Kevin Healy, Andrew Parnell & Andrew Jackson Accounting for the process of foraging in source-level variation in isotopic mixing models.

Kevin Healy, Andrew Parnell & Andrew Jackson

Accounting for the process of foraging in source-level variation in isotopic mixing models

Do Mixing models mimic ecological systems?

Sources of Uncertainty Model Behaviour

– Consumer sampling of food sources.

Newton 2010

Do Mixing models mimic ecological systems?

Sources of Uncertainty Model Behaviour

– Consumer sampling of food sources.

Newton 2010

Standard Error Vs.

Standard Deviation

Mixing Models use single draw from source distribution

~ S.D

Consumers take numerous draws from source distribution ~ S.E

Standard Error Vs.

Standard Deviation

Included in SIAR mixing models using equation

= Number of items eaten

Standard Error Vs.

Standard Deviation

New Caledonian Crows

Rutz et al 2010

Ecological importance of tool use

Standard Error Vs.

Standard Deviation

Rutz et al 2010

Diet ProportionLarvae = 50%

Standard Error Vs.

Standard Deviation

Diet ProportionLarvae = 50%Candle Nuts = 40%

Rutz et al 2010

Standard Error Vs.

Standard Deviation

Rutz et al 2010

Diet ProportionLarvae = 50%Candle Nuts = 40%Lizards = 10%

Standard Error Vs.

Standard Deviation

Simulated dataRange of Items

eaten (1-100)

Rutz et al 2010

Effect of the number of items eaten on posterior credibility intervals

Larvae iNuts Lizards

1 2 i5 20 100 ii1 12 5 20 100 1 2 5 20 100

Number of items Eaten

Pro

port

ions

0

0. 2

0

.4

0.6

0

.8

1.0

Number of items Eaten

Cre

dabi

lity

inte

rval

ran

ge

(5%

-95%

)

Effect of the number of items eaten on posterior credibility intervals

Number of items Eaten

Cre

dabi

lity

inte

rval

ran

ge

(5%

-95%

)

Effect of the number of items eaten on posterior credibility intervals

i10

Estimating number of items eaten using metabolic theory

Estimating daily energy consumption

Metabolism ~ Mass

Estimating daily energy consumption

= Metabolic rate

= Normalising constant

M = Consumer mass

Estimating number of items eaten using metabolic theory

b = daily metabolic need p = proportion of source e = energetic value of food in KJ/g a = assimilation efficiency = Mass of food source

Estimating number of items eaten using metabolic theory

Estimation of source sampling number

Crow - 300g ±1 S.D

= 6.07 (White et al 2011)

Rutz et al 2010

Estimating number of items eaten using metabolic theory

Estimation of source sampling number

Rutz et al 2010

Larvae – 2.8g ± 1 S.DNuts – 4g ± 2 S.DLizards – 18g ± 3 S.D (Rutz et al 2007)

Estimating number of items eaten using metabolic theory

Estimating number of items eaten using metabolic theory

Rutz et al (2010)

Estimation of source sampling number

Larvae e = 160 KJ/gNuts e = 120 KJ/gLizards e = 40KJ/g

Estimating number of items eaten using metabolic theory

Rutz et al (2010)

Estimation of source sampling number

a = 0.75 (Castro et al 1989)

Larvae e = 160 KJ/gNuts e = 120 KJ/gLizards e = 40KJ/g

Estimating number of items eaten using metabolic theory

Estimation of source sampling number

Rutz et al 2010

Larvae = 5.68Nuts = 4.1Lizards = 2.72

No. sampled over 7 days

Posterior proportion estimates of single Vs. multiple Items eaten

Posterior proportion estimates of single Vs. multiple Items eaten

Acknowledgments

Andrew Jackson

This work was carried out as part of the Earth and Natural Sciences (ENS) Doctoral Studies Programme, funded by the Higher Education Authority (HEA) through the Programme for Research at Third Level Institutions, Cycle 5 (PRTLI-5), co-funded by the European Regional development Fund (ERDF).

Andrew Parnell

Mafalda VianaLuke McNallyAdam Kane