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Effects of resource availability on juvenile dispersal and settlement
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Dispersal & Resources central determinant of a species’ ecology energetically expensive dispersal behaviour related to physical condition or access to energy reserves
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Energetic mediation of dispersal Belding’s ground squirrel (Spermophilus beldingi) Nunes et al. 1999 Greater flamingo (Phoenicopterus ruber roseus) Barbraud et al. 2003 Common lizard (Lacerta vivipara) Massot and Clobert 1995 Spanish imperial eagle (Aquila adalberti) Ferrer et al. 1992 photo by Don Baccus photo by Howard Inns photo from Smithsonian Institute photo from Just Birds
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Resource paradox Do increased local resources encourage or provide an advantage for dispersal or philopatry? Photo by Sébastien Descamps
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Dispersal trade-off Costs energetically expensive predation risk territory quality Benefits avoid kin competition avoid inbreeding territory quality
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Objectives and Expectations Determine energetic influences on: growth rate exploratory forays degree of dispersal or philopatry territory takeover attempts size and quality of territory settled successful settlement and survival
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maternal food supplementation autumn 2003 to Spring 2004 autumn 2003 n=31 females winter 2004 food add n=15 control n=13 Team Lloyd
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Number of breeding females
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Number of females surviving control
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food-add control 20-Mar 03-Apr 17-Apr 01-May 15-May 29-May 12-Jun food-addcontrol Parturition dates
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Litter sizes food-add control
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Juvenile emergence Number of emerged vs failed juveniles Average proportion of litter emerged food-addcontrol
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Team Lloyd Circuit trapping –all middens within 90 m radius of natal area –until 100 days old –150-175 hours of trapping per litter –weight taken at each capture
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Individual growth rates food-addcontrol
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Average growth rates
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Settlement criteria 1. rattled on midden on more than one day 2. trapped at least 3 times at same midden 3. assumption for one rattle during August census – late litters 4. day 100?
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Settlement criteria 1. rattled on midden on more than one day 2. trapped at least 3 times at same midden 3. assumption for one rattle during August census – late litters 4. day 100?
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Settlement criteria 1. rattled on midden on more than one day 2. trapped at least 3 times at same midden 3. assumption for one rattle during August census – late litters 4. day 100?
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Settlement criteria 1. rattled on midden on more than one day 2. trapped at least 3 times at same midden 3. assumption for one rattle during August census – late litters 4. day 100?
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Settlement criteria 1. rattled on midden on more than one day 2. trapped at least 3 times at same midden 3. assumption for one rattle during August census – late litters 4. day 100?
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Settlement of emerged juveniles 90% settlement in both food-add and control at individual level food-add litters n= 12 control litters n=5
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Age at settlement food-addcontrol
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Maximum foray distance food-add n = 28 from 12 litters (154.84 ± 179.60) control n= 10 from 5 litters (95.41 ± 37.96) food-add control
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Maximum settlement distance food-add n = 24 from 12 litters (116.19 ± 172.84) control n= 9 from 5 litters (76.47 ± 56.56) food-add control
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Team Lloyd Territory mapping –juveniles radio-collared –radio-tracked territory boundary –≥ 30 data points
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Juvenile territory mapping
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Team Lloyd Territory quality index Midden condition ranked midden quality and activity Cone production assessed with cone counts Tree density Spruce bark beetle kill
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Survival of settled juveniles
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Proportion of total juveniles settled
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Too cute not to include
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