their mates and non-reproducing females when attacked by a model raptor.
    • 2Initially females had 18% higher wing load than males. Non-reproducing females and females that had started egg-laying flew slower than males. Reproducing females reduced wing load during egg-laying and flew faster when the clutch was completed. Non-breeding females remained on high wing load and flow slower than breeding females that had completed their clutch.
    • 3The increase in flight speed of breeding females was explained by a reduction in wing load during egg-laying.
    • 4Zebra Finches use accumulated reserves to produce eggs and pay a cost in terms of reduced flight ability, but then regain flight performance when the clutch is laid, probably demonstrating a predation cost of capital breeding in birds.
  • 15.
    Laikre, Linda
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Jansson, Mija
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Allendorf, Fred W.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Ryman, Nils
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Hunting Effects on Favourable Conservation Status of Highly Inbred Swedish Wolves2013In: Conservation Biology, ISSN 0888-8892, E-ISSN 1523-1739, Vol. 27, no 2, p. 248-253Article in journal (Refereed)
    Abstract [en]

    The wolf (Canis lupus) is classified as endangered in Sweden by the Swedish Species Information Centre, which is the official authority for threat classification. The present population, which was founded in the early 1980s, descends from 5 individuals. It is isolated and highly inbred, and on average individuals are more related than siblings. Hunts have been used by Swedish authorities during 2010 and 2011 to reduce the population size to its upper tolerable level of 210 wolves. European Union (EU) biodiversity legislation requires all member states to promote a concept called “favourable conservation status” (FCS) for a series of species including the wolf. Swedish national policy stipulates maintenance of viable populations with sufficient levels of genetic variation of all naturally occurring species. Hunting to reduce wolf numbers in Sweden is currently not in line with national and EU policy agreements and will make genetically based FCS criteria less achievable for this species. We suggest that to reach FCS for the wolf in Sweden the following criteria need to be met: (1) a well-connected, large, subdivided wolf population over Scandinavia, Finland, and the Russian Karelia-Kola region should be reestablished, (2) genetically effective size (Ne) of this population is in the minimum range of Ne = 500–1000, (3) Sweden harbors a part of this total population that substantially contributes to the total Ne and that is large enough to not be classified as threatened genetically or according to IUCN criteria, and (4) average inbreeding levels in the Swedish population are <0.1.

  • 16.
    Lind, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Body-building and concurrent mass loss: flight adaptations in tree sparrows2001In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 268, no 1479, p. 1915-1919Article in journal (Refereed)
    Abstract [en]

    Environmental changes are responsible for the evolution of flexible physiology and the extent of phenotypic plasticity in the regulation of birds' organ size has not been appreciated until recently. Rapid reversible physiological changes during different life–history stages are virtually only known from long–distance migrants, and few studies have focused on less extreme aspects of organ flexibility. During moult, birds suffer from increased wing loading due to wing–area reductions, which may impair flight ability. A previous study found that tree sparrows' escape flight (Passer montanus) is unaffected during moult, suggesting compensatory aptness. We used non–invasive techniques to study physiological adaptations to increased wing loading in tree sparrows. As wing area was reduced during natural moult the ratio of pectoral–muscle size to body mass increased. When moult was completed this ratio decreased. We show experimentally a novel, strategic, organ–flexibility pattern. Unlike the general pattern, where body mass is positively coupled to pectoral–muscle size, tree sparrows responded within 7 days to reductions in wing area by reducing body mass concurrently with an increase in pectoral–muscle size. This rapid flexibility in a non–migratory species probably reflects the paramount importance and long history of flight in birds.

