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Only a theory: Why birds fly, why mammals stayed small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Switzerland Science and Barbecue Zürich August 2012

Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

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Page 1: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Only a theory: Why birds fly, why mammals stayed small, and why dinosaurs became

big and died out

Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of

Zurich, Switzerland Science and Barbecue Zürich August 2012

Page 2: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

... or how listening to interdisciplinary gossip, riding trains and drawing

pictures can lead to high attention-generating and completely non-

useful hypotheses.

Page 3: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

DFG Research Group 533 Sauropod Biology - the Evolution of Gigantism

Page 4: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

DFG Research Group 533 Sauropod Biology - the Evolution of Gigantism

Digestive physiology supervisors

Marcus Clauss Jürgen Hummel

Page 5: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

DFG Research Group 533 Sauropod Biology - the Evolution of Gigantism

Digestive physiology supervisors

Digestive physiology PhD students & associates

Marcus Clauss Jürgen Hummel

Julia Fritz Ragna Franz Patrick Steuer

Page 6: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

DFG Research Group 533 Sauropod Biology - the Evolution of Gigantism

(Digestive physiology) supervisors

Digestive physiology PhD students & associates

Marcus Clauss Jürgen Hummel

Julia Fritz Ragna Franz Patrick Steuer

Chris Carbone

Page 7: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

DFG Research Group 533 Sauropod Biology - the Evolution of Gigantism

(Digestive physiology) supervisors

Digestive physiology PhD students & associates

Marcus Clauss Jürgen Hummel

Julia Fritz Ragna Franz Patrick Steuer Dennis Müller Daryl Codron Irina

Nurutdinova

Chris Carbone

Page 8: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

DFG Research Group 533 Sauropod Biology - the Evolution of Gigantism

(Digestive physiology) supervisors

Digestive physiology PhD students & associates

Marcus Clauss Jürgen Hummel

Julia Fritz Ragna Franz Patrick Steuer Dennis Müller Daryl Codron Irina

Nurutdinova

Chris Carbone

Page 9: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Assumptions

- Niche stratification according to body size (=body mass) - Eggs cannot increase endlessly in size because of

physical constraints on egg shell thickness (stronger shells needed for larger eggs) and diffusion (thicker shells prevent diffusion of oxygen)

- The K-T extinction event affected all animals above a certain body size threshold

Page 10: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Niches of parent and offspring niche space

A

A - 1

A - 2

A - 3

adult

Page 11: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Niches of parent and offspring niche space

A

A - 1

A - 2

A - 3

adult

egg

Page 12: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Niches of parent and offspring niche space

A

A - 1

A - 2

A - 3

adult

egg

Page 13: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Niches of parent and offspring niche space

A

A - 1

A - 2

A - 3

adult

egg neonate

Page 14: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Niches of parent and offspring niche space

A

A - 1

A - 2

A - 3

adult

juvenile

egg neonate

Page 15: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Niches of parent and offspring niche space

A

A - 1

A - 2

A - 3

adult

juvenile

juvenile

egg neonate

Page 16: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Niches of parent and offspring niche space

adult A

A - 1

A - 2

A - 3

Page 17: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Niches of parent and offspring niche space

adult

foetus A

A - 1

A - 2

A - 3

Page 18: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Niches of parent and offspring niche space

adult

neonate

A

A - 1

A - 2

A - 3

Page 19: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Niches of parent and offspring niche space

adult

juvenile

A

A - 1

A - 2

A - 3

Page 20: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 21: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 22: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 23: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 24: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 25: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 26: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 27: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 28: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 29: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 30: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 31: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 32: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 33: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 34: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 35: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 36: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 37: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 38: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 39: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 40: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 41: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 42: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 43: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 44: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 45: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 46: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 47: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 48: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 49: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

niche space Niches of parent and offspring

Page 50: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Resulting hypothesis I

The reproductive mode of dinosaurs (ovipary), with its intrisic limited juvenile start size linked to ontogenetic niche stratification, may have led to a parallel decrease of small dinosaur species with the increase of larger species, because offspring of large species fill the niche space of the smaller species.

A catastrophic event, truncating adult body size, could therefore, in theory, wipe out the whole reproductive dinosaur population.

Page 51: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

In contrast, the reproductive mode of mammals (and also that of many birds due to parental care) does not lead to an ontogenetic niche stratification, but offspring use the parents’ niche.

Thus, with increasing body mass of larger species, niches of smaller species are not usurped by the larger species’ offspring to the same extent.

Die-offs of larger species would not leave niches of smaller life forms empty.

Resulting hypothesis II

Page 52: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Check species assemblages for distribution patterns (is there a ‘gap’)?

Design deterministic model to test effect of interspecific competition on body mass distribution of mammals and dinosaurs before and after a simulated K-T-event

Work plan

Page 53: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Check species assemblages for distribution patterns (is there a ‘gap’)?

