Evolution of migration in a changing world. Cervus elaphus (known as red deer, elk, or wapiti)

Transcription

1 Evolution of migration in a changing world Cervus elaphus (known as red deer, elk, or wapiti) 1

2 Rates of energy gain by red deer or elk are highest when feeding on young vegetation (2-4 weeks of growth) Wilmshurst and Fryxell (1995) Oecologia 104:

3 Given a choice, foragers prefer young patches that yield the highest gain atch me in pa % Tim Patch growth (weeks) Wilmshurst, Fryxell, and Hudson (1995) Behavioral Ecology 6:

4 4

5 By migrating up elevation gradient, elk could increase energy gain over growing season Bischof et al. (2012) Am. Nat. 180:

6 Coupled lattice grazing model: resource growth dv ij dt f ( Vij ) Nij[ ( Vij ) ( Vij )] W ( Vij ) dn dt ij N ij [ ( Vij ) ( Vij )] 6

7 Coupled lattice grazing model: functional response dv dt ij f ( Vij ) Nij [ ( Vij ) ( Vij )] W ( Vij ) dn dt ij N ij [ ( Vij ) ( Vij )] 7

8 Coupled lattice grazing model: dv ij dt f ( Vij ) Nij[ ( Vij ) ( Vij )] W ( Vij ) dn dt ij N ij [ ( Vij ) ( Vij )] spatial response 8

9 Adaptive rule: leave patches that are belowaverage, stay in ones that are above-average 1 Probability of dispersal Daily energy intake Z(V) 9

10 Grazer movement choices match relative energy gain in neighboring patches 10

11 Herbivores Plant biomass Y coordinate Y coordinate X coordinate X coordinate 0 11

12 Herbivores Plant biomass Y coordinate Y coordinate X coordinate X coordinate 0 12

13 Herbivores Plant biomass Y coordinate Y coordinate X coordinate X coordinate 0 13

14 Herbivores Plant biomass Y coordinate Y coordinate X coordinate X coordinate 0 14

15 Herbivores Plant biomass Y coordinate Y coordinate X coordinate X coordinate 0 15

16 Herbivores Plant biomass Y coordinate Y coordinate X coordinate X coordinate 0 16

17 Herbivores Plant biomass Y coordinate Y coordinate X coordinate X coordinate 0 17

18 N 1( t 1) N 1( t ) exp( r 1 N 1( t ) N 3( t ) s ) ( eq.1) A A Evolutionary model (2 habitats, 2 seasons) Lowland (A) resident Highland (B) resident Migrant 18

19 Partial migration is an ESS so long as both habitats are sources Fryxell and Holt (2012) Ecology 19

20 There is a lot of variation in movement behavior of red deer across different parts of Norway Bischof et al. (2012) Am. Nat. 180:

21 Where there is substantial elevation change, g, red deer are migratory, tracking the green wave Bischof et al. (2012) Am. Nat. 180:

22 Partial migration is common, becoming more pronounced where there is less heterogeneity in green wave Spatial variation in peak growth Bischof et al. (2012) Am. Nat. 180:

23 Where there is little elevation change, g, most red deer are non-migratory. Bischof et al. (2012) Am. Nat. 180:

24 Partial migration is also pronounced where red deer density is high Bischof et al. (2012) Am. Nat. 180:

25 What might be the consequences of environmental change for migration? -Habitat decline 25

26 Middleton et al. (2012) Ecology in press 26

27 In recent years green up is more intense and much faster Middleton et al. (2012) Ecology in press 27

28 slight decline in habitat B Fryxell and Holt (2012) Ecology 28

29 large decline in habitat B Fryxell and Holt (2012) Ecology 29

30 More rapid green-up is associated with declining recruitment resident migrant 30

31 What might be the consequences of environmental change for migration? -Habitat decline -Increased cost of migration 31

32 Migrants also face growing wolf and bear populations Middleton et al. (2012) Ecology in press 32

33 Elk survival in Alberta (migrants vs residents) λ=0.88 λ=0.90 Hebblewhite (2011) Oikos 120:

34 change in cost of migration Fryxell and Holt (2012) Ecology 34

35 Elk distribution in the Bow Valley y( (1985) wolves just arrived elk still largely migratory Aerial Elk Census, Spring

36 Elk distribution ib ti in the Bow Valley (1990) Aerial Elk Census, Spring

37 Elk distribution in the Bow Valley (1995) wolves well established Aerial Elk Census, Spring

38 and this is what they found so attractive about resident life 38

39 Conclusions Partial migration in ungulates has evolved to improve access to heterogeneous resources Global climate change is reducing the value of high elevation habitat Increased predator densities due to anthromorphic hi effects is increasing mortality risk to migrants Net effect may be partial or complete loss of migratory morphs 39