  • 17.
    Lind, Johan
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology, Ethology. Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Stockholm University. Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Kullberg, Cecilia
    Stockholm University. Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Impaired predator evasion in the life-history of birds: behavioral and physiological adaptations to reduced flight ability.2010In: Current Ornithology, Vol. 17, p. 1-30Article in journal (Refereed)
  • 18.
    Lind, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Kaby, Ulrika
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Split-second escape decisions in blue tits (Parus caeruleus)2002In: Die Naturwissenschaften, ISSN 0028-1042, E-ISSN 1432-1904, Vol. 89, no 9, p. 420-423Article in journal (Refereed)
    Abstract [en]

    Bird mortality is heavily affected by birds of prey. Under attack, take-off is crucial for survival and even minor mistakes in initial escape response can have devastating consequences. Birds may respond differently depending on the character of the predator's attack and these split-second decisions were studied using a model merlin (Falco columbarius) that attacked feeding blue tits (Parus caeruleus) from two different attack angles in two different speeds. When attacked from a low attack angle they took off more steeply than when attacked from a high angle. This is the first study to show that escape behaviour also depends on predator attack speed. The blue tits responded to a high-speed attack by dodging sideways more often than when attacked at a low speed. Escape speed was not significantly affected by the different treatments. Although they have only a split-second before escaping an attack, blue tits do adjust their escape strategy to the prevailing attack conditions.

  • 19.
    Olofsson, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Eriksson, Stephan
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Deimatic Display in the European Swallowtail Butterfly as a Secondary Defence against Attacks from Great Tits2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 10, p. e47092-Article in journal (Refereed)
    Abstract [en]

    Background: Many animals reduce the risk of being attacked by a predator through crypsis, masquerade or, alternatively, by advertising unprofitability by means of aposematic signalling. Behavioural attributes in prey employed after discovery, however, signify the importance of also having an effective secondary defence if a predator uncovers, or is immune to, the prey's primary defence. In butterflies, as in most animals, secondary defence generally consists of escape flights. However, some butterfly species have evolved other means of secondary defence such as deimatic displays/startle displays. The European swallowtail, Papilio machaon, employs what appears to be a startle display by exposing its brightly coloured dorsal wing surface upon disturbance and, if the disturbance continues, by intermittently protracting and relaxing its wing muscles generating a jerky motion of the wings. This display appears directed towards predators but whether it is effective in intimidating predators so that they refrain from attacks has never been tested experimentally. Methodology/Principal Findings: In this study we staged encounters between a passerine predator, the great tit, Parus major, and live and dead swallowtail butterflies in a two-choice experiment. Results showed that the dead butterfly was virtually always attacked before the live butterfly, and that it took four times longer before a bird attacked the live butterfly. When the live butterfly was approached by a bird this generally elicited the butterfly's startle display, which usually caused the approaching bird to flee. We also performed a palatability test of the butterflies and results show that the great tits seemed to find them palatable. Conclusions/Significance: We conclude that the swallowtail's startle display of conspicuous coloration and jerky movements is an efficient secondary defence against small passerines. We also discuss under what conditions predator-prey systems are likely to aid the evolution of deimatic behaviours in harmless and palatable prey.

  • 20.
    Olofsson, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Auditory defence in the peacock butterfly (Inachis io) against mice (Apodemus flavicollis and A. sylvaticus)2012In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 66, no 2, p. 209-215Article in journal (Refereed)
    Abstract [en]

    Morphological and behavioural traits can serve as anti-predator defence either by reducing detection or recognition risks, or by thwarting initiated attacks. The latter defence is secondary and often involves a 'startle display' comprising a sudden release of signals targeting more than one sensory modality. A suggested candidate for employing a multimodal defence is the peacock butterfly, Inachis io, which, by wing-flicking suddenly, produces sonic and ultrasonic sounds and displays four large eyespots when attacked. The eyespots make small birds retreat, but whether the sounds produced thwart predator attacks is largely unknown. Peacocks hibernate as adults in dark wintering sites and employ their secondary defence upon encounter with small rodent predators during this period. In this study, we staged predator-prey encounters in complete darkness in the laboratory between wild mice, Apodemus flavicollis and Apodemus sylvaticus, and peacocks which had their sound production intact or disabled. Results show that mice were more likely to flee from sound-producing butterflies than from butterflies which had their sound production disabled. Our study presents experimental evidence that the peacock butterfly truly employs a multimodal defence with different traits targeting different predator groups; the eyespots target birds and the sound production targets small rodent predators.