Design deterministic model to test effect of interspecific competition on body mass distribution of mammals and dinosaurs before and after a simulated K-T-event

Work plan

Daryl Codron

Page 54: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Species distributions

Page 55: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Deterministic model

• Populations of different sized species of: Dinosaurs: i1,i2…ik = {2 g to ~131 tons} Mammals: i1,i2…ik = {2 g to ~16 tons}

 Each structured by size (log2M increments, j) from neonate-adult

Mneonate = aMadultb bdinosaurs ~0.6

bmammals ~0.9

 For each Mi,j, estimate: 1. initial abundance n (allometry) 2. survivorship p (r-selecting or K-selecting) 3. fecundity f (allometry; add fini,k to ni,1)

• Assume: each log2M step = ontogenetic niche shift

Page 56: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Deterministic model

• Density of each i after competition:

Ni = pi,j ni,j – α(Σ[pi,j nj] – pi,jni,j)

  Independent α for D on M and M on D:

Dinosaurs: NDi = Σ[nDi,j – αDD(ΣnDj–nDi,j) - αMD(ΣnMj)]

Mammals: NMi = Σ[nMi,j – αMM(ΣnMj – nMi,j) - αDM(ΣnDj)]

 Simulate K-T: kill all individuals >25 kg

Competition-induced mortality (α) occurs amongst all similarly-sized individuals (symmetric)

Page 57: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Model results - no competition

log2Madult (kg)

relative abundance

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.00

0.02

0.04

0.06 Dinosaurs

(non-avian) Aves Mammalia

αDD = 0.00αMM = 0.00αDM = 0.00αMD = 0.00

Page 58: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Model results - mild competition-induced mortality

log2Madult (kg)

relative abundance

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.00

0.02

0.04

0.06 Dinosaurs

(non-avian) Aves Mammalia

αDD = 0.1αMM = 0.1αDM = 0.00αMD = 0.00

Page 59: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Model results - stronger competition

log2Madult (kg)

relative abundance

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.00

0.02

0.04

0.06

0.08

0.10 Dinosaurs (non-avian)

Aves Mammalia

αDD = 0.15αMM = 0.15αDM = 0.00αMD = 0.00

Page 60: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Model results - including competition from dinosaurs on mammals

log2Madult (kg)

relative abundance

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.00

0.02

0.04

0.06

0.08

0.10

0.12

Dinosaurs (non-avian)

Aves Mammalia

αDD = 0.15αMM = 0.15αDM = 0.15αMD = 0.00

Page 61: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Model results - ... and from mammals on dinosaurs

log2Madult (kg)

relative abundance

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20 Dinosaurs

(non-avian) Aves Mammalia

αDD = 0.15αMM = 0.15αDM = 0.15αMD = 0.15

Page 62: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Model results - ... and from mammals on dinosaurs

log2Madult (kg)

relative abundance

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20 Dinosaurs

(non-avian) Aves Mammalia

αDD = 0.15αMM = 0.15αDM = 0.15αMD = 0.15

Page 63: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Model results - after K/T, with competition

log2Madult (kg)

relative abundance

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.00

0.02

0.04

0.06

0.08

0.10

0.12 Dinosaurs (non-avian)

Aves Mammalia

αDD = 0.15αMM = 0.15

Page 64: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Deterministic model

• Robustness and sensitivity  Changes and variability in M effects on:

1. life history strategy 2. reproductive output 3. Madult:Mneonate ratio 4. competition co-efficient (α) 5. symmetry of α 6. abundance

 Stochastic parameter estimates (bounded within empirical limits for birds/herpetiles or mammals), 103 iterations

Page 65: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Model results - variation in neonate scaling, demography, and ecology

pre K-T post K-T

log2Madult (kg)

relative abundance

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.000.050.100.150.200.25

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.000.020.040.060.080.100.120.14

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.000.040.080.120.160.20

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.000.020.040.060.080.100.12

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.000.020.040.060.080.10

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.000.020.040.060.080.100.12

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.000.050.100.150.200.25

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.000.020.040.060.080.100.12

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.000.100.200.300.400.50

-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 170.000.040.080.120.160.20

Dinosaurs (non-avian); Aves; Mammalia

variable adult-neonate mass scaling exponent variable adult-neonate mass scaling exponent

variable initial abundance variable initial abundance

variable abundance-mass scaling exponentvariable abundance-mass scaling exponent

variable fertility (birth rate) variable fertility (birth rate)

variable α variable α

Page 66: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

Conclusions

Size-specific competition influences species diversity - Effects largest amongst species with high intraspecific

niche breadth (e.g. large, oviparous)…

- … favouring large-bodied taxa

Explains paucity of small-bodied dinosaurs - Dominance of large dinosaurs then limited max BM of

other vertebrate groups in Mesozoic…

Extinction event above body mass threshold = remaining species diversity too low for recovery

- … resultant dominance of small taxa amongst mammals further limited small dinosaurs (=aerial niche?)

Page 67: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,
Page 68: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,
Page 69: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,
Page 70: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,
Page 71: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,
Page 72: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,
Page 73: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,
Page 74: Only a theory: Why birds fly, why mammals stayed …ffffffff-f77d-1dab...small, and why dinosaurs became big and died out Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife,

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