Chapter 16

Slide1: 

Predator-Prey Interactions in the Vertebrate Community NIELS M. SCHMIDT THOMAS B. BERG MADS C. FORCHHAMMER LINE A. KYHN HANS MELTOFTE HANS PEDERSEN TOKE T. HØYE

Predator-prey interactions: 

Predator-prey interactions Integrate the available BioBasis information on terrestrial predator-prey interactions Focus on the collared lemming and its predators Build a predator-prey model (C++) that took off in the model developed for the lemming population on Traill Island (Gilg et al. 2003, 2006)

Lemmings in Zackenberg and on Traill: 

Lemmings in Zackenberg and on Traill Lemming dynamics are similar (R2 = 0.77) Smaller amplitude Contrasting predator communities Lack of owls Contrasting stoat response

Model framework: 

Model framework Based on the functional and numerical responses of all predatory species Numerical response depends on lemming density at snow melt Functional response depends on current lemming density Functional + numerical response = total impact (predation) Onset of summer start and winter start determines predator access to lemmings and lemming growth rate rsummer = 1 rwinter = 4

Model framework: 

Model framework Numerical response of predators Arctic fox None = average value Young numerical response Long-tailed skua None = average Young numerical response Stoat Combined functional and numerical response Snowy owl Random event above lemming density threshold + average young production Functional reponses adapted from Gilg et al. (2003, 2006)

Model framework: 

Model framework

ZAC and model characteristics: 

ZAC and model characteristics Our model is able to create the pattern of fluctuation observed in the ZAC lemming population But model density much lower than the density estimated from countings of winter nest R2 = 0.74

Relative importance of predators: 

Relative importance of predators The importance of the predators varies with lemming phase

Predation in spring: 

Predation in spring Habitat shift and risk of predation DOY Survival Number observed Number observed

Predation in spring: 

Lemming tracks on snow in spring Predation in spring

Predation in summer: 

Predation in summer

Lemming behaviour: 

Lemming behaviour Lemming location in summer Spent app. 2/3 of their time inside burrows And when outside…..

Lemming behaviour: 

Lemming behaviour Lemming summer time budget outside burrow

Predator-prey dynamics and climate: 

Predator-prey dynamics and climate Effects of length of winter season Via the dichotomy in growth rate (rsummer = 1, rwinter = 4) How is the pattern of fluctuation affected by length of winter?

Predator-prey dynamics and climate: 

Does the structure of lemming dynamics change with the length of winter season? Cyclic Chaotic Stable Predator-prey dynamics and climate

Predator-prey dynamics and climate: 

The structure of lemming dynamics is affected by the length of winter Cyclic Chaotic Stable Predator-prey dynamics and climate

Predator-prey dynamics at ZAC: 

Predator-prey dynamics at ZAC Conclusion Remarkably similar fluctuations at ZAC and on Traill Island despite differences in predator community Pattern of fluctuation seems driven by predators Delayed numerical response of stoats Strong density-dependent predation from fox and skua High predation pressure, which also can be traced in lemming behaviour in summer Dynamical structure of time series affected by length of winter season Additional chapter subjects Additional model parameters (alternative prey, effects of length of growing season) Indirect effects of lemming density on e.g. wader and ducks Gradients in predator community along the Greenland east coast