  • 21.
    Olofsson, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Bird attacks on a butterfly with marginal eyespots and the role of prey concealment against the background2013In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 109, no 2, p. 290-297Article in journal (Refereed)
    Abstract [en]

    Small eyespots on butterflies have long been thought to deflect attacks, and birds are the presumptive drivers selecting for these patterns; however, evidence of this function is still ambiguous. Marginal eyespots typically consist of a UV-reflective white pupil, surrounded by one black and one yellowish ring. We have recently shown that Cyanistes caeruleus (blue tits) attack such eyespots, but only under low light intensities with accentuated UV levels: the increased salience of the eyespots relative to the rest of the butterfly probably explains this result. Possibly the background against which the butterfly is concealed may deceive birds to make similar errors. We therefore presented speckled wood butterflies decorated with eyespots (or controls without eyespots) to C.caeruleus against two backgrounds: oak and birch bark. Our results show that: (1) eyespots, independent of background, were effective in deflecting attacks; (2) the time elapsed between a bird landing and the attack was interactively dependent on the background and whether the butterfly bore an eyespot; and (3) the speed at which a butterfly was attacked predicted the outcome, with faster birds being more prone to errors than slower birds. This underscores a speedaccuracy trade-off in the predators, and that background plays a role in the defensive qualities of marginal eyespots.(c) 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109, 290297.

  • 22.
    Olofsson, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Løvlie, Hanne
    Stockholm University, Faculty of Science, Department of Zoology.
    Tibblin, Jessika
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Eyespot display in the peacock butterfly triggers antipredator behaviors in naive adult fowl2013In: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 24, no 1, p. 305-310Article in journal (Refereed)
    Abstract [en]

    Large conspicuous eyespots have evolved in multiple taxa and presumably function to thwart predator attacks. Traditionally, large eyespots were thought to discourage predator attacks because they mimicked eyes of the predators' own predators. However, this idea is controversial and the intimidating properties of eyespots have recently been suggested to Amply be a consequence of their conspicuousness. Some lepidopteran species include large eyespots in their antipredation repertoire. In the peacock butterfly, Mathis io, eyespots are typically hidden during rest and suddenly exposed by the butterfly when disturbed. Previous experiments have shown that small wild passerines are intimidated by this display. Here, we test whether eyespots also intimidate a considerably larger bird, domestic fowl, Gallus gallus domesticus, by staging interactions between birds and peacock butterflies that were sham-painted or had their eyespots painted oven Our results show that birds typically fled when peacock butterflies performed their display regardless of whether eyespots were visible or painted over. However, birds confronting butterflies with visible eyespots delayed their return to the butterfly, were more vigilant, and more likely to utter alarm calls associated with detection of ground-based predators, compared with birds confronting butterflies with eyespots painted over. Because production of alarm calls and increased vigilance are antipredation behaviors in the fowl, their reaction suggests that eyespots may elicit fear rather than just an aversion to conspicuous patterns. Our results, therefore, suggest that predators perceive large lepidopteran eyespots as belonging to the eyes of a potential predator.

  • 23.
    Olofsson, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Sven, Jakobsson
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Bird attacks on a butterfly with marginal eyespots and the role of prey concealment against the background: Marginal eyespots can deflect bird attacksManuscript (preprint) (Other academic)
    Abstract [en]

    Small eyespots on butterflies have long been thought to deflect attacks and birds are presumptive drivers selecting for these patterns. However, evidence of this function is still ambiguous. Marginal eyespots typically consist of a UV-reflective white pupil, surrounded by one black and one yellowish ring. We have recently shown that blue tits attack such eyespots, but only under low light intensities with accentuated UV-levels. An increased salience of the eyespots relative to the rest of the butterfly probably explains this result. Possibly, a background against which the butterfly is concealed may deceive birds to making similar errors. We therefore presented speckled wood butterflies provided with eyespots (or controls without eyespots) to blue tits against two backgrounds, oak- and birch bark. Results show that (i) eyespots, independent of background, were effective in deflecting attacks, (ii) the time elapsed between a bird’s landing and attack was interactively dependent on background and whether the butterfly bore an eyespot and (iii) the speed at which a butterfly was attacked predicted the outcome, with faster birds being more prone to errors than slower birds. This underscores a speed-accuracy tradeoff in the predators and that background plays a role in the defensive qualities of marginal eyespots.

