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Living in Groups

Living in Groups. 吳曜如、陳彥旭 2009/10/30. Increased vigilance Dilution and cover Group defence Costs of being in a group. LIVING IN GROUPS AND AVOIDING PREDATION. Increased vigilance (1). Food ↓. Food ↑. Guppies. Sanderlings. www.wphillips.com/animals.htm. Increased vigilance (2).

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Living in Groups

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  1. Living in Groups 吳曜如、陳彥旭 2009/10/30

  2. Increased vigilance Dilution and cover Group defence Costs of being in a group LIVING IN GROUPS AND AVOIDING PREDATION

  3. Increased vigilance(1) Food ↓ Food ↑ Guppies Sanderlings www.wphillips.com/animals.htm

  4. Increased vigilance (2) (a) For goshawk Pigeon flock size ↑ Successful rate ↑ (b) For pigeons Pigeon flock size ↑Medianreactiondistance ↑ Goshawk vs. pigeon

  5. Increased vigilance (3) • Ostrich myanimalblog.wordpress.com/.../osthrich/ostrich/

  6. Increased vigilance (3) The vigilance changes with flock size depends on how individuals in the group spend their time.

  7. Increased vigilance (3) msa4.wordpress.com/.../ • The vigilance changes with flock size depends on how individuals in the group spend their time. • How about cheating?!

  8. Increased vigilance (3) msa4.wordpress.com/.../ • The vigilance changes with flock size depends on how individuals in the group spend their time. • How about cheating?! • Some spend all the time withits head down feeding.

  9. Increased vigilance (3) msa4.wordpress.com/.../ • The vigilance changes with flock size depends on how individuals in the group spend their time. • How about cheating?! • Some spend all the time withits head down feeding. • Each individual will be expected to try to get more benefit than the others.

  10. Dilution and cover (1) An individual animal in a herd of a hundred has only a one in a hundred chance of being the victim in a single attack. week.divebums.com/Sep26-2005/index.html www.animalpicturesarchive.com/view.php?did=51...

  11. Dilution and cover (1) www.butterflyutopia.com/monarch_danaus_plexip... • Monarch butterfly (Danaus plexippus) • To migrate from North America to spend the winter in warmer places such as Mexico. www.inhs.illinois.edu/.../specspot.html

  12. Dilution and cover (1) www.butterflyutopia.com/monarch_danaus_plexip... • Monarch butterfly (Danaus plexippus) • To migrate from North America to spend the winter in warmer places such as Mexico. • Predation rate is inversely related to colony size. www.inhs.illinois.edu/.../specspot.html

  13. Dilution and cover (2) www.learnnc.org/lp/multimedia/8787 • Cicada • Prime number !!13 or 17 • Why not 15, 18? www.hpjava.org/photos/cicadas/index.html

  14. Dilution and cover (2) www.learnnc.org/lp/multimedia/8787 • Cicada • Prime number !!13 or 17 • Why not 15, 18? • 15 = 3 x 5 • 18 = 2 x 3 x 3 www.hpjava.org/photos/cicadas/index.html

  15. Group defence faculty.ksu.edu.sa/.../Forms/DispForm.aspx?ID=7 • Black-headed gulls www.edsphotoblog.com/?p=438

  16. Group defence faculty.ksu.edu.sa/.../Forms/DispForm.aspx?ID=7 • Black-headed gulls • To mob a crow at the same time. www.edsphotoblog.com/?p=438

  17. Costs of being in a group www.naturephoto-cz.com/song-thrush:turdus-phi... A thrush-like Bird

  18. Costs of being in a group www.naturephoto-cz.com/song-thrush:turdus-phi... A thrush-like Bird The benefit of group mobbing by members of a colony more than offsets the disadvantage of be conspicuous.

  19. Zebra vs. hyenas www.markstivers.com/wordpress/?p=102

  20. Finding good sites Catching difficult prey Harvesting renewing food Costs associated with feeding LIVING IN GROUPS AND GETTING FOOD

  21. Finding good sites 1 2 X 3 4 (Quelea quelea) perso.wanadoo.es/.../Quelea_quelea.htm www.mangoverde.com/.../picpages/pic192-89-2.html www.biodiversityexplorer.org/birds/ploceidae/...

