A metapopulation model of the spread of the Devil Facial Tumour Disease predicts the long term collapse of its host but not its extinction

TL;DR

This study uses a spatial metapopulation model to predict that Tasmanian Devils will persist with DFTD at about 9% of their original density, leading to long-term coexistence but significant ecological impacts.

Contribution

It introduces a spatial metapopulation model incorporating disease spread and patch dynamics to predict long-term host-pathogen coexistence.

Findings

Tasmanian Devils are predicted to survive with DFTD at about 9% of original density.

The model confirms the disease originated in north-east Tasmania.

Long-term coexistence involves repeated local extinctions and reinvasions.

Abstract

The Devil Facial Tumour Disease (DFTD), a unique case of a transmissible cancer, had a devastating effect on its host, the Tasmanian Devil. Current estimates of its density are at roughly 20% of the pre-disease state, and single-population epidemiological models have predicted the likely extinction of the host. Here we take advantage of extensive surveys across Tasmania providing data on the spatial and temporal spread of DFTD, and investigate the dynamics of this host-pathogen system using a spatial metapopulation model. We first confirm a most likely origin of DFTD in the north-east corner of the island, and then use the inferred dynamics to predict the fate of the species. We find that our medium-term predictions match additional data not used for fitting, and that on the long-term, Tasmanian Devils are predicted to coexist with the tumour. The key process allowing persistence is the repeated reinvasion of extinct patches from neighbouring areas where the disease has flared up and died out, resulting in a dynamic equilibrium with different levels of spatial heterogeneity. However, this dynamic equilibrium is predicted to keep this apex predator at about 9 % of its original density, with possible dramatic effects on the Tasmanian ecosystem.