  • 24.
    Olofsson, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Vallin, Adrian
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Marginal eyespots on butterfly wings deflect bird attacks under low light intensities with UV wavelengths2010In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 5, no 5, p. e10798-Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Predators preferentially attack vital body parts to avoid prey escape. Consequently, prey adaptations that make predators attack less crucial body parts are expected to evolve. Marginal eyespots on butterfly wings have long been thought to have this deflective, but hitherto undemonstrated function. METHODOLOGY/PRINCIPAL FINDINGS: Here we report that a butterfly, Lopinga achine, with broad-spectrum reflective white scales in its marginal eyespot pupils deceives a generalist avian predator, the blue tit, to attack the marginal eyespots, but only under particular conditions-in our experiments, low light intensities with a prominent UV component. Under high light intensity conditions with a similar UV component, and at low light intensities without UV, blue tits directed attacks towards the butterfly head. CONCLUSIONS/SIGNIFICANCE: In nature, birds typically forage intensively at early dawn, when the light environment shifts to shorter wavelengths, and the contrast between the eyespot pupils and the background increases. Among butterflies, deflecting attacks is likely to be particularly important at dawn when low ambient temperatures make escape by flight impossible, and when insectivorous birds typically initiate another day's search for food. Our finding that the deflective function of eyespots is highly dependent on the ambient light environment helps explain why previous attempts have provided little support for the deflective role of marginal eyespots, and we hypothesize that the mechanism that we have discovered in our experiments in a laboratory setting may function also in nature when birds forage on resting butterflies under low light intensities.

  • 25.
    Olofsson, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Vallin, Adrian
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Winter predation on two species of hibernating butterflies: monitoring rodent attacks with infrared cameras2011In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 81, no 3, p. 529-534Article in journal (Refereed)
    Abstract [en]

    Documentation of predator attacks in nature is important for understanding how specific antipredator defences have evolved, but previous accounts have been mostly anecdotal. Therefore, we monitored predation on two closely related butterfly species, Aglais urticae and Inachis io, during winter hibernation. Butterflies were placed singly close to the floor on walls in dark, seminatural hibernation sites (e.g. unheated outhouses). We used motion-initiated infrared-sensitive cameras to record predator attacks on the butterflies. The antipredator attributes of the two species have two characteristics: during rest the butterflies reduce predators’ attention by mimicking leaves but they can suddenly change their guise by repeatedly flicking their wings. The wing flicking also produces hissing sounds and ultrasonic clicks and, furthermore, I. io, but not A. urticae, have large eyespots on the dorsal wing surface. The two butterfly species suffer from mouse predation during the winter and mice have been suggested as potential targets for the butterflies’ sound production. Results showed that (1) mice (Apodemus spp.) were important predators on butterflies, (2) I. io often survived attacks by wing-flicking behaviour, and (3) both species moved to less accessible positions after interactions with mice and other small mammalian predators, but I. io more often so. The successful predator evasion in darkness by I. io suggests a multimodal defence; in addition to the large eyespots, which intimidate birds, we suggest that the hissing and/or click sounds produced during wing flicking may have evolved as defence against rodent attacks

  • 26.
    Pizzari, Tommaso
    et al.
    School of Biology, University of Leeds.
    Cornwallis, Charles K.
    Deptartment of Animal & Plant Science, University of Sheffield.
    Lovlie, Hanne
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Birkhead, Tim R.
    Deptartment of Animal & Plant Science, University of Sheffield.
    Sophisticated sperm allocation in male fowl2003In: Nature, ISSN 0028-0836, Vol. 426, no 6962, p. 70-74Article in journal (Refereed)
    Abstract [en]

    When a female is sexually promiscuous, the ejaculates of different males compete for the fertilization of her eggs; the more sperm a male inseminates into a female, the more likely he is to fertilize her eggs. Because sperm production is limited and costly, theory predicts that males will strategically allocate sperm (1) according to female promiscuity, (2) saving some for copulations with new females, and (3) to females producing more and/or better offspring. Whether males allocate sperm in all of these ways is not known, particularly in birds where the collection of natural ejaculates only recently became possible. Here we demonstrate male sperm allocation of unprecedented sophistication in the fowl Gallus gallus. Males show status-dependent sperm investment in females according to the level of female promiscuity; they progressively reduce sperm investment in a particular female but, on encountering a new female, instantaneously increase their sperm investment; and they preferentially allocate sperm to females with large sexual ornaments signalling superior maternal investment. Our results indicate that female promiscuity leads to the evolution of sophisticated male sexual behaviour.