  22. Information Centres hymenopteran www.britannica.com/.../279337/29649/Ichneumon

  23. Catching difficult prey www.pifsc.noaa.gov/cred/mdr_photo.php Jack fish (caranx ignobilis) www.ozanimals.com/.../Caranx/ignobilis.html

  24. Catching difficult prey • Jack • Team work !!

  25. Harvesting renewing food www.wildliferanger.co.uk/ Wagtails’ problem

  26. Harvesting renewing food www.wildliferanger.co.uk/ • Wagtails’ problem • How many days I should leave? • To visit sites in a group makes sure that everyone returns at the same time.

  27. Brent geese with sea plantain www.birdphoto.org.uk/page5.htm www.floralimages.co.uk/pplantmarit.htm

  28. Brent geese with sea plantain www.birdphoto.org.uk/page5.htm www.floralimages.co.uk/pplantmarit.htm The regular cropping pattern actually stimulates the growth of young leaves which are rich and nitrogen

  29. Costs associated with feeding www.birdwatchireland.ie/Default.aspx?tabid=336 www.birdingworld.co.uk/CleySpring2006.htm Redshank

  30. Costs associated with feeding www.birdwatchireland.ie/Default.aspx?tabid=336 www.birdingworld.co.uk/CleySpring2006.htm • Redshank’s different recipes • Day and nightshrimps and snails

  31. Weighing up cost and benefits… optimal group sizes… NEXT…

  32. Weighing up costs and benefits – optimal group size

  33. Weighing up costs and benefits – optimal group size

  34. Dense flock or loose flock • Example:(1)Knot (濱鷸) (2)Ringed plovers(環頸鴴) • Touch feeders live in flocks • Visual hunters tend to be solitary • In visual hunters, individual benefit>risk of predation

  35. Charles and Mary Brown’s researching Cliff swallow (1)Cliff swallows nest in colonies ranging in size from 1 to 3000 pairs (2)Swallows often follow one swallow when collecting food for their young http://www.threadbaregypsysoul.com/2007/05/cliff-swallows.html

  36. Ectoparasitism • Nestlings are often attacked by (a blood-sucking hemipteran)Oeciacus vicarius. • These bugs spend most of their lives in swallow nest. http://bugguide.net/node/view/252639/bgpage

  37. Larger colonies of swallows have more bug per nest. • Bugs have significant negative effect on nestling growth. 10-day-old cliff swallow chicks.Fumigated chicks were 3.4g heavier than 22g non-fumigated controls

  38. Cliff swallows nestling growth is positively correlated with colony size when fumigation. • Without fumigation, there is no correlation.

  39. Time budgets • Three type behavior:(1) Scanning(2) Feeding(3) Fighting: Short-term squabble & Attack • Three behavior assumed to be mutually exclusive. • Scanning take precedence over feeding

  40. Pulliam and Caraco’s model • Yellow-eye junco • The time of scanning decrease with increased group size. • The time of fighting increase with increased group size. • The time of feeding is at a maximum in the flocks of intermediate size. • Other effect factor:(1)Dominant bird v.s subordinate (2)dilution effect and increase vigilance

  41. Average daily temperature increase. • Easy satisfy energy requirement. • More time on fighting by dominant birds. • Decrease flock size.

  42. Increase risk of predation. • More time on scanning. • Must have to feed in large flocks to maintain food intake.

  43. Result of Pulliam and Caraco’s model • Flocking allows more time for feeding because less time on scanning. • Maximum flock size depends on time available of dominant birds. • Reject the hypothesis about optimal flock size.

  44. Optimal size group stable? • The optimal group size is 7 • Newcomer join the group up to the group size is 14 • 12 divide to 6&6 • 12 divide to 7&5=>8&? • In nature: stable group is more often than optimal group Sibly’s model of optimal and stable group size

  45. Evolution of group living: schooling in guppies Schooling benefits: Anti-predator Predator-rich Predator-free 200 guppies Colonize the downstream catch Predator-rich catch Schooling costs: Guppies with high propensity to school are less good competitor over food Guppies from predator-rich stream live in tighter schools than those from Predator-free stream After 30 years catch

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