  • 27. Pizzari, Tommaso
    et al.
    Cornwallis, Charlie K.
    Løvlie, Hanne
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Birkhead, Tim R.
    Sophisticated sperm allocation in male fowl2003In: Nature, ISSN 0028-0836, Vol. 426, no 6962, p. 70-74Article in journal (Refereed)
  • 28.
    Stach, Robert
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Fransson, Thord
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Kullberg, Cecilia
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    No compensatory fuelling due to late autumn migration in the Garden Warbler Sylvia borinManuscript (preprint) (Other academic)
    Abstract [en]

    Birds migrating late in the migration season may need to compensate for the late departure by increasing migration speed. To increase migration speed late migrants should depart from stopovers along the route with larger fuel loads than early migrants. Both higher migration speeds and increasing fuel loads with the progress of the season have been reported in the literature. Here we test if Garden Warblers (Sylvia borin) show different fuelling strategies when captured on migration in the early or late part of autumn migration and given unlimited access to food. We also included a group of birds that were captured early in the season but held under a light regime with shorter day lengths to simulate thirty days advancement in time. We found no difference in maximum body mass between the groups and all groups reached fairly large fuel loads (mean: 39.2 % of lean body mass). Maximum fuel load was also strongly correlated with fuel deposition rate and this may suggest that Garden Warblers migrate at high speed during the entire season, which leaves little room for increasing speed later in the season.

  • 29.
    Stach, Robert
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Fransson, Thord
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Kullberg, Cecilia
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Wide ranging stopover movements and substantial fuelling in first year garden warblers at a northern stopover site2015In: Journal of Avian Biology, ISSN 0908-8857, E-ISSN 1600-048X, Vol. 46, no 3, p. 315-322Article in journal (Refereed)
    Abstract [en]

    Migratory birds use stopovers to replenish their fuel reserves and they generally spend more time at stopover sites than theydo in actual fl ight. When arriving at a new stopover site birds may need to search extensively to fi nd a suitable feeding areaand this search and settling period may aff ect the duration of stopover. Stopover behaviour can thus have profound eff ectson the migratory programme and studies on stopover behaviour are important to understand migratory strategies. Wefollowed 51 fi rst-year garden warblers Sylvia borin with radio-transmitters at an autumn stopover site on the island ofGotland in southern Sweden. Our aim was to determine the distance birds relocated from the coastal capture site whensearching for an area to settle in, and also to establish the duration of stopover and put it in relation to refuelling rate byrecapturing a subset of the radio-tracked individuals. Sixteen birds made an extended stopover ( 2 d), relocated inlandfrom the capture site and settled on average 5.6 km from the capture site, with the longest recorded relocation being fourteenkilometres. Birds that relocated nocturnally settled in areas further away than birds that relocated diurnally. Th irteenbirds that continued migration after a short stop carried larger fuel stores than birds that stopped over longer and theyremained close to the capture site until departure. Th ree birds were re-trapped and showed high fuelling rates, between0.3 and 1.1 g d 1 . Th ey left the stopover site with fuel loads between 40 – 56 percent of lean body mass, which possiblywould have allowed them to reach the Mediterranean area without additional refuelling stops.

  • 30.
    Stach, Robert
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Kullberg, Cecilia
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Fransson, Thord
    Geolocators reveal three consecutive wintering areas in the thrush nightingale2012In: Animal Migration, ISSN 2084-8838, Vol. 1, p. 1-7Article in journal (Refereed)
    Abstract [en]

    The winter distribution of many migratory birds wintering in tropical Africa is poorly known. After the crossing of the Sahara Desert, some long-distance migrants typically stay in the Sahel zone for an extended period before continuing migration to their main wintering areas south of the equator. Here we show how two thrush nightingales (Luscinia luscinia) fitted with light-level geolocators, after a six to seven week long stay in the Sahel zone of Sudan, moved to an intermediate area in northern Kenya for a month-long stay before continuing to their final wintering areas in southern Africa. These data indicate that thrush nightingales may use three consecutive wintering sites during their stay in Africa. The migratory movements in Africa between wintering sites are well-coordinated with high precipitation in these areas, suggesting that thrush nightingales track peaks of insect abundance occurring after rains. This three-stage wintering strategy has, to our knowledge, previously not been described, and shows that long-distance migrants can have complex wintering behaviour.

  • 31.
    Stach, Robert
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Kullberg, Cecilia
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Ström, Kåre
    Fransson, Thord
    Migration routes and timing in a bird wintering in South Asia, the Common Rosefinch Carpodacus erythrinus2016In: Journal of Ornithology, ISSN 2193-7192, E-ISSN 2193-7206, Vol. 157, no 3, p. 671-679Article in journal (Refereed)
    Abstract [en]

    Only few bird species from Western Europe migrate eastward to wintering areas in South Asia, and little is known about this migratory flyway. The Common Rosefinch has in the past century expanded its breeding range westward to include Western Europe and migrate along this flyway to wintering sites in South Asia. This is the first study describing the migration routes of Common Rosefinches between Europe and Asia in detail, revealed by light level geolocators. The rosefinches showed loop-migration with more northerly routes in autumn than in spring, possibly in order to shorten the flight over the Central Asian deserts, which are very inhospitable at this time of the year. In spring the deserts are less dry and richer in vegetation, which may have supported the more southerly routes. During autumn migration the birds used several staging sites in Central Asia for prolonged periods. Although the birds passed over mountain regions at this time, which potentially act as barriers to them, the length of the stops seem unrealistically long for only fuel deposition. Instead, this suggests that the birds temporarily suspended migration to take advantage of abundant and predictable food sources in this region. During spring migration the birds made a few longer stops while still in north India or Central Asia, before migrating at fast speeds towards the breeding grounds. The birds covered 4–5000 km with only very short stopovers and thus most of the fuel used on spring migration must have been accumulated in Asia. Our results thus indicate that Central Asia, and north India, are important staging areas for this species in both autumn and spring. During winter, birds used two sites located several hundred kilometres apart, and relocation was probably a response to local food availability.

  • 32.
    Vallin, Adrian
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Lind, Johan
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Crypsis versus intimidation - anti-predation defence in three closely related butterflies2006In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, Vol. 59, no 3, p. 455-459Article in journal (Refereed)
  • 33.
    Vallin, Adrian
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Lind, Johan
    Wiklund, Christer
    Prey survival by predator intimidation: an experimental study of peacock butterfly defence against blue tits2005In: Proceedings of the Royal Society B: Biological Sciences, ISSN 0962-8452, Vol. 272, no 1569, p. 1203-1207Article in journal (Refereed)
  • 34.
    Vallin, Adrian
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    An eye for an eye – on the generality of the intimidating quality of eyespots in a butterfly and a hawkmoth2007In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 61, no 9, p. 1419-1424Article in journal (Refereed)
    Abstract [en]

    Large eyespots on the wings of butterflies and moths have been ascribed generally intimidating qualities by creating a frightening image of a bird or mammal much larger than the insect bearing the eyespots. However, evidence for this anti-predator adaptation has been largely anecdotal and only recently were peacock butterflies, Inachis io, shown to effectively thwart attacks from blue tits, Parus caeruleus. Here we test whether large eyespots on lepidopterans are generally effective in preventing attacks from small passerines, and whether the size of insect or bird can influence the outcome of interactions. We staged experiments between the larger eyed hawkmoths, Smerinthus ocellatus, and the smaller peacock butterflies, I. io, and the larger great tits, Parus major, and the smaller blue tits, P. caeruleus. Survival differed substantially between the insect species with 21 of 24 peacocks, but only 6 of 27 eyed hawkmoths, surviving attacks from the birds. Thus, surprisingly, the smaller prey survived to a higher extent, suggesting that other factors than insect size may be important. However, great tits were less easily intimidated by the insects’ eyespots and deimatic behaviour and consumed 16 of 26, but the blue tits only 8 of 25 of the butterflies and hawkmoths. Our results demonstrate that eyespots per se do not guarantee survival, and that these two insects bearing equally large eyespots are not equally well protected against predation.

  • 35.
    Vallin, Adrian
    et al.
    Stockholm University.
    Jakobsson, Sven
    Stockholm University.
    Wiklund, Christer
    Stockholm University.
    Constant eyespot display as a primary defense – survival of male and female emperor moths when attacked by blue tits2010In: The Journal of Research on the Lepidoptera, ISSN 0022-4324 (prINt) 2156-5457 (oNlINe), Vol. 43, p. 9-17Article in journal (Refereed)
    Abstract [en]

    Large conspicuous eyespots, commonly found on the wings of butterflies and moths, have been shown to thwart attacks from predators. Previous experiments have focused on lepidopteran species that expose eyespots only when harassed by a predator. In contrast, we investigate the potential efficiency of the constantly exposed eyespots of emperor moths thus constituting a primary defense. We staged experiments between blue tits and moths having either intact or painted over eyespots. Moths with eyespots were killed as often as moths without eyespots and were, additionally, approached earlier by the birds suggesting that birds were not intimidated by their eyespots. Female moths weighed three times more than males and were less often eaten, suggesting that their large size intimidated the birds. We suggest that the constant eyespot display of the emperor moth may be associated with a cost, because potential predators seem to be attracted rather than intimidated by the display.

  • 36.
    Vallin, Adrian
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Wiklund, Christer
    Size does matter – differences in intimidation efficiency in male and female small emperor moths (Saturnia pavonia) against blue tits (Parus caeruleus)Article in journal (Refereed)
  • 37.
    Wiklund, Christer
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Ekologiska avdelningen.
    Vallin, Adrian
    Stockholm University, Faculty of Science, Department of Zoology. Etologiska avdelningen.
    Friberg, Magne
    Stockholm University, Faculty of Science, Department of Zoology. Ekologiska avdelningen.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology. Etologiska avdelningen.
    Rodent predation on hibernating peacock and small tortoiseshell butterflies2007In: Behavioral ecology and sociobiologyArticle in journal (Refereed)
  • 38.
    Wiklund, Christer
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Vallin, Adrian
    Stockholm University, Faculty of Science, Department of Zoology.
    Friberg, Magne
    Stockholm University, Faculty of Science, Department of Zoology.
    Jakobsson, Sven
    Stockholm University, Faculty of Science, Department of Zoology.
    Rodent predation on hibernating peacock and small tortoiseshell butterflies2008In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 62, no 3, p. 379-389Article in journal (Refereed)
    Abstract [en]

    Insects that hibernate as adults have a life span of almost a whole year. Hence, they must have extraordinary adaptations for adult survival. In this paper, we study winter survival in two butterflies that hibernate as adults and have multimodal anti-predator defences-the peacock, Inachisio, which has intimidating eyespots that are effective against bird predation, and the small tortoiseshell, Aglais urticae, which does not have an effective secondary defence against birds. We assessed predation on wild butterflies hibernating in the attic of an unheated house, as well as survival of individually marked butterflies placed by hand on different sites in the attic. Our objectives were to assess (1) the number of butterflies that were killed during hibernation, (2) whether survival differed between butterfly species, and (3) how predation was related to hibernation site and the identity of the predator. There was a strong pulse of predation during the first 2 weeks of hibernation: 58% of A. urticae and 53% of I. io were killed during this period. Thereafter, predation decreased and butterfly survival equalled 98% during the final 16 weeks of hibernation. There was no difference in survival between the two butterfly species, but predation was site-specific and more pronounced under light conditions in locations accessible to a climbing rodent, such as the common yellow-necked mouse, Apodemus flavicollis. We contend that small rodents are likely important predators on over-wintering butterflies, both because rodents are active throughout winter when butterflies are torpid and because they occur at similar sites

  • 39. Wiklund, Christer
    et al.
    Vallin, Adrian
    Stockholm University, Faculty of Science, Department of Zoology.
    Friberg, Magne
    Jakobsson, Sven
    Winter survival of hibernating butterflies – timing and targeting of rodent predationManuscript (Other (popular science, discussion, etc.))
1 - 39 of 39
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